The main rotor hub is designed to transmit rotation to the rotor blades from the main gearbox shaft and to perceive and transmit to the fuselage aerodynamic forces arising on the main rotor.
The main rotor hub of the Mi-4 helicopter has spaced horizontal hinges, as well as vertical and axial hinges. This articulation of the blades with the propeller hub gives them the ability to oscillate relative to the horizontal and vertical hinges under the influence of variable aerodynamic and inertial forces applied to them when the helicopter is flying at forward speed. As a result, the magnitude of alternating stresses in the rotor blades is significantly reduced. Horizontal hinges, in addition1, ‘Eliminate the effect of moment from aerodynamic forces on the fuselage. Oscillations of the blade relative to the axis of the vertical hinge are damped by a friction damper.
To change the installation angles of the blades, the latter have a hinged seal in the bushing (“axial hinge”).
Thus, the articulation of the blades with the main rotor hub housing and, accordingly, with the main gearbox shaft is carried out through three hinges. To increase the stability of the movement of the blade and improve the performance of the helicopter, a kinematic connection is provided between the installation angles of the blade and its deviation relative to the horizontal hinge (“swing angle”); The bushing has a so-called “swing compensator”.
The design of the main rotor hub 1 also includes a mechanism for a centrifugal blade overhang limiter. This mechanism allows the blades, which have an overhang angle of 1°4(Y) when the rotor is stationary (deflection down from the plane perpendicular to the axis of the gearbox shaft), to increase this value to 4° when the main rotor is rotating.
Limiting the overhang is necessary to increase the gap between the tail boom and the end of the blade at a low rotation speed of the main rotor when starting and stopping it. This gap is determined by the deflection of the blade when stationary and when rotating at low speeds,
When the main rotor rotates at operating speeds, the blade rises under the influence of centrifugal and aerodynamic forces and receives an upward deflection, which significantly increases the gap between its end and the tail boom.
To avoid hitting the horizontal hinge stop during various evolutions in flight conditions, the blade with a rotating rotor has the ability to move 4° down from the plane perpendicular to the shaft axis.
The main parts of the main rotor hub (Fig. 169)
13 Zach - 740
Fig 169. Main rotor hub.
1-sleeve body; 2-bracket; 3-trunnion axle joint; 4-axial joint housing; 5-lever blade; 6-bottom cone ring; 7-top cone ring; 8-nut of the main rotor shaft; 9-locking pin; 10, 52 and 53-cork; 11-outer ring of needle bearings of the horizontal hinge; 12-inner ring of needle bearing; 13, 20, 46 spacer sleeve; 14-finger horizontal hinge; 15 - horizontal hinge pin; 16-'bronze washer of horizontal hinge; 17, 18, 39, 40, 41, 54, 55 - O-rings; 19- outer ring of needle bearings of the vertical hinge; 21- bronze washer of the vertical hinge; 22-finger vertical hinge; 23-inner drum damper; 24-nut of the vertical hinge pin; 25-outer damper drum; 26-bolt securing the outer drum; 27-disc intermediate large; 28-disc intermediate small; 29—upper disk; 30-disc friction; 31-disc pressure; 32- damper spring; 33- — lnuzhin disk; 34-.adjusting bolt; 35-damper cover; 36 and 56 - oil seal, 37 - piston; 38-piston spring, 42-ring; 43-nut of the axle joint housing; 44 and 51-adjusting ring; 45-radial ball bearing; 47-thrust ball bearing; 48-nut of the axle joint pin; 49-pin; 50-radial ball bearing; 57-cuff; 58-bolt securing the blade arm; 59- bushing; 60-double row ball bearing; 61-ball bearing; 62- lever hinge shaft; 63-arm hinge cover.
bushing body 1, bracket 2 (4 pcs.), axial hinge pin 3, axial hinge body 4 and levers 1 5 blades.
The bushing body has a hole in the center with involute splines, with which it is put on the main gearbox shaft and centered on two cone rings 6 and 7. The lower cone ring 6 is bronze and has one cut. Top cone ring. 7 is steel and consists of two halves. Nut 8 is screwed onto the gearbox shaft and secures the housing through conical rings to the shaft. The nut is protected from unscrewing by three pins 9.
Bushing body. 1 has four wide eyes (according to the number of blades). The axes of the lugs lie in the same plane at an angle of 90° to each other. The centers of the lugs are shifted from the radial position by 60 mm.
At the top of the housing there is a flange with holes for attaching the deicer manifold, and at the bottom there are lugs for attaching the swashplate arm.
Needle bearings of horizontal hinges are mounted in the housing eyes, two bearings in each. The outer ring 11, common to both bearings, is inserted into the eye and is secured against rotation by involute splines located both in the shoulder of the outer ring1 and in the housing eye. The inner rings of needle bearings 12 have collars along the edges for axial fixation of the needles. Needles size 5X50 are collected in 106 pieces. in each bearing. A spacer sleeve 13 is placed between the inner rings of the bearings.
The eye of the housing with needle bearings is covered on both sides by the eyes of the bracket 2. The pin 14 of the horizontal hinge is passed through the eyes of the bracket and the inner rings of the bearings.
The assembly is tightened with nut 15. The pin is kept from turning in the eye of the bracket by a segment key. To absorb the axial forces that arise when the blade deviates from the direction perpendicular to the hinge axis, bronze washers 16 are installed between the ends of the housing eyes and the bracket.
To limit the rotation of the blade joint in the horizontal hinge, there are special stops on the bushing body 1 and bracket 2. Rotation of the joint upwards from a plane perpendicular to the axis of the gearbox shaft is possible by 25° and downward by 4° under flight conditions. The threaded holes on the body, closed with plugs 10, are intended for pouring oil into the horizontal hinges. The oil enters the housing cavity, and from there through the drillings in the rings and into the needle bearings. Rubber rings 17 and 18 serve to seal the oil cavity of the horizontal1 hinge.
Bracket 2 is a box-section part that has two lugs at one end for connection with the body 1 and two lugs at the other end for connection with the axle hinge pin 3. The axis of the first lugs on the bracket is perpendicular to the axis of the other two. A centrifugal1 limiter mechanism is mounted in the inner cavity of the bracket. The connection of the bracket g with the pin of the axial hinge forms the vertical hinge I1, made similarly to the horizontal hinge. The outer ring 19, common to both bearings, is inserted into the journal 3. The inner rings, as well as in the horizontal hinge, are assembled with CO’106 needles of the same size. Between them there is a spacer - a soldered bushing 20. A pin 3 with needle bearings and flat bronze washers 21 is inserted into the eyes of the bracket, and the pin 22 of the vertical hinge is passed through them and the mating parts.
There are end slots on the upper eye of the bracket. The same slots are available on the inner drum 23 of the damper, which is installed 196
It fits along the eye of the bracket and is pressed against the slots with a nut 24, pressed onto pin 22 and tightening the entire assembly.
The axle 3 has the ability to rotate around the axis of the vertical hinge from the direction perpendicular to the axis of the horizontal hinge, ‘at the angle ЇЗDO’ forward in rotation and 6°40/back. Further rotation is limited by stops located on the trunnion and on the bracket.
Trunnion 3 of the axial hinge, in addition to the vertical cylindrical part into which the needle bearings of the vertical hinge are mounted, has a threaded shank on which the bearings of the axial hinge of the blade are installed and secured. The vertical cylindrical part of the axle has two platforms at the top with end slots for attaching the outer drum of the damper. The outer drum 25 of the damper also has two platforms with end splines, with which the drum articulates with the splines of the axle (see section according to BB). The outer drum of the damper is attached to the axle with four bolts’ 26.
The outer drum of the damper has involute splines on its inner surface; Three intermediate steel disks 27 are inserted inside the drum, having the same slots on the outer surface.
The inner drum 23 of the damper on its outer surface also has involute splines. which are put on two intermediate steel disks 28 and an upper disk 29.
Thus, part of the disks is connected to the bracket, and the other part is connected to the axle hinge pin. Between the steel disks connected to the various elements of the assembly, there are 30 friction floating disks made of asbestos cardboard, six pieces in each joint. A pressure disk 31 rests on the upper disk 29, in which eighteen spiral coil springs 32 are located around the circumference.
A disk 33 is placed on the springs, having a cylindrical shank, which passes inside the vertical hinge pin and has a thread at the end for the damper adjusting bolt 34.
The damper adjusting bolt, resting its shoulders against the vertical hinge, tightens disk 33 and presses the damper disk package through the springs. In this way, you can regulate the amount of pressure of the springs, and with it the amount of friction moment of the damper.
When the blade oscillates relative to the vertical hinge, friction occurs between the disks, which dampens these vibrations.
The damper is adjusted to a friction moment of about 200 kgm. The damper is closed from above with a lid 35. Between the outer and inner drums of the damper there is a sealing gland 36 made of felt.
Thus, the damper is completely protected from dirt and moisture, which ensures a constant friction torque.
The vertical hinge is lubricated through a grease nipple in bolt 34 of the damper. The injected oil enters the needle bearings through a drilling in the shank of the disk 33 and in the pin 22 of the vertical hinge. Under oil pressure, piston 37 compresses spring 38. Subsequently, as oil is consumed, it enters the needle bearings under the pressure of this spring.
The oil is sealed in the vertical joint by rubber rings 39, 40 and 41.
The cavity of the vertical hinge, filled with oil, is connected to the atmosphere by a valve, which protects the rubber seals of the hinge from being squeezed out, and also serves to release air from this cavity into the atmosphere when oil is injected into this unit.
The axial hinge of the blade is formed by two main parts: axle 3 and the axial hinge body 4. The body is made in the form of a glass, on the bottom of which there is a comb with eyes for attaching the blade. At the other end of the cup there is an internal thread for nut 43.
A ring 42 is pressed onto the trunnion shank, which serves as a friction surface for the cuff and felt seal of the nut 43. During assembly, a nut 43, an adjusting ring 44, a radial ball bearing 45, a spacer sleeve 46, a thrust ball bearing 47 are sequentially put on the trunnion shank during assembly, and the entire package is secured with a nut 48, which is protected from unscrewing by a pin 49. A second radial ball bearing is installed on the cylindrical part of the nut 48
tire 50. The axle with the bearings attached to it is inserted into the housing of the axial joint 4 and secured in it with a nut 43. Between the bottom of the housing and the radial bearing 50 there is an adjusting ring 51. Due to the thickness of the ring 51, the preload of the bearing assembly 50 and 47 is adjusted. The plug 52 closes hole for filling oil into the axle joint. The hole, closed with plug 53, serves to drain the oil.
Rubber rings 54 and 55 are intended to seal the axial hinge between parts that do not have relative movements in operation. The nut 43 contains a felt gland 56 and a rubber cuff 57.
The blade lever 5 is attached to the axial hinge body with four bolts 58 (see arrow D, Fig. 169). Bolts 58 are relieved from shearing forces by bushings 59. The end of the blade lever has a cylindrical cavity, in which a hinge roller 62 is installed on two ball bearings 60 and 61, secured by a cover 63, pulled to the lever by four bolts.
Two ball bearings are pressed into the head of the hinge shaft. The blade lever hinge is lubricated through a grease nipple on the roller head.
The design of centrifugal overhang limiters is shown in Fig. 170. The counterweight 3 is suspended from the bracket on the axis 7 and through the glass with axles, and the rod 6 is connected to one end of the pawl 1. The axis of rotation of the pawl is the pin 2, passed through the eyes of the bracket. The second end of the pawl serves as a stop that limits the overhang of the blade. At rotor speeds below ~ 100 rpm, spring 4 holds the pawl and counterweight in the position shown in the diagram (the overhang angle of the blade is 1°40′). When 100 rpm is reached, the counterweight begins to rotate under the influence of centrifugal force, compresses the spring and turns the pawl.
When the main rotor speed reaches approximately 120 rpm, the pawl moves completely away from the bracket; a gap is formed between the housing stop and the pawl (at least 4 mm at zero overhang angle) and the overhang of the blade is limited only by the constant stops of the bracket, which allow it to deflect downward by 4°.
When the propeller rotation speed drops to approximately 120 rpm, the reverse movement of the mechanism begins, and at 100 rpm the pawl comes to a position corresponding to the blade overhang angle of 1°40/.
INTRODUCTIONThe Mi-8 helicopter was developed in the early 1960s. OKB im. M.L. Mil (now OJSC "Moscow Helicopter Plant named after M.L. Mil") in cooperation with other enterprises, and the program for its creation became the largest in the world of helicopter manufacturing.
The Mi-8 helicopter is designed to transport passengers, luggage, cargo and mail in hard-to-reach areas, as well as to carry out special aviation work in various sectors of the national economy.
In terms of weight category, the Mi-8 helicopter belongs to class 1 helicopters.
The helicopter is designed using a single-rotor design with a five-bladed main rotor and a three-bladed tail rotor. The helicopter is equipped with two TV2-117AG turboprop engines with a take-off power of 110 kW each, which makes it possible to land the helicopter if one of the engines fails.
The helicopter is operated in two main versions: the passenger Mi-8P and the transport Mi-8T.
The passenger version of the helicopter is designed for interregional and local transportation of passengers, luggage, mail and small-sized cargo. It is designed to carry 28 passengers. The transport option provides for the transportation of cargo weighing up to 4000 kg or 24 service passengers. At the request of the customer, the passenger cabin of the helicopter can be equipped with an increased comfort cabin for 11 or 7 passengers.
A helicopter with external cargo sling transports large cargo weighing up to 3000 kg outside the fuselage.
The ferry version of the helicopter is necessary to perform flights with an increased range (from 620 to 1035 km). In this case, one or two additional fuel tanks are installed in the helicopter’s cargo cabin due to the commercial load:
Existing versions of the helicopter are equipped with an electric winch, which allows, using an onboard boom, to lift (lower) loads weighing up to 150 kg on board the helicopter, and also, if a pulley is available, to pull loads weighing up to 2600 kg into the cargo cabin.
The helicopter crew consists of two pilots and a flight mechanic.
In total, about more than 11,000 helicopters (approximately 7,300 in Kazan and 3,800 in Ulan-Ude) of the Mi-8 (Mi-17) type were built in more than 150 modifications, which are operated in 70 countries around the world. The first currently produces mainly modifications of the Mi-17-1V in various configurations and designs (up to 90-95% are exported), and the second produces modifications of the Mi-8AMT (Mi-171) and MI-8ATMSh (Mi -171Ш).
Mi-8 - the basic model of the helicopter; Mi-8P - passenger (28 passengers) helicopter with TV2-117A engines (2x1500 hp); Mi-8T - transport and landing helicopter with TVZ-117A engines (24 paratroopers, in service since 1968); Mi-8TV - transport and landing helicopter with reinforced weapons (unmanned aerial weapons, ATGM "Phalanx"); Mi-8MT (Mi-17) - modernized transport and landing helicopter (1980) with a TVZ-117MT engine (2x1900 hp); Mi-18 – modified Mi-8T with a cabin increased by 1 m (1982, 38 soldiers or cargo weighing up to 6.5 tons); Mi-8MTV-1 (-2, -3, -5) - multi-purpose modifications for use in transport and landing, combat (with NAR units, bombs and small arms), search and rescue (PSS, Mi-8PS, Mi -8SPA) and sanitary options;
1. DESIGN FEATURES OF THE MI-8 HELICOPTER
The design of the Mi-8 helicopter (Fig. 1) consists of the following main parts and systems: fuselage, takeoff and landing devices, air system, power plant, transmission, main and tail rotors, anti-icing system, helicopter control system, hydraulic system, heating or air conditioning systems, devices for external load suspension, rigging and mooring, household, aviation and radio-electronic equipment.
Rice. 1 General view of the MI-8 helicopter
The helicopter fuselage includes the nose and central parts, tail and end booms. In the bow there is a cockpit, where instrument panels, electric consoles, pilot seats, and command controls are installed. The forward part of the fuselage is separated from the central part by docking frame No. 5N, in the wall of which there is a doorway.
At the front, on the wall of frame No. 5N, there are shelves for radio and electrical equipment, at the rear there are containers for batteries, a box and an electric winch control panel.
Above the cargo compartment there are engines, a fan, a main gearbox with a swashplate and a main rotor, a hydraulic panel and a consumable fuel tank.
Shock absorbers and struts for the main and front landing gear, and external fuel tanks are attached to the fuselage components from the outside. A kerosene heater is located in front of the right outboard fuel tank. The cargo compartment ends in a rear compartment with cargo doors. In the upper part of the rear compartment there is a radio compartment in which panels are installed for units of aviation and radio-electronic equipment. There is a hatch to exit from the cargo compartment to the radio compartment and tail boom. Cargo doors cover the rear opening of the cargo compartment, through which cargo is loaded and unloaded.
A tail boom is attached to the central part of the fuselage, to the components of which are attached a tail support and an uncontrolled stabilizer. At the bottom of the tail boom there are two radio altimeter antennas, inside in the upper part there is a transmission tail shaft. An end beam is attached to the tail boom, inside of which an intermediate gearbox is installed and the end part of the transmission tail shaft passes through. A tail gearbox is attached to the end beam on top, on the shaft of which a tail rotor is mounted.
The helicopter is equipped with a three-post landing gear that is not retractable in flight. Each landing gear is equipped with liquid-gas shock absorbers. The wheels of the front strut are self-orienting, the wheels of the main struts are equipped with braking devices, for the control of which the helicopter is equipped with an air system.
The power plant consists of two TV2-117AG engines and systems that ensure their operation.
To transmit power from the engines to the main and tail rotors, as well as to drive a number of system units, a transmission is installed on the helicopter, consisting of main, intermediate and tail gearboxes, a tail shaft, a fan drive shaft and a main rotor brake. Each engine and main gearbox has its own autonomous oil system, made according to a direct single-circuit closed circuit with forced oil circulation. To cool engine oil coolers and the main gearbox, starter-generators, alternators, air compressor and hydraulic pumps, the helicopter is equipped with a cooling system consisting of a high-pressure fan and air ducts. To protect engine compressor blades from premature wear, dust protection devices are installed in front of the engines.
The engines, main gearbox, fan and panel with hydraulic units are covered by a common hood. With the hood lids open, free access to the power plant, transmission and hydraulic system units is provided. In this case, the open covers of the engine hood and main gearbox are working platforms for performing maintenance of helicopter systems. The helicopter is equipped with fire protection equipment. Longitudinal and transverse fire partitions divide the engine compartment into three compartments: the left engine, the right engine, etc. main gearbox. The fire protection system provides for automatic and forced activation of fire extinguishers and the supply of fire extinguishing agent to the required compartment
The helicopter has a main rotor consisting of a hub and five blades. The hub has spaced horizontal, vertical and axial hinges and is equipped with hydraulic dampers, swing compensators, centrifugal blade overhang limiters and a vibration damper. The all-metal construction blades have a visual spar damage alarm system and an electrothermal anti-icing device. The tail rotor is a pusher, variable pitch in flight, and consists of a cardan-type hub and three all-metal blades equipped with an electrothermal anti-icing device.
The helicopter control is dual, consisting of longitudinal-transverse control, directional control, combined pitch-throttle control and main rotor brake control. In addition, separate control is provided for changing the power of the engines and stopping them. Changing the overall pitch of the main rotor and longitudinal-transverse control of the helicopter are carried out using a swashplate mounted above the main gearbox.
To facilitate control, the system of longitudinal, transverse, directional control and collective pitch control includes irreversible hydraulic boosters, for powering them, as well as for powering the hydraulic cylinder for unlocking the clutch of the STEP - GAS handle and the hydraulic stop for the longitudinal control, the helicopter has a main and backup hydraulic systems. To increase flight safety, the helicopter is equipped with a four-channel autopilot AP-34B, which ensures stabilization of the helicopter in flight in roll, heading, pitch and altitude. The main flight parameters are recorded by the SARPP-12DM system.
2. MAIN ROTOR BUSHING
2.1.General information:
The main rotor hub is the main unit of the main rotor; is intended for fastening the blades, transmitting torque from the main gearbox shaft to the blades, as well as for receiving and transmitting aerodynamic forces arising on the main rotor blades to the fuselage. There are the following types of V. n. c.: articulated, elastic and rigid.
In the design of a hinged bushing, the blades are fastened to the bushing body by means of horizontal, vertical and axial hinges.
Horizontal hinges (HS) provide the possibility of flapping movement of the blades. Vertical hinges allow the blades to oscillate in the plane of rotation (these oscillations arise under the influence of variable drag forces and Coriolis forces that appear when the blade oscillates relative to the horizontal hinge). Thanks to the articulation of the blades with the hub body, the alternating stresses in the main rotor elements are significantly reduced and the moments of aerodynamic forces transmitted from the rotor to the helicopter fuselage are reduced.
Axial hinges (OSH) V. n. V. designed to change the installation angles of the blades. In order to reduce the overhang (bending) of the blades and create the necessary gaps between the blades and the tail boom of the helicopter with a non-rotating main rotor and at a low rotor rotation speed, the design of the V.N. V. centrifugal overhang limiters were introduced.
All joints that use rolling bearings are equipped with lubrication and sealing systems. In the axial hinges, plate and wire torsion bars made of high-strength stainless steel are used as elements that absorb the centrifugal forces of the blades. There are so-called elastomeric V. n. c., in the hinges of which cylindrical, conical or spherical elastomeric bearings are used. These bearings are made of layers of steel and layers of elastomer vulcanized to them. The absence of rubbing metal parts reduces wear on components. Design of V. n. V. simplified, eliminates the need to use torsion bars, reduces maintenance time, and increases design reliability. In hinged V. n. designs. V. In order to prevent the phenomenon of “ground resonance”, vibrations of the blades relative to the vertical hinges are damped using dampers. which, depending on the working element used, are divided into friction, hydraulic, spring-hydraulic and elastomeric.
Hinged V. n. V. depending on the design, there can be three types: with spaced horizontal hinges (the axes of the horizontal hinges are at some distance from the axis of the main rotor), with combined horizontal hinges (the axes of the horizontal hinges intersect on the axis of the rotor), with combined horizontal and vertical hinges (axes both hinges intersect at one point, located at a certain distance from the axis of the rotor).
The elastic bushing can be made with an elastic element in only one vertical or horizontal hinge or in both hinges at once. Housing elastic V. n. V. It is usually made from composite materials. Behind the axial hinge, which can be made according to the scheme with rolling bearings and a torsion bar or with elastomeric bearings, there is an external elastic part of the bushing, which ensures the flapping movements of the blade. On a main rotor with such a bushing, control efficiency can be significantly increased compared to a hinged rotor. v., which helps to increase the maneuverability of the helicopter.
A rigid hub has a strong center, a body (usually made of titanium alloy) attached to a rigid drive shaft, and axial joints, to the bodies of which blades made of composite materials are attached through combs. In a main rotor with such a hub, the blade performs oscillatory motion in the plane of thrust and rotation not by turning at the hinges, but due to large deformations of the blade or its thinner butt section. These deformations are also acceptable due to the high strength of composite materials. Such a screw with a rigid sleeve can be considered similar to a screw with a hinged sleeve, which has a large spacing of horizontal hinges (10-35% of the radius of the screw).
Helicopter with rigid V. n. V. has good handling characteristics. An important advantage of rigid V. n. V. is its simplicity (the absence of highly loaded bearings in the hinges, dampers and centrifugal blade overhang limiters), which makes it easier and cheaper to manufacture the propeller and maintain it in operation.
2.2 Design of the NV Bushing:
The main components of the NV Bushing: the bushing body, five units of horizontal, vertical, axial hinges, five hydraulic dampers of vertical hinges with a compensation system, five centrifugal blade overhang limiters, parts for installing the fastening on the NV shaft.
Rice. 2. General view of the main rotor hub.
The bushing body is made of high-strength alloy steel. In the center of the housing there is a hole with involute splines, with which it is connected to the splines of the NV shaft of the main gearbox. Centering of the bushing body on the shaft is carried out using two conical rings (upper and lower), for which there are two conical surfaces in the central bore of the housing.
The lower ring is split, the upper one consists of two half rings. In the upper part of the body there is a flange to which the reservoir of hydraulic dampers of the vertical hinges is attached with studs, and in the lower part there is a hole for the fixing pin of the bracket for the swash plate supply. The swashplate is designed to change the magnitude and direction of the NV thrust; it consists of a slider guide, a slider, a bracket, an internal cardan, blade turning rods, longitudinal and transverse control rockers, a collective pitch lever and a plate driver. The brackets are attached to the housing eyes using the GSh pins. These compounds form GS VNV. In each eye of the housing, the outer rings of two needle bearings are installed, which are secured with nuts. Two bronze washers are installed between the rings, which perceive the axial forces that arise when the blade oscillates around the main shaft axis, when the blades deviate from a straight line perpendicular to the main shaft axis.
A thrust ring is installed between the bronze washers and the inner rings of the needle bearings. The inner rings of the needle bearings are installed on the main shaft pin and tightened between the eyes of the bracket using a nut.
The GSh pin has eyes for attaching a hydraulic damper. The internal cavity of the GS is sealed with reinforced rubber cuffs and O-rings. To limit the rotation of the blade around the main shaft axis, there are special stops on the bushing body and brackets. The bracket is a box-section part, at the ends of which there are lugs for connection with the body and the OSh axle. The axes of the lugs are located at right angles to each other.
At the bottom of the bracket there are two eyes into which the finger of the TsOSL pawl is installed. The bottom stops on the bracket consist of centrifugal and permanent overhang stops. The TsOSL mechanism consists of a counterweight, pins, rods, springs and pawls. Centrifugal limiters are limiters for the overhang of the blades when the engines are not running on the ground, as well as when the airspeed is less than 108 rpm. During normal operation of the NV in flight, the blades, making a flapping movement, do not reach the stops due to the presence of a large centrifugal force acting on the blade, which is a natural regulator of the flapping and holds the blades close to the plane of rotation of the hub, allowing them to make small amplitude flapping movements.
Rice. 3. Centrifugal blade overhang limiter:
1-counterweight; 2-finger; 3-spring; 4-thrust; 5-finger; 6-dog
The mechanism of the centrifugal overhang limiter (Fig. 3) consists of a counterweight-1, fingers-2 and 5, rod-4, spring-3 and pawl-6. When the rotor is untwisted and the rotation speed increases, the centrifugal force acting on the counterweight 1 begins to turn the counterweight and the pawl 6. When the rotation speed reaches 108 rpm, the stop of the limiter pawl will move down so much that during the flapping movement of the blade it will no longer limit its downward swing. When the main rotor rotation speed is more than 108 rpm, the downward flapping movements of the blades are limited by constant bracket stops, which allow the blades to deflect downward at an angle of 40 (+-10/90)
With a decrease in the rotor rotation speed to less than 108 rpm (due to a decrease in the centrifugal force of the counterweight), the reverse movement of the mechanism parts begins and at a rotation speed of 95 rpm or less, spring 3 will set the counterweight 1 and pawl 6 to their original position, at which the overhang of the blades is limited an angle of 1°40".
As mentioned above, according to the method of attaching the blade to the bushing and the bushing to the shaft of the gearbox that rotates the propeller, rotors can be divided into hinged (with spaced hinges); with a common horizontal hinge and rigid fastening of the blades.
A bushing with spaced main shafts does not intersect with the axis of rotation of the main shaft; three schemes can be distinguished for them:
Ⅰdiagram: GSh – VSh - OS: a=o, - .Perpendicular to the axis of the GSh.
This bushing has a number of disadvantages:
-in cruising modes, the blade deviates, in the plane of rotation its chord becomes not parallel to the main shaft axis, therefore, during flapping movements, the pitch spontaneously changes, which causes the blade to tilt to the stops.
- in cruising modes, the resulting force R transmitted to the propeller blade is not perpendicular to the propeller shaft axis, which causes unequal loading of the bracket eyes and propeller bearings, and this leads to their unequal wear.
Rice. 5. NV bushing with spaced main shafts (1st scheme):
Ⅱscheme: GSh – VSh - OS: a≠o, - not perpendicular to the axis of the GSh.
The magnitude of the mainshaft displacement is selected such that in cruising modes the blade deviates relative to the high-pressure hinge so that the chord of the blade becomes parallel to the mainshaft axis. Then, during swing movements, it moves parallel to itself and this does not cause a spontaneous change in step. The resulting force R equally loads the eyes and bearings of the main shaft, but this will only be in cruising modes; in other modes, the bushing has the same disadvantages as in diagram 1. In addition, it is more difficult to manufacture.
Rice. 6. NV bushing with spaced main shafts (2nd scheme).
Ⅲ scheme: VSh - OSh - GSh or VSh - OSh - GSh. For the bushings of this design, the GSh and VSh have swapped places. The bushings do not have the disadvantages inherent in the first two schemes, since the chord of the blade here is always parallel to the main shaft axis. There is no loss of stability of the swing movements, and the bearings are always loaded equally in all modes, but the VS bearings are not loaded equally here.
For a bushing with combined main shafts, the axis intersects with the axis of rotation of the main shaft. The blades are attached to the hub via a universal joint. Such bushings are less durable, so they are used on light helicopters.
Rice. 7. NV bushing with spaced main shafts (3rd scheme):
1-GSh;2-VSh;3-OSH;4-Bushing;5-blade.
The articulated bushing has a body with lugs sitting on the splines of the shaft, GSh, VSh, connected by a trunnion bracket OSh, to which the blade is attached. A nut is screwed onto the shaft, which holds the bushing through a centering ring.
Rice. 8. HB articulated bushing:
1-centering ring; 2-nut; 3-GSh; 4-VSh; 5-trunnion; 6-blade; 7-OSH;
8-bracket; 9-body; 10-shaft
The articulated bushing has three hinges: GSh; VSH; OSH. Thanks to the presence of hinges, the blade can perform three types of rotational movements: flywheel (relative to the main shaft, swing angle β), oscillations in the plane of rotation of the propeller (relative to the main shaft, angle θ), change in the installation angle, i.e., blade pitch (relative to the main shaft, angle φ).
The main propellers prevent the helicopter from tipping over relative to the longitudinal axis in oblique flow modes around the air intake and relieve the blades from bending moments in their root parts. The main shaft is formed by the lug of the bushing body, which houses two support needle bearings. The internal cavity of the pin is filled with lubricant, which enters the bearing track through the holes. The needle bearing contains 43 needles measuring 6.5-60 mm. The outer races of the bearings are secured with nuts that are screwed from the ends into the eye holes of the bushing body and have reinforced rubber cuffs. There are two thrust rings between the outer races. The finger is connected through an eyelet to the hydraulic damper body. The coupling nut is screwed onto the pin and secured with a plate lock. To prevent oil leakage through the seals when the pressure inside the joint increases, a pressure compensator with a finger diaphragm is installed in the filler hole, the internal cavity of which is exposed to the atmosphere. Loads during flapping movements of the blade in the vertical plane are perceived by needle bearings, axial loads from the bracket eyes are transmitted through chrome rings. Oil from the cavity in the housing of the HB bushing is supplied to lubricate the needle bearings.
Rice. 9. Horizontal hinge:
1-sleeve body; 2-hull eye; 3-finger; 4-eye bracket; 5-bearing
The VH, formed by the eyes of the bracket and the head part of the axial hinge trunnion, provides unloading of the blade in the root part of the blade from the bending moment acting in the plane of rotation. A pressure compensator with a finger diaphragm is installed in the top cover on the finger, and a drain plug is installed on the bottom of the finger. Oil from the inner cavity of the pin flows to the rubbing parts of the bearings, through the radial holes and inner races of the bearings. To remove air plugs from the oil cavity under pressure, a grease nipple and a control valve are installed on the stops of the head part of the OSh axle.
OSH allows you to change the blade installation angles. The OS consists of a trunnion, a thrust nut, two support ball bearings, a nut, a housing, and eyes to which the blade is attached. Inside the housing there is an adjusting ring and disc springs. On the body there is a filler plug on top, a magnetic plug and a control cup on the bottom; The blade rotation lever is attached to the side surface, and the blade mounting comb is attached to the outer end surface. Radial loads when changing the installation angles of the blades are absorbed by ball bearings, the centrifugal force of the blade is transmitted through a double-row roller thrust bearing to the OS trunnion and then through the VSh, bracket, GS to the NV bushing body.
Rice. 10. Axial joint:
1-axle; 2.8-nut; 3.7 ball bearing; 4.6-spacer sleeve;
5-roller bearing;9-housing;10-eyes
3. ORGANIZATION OF THE PRODUCTION PROCESS FOR REPAIR OF THE MAIN ROTOR BUSHING AT SPARK JSC
The enterprise JSC SPARK began its history on June 4, 1931, it was then that by Order No. 364 of the Head of the UKGVF, the aviation repair enterprises of Leningrad were reorganized into the Aviation Repair Base of the Civil Air Fleet.
Currently, the company offers its services for the repair of the following types of helicopters:
Overhaul of Mi-8/Mi-17 helicopters of all series and modifications and their components.
- Overhaul of Ka-27 helicopters of all series and modifications and their components.
- Overhaul of Ka-32T and Ka-32S helicopters and their components.
Also, the company SPARK OJSC offers its services for extending the assigned resources of the supporting system, control and transmission units.
SPARK OJSC has the right to extend the assigned resources for the following units of the MI-8MTV (AMT) helicopter:
- main rotor hub 8-1930-000 ser.02., produced after 01/01/1987;
- tail rotor bushing 246-3914-000 ser.01;
- swashplate 8-1950-000;
- intermediate gearbox 8A-1515-000;
- tail gearbox 246-1517-000;
- tail shaft 8A-1516-000.
Extension of the assigned life of the main rotor hub 8-1930-000ser.02. and swashplate 8-1950-000, according to decision No. 24.2.5-1000GA dated 08.28.2003 DPLGGVS and TRGAMT of Russia, is carried out within the assigned resource of 5000 hours with a time between repairs of 1500 hours and a service life between repairs of 8 years.
Extension of the assigned resource for the intermediate gearbox 8A-1515-000; tail gearbox 246-1517-000; tail shaft 8A-1516-000 and tail rotor hub 246-3914-000 gray. 01, is carried out in accordance with decision No. 24.2.5 - 1659 GA dated December 17, 2003 of the DPLGGVS and TRGAMT of Russia.
Extension of the assigned life of the tail transmission units (intermediate gearbox 8A-1515-000; tail gearbox 246-1517-000; tail shaft 8A-1516-000) of Mi-8MTV-1, Mi-8AMT helicopters and their modifications when they perform transport work is carried out within the designated resource of 4500 hours with a TBO resource of 1500 hours and a TBO service life of 6 years, tail rotor hub 246-3914-000ser. 01 Mi-8MTV-1, Mi-8AMT helicopters and their modifications within the assigned resource of 5000 hours with a turnaround time of 1000 hours and a service life between overhauls of 7 years.
Representatives of GosNIIGA and OJSC Moscow Helicopter Plant im. M.L. Mile."
Also, SPARK OJSC, in accordance with bulletins, instructions and decisions of the industry, organizes work to assess the technical condition of aircraft products in order to increase the calendar service life and (or) resources:
helicopter airframe Mi-8/Mi-17 (all modifications);
TV3-117 engine;
TV2-117 engine;
auxiliary power unit AI-9(V);
main gearbox VR-14;
main gearbox VR-8A;
rotor blades;
tail rotor blades.
Specialists from GosNIIGA, OJSC Moscow Helicopter Plant named after. M.L. Mil", OJSC "Klimov", OJSC "Perm Motor Plant", OJSC "Reductor-PM", ZMKB "Progress", OJSC "Motor Sich", etc.
The enterprise carries out comprehensive work to extend the resources and service life of helicopters and their components. Together with OJSC Moscow Helicopter Plant named after. M.L. Mil" and research institutes of OJSC "SPARK" carry out endurance testing programs for the airframe, transmission units and the helicopter's load-bearing system.
For all this, the enterprise has the material base in the conditions necessary for this; the area of the enterprise is more than 2 hectares. For all types of work offered, there are specialized premises, hangars, stands, special equipment and special vehicles.
Let us dwell in more detail on the area for repairing the main rotor hub; the room provided for this type of work has an area of 450 square meters. The site staff consists of the following numbers:
The work shift is headed by a foreman (1 person)
Foreman (1 person selected from among the workers)
Workers (5 people)
The shift works on a schedule of 5 through 2 with a normalized working day until 17-15 and a lunch break.
Now directly organize the production process and describe jobs.
As you know, a rationally organized workplace provides working conditions, the correct structure of the work process, eliminates unnecessary and inconvenient movements, reduces time spent, improves the use of equipment, improves the quality of work performed, and ensures the safety of equipment.
In order to ensure this, the organization of labor involves the implementation of a set of measures:
1. development of a list of works and operations of the main production and establishment of the sequence of their implementation;
2. selection, professional training and placement of personnel, clear definition of the responsibilities of each employee;
3. organization and equipment of workplaces, ensuring the effective fulfillment of production tasks by each employee;
4. introduction of the most rational techniques and methods for performing work;
5. creation of the necessary sanitary and production and living conditions that ensure occupational hygiene and safety, regulation of work and rest regimes for workers;
6. establishing labor standards and their remuneration, choosing forms of moral and material stimulation of labor productivity growth;
The production site for the repair of load-bearing bushings undoubtedly meets all these requirements. According to the governing documents, the site is certified and has a passport that displays all the necessary aspects relating to the production process as a whole.
Table 1
Information about the production personnel of the site.
No. Last name, First name, Patronymic Year of birth Education Rank No. of the certificate for the right to repair aircraft equipment No. of the certificate of completion of the technical and technical training Code of instr. stamps Master's notes
1 2 3 4 5 6 7 8 9
1
2
Foreman__________________________
"_____" ____________________________2010
Table 1 shows the appearance of the passport page, showing the level of technical training of the personnel, there is a column for complaints from the foreman, information about the date of the last PTC, which allows the inspection or certification body to independently assess the qualifications and hierarchy of the site team.
Table 2 shows a passport page presenting a list of documents in force at a given site, which helps staff in their work evaluate additions to previously issued documents, the date of changes, and a complete list of what may be needed in their work.
Table 2
List of technological documents in force in this area.
No. Name of technological document CIFR Date of implementation Implemented sheets of changes to technological documents, technical. Instructions, Additions
1 2 3 4 5
1
2
The title of the third table indicates the page of the passport, which contains a list of those nomenclature documents that site workers must directly know and comply with all points of these documents. Responsibility for implementation rests with the site foreman and supervision of the leading technologist.
Table 3
List of orders, instructions and bulletins to be carried out at this site.
No. Name of the document Date of implementation Place of storage of the document Notes
1 2 3 4 5
1
2
Site foreman________________ Leading technologist_________
"___" ________2010 "___" ________2010
As mentioned above, the main rotor hub repair section fully meets all the requirements of labor legislation, fire safety standards, information about this and documentation on this topic is included in the next page of the passport, shown in Table 4.
Table 4
List of instructions to NGOs, Occupational Health, Safety and Fire Regulations in force at the site.
Item No. Document name CODE Notes
1 2 3 4
1
2
Site foreman________________ Leading technologist_________
"___" ________2010 "___" ________2010
Also, the passport displays all the equipment (Table 5), which is convenient for taking inventory and delineating the responsibilities of workers for their jobs.
Table 5
List of site equipment.
No. Name of equipment No. of operational passport/inventory No. Last name of the responsible person Notes
1 2 3 4 5
1
2
Site foreman________________ Leading technologist_________
"___" ________2010 "___" ________2010
The site passport (Table 6) must have a page on which the quality control or OGT inspector can leave a record of violations identified during the inspection when extending the validity period of the passport or check compliance with previously left comments; the inspector can familiarize himself with the validity period of the passport or the last extension on next page of the site passport (Table 7).
Table 6
Comments on the implementation of technologies, technical culture and condition of the site.
Item No. Comments of inspection persons: foreman, quality control foreman, HS engineer, etc. Signature, position, date. Execution according to comments. Signature, position, date.
1 2 3
1
2
Table 7
Information on verification and renewal of the production site passport.
Passport renewal note DATE Position Signature
1 2 3 4
The site passport has been checked and supplemented. Validity period extended Until "__"________20__.
On the last page of the passport, the inspector often makes sure that the declared number of sheets coincides with the actual number, whether there are stickers or not, the state of the passport, the conditions of its storage, from which he can draw a conclusion about the state of humidity during working hours at the site. The technologist, the Head of the Quality Control Department and the Chief Engineer put their signatures when producing a passport or when replacing it with a new one. The appearance of the last page is shown schematically (Table 8).
The main rotor hub is designed to secure the blades, to transmit torque from the main gearbox shaft to the blades, as well as to receive and transmit forces arising on the blades to the fuselage.
The main elements of the bushing are: the bushing body, horizontal hinges, intermediate brackets, vertical hinges, axial hinges, blade rotation levers, hydraulic dampers, centrifugal blade overhang limiters, pendulum vibration damper.
The splined bushing body is installed on the main gearbox shaft, centered on the shaft with lower and upper cone rings and secured with a nut. A compensation tank for hydraulic dampers, an NV current collector and a pendulum vibration damper are mounted on top of the bushing body.
Each horizontal hinge is formed by an eye of the bushing body, two eyes of an intermediate bracket and a pin, which is mounted on two needle bearings. The forces acting along the axis of the finger are perceived by two bronze rings. The pin is secured against axial movement with a nut, and against rotation relative to the bracket - with a key. The pin on one side has two eyes for attaching the hydraulic damper rod, and on the other side there is an eye for attaching a storm clamp.
The intermediate bracket is a box-section part with two pairs of eyes at the ends. A mechanism for a centrifugal blade overhang limiter is mounted inside each bracket.
The vertical hinge is formed by two eyes of the intermediate bracket, the eye of the axle hinge pin and a pin, which is mounted on two needle bearings and two bronze rings.
The axial joint is formed by the connection of the trunnion and the axial joint body. The axial hinge bearings are installed on the trunnion shank: two radial ball bearings that take the load from the bending moment, and one roller thrust bearing that takes the load from the centrifugal force. The body of the axial hinge is made in the form of a glass, on the bottom of which there is a comb with eyes for attaching the blade on the outer side.
The blade rotation lever is rigidly attached at one end to the axial hinge body, and at the other end it is pivotally connected to the vertical rod of the swashplate.
The hydraulic damper consists of a cylinder, a rod with a piston and a cover. The damper cylinder is hingedly mounted on the axle joint trunnion brackets. The piston has eight bypass valves, which open when the pressure difference between the cylinder cavities reaches 20 kgf/cm2. The valves are installed so that four bypass fluid in one direction, and four in the opposite direction. A ball compensation valve is installed in the hydraulic damper cover, through which the cylinder cavities communicate with the compensation tank to remove air bubbles and compensate for temperature changes in the volume of liquid.
The mechanism of the centrifugal blade overhang limiter is installed on an intermediate bracket and consists of a counterweight, a spring, a rod and a pawl. When the main rotor is not rotating, the spring holds the mechanism in such a position that the pawl stop limits the overhang of the blade to 1 ° 40 /. When the main rotor spins up under the action of centrifugal forces, the counterweight retracts the pawl and the angle of the maximum possible overhang of the blade increases to 4°. When the main rotor rotation speed decreases to 108 rpm (54.5%), due to a decrease in centrifugal forces, the counterweight begins to move backwards, and when the main rotor rotation speed is 95 rpm (50%) or less, the spring will set the counterweight and pawl to their original position.
The pendulum vibration damper is installed on the hub body and consists of a bracket, a hub with five sleeves and five pendulums, which are connected to the hub sleeves by bifilar suspensions. Each bifilar suspension consists of two roller links loosely seated in the holes of the pendulum bushings and the hub. The bracket is attached to the main rotor hub with five hollow bolts, through the cavities of which oil is poured into the horizontal hinges. The hub is secured to the bracket with studs.
Main and tail rotors
1. MAIN ROTOR BUSHING.
The main rotor hub is designed to transmit torque to the blades from the main gearbox, as well as to perceive and transmit to the fuselage the forces and moments occurring on the main rotor.
The Mi-8T main rotor hub has five blades with spaced and rotated horizontal hinges, vertical hinges, a flapping compensator and a centrifugal overhang limiter.
The flapping compensator serves to reduce the amplitude of the flapping movements of the blades and the tilt of the main rotor cone. The design of the sleeve is made so that when the blade flaps at an angle relative to the horizontal hinge? the installation angle changes by the amount ??=-k?, where k is the swing compensator coefficient. Thus, when swinging up, the installation angle decreases, and when swinging down, it increases.
The centrifugal overhang limiter is designed to prevent blades from hitting airframe structural elements at low rotor speeds.
Basic technical data:
The horizontal hinge spacing is 220 mm.
The vertical hinge spacing is 507 mm.
Horizontal hinge offset 45 mm.
Coefficient value
swing compensator 0.5
The maximum upward swing angle is 25? ± 30"
Downward swing angle (overhang from the plane,
perpendicular to the axis of rotation of the HB):
When focusing on the bracket 3°40"...4? ± 10";
With emphasis on pawl 1? 40"±20"
Angles of rotation relative to the VSh:
Forward rotation 13? ± 15"
Back against rotation 11? ± 10"
The angle of inclination of the NV axis forward is 4? 20"±10"
The diameter of the HB bushing is 1744 mm.
Height 321 mm.
Bushing weight (dry) 610 kg
Lubrication of bushing components:
1). Horizontal and vertical hinges:
TS-GIP oil at atmospheric temperature T H above +5° C;
TS-GIP and? AMG (SM-9) at T H = -50? +5° C.
2). Axial joint:
MS-20 at ТH above +5°С (short-term reduction of ТH to -10°С is allowed for up to 10 days);
VNII NP-25 (SM-10) at stable low T H = -50? +5 °C (a short-term increase in T H up to +10 °C is allowed for up to 10 days);
The main rotor hub includes the main structural components:
Bush body;
Axle joint housings;
Blade rotation levers;
DSP (in the eyelets of the brackets);
Hydraulic dampers VSh.
The bushing body is made of high-strength alloy steel. It is a cast part with internal involute splines for installation on the main gearbox shaft. The housing is centered on the shaft by two cones: the lower one is a bronze split one and the upper one is steel, consisting of two halves. The splines are lubricated with NK-50 grease. The entire package is tightened with a nut using a special hydraulic wrench and secured with pins.
The body has five (according to the number of blades) wide lugs lying in the same plane at an angle of 72? to each other. The centers of the lugs are shifted in the direction of rotation by 45 mm along the axis of the horizontal hinge. The lugs in connection with the bracket form horizontal hinges. To fill and drain oil from the joint, there are holes in the bushing body that are closed with plugs. The top plugs are also used as lugs when removing the bushing.
In the upper part of the body there is a flange to which the reservoir of hydraulic dampers of the vertical hinges is attached with studs, and in the lower part there is a hole for the fixation pin of the swash plate arm bracket.
Each eye has bosses that, together with the bracket bosses, form upper and lower stops that limit the flapping movements of the blades. The lower stops are removable, which allows them to be replaced during operation in the event of defects (hardening).
The bracket is a cast part of a box-section with two pairs of mutually perpendicular platforms. The eye pads are designed to connect the bracket with the bushing body and with the axle hinge pin. The connection with the bushing body forms a horizontal hinge, and with the trunnion - a vertical hinge. The parts of the centrifugal overhang limiter are mounted inside the bracket, and in its lower part there are eyes for the pawl axis of the centrifugal overhang limiter.
The axle joint journal is a steel forging consisting of a head and a shank with a threaded section at the end. The head has a central bore for mounting vertical joint bearings. In addition, the head has stops that limit the vibrations of the blades in the plane of rotation and two brackets for attaching the vertical hinge damper. The axial hinge parts are mounted on the shank and then tightened with a nut.
The horizontal hinge is designed to unload the butt part of the blade from a variable bending moment by allowing the blade to oscillate in the vertical plane.
The horizontal hinge is formed by the articulation of the lugs of the bushing body and the vertical lugs of the bracket. The design also includes:
Two needle bearings;
Thrust ring;
Two bronze washers;
Seal details.
The outer races of needle bearings are installed in the housing eye and secured with nuts. Between the outer races there are two bronze washers, between which a steel thrust ring is installed. Bronze washers act as sliding bearings, transmitting axial forces that arise when the blade deviates from the direction perpendicular to the axis of the horizontal hinge.
Axial fixation: the horizontal hinge pin rests against the wall of the bracket eye with a split insert ring, and on the other side is secured with a nut and is secured against rotation by a segment key.
The pin is equipped with internal races of needle bearings and chrome-plated rings, along which reinforced cuffs operate. Needle bearings absorb the largest loads from the action of the centrifugal forces of the blade.
Rice. 26 Main rotor hub.
1-shaft nut; 2-upper cone; 3-hydraulic damper reservoir; 4,17,25-cork; 5-sleeve body; 6-bracket; 7,28,73-thrust ring; 8.74 bronze washer; 9-trunnion axle hinge; 10,31,59,63,67,82,71-nut; 11.72 - outer race of the bearing; 12.69-inner race of bearing; 13,18-ring; 14,20,40, 62,70-O-ring; 15-finger vertical hinge; 16-glass; 19,38,64-cuff; 22-nut of the axial joint housing; 23-oil reflective ring; 24,30-radial ball bearing; 26,79,80 - spacer sleeve; 27-row roller bearing; 29-axial joint housing; 32-stop; 36-washer; 37-plug; 39-nut of the vertical hinge pin; 41-springs; 42-counterweight; 43,56,83 - grease fitting; 44-axis pawl; 45-dog; 46-stop; 47-lower cone; 48,49-locking plate; 50-screw locking plate; 51-locking pin; 52-mortgage ring; 53-earring; 33,34-adjusting ring; 35 Belleville Spring; 54,60-needle bearing; 55-finger; 57-finger earrings; 58-hydraulic damper; 61-bracket; 65-ring horizontal hinge; 66-key; 68-finger horizontal hinge; 75.81-ball bearing; 76-roller of the blade rotation lever; 77-cover; 78 roller bearing; 84-blade rotation lever; 85-bolt; 86-bushing.
The bearing cavities are sealed with rubber sealing rings and reinforced cuffs. Oil circulation is carried out using special grooves under the influence of centrifugal forces. A pressure compensator can be installed in the filler plug, which, when the oil pressure in the joint increases (as the temperature increases), prevents oil from being knocked out through the seals thanks to the rubber working element.
On one side, the finger is connected to the hydraulic damper earring using a needle bearing. Here, on the side of the earring, to protect the internal cavity of the finger from moisture entering the finger, a rubber plug is inserted. On the other hand, a plug with an eye is installed on the finger to connect a clamp for fixing the blades in the parking lot.
The vertical hinge serves to unload the butt part of the blade from variable bending moments by allowing the blade to oscillate in the plane of rotation.
The vertical hinge is formed by the articulation of the horizontal eyes of the bracket and the axle hinge pin. The design of the vertical hinge is fundamentally similar to the horizontal one. Two needle bearings are mounted in the cylindrical cavity of the axle head, consisting of outer and inner races with a set of needles. The outer clips are attached to the trunnion, the inner ones are put on the finger. To absorb axial forces, bronze washers are provided, located between the ends of the outer races and the thrust ring.
There is a glass inside the hollow finger. The glass has radial holes and is fixed at the top of the finger. A plug is screwed onto the finger, which closes the hole for filling oil into the joint. Oil enters the needle bearings through the holes in the cup, drillings in the pin and in the inner races of the bearing. The hinge seals are rubber rings.
Rice. 27 Axial hinge.
1-Pressure compensator; 2-Cork; 3-Cup; 4-Magnetic plug.
An oil can is screwed into the lower part of the glass, through which oil is injected into the vertical hinge during initial filling (during assembly). When injecting, oil flows to the needle bearings, displacing air from the joint through a bypass valve located in the axle stop. Oil is refilled directly into the glass through the filler plug.
The axial hinge is designed to allow changes in the installation angles of the blades.
The axial joint is formed by the connection of the trunnion and the axial joint body.
In the head part of the axle there are two flanges for fastening the hydraulic damper brackets. There are also bosses here that limit the rotation of the blades around the axis of the vertical hinge. The internal cylindrical cavity of the head part is used for mounting needle bearings of the vertical hinge.
The trunnion has a shank with a threaded section at the end. The axial hinge bearings are installed and secured on the trunnion shank. The thrust roller is designed to perceive centrifugal force and two radial balls are designed to perceive bending moments transmitted from the blade.
When assembling, the trunnions are sequentially put on the shank:
Axle joint housing nut with collars;
Separator with two rows of rollers;
Thrust ring;
Oil reflective ring;
Radial ball bearing;
Radial ball bearing;
Trunnion nut.
Spacer sleeve;
The trunnion nut tightens the entire assembled package and is secured with a retaining ring.
During assembly, an adjusting ring with two disc springs and a protective washer (to preload the bearings) is first installed into the axial hinge housing, then a shank with parts is inserted, after which the entire assembly is tightened with a housing nut, which is locked with a plate.
The axial joint is sealed with rubber rings and cuffs.
Are the roller bearing cage seats angled? = 0°50" to the radial direction. Due to this, when the angle of installation of the blade is cyclically changed, the separator, together with the oscillatory-rotational movements of the blade, slowly turns towards the inclination of the rollers. The separator makes a full revolution in 50–80 minutes of rotor operation at an oscillation frequency of 3–3 .5 Hz (190?200 rpm of the rotor) and the angular amplitude of oscillations is 4.5?5°.Continuous rotation of the cage ensures that the bearing ring raceways are fully involved in the work, and also reduces the number of repeated stresses experienced by individual sections of the raceways. This ensures the durability of the bearing and increases the service life of the axial hinges and the rotor hub as a whole.
The body of the axial hinge is made in the form of a glass, on the bottom of which there is a comb with eyes for attaching the blade. At the other end of the glass there is a thread for a nut and a flange, to which the blade rotation lever is attached with four bolts. The bolts are relieved from shearing forces by bushings. The end of the turning lever has a cylindrical cavity in which a roller is mounted on a double-row ball bearing and a roller bearing, which is held from displacement by a cover. An oil can is screwed into the lever to lubricate the CIATIM-201 bearings. A pin is installed in the eye of the roller on two bearings, connecting the blade rotation lever with the swashplate rod. The body also contains:
Transparent cup;
Drain plug;
Filling plug with pressure compensator.
The pressure compensator consists of a housing with holes, a cover and a membrane. When the temperature and pressure of the oil inside the axial joint increases, its vapors squeeze out the membrane and escape into the atmosphere through the holes in the housing.
Vertical hinge damper.
The vertical hinge damper serves to dampen blade vibrations in the plane of rotation in order to prevent “ground resonance”, as well as to eliminate blade shock loads that occur during vigorous rotation of the rotor.
The damper is of a hydraulic type; its operating principle is to absorb the vibration energy of the blade and dissipate it in the environment in the form of heat.
The vertical hinge damper consists of the following main parts:
Cylinder; - shock absorber;
Lid with glass; - compensation valve;
Bronze bushings; - fittings;
Rod with piston; - sealing parts;
Bypass valves; - corrugated cover.
The damper body includes a cylinder and a cover. The steel cylinder, using axle pins and needle bearings, is fastened with tight-fitting bolts to the brackets, which are installed on the bosses of the axle hinge pin.
On one side there is a hole in the bottom of the cylinder for the passage of the rod. On the other side, the cylinder is closed with a cover with nine bolts. A glass is attached to the lid, covering the open end of the rod. Bronze bushings are pressed into the bottom of the cylinder and in the cover, along which the rod moves.
The rod is made integral with the piston on which the piston rings are installed. The piston has eight bypass valves (four in one direction, four in the other direction). Each valve includes a valve body with nut, cone, seat and spring. The spring, resting against the nut, presses the cone to the body seat.
A stop body is screwed onto the threaded end of the rod, to which a shock absorber consisting of two steel plates and rubber vulcanized to them is attached with six bolts. The shock absorber serves to soften the impact on the rear vertical hinge limiter when the main rotor is launched.
The stop body is connected to the horizontal hinge pin using an earring. A corrugated rubber cover is attached to the stop housing and the cylinder, protecting the hydraulic damper rod from contamination. The sealing of structural elements is ensured by rubber rings. The hydraulic damper cover has a boss in which a compensation valve is placed, which includes three balls (two large and one small) and grooves in its design. The grooves perform the following functions:
A compensation tank is connected to the damper through a fitting and hoses;
Through channels drilled in the thickenings of the cylinder walls, they are connected to both cavities of the cylinder.
The compensation valve ensures that the internal cavities of the cylinder are replenished with working fluid, as well as air bubbles are removed from them.
Rice. 28 Vertical hinge damper
1,14,19-Bronze bushings; 2-Finger; 3,13,20,28-O-rings; 4-Plug; 5.7-Large balls; 6-Small ball; 8,16,27-Valves; 9-Cork; 10-Glass; 12-Fitting; 15-Valve body; 16-Cone; 17-Spring; 18-Nut; 21-Case; 22-Shock absorber; 23-Stop housing; 24-Cylinder; 25-fluoroplastic ring; 26-Piston ring; 29-Bolt; 30-Cap.
The hydraulic damper reservoir, designed to replenish possible fluid leaks and drain the compensation system, is installed on the main rotor hub on studs. The tank is of a cast design made of AL9 with a glued plexiglass cap, which provides good visibility of the presence of oil in the tank. Liquid (AMG-10 hydraulic oil) is added to the tank through the filler neck with a lid on the cap. The liquid level should be no higher than the mark on the reservoir cap and no lower than the lower edge of the cap.
Hydraulic damper operation:
When the blade oscillates in the plane of rotation, the cylinder moves and liquid flows from one cavity to another through the calibrated holes of the bypass valve cones. In this case, hydraulic resistance arises, which dampens the vibrations of the blade.
At the same time, the increased pressure of one of the cavities presses on the large ball, pressing it against the seat, while the cavity is disconnected from the compensation tank. The large ball of the compensation valve presses the second large one through the small one - this ensures the connection of the low-pressure cavity with the compensation tank.
With an increase in the amplitude of vibration of the blade relative to the vertical hinge, the increase in force on the damper rod decreases, which eliminates an unacceptable increase in bending stresses in the butt of the blade. This is ensured by the opening of the bypass valves when the pressure drop in the cylinder cavities increases to 20–28 kgf/cm?.
Centrifugal overhang limiter.
The centrifugal overhang limiter is designed to prevent impacts of the main rotor blades on the tail boom at low rotation frequencies (spin-up and stop of the main rotor, helicopter parking).
The stops must provide sufficient angles of rotation relative to the horizontal hinge when tilting the main rotor cone while controlling the helicopter, while the blade should not touch the stops. However, when the main rotor is stopped or at low rotation speeds, the blades have a significant deflection under their own weight due to the lack of tensile centrifugal force. Ensuring the required clearance between the tip of the blade and the tail boom at low rotor speeds is the task of the centrifugal overhang limiter (DOS).
Rice. 29 Centrifugal overhang limiter.
1-Counterweight; 2.5-Fingers; 3-Spring; 4-Traction; 5-Dog.
The DSP is located in the main rotor hub bracket and structurally consists of:
Counterweight with spring;
A dog that serves as a movable stop;
Finger – axis of rotation of the pawl;
The rod that connects the counterweight to the pawl.
When the main rotor is not working and during its spin up to 108 ±3 rpm, the spring holds the counterweight and the pawl in the position in which the blade is on the stop: the overhang angle is 1? 40". When the rotation speed reaches 108 rpm, the counterweight, under the influence of centrifugal forces, begins to rotate, stretching the spring, and rotates the pawl. At a frequency of 111 rpm, the pawl completely moves away from the bracket: the overhang of the blade is limited only by constant stops, which allow it to deflect downwards by 4?.
When the NV speed drops to 108 rpm, the mechanism reverses and at 95 rpm the pawl returns to the position corresponding to the blade overhang angle 1? 40".
The frequency of the main rotor at which the DSP is triggered during spin-up is higher than when it stops due to a change in the arm of application of the centrifugal force when the counterweight is rotated. Due to this, the actuation process occurs without delay, thereby eliminating impacts on the movable stop in its intermediate positions.
MAIN ROTOR BLADES.
The main rotor is designed to generate lifting and driving forces in all flight modes, as well as to create longitudinal and lateral moments of helicopter control.
The Mi-8T helicopter is equipped with a five-blade main rotor, which consists of a hub and blades.
The bushing is designed to fasten the blades, transmit rotation to them from the main gearbox, as well as perceive and transmit to the fuselage aerodynamic and inertial forces arising on the main rotor. The bushing is installed on the main gearbox shaft.
The main rotor blade is designed to create lift.
The main rotor blades are attached to the hub body with two bolts each, using horizontal, vertical and axial hinges. Vibrations of the blades relative to the vertical hinge (in the rotation cavity) are damped by hydraulic dampers. To protect the blades from icing, they are equipped with electrothermal anti-icing devices. In addition, the blades have a pneumatic alarm system for damage to the side members.
Main rotor data:
NV diameter 21.3 m.
Direction of rotation clockwise (top).
The area swept by the NV is 356 m2.
Fill factor 0.0777.
Weight 1285 kg.
Basic technical data:
Blade chord 520 mm;
The blade shape is rectangular in plan with a geometric twist:
at the end of the blade (section No. 22).
Blade weight 135 kg.
Blade profile between sections 0...1 - NACA-230, 2...3 - NACA-230-12, between 4...22 to 50% of the chord -NACA-230-11 increasing its ordinates from the chord by 1 mm, and from 50 to 95% change of ordinates to 0 according to a linear law.
Structurally, the blade consists of the following main elements:
Spar;
Twenty-one tail section;
Tip;
ending;
Anti-icing system;
Spar damage detection system.
The spar is the main power element of the blade, which absorbs aerodynamic and mass loads that arise when the rotor pitch changes.
The spar is a hollow beam with an internal contour of constant cross-section, made of aluminum alloy AVT-1 in the shape of a blade tip in accordance with the theoretical profile. The surface of the spar is hardened by cold hardening with steel balls on a vibration stand. In this case, the depth of the cold-worked layer reaches 0.3–0.4 mm, which significantly increases the service life of the blade.
Rice. 22 Main rotor blade.
a) Plan view of the blade; b) Butt part of the blade; c) Section of the blade; d) The end of the blade.
1-pin connector; 2-tip; 3-charge valve with spool; 4.12-plug; 5-pressure alarm; 6-bolts securing the tip to the spar; 7-spar; 8-compartment blade; 9-contour light lamp; 10-removable end piece; 11-plates of balancing weight; 13-sealant; 14-clamp; 15-screw stop; 16-anti-flutter weight; 17-compartment liner; 18 honeycomb core.
To increase the rigidity of the structure, the upper and lower flanges of the spar have smooth thickening ribs inside. The first of them from the toe of the spar are used as guides for installing anti-flutter weights.
In total, in each blade to obtain the necessary transverse alignment, which is necessary to increase the critical flutter speed, in the toe of the spar between compartments No. 18? 22 eight counterweights (anti-flutter weights) 400 mm long and weighing about 1 kg each are inserted. Each counterweight is rubberized, which allows it to be tightly inserted along the front stiffeners into the cavity of the spar. The centrifugal forces of the counterweights that arise during rotation of the blade are perceived by a screw stop screwed along the thread inside the end part of the blade.
The end part of the spar is closed with a plug consisting of two halves (plug and clamp), between which there is a sealant. When the halves are pulled together, the sealant is squeezed out and seals the end part of the spar. The plug has 2 bolts and 2 studs on which the balancing weight plates are assembled.
The end of the butt part of the spar is also closed with a cover installed on 9 bolts and sealed. The cover has a plug connector for supplying power to the heating elements of the blade anti-icing system and the contour fire, as well as a charging valve designed to pump air into the spar cavity. On the rear wall of the spar, near the end of the butt part, a pressure alarm is installed for the spar damage alarm system.
A cover is attached to the end cap with screws (and to the spar) to cover the wires running to the plug connector.
The blade spar damage signaling system is pneumatic with a visual pressure indicator. The system includes plugs installed at the ends of the spar to seal the internal cavity, a valve with a spool and a pressure alarm.
The pressure alarm consists of:
Transparent plexiglass cap;
Aneroid sensor element;
Red cylinder.
The aneroid sensitive element is a bellows, inside of which there is an inert gas - helium with a pressure of 1.05? 1.1 kgf/cm?.
In operating condition, the cavity of the spar is under increased air pressure: air is pumped through the charging valve with a hand pump with a pressure p spar, which should be 0.15 kgf/cm? greater than the pressure p SPL the alarm starts to operate. The internal cavity of the signaling device body communicates with the cavity of the spar. If cracks appear in the spar or its seal is broken, the air is released and the pressure in the cavity of the alarm body is equalized to atmospheric pressure. By forces of elasticity and internal pressure, the bellows opens and pushes the red cylinder into the visibility zone through the plexiglass cap.
Rice. 23 Blade pressure indicator.
1-plexiglass cap; 2-cylinder; 3-sealant; 4-gasket; 5-guide ring; 6-guide; 7-body; 8-aneroid sensitive element; 9-plug.
The pressure of the injected air depends on the temperature ТН and pressure РН of atmospheric air and is determined by special monograms and graphs. At temperatures ТН< -40°С давление воздуха в лонжероне р лонж должно превышать давление срабатывания сигнализатора р СПЛ на 0,25 кгс/см?.
The tip is designed to attach the blade to the bushing and consists of a comb and two jaws.
Using a comb, the blade is attached to the axial hinge body with two bolts with a tightening torque of 8...10 kgf m.
The tip is attached to the spar with cheeks using 9 through bolts and 12 (6 on each side) bolts with bushings. The bushings are designed to relieve bolts from shearing forces. In addition, in places where through bolts pass, in order to prevent deformation of the spar, there is a textolite spacer.
When installing the tip, an MPF-1 adhesive film is applied to the spar, and the ends of the cheeks are coated with VITEF-1NT sealant to prevent electrochemical corrosion.
For transverse balancing of the blade, a counterweight (eight bars of 40 cm each and weighing 1 kg) is inserted into the toe of the spar. The centrifugal forces arising during rotation of the blade are perceived by a screw stop installed inside the spar at the end of the blade.
The tail part of the blade is formed by separate compartments. In total, the blade includes 21 tail sections. The compartments are glued to the trailing edge of the spar and are structurally exactly the same.
Each compartment consists of:
Sheathing;
Tail stringer;
Two ribs;
Honeycomb filler.
Rice. 24 Tail section of the blade.
All components of the compartment are glued together with VK-3 adhesive film.
The ribs are made of 0.4 mm thick aircraft material. At the junction of the rib to the spar, the back of the rib is bent and represents a tab that is glued to the rear wall of the spar. The skin, 0.3 mm thick, is made of avial, at the tail stringer it is not cut, but curved around it. The stringer itself is textolite.
The honeycomb core is made of aluminum foil with a thickness of 0.04 mm and forms a hexagonal honeycomb on a side of 5 mm. On compartments No. 16 and No. 17 in the area of the tail stringers, flaps are fixed in the form of plates 40 mm wide and 1.5 mm thick, which serve to regulate the cone of the main rotor blades.
The compartment is glued to the rear wall of the spar with VK-3 adhesive film.
The compartments are not secured to each other, but to prevent air flow, inter-compartment liners are placed between them, made either of sponge rubber or in the form of duralumin rubberized boxes.
The tip (end fairing) ensures smooth flow around the end part of the blade.
For mounting blades
use special
device
The end fairing consists of fixed and removable parts. The fixed part is glued to the rib of the last compartment. The removable part is mounted on screws, has a cutout covered with a plexiglass lamp and a titanium reinforcing plate. When the removable part is removed, access to the mounting unit for the balancing plates (steel for weight balancing) and to the contour light lamp mounted on the bracket is available.
Electrothermal blade anti-icing system. The heating pad consists of:
Six layers of insulating fiberglass;
Metal heating elements;
Power wires;
Connecting bars;
Surface anti-abrasive rubber layer.
The heating elements are powered by current through a plug connector to which the power drives are connected. The other end of the power drives is soldered to the busbars of the heating devices. On the toe of each blade, in sections 5 m long from the end, split metal (stainless steel) fittings are glued to protect the toe from abrasive wear. A layer of polyurethane 0.8...1 mm thick is applied to the fitting.
2. TAIL PROPELLER
The tail rotor is designed to create a thrust force, the moment of which relative to the center of mass of the helicopter balances the reaction moment of the main rotor, and also provides the ground moment for controlling the helicopter.
When the helicopter is in directional equilibrium, the moment of thrust of the tail rotor relative to the helicopter's center of mass is equal to the reaction moment of the main rotor.
When the pitch of the tail rotor is reduced or increased, which is carried out using foot control, the thrust of the propeller changes accordingly. The helicopter's directional balance is disrupted, and the helicopter turns left or right depending on which moment is greater - the reactive moment of the main rotor or the thrust moment of the tail rotor.
When flying in the self-rotating mode of the main rotor, when there is no reactive moment of the main rotor, the helicopter is subject to a moment from the friction forces in the main rotor shaft supports, in a direction coinciding with the direction of rotation of the main rotor. In this helicopter flight mode, for directional balance, the thrust force of the tail rotor must be directed in the opposite direction, and its moment relative to the helicopter’s center of mass is equal to the moment of the friction forces in the main rotor shaft supports. Therefore, the tail rotor is reversible and can be used not only as a pusher propeller, but also as a pusher.
The tail rotor is also an element of the helicopter's static directional stability, since in flight the disk swept by the propeller has a positive effect on the stability of the helicopter.
To ensure uniform distribution of thrust over the disk swept by the tail rotor in conditions of oblique flow, the propeller hub has combined horizontal joints of the “cardan” type, which allows the blades to make flapping movements relative to the plane of rotation of the hub. However, as a result of the deviation of the plane of rotation of the tail rotor during flapping movements of the blades, the unevenness of rotation inherent in a simple cardan appears.
The presence in the design of the rotor hub of a flapping compensator with a coefficient of K-1 leads to a decrease in the amplitude of the flapping oscillatory movements of the blades and, consequently, reduces the uneven rotation of the tail rotor. To change the pitch of the blades, the propeller hub has axial hinges. The tail rotor is driven from the main gearbox using a transmission.
The tail rotor blades have an electrothermal anti-icing device that ensures normal operation of the propeller in icing conditions. The direction of rotation is clockwise when looking at the helicopter from the tail rotor.
The tail rotor consists of a hub and three blades.
Basic technical data
Screw diameter, m................................................... ........ 3,908
Swept area, m 2 ……………………………… 12
Fill factor………………………………0.135
Weight …………………………………………………… 121 kg.
Tail rotor bushing.
The tail rotor bushing is designed to secure the tail rotor blades and impart torque to them from the tail gearbox shaft, as well as to absorb aerodynamic forces and moments that arise when changing the pitch of the tail rotor, and transmit them through the gearbox to the end beam.
Basic technical data:
Bushing type………………………………………………………. cardan with combined main shaft.
Direction of rotation…………………………………... clockwise when viewed from the tail rotor.
Compensator coefficient
swing k ……………………………………………………… 1.0.
Deflection angles of the bushing from
neutral position:
To the hub flange……………………………………………. 10? ±10? ;
To the leash cross ………………………………………… 12? +20?/ -10? .
Full range of rotation angles
blades relative to OS…………………………………….. 29? +1? 40?/ -1? ;
The smallest angle……………………………………... - 6? +1? 10?/ -50? ;
Maximum angle………………………………………….. 23? +30?/ -10? .
The tail rotor hub consists of the following main components:
Hub with flange for fastening to the tail gear shaft;
A cardan, including a yoke, a cardan body and a bushing body;
Axial hinges, ensuring rotation of the blades when changing the pitch of the tail rotor;
Leash with a slider and rods for rotating the blades.
Bushing lubrication:
1). Axial joint:
MS-20 at outside air temperatures (ТH) above +5 °С (short-term reduction of ТH to -10 °С is allowed for up to 10 days);
MS-14 at T H = -15? +5 °C (possibly SM-12);
VNII NP-25 (SM-10) at stable low T H = -50? +5°C (a short-term increase in T H up to +10°C is allowed for up to 10 days);
VO-12 all-season at T H = -50? +50 °C with replacement every 200 +10 hours of bushing operation.
2). The bushing bearings are lubricated through grease nipples with CIATIM?201 lubricant.
The hub is used to attach the bushing to the output shaft of the tail gearbox and transmit torque to the tail rotor cardan.
The hub of the hub is made of steel, made in one piece with a flange, which is attached to the flange of the output shaft of the tail gearbox using eight bolts. The fastening bolt nuts are tightened with a tightening torque MZ = 8 +3 kgf m.
The hub is equipped with a swing limiter and a crossbar, tightened with a nut and a lock washer.
Inside the hub there are involute splines along which the slider moves. The slider guides are two bronze bushings pressed into the hub bores.
Lubrication of the bushings and spline joint is carried out by CIATIM-201 through a grease nipple made in the yoke fastening nut. The lubricant is refilled until fresh lubricant flows out of the safety valve installed in the hub flange.
The cardan is designed to ensure the flapping movement of the blades relative to the plane of rotation of the tail rotor, imparting torque to them, as well as transmitting the thrust force of the tail rotor to the tail gearbox.
The cardan includes, made of high-alloy steels:
Traverse; - cardan body; - bushing body.
Rice. 30 Tail rotor bushing.
1. Slider; 2, 12. Bronze bushing; 3. Hub; 4. Swing limiter; 5, 11, 31, 36. Nut; 6, 32. Tapered roller bearing; 7, 38, 41 Adjusting ring; 8, 33, 37. Cup (bearing housing); 9, 40, 43. Reinforced cuff; 10. Grease fitting; 13. Rubber cover; 15, 30. Cover; 16, 27 Double row ball bearing; 17. Pin; 18. Leash; 19. Adjustment rod; 20. Spherical spherical plain bearing; 21. Oil tank; 22. Bolt; 23. Cap; 24. Cork; 25. Special screw; 26. Cap nut; 28. Roller; 29. Needle bearing; 34. Cardan housing; 35. Traverse; 39. Washer; 42, 44. O-ring; 45. Nut of the axle joint housing; 46. Bulk roller bearing; 47. Thrust ring; 48. Double row roller bearing with cage; 49. Trunnion nut; 50. Thrust roller bearing; 51. Thrust bearing ring; 52. Axial joint housing; 53. Bushing body.
The traverse has two trunnions, on which the internal races of tapered roller bearings and adjusting rings are mounted using nuts. Adjusting rings provide the necessary preload of the bearings. The outer races of the bearings are pressed into the cups. The glasses are mounted in cylindrical grooves in the cardan housing. The bearing cavities are protected by cuffs and closed with covers. Bearings are lubricated by CIATIM-201 through grease nipples installed in cups.
The cardan body is made in the form of a cross and also has two axles, which are located perpendicular to the traverse axles. Tapered roller bearings are mounted on these axles, the outer races of which are pressed into the cups. In turn, the cups are installed in the bores of the bushing body and secured with nuts. The cavities of the glasses are sealed with rubber reinforced cuffs and closed with lids. The covers have grease fittings through which CIATIM-201 lubricates the bearings.
The bushing body has three trunnions, which together with the axial hinge bodies form the axial hinges of the bushing.
The sleeve cardan is a combined horizontal hinge and provides freedom of deviation of the sleeve body relative to the plane of rotation of the tail rotor at an average angle of ± 11? in any direction.
The axial hinge is designed to ensure rotation of the rotor blades when the propeller pitch changes.
The axial joint is formed by the articulation of the bushing body journal and the axial joint body.
In addition, the hinge design includes:
Trunnion nut;
Thrust bearing ring;
Thrust roller bearing with cage;
Double row thrust bearing with cage;
Thrust ring;
Axle joint housing nut;
Bulk roller bearing;
O-rings;
Reinforced cuff.
The axial hinge assemblies are mounted on the journals of the bushing body. A thrust ring is pressed onto the axle, which is the inner race of the bearing with bulk cylindrical rollers. The bearing absorbs radial loads, while the nut of the axial hinge housing acts as the outer race.
The raceways of a double-row thrust bearing are the cemented ends of the trunnion nuts and the axial joint housing. It absorbs the main loads from the action of centrifugal forces and most of the bending moments. Are the bearing cage seats angled? = 0° 32? ±6? to the line of radii, therefore, when the axial hinge body swings to change the pitch of the tail rotor, the separator continuously rotates around its axis. As a result, the surface of the nut raceways wears out more evenly, which can significantly increase the operational reliability and service life of the axial joint.
A thrust bearing with a cage is also mounted on the axle nut, which, together with the ring, performs the function of preloading the axial hinge assembly by selecting the thickness of the ring.
The cavity of the axle joint housing is protected by a reinforced rubber cuff and rubber rings. The cuff is installed in the bore of the nut of the axle joint housing and is secured against axial displacement by a spring ring.
The axial hinge body is made in the form of a glass and has a comb for attaching the tail rotor blades. There is also a boss on the body, in the bore of which a blade rotation roller is mounted on needle and double-row ball bearings. The roller bearings are lubricated through the CIATIM-201 grease nipple.
An oil tank with a transparent control cup is attached to the axial joint body with a special bolt (red) to determine the presence of oil in the joint. There are holes on the reservoir and in the body, closed with yellow plugs, used for draining oil and refilling the axle joint. The oil level in the joint is checked using the marks on the control cup when the blade is pointing down.
The driver assembly ensures rotation of the tail rotor blades in accordance with the control action from the mechanism for changing the pitch of the tail rotor.
The node includes:
leash,
Adjustable traction.
The driver is pressed onto the slide and tightened with a nut, which is secured with a lock washer. The position of the slider mounting slot relative to the driver is fixed with pins.
A double-row ball bearing is installed in the slider head. The outer ring of the bearing is pressed through the flange of the cuff housing to the end of the slider by a threaded cover. The inner ring of the bearing with a sleeve is attached to the tail gear rod with a nut.
To lubricate the CIATIM-201 bearing, there is a grease nipple on the driver, and on the threaded cover there is a pressure limit valve through which used grease comes out when it is replaced.
The leash has three levers ending in forks, which include the ears of the blade turning rods. The blade turning rod consists of an eye, a rod and a fork. The connection of the rod ear with the driver is carried out using a spherical self-lubricating bearing. The part of the slider protruding from the hub, between the driver and the hub, is protected by a rubber corrugated cover.
When changing the pitch of the tail rotor by moving the rod of the tail gearbox, the slider moves and, with the help of a leash and adjustable rods, rotates the axial hinge to a given installation angle.
Tail rotor blades.
The tail rotor is designed to balance the reaction torque of the main rotor and ensure directional stability and controllability of the helicopter.
The tail rotor is mounted on the flange of the tail gearbox output shaft and is located on the right side of the end beam. Three-blade pushing propeller with pitch variable in flight. Structurally, it consists of a sleeve and three blades.
The tail rotor rotates from the main gearbox through transmission shafts, intermediate and tail gearboxes.
The tail rotor hub is of a cardan type with a combined horizontal hinge; each blade is fastened to the hub with two bolts. To change the pitch of the tail rotor, the hub has axial hinges that ensure rotation of the blades.
To protect against icing, the blades are equipped with electrothermal anti-icing devices.
The tail rotor blade is designed to create thrust force in order to balance the reactive torque of the main rotor and provide directional control of the helicopter.
Basic technical data:
Chord……………………………………………………….. 305 mm.
The shape of the blade in plan is ……………… rectangular, without geometric twist.
Profile………………………………………………………NACA-230M.
Blade weight…………………………………….. 13.85 kg.
The tail rotor blade consists of:
Spar;
Tail section;
Spar tip;
End fairing;
Anti-icing system heating pad;
Blade static balancing unit.
The spar is made of AVT-1 material and is a hollow beam with an internal contour of constant cross-section. The outer contour is machined according to the theoretical contour of the blade and polished in the longitudinal direction. The spar is strengthened from the inside by cold hardening. In the butt part of the spar, two parallel platforms are milled for installing the tip.
Rice. 25 Tail rotor blade.
1. Bracket; 2. Honeycomb filler; 3. Spar; 4. Heating pad; 5. Forging; 6. Hairpin; 7. Balancing plates; 8. Fairing (removable part); 9. Rib; 10. Fairing (fixed part); 11. Sheathing; 12. Tail stringer; 13. Bushing; 14. Bolt; 15. Tip; 16. Plug.
At the end part, two studs are riveted to the spar, onto which balancing plates are installed.
The tip is made of high-strength alloy steel 18Х2Н4МА and is used to attach the blade to the PB bushing. The tip is attached to the spar with eight bolts and using MPF-1 adhesive film.
A bracket made of AK6 material is attached to the rear wall of the spar in the butt part using VK-3 adhesive film and using two butt bushings for attaching the tip.
The tail part consists of:
Sheathing,
Cell block,
tail stringer,
End rib.
Fiberglass sheathing 0.4 mm thick made of two layers of fiberglass, glued top and bottom to the honeycomb block with VK-3 adhesive film.
The stringer is made of two layers of fiberglass and glued from the outside along the tail part of the blade to the skin, covering it from above and below. The front ends of the tail stringer protruding under the skin are sealed with putty, so that the aerodynamic quality of the blade is not reduced.
The end rib is made from avial sheet. The wall is glued to the outer end of the honeycomb block, and the shelves are glued to the casing of the tail section.
The connection of individual elements of the tail section, as well as fastening to the spar, is carried out with glue. The connection of the tail section with the spar is supported by a duralumin bracket.
Tip - the end part of the blade is covered with a fairing consisting of two parts:
Fixed part riveted to the rib,
The removable part, made of stainless steel, is attached to the spar with four anchor nuts. Removing it provides access to the balancing plates.
3. SWAVER.
The swashplate is a control mechanism designed to change the magnitude and direction of the rotor thrust force.
The change in magnitude of the resultant aerodynamic forces of the main rotor is carried out by changing the total pitch of the main rotor, i.e. simultaneous change in the installation angle of all blades by the same amount. The direction of the resultant changes by tilting the plane of rotation of the swashplate, resulting in a cyclic change in the installation angles of each blade, i.e. depending on their azimuthal position.
The swashplate is placed on the housing of the main gearbox VR-8A and is attached to it using a guide on eight studs with a tightening torque of 5–6 kgf m.
The swashplate consists of:
Slider guide;
Cardan (consists of outer and inner rings);
Swashplate;
Leash (two-link);
Bracket;
Five vertical rods;
Collective pitch lever with support;
Leash displacement limiter;
Rockers and rods of longitudinal and transverse control.
The slider guide is a hollow cylinder with a flange, inside which the main gearbox shaft passes. The guide is made of chrome steel 30KhGSA and has a chrome-plated outer surface along which the slider bushings slide.
The slider is made in the form of a steel cylinder. Inside it, bronze bushings are installed on rivets, with which it slides along the guide. CIATIM-201 lubricant is supplied to the cavity between the bushings through grease fittings. On the outer surface of the slide in its central part there is a flange to which the bracket is attached with studs.
In the upper part of the slide, two diametrically located holes are bored into which radial ball bearings are pressed. With the help of these bearings and two fingers, the inner ring of the cardan is pivotally connected to the slider. The bearings are lubricated through the slider's oiler at the same time as the bronze bushings are lubricated.
To protect rubbing surfaces from dirt and retain lubricant in the cavities of the slider and bearings, two rubber cuffs are installed in special grooves of the slider. On the outer ring of the cardan at an angle of 90? Two cantilever pins are attached to each other, to which longitudinal and lateral control rods are attached through ball bearings. The bearings are covered with rubber covers and lubricated through oil nipples screwed into the fingers.
The fingers are located in such a way that the attachment points of the longitudinal and lateral control rods to the outer ring of the cardan are shifted relative to the corresponding axes by 21? against the direction of rotation of the main rotor. This design solution achieves advanced longitudinal-transverse control, which is necessary for strict correspondence of the inclination of the axis of the main rotor cone of rotation to the deflection of the control handle.
The swashplate is mounted on the cylindrical surface of the outer ring of the cardan using a double-row angular contact bearing. The inner rings of the bearing are tightened with a nut locked with a stopper. The outer rings of the bearing are pressed by a flange to the inner shoulder of the bushing, pressed into the plate.
The bearing cavity is sealed by two (top and bottom) reinforced rubber cuffs. The upper cuff, in addition, is protected from water and dirt by a screen mounted on the nut. Bearing lubrication is carried out by CIATIM-201 through grease fittings and is controlled by the release of lubricant through a warning valve.
The swash plate is stamped from aluminum alloy in the shape of a five-pointed star. At the ends of the plate legs there are cylindrical bores and square flanges for mounting end hinges.
Each end hinge includes in its design:
Double row ball bearing;
Spacer sleeve;
Needle bearing;
The cavity of the end hinge is sealed with rubber rings and closed with a lid. The hinge rollers are connected by pins to the rotating rods of the blades.
The cardan is a universal joint consisting of an inner and outer ring.
The outer ring is attached to the inner ring of the universal joint using a second pair of pins and radial bearings. The bearings are lubricated with CIATIM-201 through grease nipples screwed into the bearing caps.
The common axis of the fingers connecting the inner ring of the cardan with the slider is located perpendicular to the common axis of the fingers connecting the outer and inner rings. With this connection, the outer ring of the cardan, and with it the swashplate, can tilt in all directions relative to the slide.
Rice. 63 Vertical thrust.
1. Upper fork; 2. Traction; 3. Lower fork.
Vertical rods include:
Threaded rod;
Upper fork;
Bottom fork.
In the internal cavity of the lower fork there is an axial hinge in the form of a double-row ball bearing, the cages of which are clamped with nuts. To protect against dirt, a rubber cover is placed on the hinge. The axial joint allows the upper fork to rotate relative to the lower one. The upper fork screws onto the threaded end of the rod and has a cut that allows it to be locked using a coupling bolt. This design makes it possible, if necessary, to change the length of the vertical thrust and, therefore, change the angle of installation of the blade.
Rice. 62 Swashplate.
1. Rocking fork; 2. Scale; 3. Nut; 4. Washer; 5. Roller; 6. Bushing; 7. Screw; 8. Longitudinal control rocker lever; 9. Slider guide; 10. Finger; 11. Ball bearing; 12. Case; 15. Cross control rocker fork; 16. Rubber cover; 17. Nut; 18. Ball bearing; 19, 20. Fingers; 21. Ball bearing; 22. Roller; 23. Lower traction fork; 24. Ring; 25. Rubber ring; 26. Cover; 27, 29. Nuts; 28. Ball bearing; 30. Rubber cover; 31. Oil can; 32. Glass; 33. Bolt; 34. Rod; 35. Upper traction fork; 36. Oil can; 37. Body; 38. Cuff; 39. Bearing; 40. Bushing; 41. Flange; 42. Cuff; 43. Ring; 44. Screen; 45. Nut; 46. Cardan outer ring; 47. Leash clamp; 48. Bolt; 49. Cuff; 50. Nut; 51. Hairpin; 52. Cover; 53. Axis; 54. Pin; 55. Finger; 56. Cardan inner ring; 57. Nut; 58. Leash earring; 59. Plate; 60. Lever; 61. Blade rotation thrust; 62. Cover; 63, 64. Fingers; 65. Oiler; 66, 68. Nuts; 67. Leash lever; 69. Body; 70. Fork; 71. Roller; 72. Finger; 73. Needle bearing; 74. Roller; 75. Ball bearing; 76. Bronze bushing; 77. Crawler; 78. Slider bracket; 79. Bronze bushing; 80. Cuff; 81. Finger; 82. Bolt; 83. Vernier longitudinal control; 84. Nut; 85. Lateral control scale; 86. Disc; 87, 88. Pins; 89. Bushing; 90. Axle; 91. Nut; 92. Earring; 93. Finger; 94. Collective pitch lever support.
I - on the transverse control rocker; II - along the cardan of the plate; III - collective pitch lever supports.
The swashplate is rotated by a drive.
The leash is a kinematic link consisting of a clamp (bracket), an earring and a lever, hingedly connected to each other. The presence of five hinges on the leash ensures rotation of the plate at any tilt and translational movement along with the slider along the guide. The driver clamp is attached to the lower part of the NV bushing body and is secured against rotation with a pin. In order to monitor the condition of the driver clamp and prevent its deformation from the landing site, a clamp displacement limiter is installed on the sleeve above the clamp.
The clamp displacement limiter consists of two half-rings, which are tightened with screws, two plates, which are attached to one of the half-rings using brass screws. The limiter is installed in such a way that the gap between the control plate and the swash plate clamp is 0.8–1.6 mm. If the driver clamp is deformed, it presses on the end of the plate - the soft brass screws are cut off, and the plate hangs on the safety wire. In this case, a section of the half-ring, painted orange, opens, which signals the beginning of deformation of the clamp. This allows for increased flight safety.
The bracket is stamped from aluminum alloy and is attached with studs to the outer flange of the slide. Steel bushings are pressed into the bracket boss. The following are installed on the bracket:
Longitudinal control rocker;
Cross control rocker;
Collective pitch lever.
The longitudinal control rocker has a roller to which, on one side, the rocker lever is attached with end splines and a screw, and on the other side, a rocker fork is installed on involute splines, which is tightened with a nut. The longitudinal control rocker arm has a hole for mounting a ball bearing. Using a bearing and a rocker pin, the lever is connected to the longitudinal control rod, and the fork is connected to the rod coming from the hydraulic booster.
Rice. 64 Fastening the collective pitch lever.
The cross control rocker is mounted on the bracket using an axle and two needle bearings. The bearings are lubricated by CIATIM-201 through grease fittings screwed into the bracket.
The rockers have adjustment scales and verniers to control the deviations of the longitudinal-transverse control rods, which allows you to adjust the control without the use of inclinometers with an accuracy of up to 6?.
The collective pitch lever is attached to the support through a shackle. The support is fixed to the main gearbox shaft housing. This fastening of the lever allows the bracket, together with the slider, to move strictly vertically along the guide, and not along an arc.
Basic data of the swashplate:
| Control knob position | Deviation of the control handle from the neutral position, mm | Swash plate tilt |
| Neutral (with the lock installed): - forward - left | -- | 2? ± 12? 0? thirty? ± 6? |
| Forward all the way | 170 ± 10 | 7? thirty? ± 30? |
| Back all the way | 160±10 | 5? ± 6? |
| Back to the hydraulic booster when the hydraulic stop is turned on | - | 2? ± 12? |
| All the way to the right | 155 ± 10 | 4? ± 10? |
| Left all the way | 157 ± 10 | 4? 12? ± 12? |
The invention relates to the field of aviation, more specifically to rotor bushings. The main rotor hub consists of a star, sleeves attached to it, consisting of the sleeve axis, spacer sleeves, a rubber damper, support bearings and a fork with a driver and a blade. The star rests on the drive shaft using a spherical hinge, and torque is transmitted to the sleeves using a carrier consisting of upper and lower housings, profiled plates and trunnions. The bushing is made with a combined horizontal hinge, with the ability to implement the calculated offset of the sleeve axis from the axis of rotation of the rotor, the cone angle of the main rotor and the vertical offset of the combined horizontal hinge relative to the apex of the main rotor cone. The hub can be upgraded for a rotor with any number of blades by changing the number of star rays and the profile of the plates. The invention is aimed at creating a rotor hub with any number of blades. 2 ill.
Drawings for RF patent 2363620
Use: for attaching main rotor blades to the drive shaft.
Essence: the main rotor hub is a unit consisting of a carrier and a star with sleeves attached to it. The carrier consists of upper and lower housings, profiled plates and trunnions for supporting rubber dampers. The carrier serves to transmit the torque of the drive shaft to the star with sleeves and blades, as well as to transmit lifting force and control moments from the main rotor to the drive shaft. The sleeve consists of a fork, which, through a radial and thrust bearing, is mounted on an axis on which a rubber damper is installed. The position of the damper is set by spacer bushings. The sleeve is screwed into a star, supported by a spherical bearing on the drive shaft. Drivers are attached to the forks of the bushing, with the help of which the angle of installation of the forks with the blades attached to them is set. This rotor hub is intended for use on unmanned helicopters that do not require inverted flight. This rotor hub can be upgraded for a rotor with any number of blades by changing the number of star rays and the profile of the plates. The stiffness of the damper can be changed either by its configuration or by using rubber of a different composition for its manufacture.
DESCRIPTION OF THE INVENTION
Main rotor hub
The invention relates to rotor bushings with a combined horizontal hinge and can be used on unmanned helicopters.
The installation is known, patent RU 2061626 C1, class. 6 В64С 27/605, containing a main rotor with blades rigidly installed (there is only an axial hinge) in a sleeve fixed to the shaft. The design makes it possible to use it for multi-blade propellers. When used on an unmanned helicopter for television filming, the disadvantages of the main rotor hub included in the described system can be attributed to its high rigidity, which leads to a high reaction rate, i.e. jerking and shaking. In addition, the absence of an angle between the longitudinal axis of the hose and the plane of rotation and the absence of offset of the hose from the axis of rotation of the shaft causes high bending moments of the rotor blades and, as a consequence, their short service life.
A known installation is known, patent RU 2235662 C2, B64C 27/48, containing a rotating outer housing with a preliminary spinning gear connected to a non-rotating internal shaft, inside of which there is a lever control mechanism that tilts the axis and moves the rocker arm connected to it in the vertical direction. The rocker arm is mounted on the control lever mechanism and is connected to each of the blades through a bracket with an axial hinge. The latter is made in the form of a finger and is located in the body of the rocker at a design angle of taper to the plane of rotation of the bushing. A bracket and a support with a thrust bearing are installed on the cantilever parts of each finger, which can be rotated relative to the axis of the finger. The bracket is connected to a support with a thrust bearing, through which the centrifugal force from the blade is transmitted to the rocker body. The rocker body is pivotally connected to the rotating outer body of the bushing through a cardan frame located above the rocker body. The axes of the frame are mutually perpendicular, and the point of intersection of their axes lies on the axis of rotation of the sleeve. The axis of the frame, parallel to the axis of the blades, is the axis of the common axial hinge, relative to which the rocker body deviates when the rocker arm is deflected, and the axis of the frame, perpendicular to the axis of the blades, is aligned with the axis connecting the rocker arm to the blade rotation levers at one of the blade installation angles, and is the axis common horizontal hinge. The lever control mechanism has three separate rods. The disadvantages of the main rotor hub, which is part of the described system, may include its technological complexity, the inability to control the overall pitch of the rotor, as well as the ability to use such a design only for two-blade propellers. The main rotor hub of this installation is similar to the design of this invention and, in terms of the totality of essential features and technical essence, is closest to this invention and was therefore chosen as a prototype.
In the present invention, the design of the sleeve allows the joint movement of the star with the sleeves of the sleeve relative to the spherical hinge, put on the drive shaft and placed at a calculated height relative to the apex of the cone along which the blades move during rotation of the propeller. The torque is transmitted to the blade system from the drive shaft by the carrier. The carrier is rigidly attached to the drive shaft by upper and lower housings, on which profiled plates are installed that hold pins for supporting rubber dampers. The movement of the star with sleeves and blades is not free and encounters resistance from deforming rubber dampers. This main rotor hub can be upgraded for a main rotor with any number of blades by changing the number of star rays and the profile of the plates, as well as with the ability to implement the calculated offset of the hose axis from the rotor axis of rotation, the taper angle of the main rotor and the vertical offset of the combined horizontal hinge relative to the top of the rotor cone screw
Thus, in comparison with the closest analogue, this invention is novel, and the set of distinctive features is not obvious to a specialist from sources corresponding to the level of modern technology. As for industrial applicability, it is proven by the description below and the application of the present invention in one of the author’s projects. Therefore, this invention satisfies all three conditions for patentability.
Figure 1 shows a diagram of the main rotor hub, which is the subject of the present invention. The main rotor blades are not shown. Figure 2 shows a diagram of the main rotor hub assembly.
The positions in Fig. 1 and 2 mean: 1 - spherical joint, 2 - star, 3 - sleeve axis, 4 - spacer sleeve, 5 - spacer sleeve, 6 - rubber damper, 7 - radial bearing, 8 - fork, 9 - bearing thrust, 10 - upper body, 11 - profiled plate, 12 - trunnion, 13 - lower body, 14 - driver, 15 - spherical support.
The main rotor hub has a star 2, which rests on the drive shaft with a spherical joint 1. The axes of the sleeves are screwed into the rays of the star, on each of which are assembled: spacer bushings 4 and 5, a rubber damper 6, a radial bearing 7, a thrust bearing 9 and a fork 8. The torque from the drive shaft to the sleeves is transmitted by the carrier, which consists of the upper 10 and lower 13 housings, profiled plates 11 and trunnions 12. The place where the torque is transmitted is the contact patch of the rubber damper with the trunnion. Changing the angle of installation of the blade is done by turning the fork by the leash 14, to which the rods coming from the swashplate are attached.
The main rotor hub works as follows. Cyclic changes in the angles of installation of the blades during rotation of the rotor lead to the emergence of moments that try to lower one part of the propeller and raise the opposite one, while the propeller until the damper 6 is completely compressed can move relative to the spherical hinge put on the propeller shaft, increasing the transmitted moment gradually. This ensures, firstly, the non-rigid nature of helicopter control, and secondly, lower loads on the butt parts of the blades. The design makes it possible to provide for the design angles of installation of the hoses relative to the plane of rotation of the propeller and the offset relative to the axis of rotation of the propeller, which can significantly reduce variable loads on the butt parts of the blades. Using dampers of various shapes or types of rubber, it is possible to select the characteristics of the main rotor for typical flight conditions, the habits or capabilities of the operator, and the operational assumptions of the on-board equipment.
CLAIM
A rotor hub consisting of a star, sleeves attached to it, consisting of a sleeve axis, spacer sleeves, a rubber damper, support bearings and a fork with a driver and a blade, characterized in that the star rests on the drive shaft using a spherical hinge, and the torque it is transmitted to the sleeves using a carrier consisting of an upper and lower housing, profiled plates and trunnions, while the sleeve is made with a combined horizontal hinge, with the ability to implement the calculated offset of the sleeve axis from the axis of rotation of the rotor, the taper angle of the main rotor and the vertical offset of the combined horizontal hinge relative to the top of the rotor cone and can be upgraded for a rotor with any number of blades by changing the number of star rays and the profile of the plates.
Loading...
