That is 1 chassis of the car. Chassis and body maintenance

Maintenance of the chassis consists of checking the condition of the tires and fastening of wheel disks, shock absorbers and springs, lubrication of bearings, bushings, hinge joints of rods and adding fluid to shock absorbers, adjusting bearings, toe of the front wheels and angles of installation of pins and hinges of pusher and reaction rods.

Examination

Checking the condition of tires includes an external inspection of them and measuring the internal pressure with a tire pressure gauge. On vehicles with a tire pressure regulation system, check the tightness of the entire system: at a tire pressure of 3.5 kg/cm 2, with open tire and shut-off valves and the middle position of the central valve lever, the pressure drop in the system during a 12-hour stop should not exceed 1 kg/cm 2. The fastening of disks, springs and shock absorbers is judged by the presence and tightening of the nuts.

Lubrication

Lubrication of spring pins installed in steel or bronze bushings, front suspension arms and rear suspension rod hinges is carried out using a solid oil pump through oil nipples screwed into the pins and rod heads (hinge covers) until oil comes out through the gaps.

To lubricate the wheel bearings, the cavity of the hub, removed from the axle, is filled with UTV grease (1 - 13). When installing the air supply head, it is necessary to lubricate it and purge the line with air before connecting the air duct.

The pin bearings and constant velocity joints are lubricated with AM cardan grease through the grease nipple in the top cover until the oil exits through the control hole in the ball joint, closed with a plug.

The bearings of the double joint of the front wheel drive of the MAZ-502 car are lubricated through oil nipples with transmission oil, and the kingpin bearings are lubricated with grease through oil nipples on the covers.

The rear suspension hub is filled with transmission oil to the level of the filler hole in the cover.

The spring leaves are lubricated with USs-A graphite lubricant. To do this, release the clamps, open the covers (on passenger cars), loosen the nuts of the stepladders and unload the springs, hanging the frame. The lubricant is introduced into the spaces between the sheets with a thin steel plate or using a device for anti-corrosion coating produced by the GARO trust.

Lever shock absorbers are filled with AU spindle oil through a hole in the body closed with a plug, without removing them. To remove air from the channels and cavities, it is necessary to disconnect the strut and rock the shock absorber lever until resistance appears. If oil leaks through the knuckle shaft seal, the latter can be tightened with a nut.

Telescopic shock absorbers are filled with oil after removal and disassembly. A certain amount of oil is poured into each shock absorber.

Adjustment

The wheel hub bearings are adjusted by tightening the bearing nuts after removing the flange, air supply head and hanging the wheel. The nut is first tightened so that the wheel immediately stops after a push by hand, and then released one or two edges. After adjustment, the wheel should rotate freely and have no axial play.

The toe-in of the front wheels is checked by measuring the distance between the wheel rims in front and behind the axle at its level with a special GARO ruler. The ruler must be installed at the same points on the rim; therefore, marks are made on it even when it stops. New rulers roll a car or rotate suspended wheels. Toe-in is adjusted by rotating the ends of the tie rod after they are disconnected from the steering arms.

The tension of the tapered bearings of the pivot pins is adjusted using gaskets 2 (Fig. 99) located between the covers and the housing.

To eliminate the body play, remove gaskets of equal thickness from under the top 1 and bottom 4 covers. The correct adjustment is determined by the force required to turn the body at the end of the swing arm. With the oil seals removed, the constant velocity joint removed and the transverse link disconnected, the force measured with dynamometer 3 for GAZ and ZIL vehicles should be 2.25 - 2.75 kg.

The thrust bearing 12 (Fig. 92) of the steering axle of the KrAZ-214 vehicle is adjusted by screwing in the cover 11 (the upper king pin should be 0.5 mm below the plane of the housing connector and the axle cover).

The camber of the wheels and the inclination of the kingpins are measured with a special inclinometer. To adjust the inclination of the kingpin on the M-21 Volga car, change the inclination of the rack 4 (Fig. 97) by rotating the bushings 16 on the upper pin 3 (the tilt of the kingpin changes backwards) and on the lower pin 15 (the inclination of the kingpin changes sideways).

After adjusting the tilt of the kingpins, it is necessary to check the camber and toe of the wheels. The hinges of the rear suspension rods of the KrAZ-214 vehicle are adjusted with plugs 28 (Fig. 96): unpin the plug, screw it until it stops and then unscrew it so that the cotter pin can be inserted into the nearest hole on the head of the rod 7.

To eliminate the axial play of the rear suspension hub, tighten nut 20 until it stops and then unscrew it 1/6 - 1/4 turn.

The gaps between lever 18 (Fig. 94) and valves 13 and 16 of the central control valve with the middle position of lever 26 should be 0.5 mm. The gaps are adjusted by rotating the screw at the end of the lever 18, as well as by rotating the tip of the rod 25.

Daily maintenance.

Check: the condition of the springs and pneumatic cylinders, shock absorbers, body position regulator, recoil limit cables, tire pressure and wheel fastenings, the operation of the level regulator, the condition of the body and its paint, the fastening of mirrors, license plates, the condition of doors, handrails, seats, ventilation , savings cash desks, the operation of door opening mechanisms.

First maintenance.

Check: fastening of stepladder nuts, spring brackets and spring pins, tightness of the air suspension, fluid level in the body position regulators, condition of the tires and air pressure in them, fastening of doors, hatches, seats, handrails, mirrors, sun shield, as well as window regulator, door locks driver and hatches, seat adjustment mechanisms and the action of its shock absorber. Tighten any loose mounting screws in the interior. Lubricate the press with grease, the pivot pins of the steering axles, the door leaf supports, the leaf spring pins; Wash the bus outside and inside, followed by wiping the windows, mirrors, handrails, and wipe the bus seats with a wet sponge. After one TO-1, wipe the outer and inner surfaces of the body with polishing liquid.

Check the condition of the front axle beam and wheel alignment at https://furacenter.ru. If there is increased wear on the front wheel tires, check the camber, longitudinal and lateral inclination of the kingpins, and wheel rotation angles, as well as wheel toe.

Rearrange the wheels in accordance with the wheel rotation diagram. Check the condition of the bolted, rivet and welded connections of the bus base, the reliability of the ball connection of the reaction rods, the absence of distortions of the driven and driven axles, the height of the pneumatic cylinders of the bus suspension.

Check the sealing of doors, posts, moldings, profiles, and the condition of painting. After one TO-2, lubricate all the rubbing parts of the window regulator, as well as the brake spring, with heat-resistant grease MZ-10. Lubricate the front wheel hub bearings with YANZ-2 or 1-13 grease.

Check the fluid level and add polysiloxane fluid to the top edge of the pneumatic valve stem. After one TO-2, change the fluid. Lubricate the axles, door supports and door opening mechanisms with grease.

Adjusting the front wheel hub bearings. The front wheel bearings must be adjusted with special care, since if the bearings are loosely tightened, they can be destroyed by impacts while driving. Over-tightening the bearings leads to bearing destruction from heat and lubricant leakage.

To adjust the front wheel hub bearings, you must: hang the front wheel, check for play by rocking the wheel along the axle axis, if play is detected, remove the cap, lock nut, lock washer and lock washer, turning the wheel, tighten the bearing nut until the wheel rotates tightly; unscrew the nut approximately 30° (the distance between two adjacent holes of the lock washer); assemble all fastening parts.

The correctness of the adjustment is checked while the car is moving by heating the hub. When touching the hub for a long time, your hand should not feel too hot.

Adjusting the axial clearance between the steering axle and the eye of the front axle beam. Increased play of the pivot pin in the vertical plane between the inner end plane of the beam eye should not be allowed. This gap should not exceed 0.3 mm. If this gap when moving the axle up and down on a suspended wheel is greater than normal, it is necessary to install an adjusting washer. Failure to install this washer in a timely manner can lead to the destruction of the thrust bearing and jamming of the steering axle. Check the gap with a flat feeler gauge.

Wheel alignment on a bus must be checked with fully inflated tires using a special ruler with stops and a pointer. The ruler is installed between the wheel rims at the level of the hub axis or at a height along the length of the chain, the indicator arrow is set to zero. Then chalk marks the places where the ruler was installed. After making the mark, remove the ruler and move the car so much that the chalk marks are again at the level of the rear axle; set the ruler again and use the scale to determine the amount of wheel toe. If the toe does not meet the established standard, then it is adjusted by changing the length of the transverse rod. To change the length of the rod, it is necessary to loosen the bolts of the rod ends and use a pipe wrench to turn the rod in one direction or another until the required wheel alignment is achieved, then secure the coupling bolts.

Dismantling and installation of tires on bus wheels. To remove the tire from the rim, you need to unscrew the cap, unscrew the valve spool and completely release the air from the tire: insert a straight mounting blade between the bead ring and the tire. In the gap formed between the bead ring and this blade, use a second blade to press the tire bead down. Moving sequentially around the circumference with both blades, remove the tire bead from the conical flange of the bead ring. Then press the bead ring and remove it from the lock groove. Turn the wheel over and remove the tire from the other side. Place the wheel vertically and, pressing the valve into the groove of the rim, remove the tire and remove the rim tape and tube from the tire.

To install a tire on a wheel rim, you need to clean it from dirt and rust, then slightly inflate the tube, powder it with talcum powder and place the tube in the tire: place the rim tape in the tire, tucking it over both sides of the tire. Place the tire on the rim and insert the valve into the groove. Lift the tire on the valve side and place the opposite side on the rim.

Insert the bead ring with one end into the groove of the rim and, using a hammer and a mounting blade, gradually insert the ring until it fits into the lock groove. Turn the wheel over with the bead ring down and first inflate the tire to approximately a pressure of 1.5 kgf/cm2. After making sure that the tire extends beyond the bead along its entire circumference, bring the air pressure in the tire to normal.

Tightening the fastening of clamps, spring ladders and wheel nuts. Loosening of the spring clamps can lead to breakage of the spring leaves, so it is necessary to periodically check and tighten the clamps. Loosening the stepladders can lead to misalignment of the axle and increased play in the steering wheel. It is strictly forbidden to leave the garage if at least one wheel nut has become loose, as this can lead to the shear of the stud and the wheel falling off when moving. Therefore, at each TO-1, it is necessary to check all spring fastenings, fastenings of brackets, pins, clamps, and stepladders.

Wheel balancing. As a result of uneven wear of the tire tread, the application of patches during repair of a tire or tube, or deformation of the disc or wheel rim, imbalance (imbalance) of the wheel appears. When a car moves (especially at high speed), significant centrifugal forces arise when such a wheel rotates, causing wheel vibration and increased tire wear. Therefore, balancing of the front wheels of cars and buses has now been introduced.

To balance the wheels, you should hang the front axle and, having loosened the bearings, set the wheel in rotation with a hand push, noting the lower stopping point of the wheel. After stopping, turn the wheel again. If it stops a second time at the same point, then the wheel has an imbalance, which is eliminated by installing weights 4 (Fig. 186), attached to the bead ring 2 or to the rim 6 using a leaf spring 3. The end of the plate is pressed by the tire bead 1 to the lock ring 5 To make it easier to install the weights, reduce the air pressure in the tires. The weight is attached on a diametrically opposite section to the heavier section of the wheel.

Installing discless wheels on hubs. Before installing the wheels on the hubs, you must make sure that the mating surfaces of the wheels and the hub, as well as the clamps, are free of nicks and bends. After making sure that there is a limiter on the rim that prevents it from turning, you should put the wheel and tire assembly on the hub. Make sure that the valve chamber and limiter, welded to the rim on both sides of the valve groove, are located between the spokes of the hub.

Supporting the wheel on the hub, place two clamps diametrically opposite and screw the nut on by hand. After this, turn the wheel so that these two clamps are in a vertical plane and, starting from the top nut, begin tightening them evenly. Install all subsequent pairs of nuts in the same way.

Installation of the rear wheels is carried out similarly to the above method. After installing the inner tire, it must be secured all the way, install the spacer ring, and then install the outer tire and secure it with clamping wedges and nuts. When installing rear tires, it is necessary to align the tube valves on the same line. After the first trip of the bus, the spoke nuts should be tightened.

Checking the serviceability of bus heaters is carried out in various operating modes by changing the position of the dampers. The operation of the LAZ bus heater must be checked in three modes. During the non-heating period, it is necessary to open the dampers so that the air is thrown down, and part of the air is used to blow the engine.

When the outside air temperature is above - 10° C, the bottom damper should be closed and the side damper should be opened slightly. The main flow of air will go into the cabin, and part of it will heat the engine.

In severe frosts, close the blinds, ventilation hatches, damper, and recirculation casing cover. After checking the operation of the dampers and blinds, turn on the fans and check the air flow to the windshield nozzles. On LiAZ and PAZ buses, the cabin heater checks the movement of the damper handle to various positions of the cable drive of the blinds.

In the back of an Ikarus bus, it is necessary to systematically check the suspension of the passenger compartment doors. Lubricate the hanging parts of the door opening mechanism with the Hungarian-made Fimon mixture, and also check the tightness of the connections of the heater system.

Adjusting the height of the body floor. Violation of the established height of the body floor leads to premature wear of the tires, makes it difficult to drive the bus and leads to the destruction of the suspension cylinders.

Before adjusting the height of the body floor, you must make sure that all body level regulators are in working order, the pneumatic system of the bus is sealed and the cylinders are not damaged.

To make adjustments, the bus is placed on an inspection ditch or on a flat horizontal platform and a pressure is created in the pneumatic system equal to 6-7 kgf/cm 2 . Starting with the rear adjusters, it is necessary to disconnect the lower end of the drive rod from the horizontal link, and set the drive lever to the intake position. When the height of the cylinders reaches 210 - 10 mm, set the drive lever to the horizontal (neutral) position, and connect the lower end of the drive rod 15 to the horizontal rod 4. Repair and disassembly of the regulator is carried out as needed in case of loss of tightness of the movable rubber seals and valves.

Purpose of the work: get acquainted with and learn how to perform diagnostic and maintenance operations of the chassis; study the main malfunctions inherent in it and their symptoms; learn to carry out practical execution of operations of diagnostics, testing and regulation of chassis elements using special stands and equipment with appropriate technical conclusions and regulatory influences.

As a result of execution laboratory work, preparation and defense of the report, students must:

− purpose, main types, structure and operation of elements and components chassis of modern cars, trucks and buses, diagnostics and maintenance;

− main malfunctions of the chassis of cars and their symptoms;

− methods and methods for monitoring the operation of the chassis of vehicles;

− the main work performed during the maintenance of the vehicle chassis;

− design and work control and measuring equipment, stands and instruments for diagnosing, checking and regulating elements of the chassis of automobiles; be able to:

− use theoretical knowledge of the design and operating features of cars when carrying out practical work for diagnosing, checking and adjusting chassis elements using special stands and equipment with the issuance of appropriate technical reports;

− perform maintenance operations on vehicle chassis;

− identify the main malfunctions of the vehicle chassis and highlight their dominant symptoms.

Workplace equipment: a standard platform or inspection pit with a working car, a lifting device, diagnostic instruments, devices, a compressor with an air-dispensing column, a wheel balancing machine, a stand for dismantling and mounting tires, an electric vulcanizer,

sets of measuring tools, auto mechanic tool kit.

Brief theoretical information, composition and procedure for performing the work.

Main malfunctions of the chassis. Malfunctions of frames, cabs and bodies:

- deformation and distortions of truck frames and bodies passenger cars

(violation of vehicle geometry). May lead to deterioration of vehicle stability when driving on the road (“pull” to the side, skidding), to increased wear of the tire tread, etc.;

- deformation, twisting or cracking of load-bearing elements

frames and bodies(spars, traverses, etc.);

- destruction of welds, loosening of rivets or breakdown of brackets for various purposes, gussets(providing gesture

- corrosion of the bottom and other elements of bodies or frames(with chipping

eat individual sections of metal parts);

- dents, tears or cracks in the surfaces of cabins or bodies;

- damage or aging of paintwork(matting,

numerous scratches, paint peeling, etc.);

- damage to hinges, hooks, door locks, sagging and sagging doors, hoods, damage to glass seals and power windows

And other fittings, damage to elements of wooden platforms and sides, locking hooks, etc.

Malfunctions of car suspension elements:

- the condition of the springs or springs and fastening elements is not appropriate

meets technical requirements- decrease in elasticity or breakage (primarily of the main ones) of spring sheets, weakening of the fastening of the sheets or the springs themselves, wear or destruction of the spring fastening elements (tie clamps, stepladders, pins and earring bushings, support cushions), wear of interleaf gaskets or corrosion of spring leaves, accompanied by loss of elasticity of the springs;

- poor performance of shock absorbers- occurs when not

tightness (as a result of loosening of the tank nut or wear of the stuffing box) and liquid leakage or contamination, in case of nicks of impact origin on the tank body or in the presence of marks and burrs on the rod, in case of breakage or wear piston ring, nadir on the piston, when the bypass valve or compression valve does not close tightly (or excessive settlement of its spring), when the shock absorber itself is loosened or the pins of the metal and rubber bushings wear out;

- non-compliance with the technical requirements of the condition of the elements of the independent suspension of the front axlespassenger cars - bent

thinness, twisting, breakage of the upper or lower arms and struts, weakening

failure of their fastening, wear of the axis of the upper arms, threaded connecting pins and bushings, damage to the protective rings; in some models, with pinless independent suspension- wear of the pins and bearings of the upper ball joints or lower ball joints, leading to increased play and runout of the wheels (sometimes to complete destruction of the joints and “collapse” of the wheel with the hub);

non-compliance with technical requirements of additional elements

suspension components - bent or twisted reaction rods, loosening of their fastenings or increased wear of the pins and joint bearings (which can lead to misalignment of the drive axles and increased wear of the treads of several wheels at once, which may be accompanied by a strong hum in the main gears at high speeds); In passenger cars, the stabilizer bar may lose elasticity or be bent, its fastening may become loose, or the support rubber bushings may wear out severely.

Wheel faults:

- bent, dents, cracks of wheel rims, failure of welding on stamped rims, malfunction of locking rings;

- development of holes in wheel rims for fastening bolts;

- destruction of the threads on the bolts and wheel fittings;

- wheel imbalance- leads to strong wheel runout, especially the front ones, at high speeds;

- the installation of the front steered wheels does not comply with the technical specifications and standard values- incorrect installation of toe-in and camber angles (if there is deformation or increased wear of suspension elements, including front axle beams, deviations from the norm in the transverse and longitudinal inclination of the king pin may occur);

- violation of adjustment of the steering linkage and the ratio of wheel rotation angles;

- tire pressure does not correspond to standard(for specific operating conditions) - low tire pressure leads to cord destruction, sidewall rupture, increased wear of the tread edges, and rapid failure of the tubes; increased pressure reduces ride comfort, increases the dynamic load on the chassis elements, and accelerates wear of the middle part of the tread;

- increased or uneven tread wear, tire damage- the depth of the tread grooves is less than permissible, the presence of “spotted” wear, various damage to the tires, incl. through cuts, tears, swelling, etc.

All of these malfunctions significantly worsen the stability of the car on the road, make it difficult to control, sharply increase the wear of the chassis elements, increased play in joints appears, and dynamic shock loads increase, leading to complete destruction.

the destruction of individual components and parts, up to the breakdown of the wheels - in the presence of individual above-mentioned malfunctions, the operation of the vehicle is classified as

strictly prohibited.

Chassis maintenance work.

EO - before going to the line, check by external inspection: whether there is any visible distortion of the geometric shape (deformation) of the frame or load-bearing part of the body; condition of the springs (are there any breakages of the leaf springs or fan-shaped displacement of them, the presence of clamps, fastening of the stepladder block, etc.); the condition of the shock absorbers, paying attention to their fastening, possible mechanical damage and fluid leaks.

For passenger cars, check the general condition of the front axle independent suspension elements; condition of wheels and their fastening; by the outline of the tire profile at the point of contact with the road - whether the tire pressure corresponds to the norm.

On the road, you should monitor for signs of the above-described malfunctions. During stops, you should check the hubs for the degree of heating and remove foreign objects from the tire treads.

V as a result of wear of parts. In addition to checking the play in the wheel bearings

And bearing adjustments, check (by rocking the wheel in a vertical plane) possible play in the pivot joints, and for cars with independent suspension - in threaded connections struts and suspension arms, in the joints of the axis of the upper arms, etc. These gaps can only be eliminated by replacing worn parts in the area of ​​current repairs. On the road, through 10-15 minutes of movement, it is necessary to check the hubs for heating, the degree of which characterizes the quality of the adjustment; in addition, if the hubs overheat, grease can leak through the seals, aggravating the wear of the bearings and oiling the brake pads. It is necessary to lubricate all points indicated in the lubrication chart for this car model, included in the scope of TO-1, starting from the pins of the earrings (lubricated with grease) and ending with the threaded hinge joints of independent suspensions (lubricated with liquid transmission oils), pivot joints (pivot joint bearings passenger cars are also lubricated through oil nipples with transmission oil until the old lubricant is completely released). The pin connections of trucks are lubricated with grease (for ZIL-4331, for lubrication of the specified points

Litol-24 is used instead of grease).

TO-2 - in addition to the scope of work during TO-1, a thorough diagnosis is carried out, which consists of checking the general geometry of the frame (body) of the car, the parallelism of the installation of axles and the camber and toe angles of the steered wheels, the condition of the coupling device, securing clamps, stepladders and front pins and rear springs, airbags and shock absorbers. In addition, check the condition of the springs and front suspension arms. After a certain mileage interval, the wheels on the car are rearranged according to established patterns (Fig. 1.1). This operation ensures more uniform wear of the treads and, ultimately, increases their service life. Wheels whose tires have excessive wear or other damage are removed and sent to a tire shop. During TO-2, as part of the accompanying repairs, you can change any worn or damaged parts and components, including springs.

Rice. 1.1 Scheme for rearranging truck wheels:

a, b, c – wheel movement patterns for specific car models

For seasonal service,

once a year, it is necessary to remove the wheel hubs, remove the old grease from them, wash the internal cavity and fill with fresh grease, and to increase the elasticity of the springs (without spacers), between the sheets of springs (previously weakened and wedged)

Basic methods of control and diagnostics, equipment and instruments for their implementation

1. Checking the condition of the frame. When inspecting the frame, check for visible distortion of its geometric shape, cracks and bends in the side members and cross members, and weakening of the rivet joints. The integrity of the spring brackets and suspension brackets, the housings of lever shock absorbers or the mounting brackets of telescopic shock absorbers is also revealed. If during the inspection a noticeable deformation of the frame is detected, then the degree of distortion of its geometric shape is checked.

Pre-clean the frame from dirt and perform the following procedure10

Verku. Measure the width of the frame front and back. For trucks of the Gorky Automobile Plant, the difference in frame width should not exceed 4 mm. The curvature of the frame can be determined by measuring the diagonals between the cross members of the frame in its individual sections (Fig. 1.2). The difference in the length of the diagonals in a separate section of the frame between two cross members should be no more than 5 mm.

Rice. 1.2 Frame check diagram:

D, E, F - checked dimensions between the cross members of the frame.

Correct position of the front and rear axles towards

The frame is determined by measuring the distances A and B, which must be equal to each other (a difference of no more than 4 mm is allowed). Distance C, equal to the length of the vehicle's base, must be the same on the right and left sides of the frame.

When checking the frame, the condition of its painting is also monitored. To avoid corrosion, surfaces with damaged paint must be promptly repainted.

The weakening of the rivets is detected by lightly tapping the frame side members, during which the weakened rivets emit a characteristic rattling sound.

2. Checking the condition of suspension parts.When inspecting the springs and

weeds are identified whether there are any breakages or cracks in the sheets. The sheets should not have longitudinal displacement, which could occur as a result of shearing the center bolt. The deflection of the right and left springs should be the same.

When checking the reliability of the fastening of the spring pins on springs with overhead lugs (ZIL-130), pay special attention to the tightening of the stepladder nuts securing the overhead lugs. These nuts must be tightened until the spring washers compress.

For cars that have springs mounted in rubber cushions (GAZ53A, GAZ-66, etc.), check whether the rubber cushions have been destroyed, and also monitor their correct position and the absence of distortions.

The nuts of the stepladders securing the springs should be tightened evenly, first both front ones, and then both rear ones (along the vehicle's direction) with a torque of 25-30 kgm.

The elasticity of the spring is checked by its deflection in the free state. The deflection arrow is determined by pulling a thread along the upper part of the root sheet along its end ends or the roundings of the rubber cups.

The distance from the thread to the surface of the root sheet is taken as the deflection arrow. The difference in deflection for right and left springs of the same name should not exceed 10 mm.

3. Determination of the presence of backlashes resulting from wear of parts.

First, you should check for play in the tapered bearings of the wheel hubs. To do this, the wheels are hung with the help of lifting devices and rocked in a vertical plane (away from you). To more accurately determine the play, portable devices with indicator heads and a fastening mechanism (for fixed elements of the car) are used - see fig. 1.3. If play is detected, it is necessary to adjust the hub bearings.

Fig. 1.3. Devices for checking the front axles of cars:

a - mod. RE - 4892; 6 - mod. T-1; c - installation of the device on a car

4. Diagnosis of pivot joints and wheel hub bearings.Radial clearance A and axial clearance B in the pivot joint (Fig. 1.4) are determined by the movement of the pivot pin relative to the pivot when raising and lowering the front axle using a device T-1, which consists of a tripod and a dial indicator.

Rice. 1.4. Scheme for measuring backlash in pivot joints.

The instrument tripod must be secured to the front axle beam of the truck near the previously suspended wheel, and the measuring pin of the indicator is in contact with the bottom of the support

brake disc. The indicator arrow is set to scale zero. At

When lowered, the wheel will deflect outward, and as a result, a radial clearance A can be detected in the pivot joint, and the axial clearance B can be measured with a flat feeler gauge. The values ​​of the gaps in the pivot joints are given in table. P.1.

In order to increase the accuracy of measurements, it is recommended to first determine the play in the bearings of the front wheel hubs, for which you need to move the indicator pin to the brake drum and use a special wedge to select the play in the pivot joints, and then, by rocking the suspended wheel in a vertical plane, determine the play in the bearings. The resulting value must be subtracted from the total play in the pivot joints.

Play in the bearings of all wheels of passenger cars is not allowed, and on the front wheels of trucks up to 0.15 mm.

At adjusting the front wheel hub bearingscar GAZ3102 (Fig. A.1) it is necessary:

- remove the wheel cap, unscrew the hub nut 14 and hang the wheel; Unscrew and loosen adjusting nut 15 by 1/4 turn, check the free rotation of the wheel; if necessary, eliminate the cause of its braking;

- smoothly tighten the adjusting nut to a torque of 60 - 90 Nm. At the same time, you must turn the wheel so that the bearing rollers 16 take the correct position;

- loosen the nut 1/8 - 3/8 of a turn so that the hole in the trunnion for the cotter pin coincides with the slot in the nut;

- check the ease of rotation of the wheel (6 - 8 revolutions) and the absence of play

in bearings.

For adjustment of truck wheel hub bearings

ZIL, MAZ, and KamAZ:

- lift the front axle or wheel with a lift, remove the hub cover

And unscrew the locknut;

- turning the wheel in both directions, tighten the adjusting nut to a torque of 60 - 80 N.m, then unscrew it 1/4 - 1/3 turn (90 - 120°) until the nut pin aligns with the nearest hole in the lock ring, install the lock washer, tighten the locknut to a torque of 250 - 300 Nm and bend the lock washer;

- Check the free rotation of the wheel in both directions (4 - 6 revolutions) and the presence of clearance in the bearings.

The correct adjustment of the front axle hub bearings can be judged by the heating of the hub while driving. If the heating of the hub is felt by hand, it is recommended to loosen the nut by one cotter pin hole.

Adjusting the rear wheel hub bearings.To determine the axial

there is play in the rear wheel bearings, hang it up and disconnect the semi-

axle from the hub.

Before adjusting the bearings, check to see if the pads are touching the drums, which makes it difficult to turn the wheel. If adjustments are necessary, unscrew the lock nut 1 (Fig. 1.5) and remove the lock washer 2 with the oil seal 4. Loosen the bearing mounting nut 3 by 1/2 turn and check the rotation of the wheel. Then tighten nut 3 with one hand using a wrench with a crank 350-400 mm long until the hub begins to brake. At the same time, rotate the hub in both directions so that the bearing rollers are correctly installed on the conical surfaces of the rings. After this, loosen the bearing fastening nut 1/5 of a turn and insert the locking pin into one of the slots in the lock washer. If the pin does not fit into the slot, then turn the nut in one direction or the other so that the pin fits into the nearest slot. Having completed this operation, tighten and slightly tighten the lock nut and check the degree of tightening of the bearings. If the bearings are tightened correctly, the wheel should rotate without noticeable axial play or rolling. Having put the axle shaft in place, finally tighten the locknut.

Rice. 1.5. Adjusting the rear wheel bearings:

1 - lock nut, 2 - lock washer, 3 - nut, 4 - oil seal.

P Adjusting the bearings of the steering knuckle pins.

For vehicles with front drive wheels, it is necessary to adjust the tightening of the steering knuckle bearings. For GAZ-66 cars, the king pins turn conical roller bearings. These bearings must be

adjusted so that no play is felt in them.

5. Checking and adjusting the alignment of the front wheels.The front steered wheels of vehicles must be installed with certain wheel camber and toe angles (in practice, sometimes instead of toe angles they use the linear value of toe - the difference between distances A and B (Fig. A.2), measured in the horizontal plane), which makes driving easier (especially at high speeds), reduces dynamic loads on components and front axle parts and tire wear rate (Fig. A.3). An important factor in increasing

stability of the car, by stabilizing the steered wheels (their desire to return after turning to their original position, corresponding rectilinear movement etc.), is the presence longitudinal angles

th and transverse inclination of the kingpin. In addition, the vehicle must comply with wheel angle ratio (characterizing the correct installation of the steering linkage as a whole) - when turning (to the left) the left wheel by 20°, the right wheel, which has a larger turning radius, should turn to a smaller angle corresponding to the standard (for different models from 17.5 to 18.5° ) - if the ratio of the turning angles is violated, the process of normal rolling of the wheels when turning is disrupted, the “squealing” of the tires is heard, and tread wear can increase several times. It must be remembered that if linear toe is adjustable on all car models, and camber angles are only for passenger cars, then the longitudinal and transverse inclination angles of the king pin are not adjustable at all - their deviation from the norm indicates bent beams, suspension arms, etc.

Wheel toe angle for passenger cars is from +20" to

1°, and the linear value is from 1 to 4 mm. The camber angle ranges from -30" to +45". Kingpin lateral inclination angle ranges from 5°30" to 6°, and pro-

lobular from 0 to 3°.

For trucks linear toe ranges from 1.5 to 12

mm. The camber angle is usually 1°. Cross pin angle

for most models - 8°, longitudinal - from 1.25 to 3°.

A change in the backward angle of the kingpin can occur in trucks due to deflection or twisting of the front axle beam, breakage or large deflection (sagging) of the front springs, or wear of parts of the kingpin joints.

Restoring the backward angle of the kingpin requires replacing deformed parts. In some cases, the angle can be brought to the required value by using a steel lining (wedge), installing it between the front axle beam platform and the spring.

The lateral inclination angle of the kingpin may be disrupted as a result of a bent front axle beam. The reason for the change in the camber angle may be deflection of the front axle beam, wear of the pivot joint parts, or insufficient tightening of the front wheel hub bearings.

The specified angles for trucks cannot be adjusted. To restore them, the bent front axle beam is straightened in a cold state under a press, and the worn parts of the pivot joint are replaced with new ones.

The amount of toe-in of the front wheels can be adjusted. To do this, unscrew the nuts of the coupling bolts of the ends and turn the transverse steering rod, which has threads at its ends in different directions. Having set the required amount of toe-in by turning the rod, tighten 15

Bend and cotter the nut bolts of the tips.

Control and installation steered wheels of passenger cars

are carried out at specialized posts on wide-type inspection ditches equipped with a lift for hanging bridges, or on four-post lifts with track-type lifting frames. In both cases, they are equipped with appropriate instrumentation and various additional devices and, in general, are called stands for monitoring and adjusting wheel alignment angles. Typically, checking the installation geometry of the front controls

wheels of cars, trucks and buses is carried out using portable devices (special posts are not equipped for this). For this purpose, special instruments are used: a ruler for checking wheel alignment, instruments for checking wheel alignment angles

A ruler for checking the toe-in of the front wheels of a model 2182 car (Fig. 1.6, a) is universal, rack-and-pinion, telescopic, and consists of four tubes. A telescopic two-tube extension is inserted into the outer body tube on one side, through which the ruler is adjusted to the vehicle track, and on the other, a movable spring-loaded tube with a scale. Chains are suspended from the stop rods at the ends of the ruler, which determine, when the ruler is applied to the tires of the wheels, its height position above the floor level. The amount of wheel toe is recorded by the displacement of the scale relative to the arrow on the body tube. Ruler length 942 mm, piston tube stroke 170 mm.

Rice. 1.6. Ruler for checking the toe-in of the front wheels of cars model:

a – 2182; b – K-463

The K463 model line (Fig. 58, b) is a rack-and-pinion telescopic, universal with a drum indicator, designed to check the toe-in of the front wheels of trucks and cars. Toe measurement accuracy ±0.5 mm, ruler length 1880-1040 mm (unfolded and compressed), scale range from +20 to -6 mm.

Devices models 2142 and 2183 (Fig. 1.7, a, b, c) are designed to check the wheel alignment angles of passenger cars and trucks, respectively. The devices include three separate devices. Liquid device 2 with four levels 3, 5 and 7; two of them (without scales) are located on the back side and are intended for the initial installation of the device, and the other two with scales, located on the front side of the device, are used for

counting camber angles, transverse 4 and longitudinal 8 tilts of the king pin. The body of the device 2 is hingedly connected to a gripper, which is mounted on the wheel nut 1. Two wheel angle meters with a scale and an arrow 11, with a turn indicator 12 and an extension 13 are mounted in a special box 10. Device 9 consists of two movable disks that make it easier to turn the wheels when checking.

Rice. 1.7. Device model 2183 for measuring vehicle wheel alignment angles

The instrument set of model 2142 for passenger cars differs from model 2183 in the size of the disks.

Checking and adjusting the toe of the front wheels:

- Place the car on a level surface so that the front wheels are in a straight-line position;

- check the fastening of the steering gear arms, eliminate play in the steering rod joints, front wheel hub bearings, independent suspension joints and pivot joints;

- check the air pressure in the tires with a pressure gauge and bring it to normal (see Table P. 1);

- install the ruler in a horizontal position between the inner sidewalls of the tires (according to the GAZ method) or the wheel rim (according to the ZIL method) at the height of the center of the wheels in front of the front axle of the car, secure the ruler scale to the zero division and mark with chalk the places where the tips touch;

- move the car forward so that the marks are at the same height at the rear, and again measure the distance between the marked points; the difference between the second and first measurements will be equal to the wheel toe value, the standard values ​​of which are given in the table. P. 1;

- Adjustment of the toe-in of the front wheels of trucks is carried out by changing the length of the tie rod (by rotating the adjusting sleeve 2 (Fig. 1.8)), with the nuts and tie clamps 3 of both ends loosened.

Rice. 1.8. Changing the length of the tie rod when adjusting wheel toe and steering angle ratio.

Adjusting the maximum steering angle of the front wheels.The maximum (maximum) angle of rotation of the front wheels is limited by the position of the thrust bolts located on the swing arms. When the limit is reached

At a given rotation angle, these bolts rest against the protrusions of the front axle beam. The largest angle of rotation is selected so that when turning, the wheels do not touch any parts.

Adjust the maximum angle of rotation by tightening the thrust bolts. The greatest angle of rotation of the outer wheel is given when the inner wheel is turned by 20°. The rotation angle of the outer wheel when turning the inner wheel by 20° for domestic trucks is:

UAZ-451M - 18°30", GAZ-53A - 17°30", "Ural-375", "Ural-377" - 18°30", ZIL130 - 18°, ZIL-131 - 18°.

Checking the maximum angle of rotation of the inner wheel is carried out using a special meter (see Fig. 1.7, c), for which the car must be placed with the front wheels on rotary disks 9, the turn signal 12 must be pressed tightly to the wheel rim and the arrow 11 must be set to zero. Turn the steering wheel to the left all the way and measure the maximum angle (Table A.1). Adjustment to trucks is carried out using stops installed in the flanges of the pivot pins.

Measuring the camber of the front wheels and the inclination of the king pins (transverse and longitudinal)on trucks are carried out using a model 2183 device (see Fig. 1.7), for which it is necessary to secure the liquid device 2 with its back side on the disk in a strictly horizontal position according to levels 3, then turn the wheels 180° and according to the division of the scale 6, against which the level has stopped, the camber is determined. By turning the wheels 20° in one direction or the other, while setting the scale levels to 4 and 8, the longitudinal and transverse inclinations of the king pins are determined (which are for informational purposes about the condition of the suspension and are not adjustable). On trucks, wheel camber and king pin angles are not adjusted, but are restored by replacing worn parts. On most domestically produced passenger cars, adjustment is carried out by changing the number of shims, as a result of which the position of the upper arm of the suspension strut changes.

In addition to the parameters described above, it is also necessary to determine rear wheel position relative to the longitudinal axis of the car and the misalignment of the rear axle in relation to the front, i.e. non-parallelism of the axes and, even more so, in the presence of two or more rear axles, because under the negative influence

It is not just two wheels with their tires that suffer from improper wheel installation, but 6-8 or more wheels. In addition, misalignment of the rear axles leads to increased wear of the cardan shafts and main gears, accompanied by strong vibration and noise during operation, especially at high vehicle speeds. Therefore, the old methods of measuring using plumb lines, measuring rods, etc. are completely unsuitable at the moment. It is necessary to introduce advanced technologies into modern measurement methods, which, in addition to high accuracy, should be as comprehensive as possible, with minimal labor costs for verification operations.

6. Inspection and maintenance of wheels and tires.Wheel rims must have the correct external shape. The presence of nicks, dents, and bends on the rim is not allowed. If rust is found on the rim, it is cleaned and painted.

The vehicle must be properly equipped with tires, that is, its wheels must be equipped with tires that match the rim size and the vehicle's load capacity.

IN When installing tires that were previously in service, tires with the same pattern and the same degree of tread wear must be installed on wheels of the same axle. The difference in tread wear should not exceed 5 mm along the outer diameter of the tire.

It is necessary to ensure that the tires are installed correctly; the tube must not be pinched or sand and dirt can get inside the tires. For installation work, only tools specifically designed for this purpose should be used.

IN tires must be maintained at a pressure set depending on

from the load on the wheel. The pressure in individual vehicle tires should not deviate by more than 0.2 kg/cm2. During vehicle operation, the tires must not be overloaded, avoiding loading the vehicle in excess of the established load capacity, evenly distributing the load in the body, and preventing the truck from moving with a flat tire on at least one of the double rear wheels. Objects stuck between the double tires of the rear wheels should be promptly removed. To prevent rubber destruction, do not allow gasoline and mineral oils to come into contact with the tires.

When installing tires, consider their tread pattern. Tires with directional tread must be installed in such a way as to maintain the correct direction of the tread pattern as the vehicle travels:

WITH For this purpose, there is an arrow on the sidewalls of tires with a directional tread pattern. If the tires are installed correctly, the direction of rotation of the wheels (forward movement) and the arrows coincide.

The durability of tires is greatly influenced by the technical condition of the vehicle. In particular, increased tire wear is caused by: violation of the installation angles and toe values ​​of the front wheels, incorrect adjustment

brakes slipping, wheel imbalance, sagging springs, lubricant leaking from oil seals and wheel hubs and getting onto the surface of the tires.

Timely elimination of noticed damage is of great importance in increasing the durability of tires. Tires with mechanical damage (punctures, cuts) must be removed from the vehicle and repaired. Minor damage to tires should be repaired using special first aid kits; larger damage should be repaired by hot vulcanization.

Minimum allowed value residual height drawing about

tector (see Table A. 1) is determined according to the drawing on an area equal to half the width and 1/6 of the circumference of the treadmill. The width of the wear limit zone should be no more than half the width of the treadmill, and the length of the zone should be no more than 1/6 of the tire circumference (1/6 of the circumference is numerically equal to its radius). The tread pattern height is checked using a measuring tool (vernier caliper) that provides an error of no more than ±0.1 mm. The remaining tread height values ​​are measured in areas of greatest wear. The air pressure in the tires is checked when the tires have completely cooled down without disassembling the spool assembly. The error in measuring air pressure should not be more than: ±0.02 MPa for truck and bus tires and ±0.01 MPa for passenger car tires.

7. Balancing car wheels.When cars move at high speeds and, first of all, cars with independent suspension, wheel runout (in the horizontal plane) and “bouncing” (in the vertical plane) appear. At the same time, the grip of the wheels on the road deteriorates, it becomes difficult to control the car, and in certain driving conditions (for example, on a slippery road), the car may become completely uncontrollable. In addition, the additional dynamic loads that arise cause increased wear on the chassis parts, steering and tire treads of the wheels themselves (the so-called “spotted” wear, which further aggravates the tendency of the wheels to run out). The cause of this common phenomenon is imbalance (imbalance across the entire mass of the wheel) as a result of uneven wear of the tire tread, the application of cuffs and patches during repairs, deformation of the disk or rim, cord breakage and the formation of blisters on the tire, a manufacturing defect in the manufacture of the tire, etc. Uneven distribution of material over the entire tire profile leads to the formation of “heavy spots”, to a discrepancy between the center of gravity of the wheel and its geometric axis.

There are static and dynamic imbalances of wheels. At static imbalance the center of gravity of the wheel does not coincide with the axis of its rotation. Dynamic imbalance characterized by an uneven distribution of mass across the width of the wheel, as a result of which an additional moment of force is created when the wheel rotates, causing

his hesitation. To eliminate the imbalance of the wheels, they are statically balanced, and if this is not enough, then dynamically balanced, using lead weights with plate clamps.

When balancing wheels against static and dynamic imbalance, stationary, electromechanical machines with electronic elements are widely used. They have great measurement accuracy and safety in operation.

Machine model K125 (Fig. 1.9) for static balancing of passenger car wheels without removing them consists of a mobile electric

a new installation for spinning a suspended car wheel with a drive disc on a shaft, which is pressed against the sidewall of the tire, an induction sensor installed under the car. Its moving system is attached to the wheel suspension using a permanent magnet. The machine body contains an electronic unit with a sensor, which serves to register the size and location of the unbalanced mass on the wheel.

Rice. 1.9. Machine model K125 for balancing removed wheels of passenger cars

Mechanical vibrations arising due to wheel imbalance are converted by the sensor into electrical signals, which, through amplifiers,

The body is fed to a measuring device that registers and displays the amount of imbalance in weight units and to a device for determining the angle, i.e., the location where the balancing weights are attached. Diameter of balanced wheels 595-800 mm, wheel weight up to 40 kg, balancing accuracy 15 g, measurement range 0-150 g, scale division 5 g, simulated vehicle speed up to 170 km/h, mains power alternating current voltage 220/380 V.

Static balancing performed on the K125 machine (see Fig. 1.9) directly on a passenger car without removing the wheels. Before balancing, it is necessary to perform a number of preparatory operations:

- hang the front wheels from the surface of the platform by 50 - 90 mm, remove

With rim balancing weights, check the ease of rotation of the wheel and play in the hub bearings, place stops under the rear wheels;

- install the sensor under the lower arm of the front suspension closer to the wheel; The correct connection of the sensor is checked by lightly tapping the tread of the upper part of the wheel. At the same time, the stroboscopic lamp of the machine should flash;

- check the air pressure in the tires and, if necessary, bring it to a normal value (see Table P. 1);

- Using an indicator, check the radial and axial runout of the wheel rim and tire, as well as the total play in the front suspension joints. They should not exceed the values ​​​​specified in the table. P. 2.

An arbitrary mark is applied to the wheel, which in the light of a flash lamp will appear stationary on the rotating wheel (due to the fact that the frequency of ignition of the lamp is equal to the frequency of vibration of the suspension, which, in turn, depends on the speed of rotation of the wheel); The position of the mark is remembered and, having stopped the wheel with the brake, they turn it by hand so that the mark takes the same position in relation to the vertical axis on the plane of the wheel. After this, a weight with a mass corresponding to the readings of the measuring device is installed on the upper point of the wheel rim from the outside. The operation is repeated until the wheel is statically balanced, as evidenced by the presence of the instrument needle within a certain scale zone. The permissible static imbalance of passenger car wheels should not exceed 5-10 Ncm (depending on the tire size).

Machine model K121 (Fig. 1.10) for static and dynamic balancing of removed passenger car wheels. The main components of the machine are: a suspension with a shaft (on which a wheel is mounted on a faceplate) and a movable support that perceives vibrations of the shaft; a shaft drive electric motor with a belt drive, on the driven pulley of which there is a scale for determining the angle of position of the unbalanced masses when the wheel rotates; intermediate cardan transmission; suspension locking mechanism when spinning the shaft; measurement block; power supply providing voltage to the measuring system; induction sensor.

The diameter of the wheels being balanced is 595-800 mm, the weight of the wheels is 15-40 kg, the balancing accuracy is 15 g, the measurement range is 0-250 g, the scale division price for

determining the weight of the weights is 5.0 g, the scale division value for determining the angle of position of the unbalanced masses is 5°, the shaft rotation speed is 780 min-1. Powered by AC mains voltage 220/380 V.

Dynamic balancing performed on a machine model K121 (see Fig. 1.11) with the removal of passenger car wheels is carried out in the following order:

- Before balancing, it is necessary to check the technical condition of the rim and wheel disk, the degree and uniformity of wear of the tread pattern, and remove objects stuck in the tread. If there are cuts or cracks in the tire, and the rim is deformed, the wheel cannot be balanced until the problem is eliminated.

- the wheel must be clean and in good condition (balancing weights are removed). After this, the wheel is installed on the machine shaft, securely attached to its faceplate and covered with a restrictive mesh.

A) b)

Rice. 1.10. Wheel balancing machine mod. K121:

A - appearance; 6 – layout diagram; 1 - machine body; 2 - electric motor; 3 - belt drive; 4 - brake; 5 - balancing mechanism; 6 - resonant indicator; 7 - handle of the movable fist; 8 - pedal to disable and stop the balance shaft;

Rice. 1.11. Machine diagram mod. K121 for

1 - induction sensor; 2 - shaft; 3 - wheel being tested; 4 - electronic measuring unit; 5 - measuring device; 6 – resonant indicator

(stroboscopic lamp); 7-

graduated disc; 8 - oscillating system

The machine shaft with the wheel spins up to certain frequencies (usually from 500 to 800 min-1). The basis for determining the magnitude and location of unbalanced masses on the wheel is the principle of the occurrence of a difference in centrifugal forces located asymmetrically relative to the axis of the tire profile. The unbalanced mass of the wheel, due to the difference in centrifugal forces, causes mechanical vibrations of shaft 2 (Fig. 1.11), mounted on supports 3, which, through an oscillating system 8, with opposite springs, are transmitted to the induction sensor 1, which converts them into electrical impulses received into the electronic measuring unit 4, where they are converted into the corresponding voltage

tion supplied to the measuring device 5. Depending on the pulse duration, it shows the value of the unbalanced masses in grams, the position of which on the wheel is determined using a graduated disk 7 (rotating synchronously with the wheel under test) and a stroboscopic lamp 6 - the moment the lamp flashes corresponds to the lowest position unbalanced mass of the wheel, and due to the stroboscopic effect, it is fixed on a graduated disk, determining the exact location of the imbalance on the wheel.

At static wheel balancing(which should be carried out

ed dynamic), the machine shaft is disconnected from the drive, and it is performed as described above, only with the wheel positioned vertically.

- Balancing with weights is carried out in two planes: with dynamic balancing - in the external, with static balancing - in the internal.

8. Dismantling and installation of car wheels and tires.

Dismantling and installation of truck tirescars (for example, the front wheel of a car ZIL-130):

- apply the parking brake to the car and engage one of the gears;

- loosen the nuts securing the wheel to the hub. Using a jack, raise the end of the front seat until the wheel does not touch the platform. For safety, place a trestle and lower the end of the front axle onto it;

- Unscrew the loosened nuts securing the wheel to the hub, remove the wheel

With tire and place it on the platform with the locking wheel facing up;

- turn off the valve key cap, bleed air from the chamber, unscrew the spool from the valve. Study the structure and operation of the spool. Reinstall the spool and cap-key;

- remove the lock (split) and bead (uncut) rings (Fig. 1.12 a) to do this: insert a straight blade into the cut between the bead ring and the tire, press the tire bead down I; Insert a spatula into the gap formed with the curved grip II and press the tire bead down even more III; moving both blades sequentially around the circumference of the tire and pressing the tire bead down, remove it from the conical flange of the locking ring; insert a straight blade into the slot on the lock ring and press it out of the groove of the rim of wheel IV; Using a spatula with a curved grip, lift the lock ring V and, holding it in this position, place a straight spatula under the lock ring VI; Supporting the locking ring with your hands and a straight spatula, squeeze it until it completely comes out of the groove of the VII wheel rim; remove the side ring;

- turn the wheel and tire over and, using both mounting blades, remove the tire bead from the conical flange of rim VIII, repeating the operations described above;

Rice. 1.12. Truck wheel removal operations:

a - tires from a wheel, b - wheel disk with a straight mounting blade installed, c - sequence of tightening the wheel nuts.

Place the wheel and tire vertically and remove it from the tire, and remove the rim tape and tube from the cover.

Tire mounting on the wheel in this order:

Powder the inner and outer surfaces of the tire with talcum powder;

- insert the tube into the tire;

- pump some air into the chamber so that it takes its shape;

- insert a rim tape between the tire and the tube, spreading it evenly around the entire circumference;

- put the assembled tire on the wheel rim, simultaneously inserting the inner tube valve into the rim slot, and the bead ring onto the rim;

- press the bead of the tire in a place located at a distance of 1/4 of a circle from the valve, and insert one end of the locking ring into the groove of the wheel rim. Then, pressing the lock ring with your feet (starting from the inserted end and moving towards the other), insert it completely into the groove of the wheel rim. Place the other end of the locking ring into the groove of the wheel rim with a spatula;

- inflate the tire to a pressure of 60 kPa. If the bead of the tire in some places rests against the end of the lock ring, insert the lock ring under the bead of the tire by striking the outer bevel of the lock ring with a wooden hammer;

- inflate the tire with air to normal pressure (Table A.3), taking into account that when inflating the tire after installation, the locking ring can jump out of the rim groove and injure people standing nearby. Therefore, when inflating the tire with air, it is necessary to insert a mounting blade with a straight end into the holes of the wheel disk (Fig. 1.12 6) or place the assembled wheel with the tire under a safety grille, or a locking ring to the wall.

Wheel installation per car. When tightening nuts intended for wheel fastenings, the car is not suspended. The nuts are tightened gradually, alternating tightening through two nuts or crosswise (Fig. 1.12 c), which ensures uniform fit of the wheel disk to the hub flange. When tightening the nuts, you must ensure that their cones align with the holes.

on disk. When tightening the rim mounts of dual wheels, unscrew the outer wheel nuts at least two turns, and then tighten the nuts of the inner and outer wheels.

Dismantling and installation of passenger car tires(using the example of stand Ш501М).

The stand model Ш501М (Fig. 1.13) is designed for dismantling and mounting passenger car tires with a rim diameter of 13 to 16 inches (1 inch = 2.54·10-2 m). Air pressure in the cylinder is 0.5 MPa, productivity is 24 tires per hour. The working part of the stand is a pressure device - two levers with disks that are driven by a cylinder, and the rotation of the wheel is carried out by an electric motor.

bracket; 11 - pneumatic cylinder; 12 - control housing lever; 13 - stand cover

Dismantling and installation of passenger car tires on the stand of model Ш501М (see Fig. 1.13):

- install and secure the car wheel on stand 5 of table 4, place disks 7 under the tire beads, rest roller 6 on the wheel rim, supply compressed air to cylinder 11 and turn on electric motor 2 to drive the wheel rotation; the top side is brought out to the top shelf using a lever

- when mounting the tire, the tire is placed on the rim of the disk so that it is shifted slightly towards the levers of the pressure device, and the lower bead on the opposite side is placed under the upper shelf; tuck the tire into the rim of the disc on the machine, then remove its top bead using the dismantling lever, insert a slightly inflated inner tube into the tire

and roll up the side again.

The stand is controlled by a pedal for supplying air to the cylinder, a button for turning on the electric motor and a button for reversing it.

9. Camera repair. Camera repairs are performed on a model 6134 device (see Fig. 1.14). To do this, you need to: roughen the damaged area of ​​the chamber (up to 30 mm in size) on a corundum wheel and clean it of dust; coat the prepared patch made of unvulcanized inner rubber with glue once, apply it to the damaged area of ​​the inner tube and roll it with a roller from the middle to the edges; roughen the vulcanized rubber patch along the edge to a width of 40 - 45 mm, coat it with glue, dry it and cover the side coated with glue with a strip of raw chamber rubber 8 - 10 mm wide, then stick it on the camera and roll it with a roller; the chamber to be repaired is applied as a patch to the working plate 4 with a heating element and, using a pressure screw 1 and a special tile, is pressed tightly against the body 7, creating a pressure of 0.4 - 0.5 MPa (while the screw 1 is held by the clamp 2); signal lamp 6 lights up when the vulcanization temperature is reached (143° C).

The repaired chamber is checked for leaks by immersing it in a bath of water. The air pressure in the chamber is 0.05 - 0.1 MPa.

10. Diagnostics of shock absorbers.

The performance of shock absorbers determines the smoothness, stability and safety of vehicle movement. Insufficient smoothness, in case of faulty operation of shock absorbers, accompanied by frequent “breakdowns” and rocking of the car, reduces comfort, increases dynamic loads on the elements of the car and shortens their service life, contributes to uneven wear tire treads, etc.

In the auto repair industry, they mainly check removed shock absorbers on small power plants, driving them (according to the sinusoidal law) using crank mechanism, with variable stroke and rotation speed, determining graphically the dependence of the resistance force on the movement of the shock absorber. But for diagnostic purposes in ATPs and service stations, they use a method for quickly detecting shock absorber faults directly on the car, on special stands. There are two types of such stands: the first type of stands allows you to create long-term fluctuations wheels with variable frequency, at which it occurs resonance, amplitude which is an evaluation parameter; the second type of stands creates short-term fluctuations and is fixed number of decay cycles hesitation. For example, for domestic middle-class passenger cars, the amplitude of resonant oscillations should not exceed 50 mm, and the number of damped oscillations should be no more than one half-cycle. Stand of domestic production fashion. K-491, is almost identical in design to the stand of the Boge company (Germany) - see fig. 1.15.

Rice. 1.15. Shock absorber testing stand:

1 - lever; 2, 8 - electric motor; 3 - recorder; 4 - adjusting screw; 5 - spring; 6 - chart disks; 7 - flywheel; 9 - device for converting the rotational motion of the shaft into oscillatory; 10 - frame; 11 - platform for vehicle entry

These stands belong to the first type. Platforms with car wheels are set into oscillatory motion through springs (working in compression) using eccentric vibrators connected to electric motors. The shock absorbers (right or left) are checked one at a time. After starting one of the vibrators, it is turned off by pressing a button after 2-3 s, and after 10 s the relay turns on the drive for rotating the diagram disk and the recorder - recording the diagram of resonant oscillations lasts 5 s, after which the stand automatically turns off. Combined stands of foreign companies make it possible to measure both the amplitudes of resonant oscillations

tions and the number of damped cycles, and the measured parameters are given in the form of a digital indication on the scoreboard and on diagram cards (Fig. 1.16).

Rice. 1.16. Registration tapes of resonant vibrations of the suspension (body), issued when checking shock absorbers at the stand of the Boehm Muller company (France)

Upon completion of the work, students must write a report and make a technical conclusion.

Work order

1. Consider the classification, purpose, general structure and components, layout diagrams chassis of cars.

2. Familiarize yourself with textbooks, posters and diagrams, using existing equipment, with the main malfunctions of the chassis of cars,

with maintenance work, with basic control methods

And diagnostics, equipment and devices for their implementation

3. Carry out the necessary work specified in the task.

4. Prepare a report and make a technical conclusion.

Report preparation.

After completing the work, the student completes a report in which the following should be written:

1) topic and purpose of the work;

2) basic malfunctions of the chassis of vehicles;

3) installation angles of steered wheels and king pins, standard parameters;

4) basic methods of monitoring and diagnostics, equipment and instruments for their implementation, used when carrying out maintenance of vehicle chassis;

5) wheel balancing;

6) diagnostics of the technical condition of shock absorbers;

7) repair of tires and tubes, equipment for tire fitting and repair shops

8) make a technical conclusion about the work performed and the condition of the vehicle;

9) draw up an algorithm for diagnosing the chassis of a car, according to the option given by the teacher (execution sample

given in the appendix).

1) diagrams for diagnosing and maintaining the chassis of cars (Fig. 1.1, 1.2, 1.4, 1.7, 1.10, 1.11, 1.13);

According to option(Table 1.1) describe the process of adjusting the chassis of the car (if necessary, provide diagrams):

Table 1.1.Task options

Control questions.

1. List the typical malfunctions of frames, cabs and bodies, what are their causes, symptoms and possible consequences.

2. List the main malfunctions of suspension elements, their causes, symptoms and possible consequences.

3. Name the typical wheel malfunctions, their causes, symptoms and possible consequences.

4. What is the purpose of the installation angles of the steered wheels and king pins? What are the regulatory parameters?

5. List the main operations carried out by the driver when EOing the chassis of cars.

6. List the main operations TO-1 of the chassis of cars, characterize the equipment used in their implementation.

7. What is the procedure for checking the play and adjusting the bearings

8. What is the procedure for checking possible play in pivot joints, threaded and hinged joints of independent suspensions?

9. List the main operations performed during TO-2 of the chassis of cars, characterize the equipment used in this case.

10. Describe the posts for monitoring the installation of steered wheels and what equipment is used.

11. What is the method for adjusting the camber and toe angles of wheels, and for what purpose are non-adjustable parameters controlled?

12. What is the essence of static and dynamic imbalance of wheels?

13. Describe the method of static and dynamic balancing of removed wheels and what equipment is used.

14. What is the method for checking wheel balancing directly on a car, what equipment is used?

15. What are the main methods for diagnosing shock absorbers, what is their difference, what equipment is used for this purpose?

16. What is the procedure for mounting and dismantling tires on stands, characterize their design?

17. What is the technology for repairing tires and tubes, describe the equipment and technological equipment used in this?

When EO check the condition of the frame, springs, wheels.

At TO-1 check the play of the front wheel hub bearings; control the condition of shock absorbers, fastenings of stepladders, spring pins, wheels; check the condition of the tires and the air pressure in them; lubricate the joints of the vehicle's chassis.

At TO-2 check the condition of the front axle beam; Are the front and rear axles skewed? fastening spring clamps and shock absorbers; condition of wheel rims.

Maintenance of the vehicle chassis includes:

• periodically checking and adjusting the alignment angles of the front wheels
• checking clearances in front and rear wheel hub bearings and front suspension pivot joints
• checking the condition of the frame and spring suspension, including shock absorbers
• checking the condition of the tires and creating normal internal air pressure in them
• fastening and lubrication of chassis parts

Rice. Front wheel alignment angles

Checking the alignment of the vehicle's front wheels consists of measuring the toe angle of the wheels, the camber angle a, the transverse inclination angles p and the longitudinal inclination of the king pin.

Maintaining optimal steering wheel alignment angles ensures normal work front axle, stabilization of steered wheels, vehicle stability and controllability, reduction of wear of tires and front axle parts, as well as reduction of fuel consumption.

The steering wheel alignment angles of modern domestic cars vary within the following limits: the wheel toe angle ranges from +3′ to +45′. In practice, instead of angle b, the linear value of wheel toe is used, defined as the difference between distances A and B, measured in a horizontal plane passing through the centers of both wheels in their neutral position. The linear toe-in value ranges from 1.5 to 3.5 mm for cars and from 1.5 to 12 mm for trucks; The camber angle a is from -30′ to +30′ for cars and from +45′ to +1°30′ for trucks. This angle is considered positive when the wheel is tilted outward and negative when tilted inward; the lateral inclination angle of the kingpin is from 5°30′ to 7″50′ for cars and from 6 to 8° for trucks, and the longitudinal inclination angle of the kingpin is from 0° to 1°47′ for cars and from 1° to 3° 30′ for trucks. Full control of the front wheel alignment angles is carried out only on passenger cars with independent front wheel suspension and low air pressure in the tires. In this case, even small (15’-20′) deviations from the norm in the camber and kingpin angles significantly affect tire wear and worsen the vehicle’s driving stability. For trucks, they are limited to checking the amount of toe-in of the front wheels and the clearances in the pivot joints and wheel hub bearings.

Vehicle wheel alignment angles are checked using stands and portable instruments.

According to the principle of operation, stands are divided into mechanical, optical, optical-electrical and electrical, and portable devices - into mechanical, liquid and optical-electrical.

Before checking the vehicle wheel alignment angles, the air pressure in the tires is checked and adjusted to normal, the chassis and steering parts are inspected, the fasteners are tightened, and faulty parts are adjusted and replaced. If necessary, adjust the tightening of the front wheel hub bearings, eliminate excessive clearances in the steering rod joints, secure the steering gear housing and add fluid to the shock absorbers.

Telescopic (sliding) ruler for checking the toe-in of the front wheels

The simplest device for monitoring the toe-in of the front wheels is a telescopic (sliding) ruler.

Rice. Ruler for checking the toe angles of the front wheels of a car:
a - ruler; b - installation of the ruler;
1 - movable pipe; 2 - fixing screw; 3 - scale; 4 - fixed pipe; 5 - intermediate pipe; 6 - clamp; 7 - extension; 8 - tip; 9 - chain; 10 - spring; 11 - arrow

The ruler is installed between the wheels in front of the front axle in a horizontal position so that the conical stops are in the same vertical direction. plane a-a with the edges of the rims located at the level of the wheel centers; in this case, the chains at its ends should touch the floor. The scale is moved until the pointer aligns with the zero division, then the car is moved forward until the ruler takes a symmetrical position behind the front axle. Moving the scale relative to the fixed pointer allows you to determine the linear amount of wheel toe.

When measuring with a ruler, it must be borne in mind that automobile factories in technical specifications For cars, the dimensions that determine the amount of toe-in are referred to the wheel points located on the inner edge of the rim or on the side surface of the tire at the height of the center of the wheel. Using data from automobile factories when measuring with a ruler leads to inevitable errors reaching 30-35%.

Therefore, when taking measurements with a GARO ruler, it is necessary to be guided by the control wheel toe values ​​specified for this ruler.

The toe angle of the wheels is adjusted by changing the length of the tie rod.

Rice. Scheme for measuring the toe-in of the front wheels: AA’ - according to the method of the Automobile Plant named after. Likhacheva; BB’ - according to the Gorky Automobile Plant method; BB’ - when measuring with a GARO ruler

Rice. Scheme of independent car wheel suspension

The camber angle of the wheels on cars with a solid front axle is not adjusted. Its deviation from the normal value indicates wear of the pins and pin bushings or bending of the axle.

For vehicles with independent wheel suspension, angle a is adjusted using an eccentric bushing and a threaded pin 2 connecting the suspension strut 3 to the lower arm 1.

In similar suspension designs that have eccentric bushings with threads, these bushings also regulate the longitudinal angles of the king pins.

Regardless of the design of the device or stand, the principle of determining the camber angles of the wheel and the inclination of the king pin is the same.

The camber angle a of a wheel is measured in two ways: as a geometric angle between the middle plane of the wheel and the vertical or as an angle between the axis of the steering axle and the horizontal plane. Since physically the middle plane of the wheel and the axis of the steering axle cannot be used to directly measure the angle, the sidewall of the tire or the flange of the wheel rim is almost often taken as the basis for measuring it.

The angles of inclination of the kingpin are measured on the basis of established geometric relationships and patterns of changes in the camber angle of the wheel depending on its rotation.

Rice. Methods for measuring the camber angle of the front wheel

Portable liquid device (model M-2142) for determining all front wheel alignment angles

Rice. A portable liquid device for checking the alignment angles of the front wheels of a car: 1 - rod; 2 - bracket; 3 - wheel angle meter arrow

A portable liquid device (model M-2142), with the help of which all angles of the front wheels of a car can be determined, consists of two independent parts:

• spirit level A with double level
• wheel rotation angle meters B, mounted in boxes (for right and left wheels)

Rice. Spirit level of the M-2142 device for determining wheel alignment angles

The spirit level has two mutually perpendicular levels on the front side with three scales. Scale 3 is used to determine the angle of transverse inclination of the kingpin, scales 5 and 6 - respectively, to determine the angles of longitudinal inclination of the kingpin and wheel camber. On the back of the device there are two installation levels without scales.

To determine the camber angle of the wheels, the car is placed on a horizontal floor area; The front wheels should be in a neutral position (corresponding to straight motion). The device with levels is secured using clamp 2 on nut 1 of the disk or on the wheel hub in a horizontal position with the back side up.

Rice. Diagram for determining the wheel camber angle

Rice. Scheme for determining the angle of transverse inclination of the king pin: 1st level of the device; 2-pin

The edge of the device body on the side of scale 3 should be parallel to the wheel rim. Turning the device on the hinged head of the clamp, install it so that the bubbles of 4 levels are located in the slots on the back of the device, and tighten the screw of the hinged head. Then move the car forward or backward so that the wheel turns half a turn, i.e. 180°, relative to its original position. As can be seen from the figure, after the wheel rolls, the level plane will make an angle with the horizontal plane that is twice as large as angle a. The displacement of the level 4 bubble indicates on scale 6 the actual camber angle of the wheels.

The lateral inclination angle of the kingpin is measured using the dependence of the change in angle made by a straight line located in a horizontal plane parallel to the plane of the wheel disk. First, level 1 of the device is placed horizontally and parallel to the plane of the wheel disk, then it is rotated around the axis of the king pin 2. In the figure, the wheel is conventionally rotated by 90°. In this case, level 1, remaining parallel to the plane of the wheel, will take an inclined position to the horizon at an angle B.

When measuring the longitudinal inclination angle of the kingpin, the level is placed perpendicular to the plane of the wheel disk. If you conventionally turn the wheel from the neutral position through an angle of 90°, the level will deviate from the horizontal by an angle equal to y.

Since it is not possible to actually rotate the wheel by 90 or 180°, when using the device the wheels are turned to a smaller angle (40°); in this case, the levels will deviate by an angle slightly smaller than B or y, but the instrument scale is calibrated to the values ​​of the actual angles.

The angles of inclination of the king pin using the above device are determined as follows. Wheels mounted on swivel rims must be in the neutral position. The boxes with scales are moved towards the wheels so that the rods 1 with the bracket rest on the wheel tire below the hub, and the arrow of the wheel rotation angle meter is positioned against the zero division of the scales. Then the wheel is turned to one side by 20° according to the left wheel scale indicator and braked. After this, spirit level A is installed so that the bubbles of the transverse and longitudinal levels are at zero division, and the edge of the spirit level on the side of the transverse level is parallel to the wheel.

Rice. Scheme for determining the longitudinal inclination angle of the kingpin: 1 - device; 2 - kingpin

Having installed the device, turn the wheels in the other direction from the zero division of the rotation angle meter scale by 20° and use scales 3 and 6 to determine the angles of inclination of the kingpin of a given wheel. In the same order, determine the installation angles of the other wheel. At the same time, by the position of the meter arrows and scales, the ratio of the wheel rotation angles can be determined. Incorrect steering angles lead to increased tire wear.

Stationary optical stand for monitoring the alignment of the front wheels

The figure shows a diagram of a stationary type optical stand for monitoring the installation of the front wheels. At this stand, all installation angles are measured using the optical method, with the exception of the lateral inclination angle of the kingpin, which is determined by a level.

The optical system of the stand consists of a stand 3 with a measuring microscope 4 and an inclined mirror 2, a platform with a measuring scale 1 and a mirror reflector 5 mounted on the front wheel, to the rim of which it is attached using a bracket 7. The mirror reflector consists of three mirrors. The middle mirror is located parallel to the plane of the wheel, and the other two are inclined to it in a vertical plane at an angle of 20°. On the upper side of the mirror reflector frame there is a level 6, on the scale of which the lateral inclination of the car’s wheels is determined. Microscope 4 is mounted on prismatic guides that allow it to move along the optical axis perpendicular to the longitudinal axis of the stand. On the objective lens of the microscope telescope 4 there are two mutually perpendicular lines I-I and II-II.

Rice. Diagram of the optical stand GARO model 1119 for measuring the alignment angles of the front wheels of a car

On the platform with measuring scale 1 there are also two mutually perpendicular lines with divisions (scales), of which the vertical one serves to measure camber angles, and the horizontal one serves to measure toe angles and wheel rotation angles. The longitudinal angle of inclination of the king pin, determined by the change in the camber angle when turning the front wheel to the right and left by 20″, is measured on a vertical scale. The transverse angle of inclination of the king pin is measured at level 6 as a result of a change in its inclination also when the wheels are turned to the right and left by 20° from the average position. When measuring the angles of their installation and the correct rotation angles, the wheels are installed on rotary disks 8.

The principle of measurement on an optical stand is to determine the angle of inclination of a mirror reflector installed parallel to the plane of the wheel by the amount of displacement of the cross-shaped scale image relative to the reticle of the microscope or two intersecting lines marked on the lens of its telescope.

When determining the camber angle, the wheel is turned to a position in which the vertical line of the microscope lens coincides with the vertical measuring scale; then the horizontal line I - I of the microscope lens will show the wheel camber angle on the camber scale.

When measuring the camber angle of the wheel using the 4th scale division visible in the microscope eyepiece, we obtain a double angle. Increasing the angle of reflection visible on the scale compared to the actual tilt of the mirror or wheel increases the accuracy of the measurement.

The toe-in angle of the wheels is determined using the same stand installation as for measuring the camber angle, i.e., when installing one wheel (right or left) parallel to the longitudinal axis of the car. In this case, the second wheel turns to double the toe angle.

Figure d shows a diagram for measuring the toe-in of the wheels of a car with a front-mounted steering linkage. The displacement of the vertical sighting line of the microscope eyepiece crosshair to the right (line II-II) or to the left relative to the zero point of the horizontal scale of the measuring platform indicates, respectively, a negative or positive toe-in of the wheels.

Kingpin casting angle Measure with the wheels braked by turning the wheel first to the right by 20° until the vertical sighting line of the microscope coincides with the zero of the convergence scale, then to the left also by 20° until the vertical line of the microscope and the scale coincide. Using the camber scale, the angle a is measured in two positions and the angle y is found from the difference of these angles.

Kingpin lateral inclination angle determined by the level installed on the frame of the mirror reflector. To do this, turn the wheel 20° to the left, set the level to zero on its scale, then turn the wheel 20° to the right and read off the value of angle B using the level scale.

Mechanical stands

Mechanical stands, which are currently most widespread, are simpler and more common. These stands have a metal platform on which the car is mounted, turntables for the front wheels and two measuring heads with scales. In mechanical stands, only three out of five angles are usually measured: camber, toe and wheel steering ratio.

The figure shows a general view of the mechanical stand. Measuring head 1 is installed on a special frame 4 located across the inspection ditch. In the middle part of the frame there are rotary disks 2 and hydraulic jacks 3.

Rice. General form mechanical stand for measuring wheel alignment angles of passenger cars

The rotary discs are equipped with a scale 5 and an indicator 6, allowing you to check the ratio of the steering angles of the front wheels. Jacks are used to hang wheels while determining their points of equal runout in order to more accurately measure angles. The measuring head has a rod 1 that moves longitudinally in conical bushings 2. At the end of the rod there is a roller 8, around which a rod 10 rotates. Thrust tips 9 move along the rod, coming into contact with the side surface of the tire or the edges of the wheel rim when measuring angles. The rod 10, turning with the rod 1, can be installed in horizontal and vertical positions.

The rotation of the rod relative to the roller 8 through the lever mechanism 4, 5 and 6 is transmitted to the arrow 3, indicating the measured angle on the scale.

To measure toe angles, the rod is installed in a horizontal position and moved together with the rod towards the wheel until the thrust tips come into contact with it. When measuring camber angles, the rod is installed in a vertical position. The angle of rotation of the rod relative to axis 8 is fixed by arrow 3 on scale 7. The ratio of the angles of rotation of the car wheels is determined by the scales of the rotary disks. It must be borne in mind that in the factory instructions the installation angles of the front wheels of domestic passenger cars are indicated taking into account their full load.

On passenger cars with independent front wheel suspension, when there is no load, the camber and lateral inclination angles of the kingpins are significantly reduced. Therefore, in order to avoid errors when adjusting the alignment of the front wheels of unloaded vehicles, it is necessary to adjust the value of the adjustable angles in the direction of increasing the minimum angle value (for example, for GAZ-21 Volga vehicles by 20″).

Measuring radial and axial clearances in kingpins

Wear in the pivot joint of the front wheels of trucks is controlled by the size of the radial and axial clearances.

The radial clearance (LR) in the pivot joint is determined by the movement of the steering axle relative to the pivot when lifting and lowering the front axle with a jack (until the wheel rests on the floor).

As can be seen from the diagram, the camber angle of the wheel when lowered to the floor decreases due to the gaps formed due to wear of the pin and bushing.

Rice. Stand measuring head

The movement of the axle is recorded using indicator 1, installed on the front axle beam using clamp 3. The indicator rod is in contact with the lower part of the supporting brake disc 2. Since the diameter of the disc is approximately twice the length of the kingpin, the indicator shows a radial clearance twice as large as the actual one, which increases measurement accuracy. The radial clearance for trucks (such as ZIL and GAZ) should not exceed 0.75 mm.

The axial clearance is measured with a flat feeler gauge inserted between the upper eye of the axle and the front axle knuckle.

An increased gap between the bearing race and its seat in the hub and the degree of tightening of the wheel hub bearings can be detected by rocking the wheels in the transverse plane after eliminating the play in the pivot joint. When adjusting the clearance in the bearing, its nut is tightened with a wrench with a torque handle with a certain force. When using a simple wrench to adjust, the nut is first tightened before the wheel starts braking in a suspended state, and then unscrewed 1/3 - 1/2 turn until the wheel begins to rotate freely. A correctly adjusted wheel should rotate at least 8-10 revolutions when pushed by hand.

Rice. Changing the position of the front wheel in the presence of a gap in the pivot joint: a - in a raised state; b - in a lowered state

Checking dynamic wheel balancing

For passenger cars, dynamic wheel balancing must be checked periodically.

When monitoring the technical condition of tires, they are inspected, the air pressure is checked, the tires are inflated, sharp objects stuck in the tread are removed (glass, nails, etc.), the gap between dual tires is checked (20-30 mm for small tires and 40- 50 mm - large size), check the condition of the valve and wheel rim (presence of dents, burrs and corrosion). The production of vehicles whose tire pressure does not meet the standard is not permitted.

To measure air pressure in tires, piston or spring type pressure gauges are used. The piston-type pressure gauge is pressed with tip 1 to the chamber valve, recessing the spool. From the chamber, air enters through the channel of the tip under the piston 2 and moves it, compressing the calibrated spring 3. Along with the piston, a brass cylindrical screen 4 painted in red moves, sliding along the guide tube 5. When the pressure gauge is removed from the valve, the piston under the action of spring 3 will return to original position, and the screen will remain in place.

In the upper part of the pressure gauge body there is a window covered with transparent celluloid, on which a scale of divisions 6 is applied. The air pressure in the tire is determined by the edge of the screen 4 and scale 6. The accuracy of the pressure gauge readings is within the price of one scale division (0.1 or 0.2 kg/cm2).

Rice. Piston type pressure gauge

Rice. Diagram of a tip with a pressure gauge for inflating tires with air:
1 — button; 2 and 10 - springs; 3, 6 and 8 - saddles; 4 and 9 - valves; 5 - pressure gauge; 7 and 11 - fittings

Piston pressure gauges are used primarily in road conditions. To monitor air pressure in tires in garages, nozzles with a pressure gauge are used for the air distribution hose from the compressor or air line. The diagram of a tip with a spring-type pressure gauge is shown in the figure.

When the button is released (position I), valve 4, under air pressure entering through fitting 7 from the hose connected to the tire, and valve 9, under the action of spring 10 and air pressure entering through fitting 11 from the line, are pressed against seats 3 and 8, respectively. Pressure gauge 5 in this case shows the air pressure in the tire. When button 1 (position II) is pressed all the way, air from the air line enters the tire.

When button 1 is pressed incompletely (position III), valve 9 will be pressed against seat 8, and valve 4 will be in an intermediate position. In this position, the air from the tire can escape and the air pressure in it will decrease until the button reaches its extreme position (I). This makes it possible to set the required air pressure in the tire.

Compressed air for inflating tires is obtained from compressor units, and air dispensers are used to distribute air.

An air dispenser is a device consisting of a mechanism (pressure regulator) that controls the air pressure to which the tire should be inflated, and a hose that automatically turns off the compressed air supply; sometimes the column has a mechanism for automatically winding a long hose onto a drum.

Automatic pressure regulators according to their operating principle can be divided into pneumomechanical and electromechanical.

The setting and adjusting device in regulators of the first type is an air pressure gauge and a spring that balances the air pressure, and the second type is an electric contact pressure gauge. The actuator in pneumomechanical regulators is a shut-off flat or ball valve, and in electromechanical regulators it is a solenoid solenoid valve. The schematic diagram of the first type of regulator is shown in the figure. The air pressure regulator is set to the required position by turning the handwheel 1, which compresses the spring 3; spring 3 through pusher 2 presses on diaphragm 4 and then on valve 5, which in this case will be in the open state and allow air from the air line into the cavity under the diaphragm.

Rice. Air pressure regulator operation diagram

By turning handwheel 1 with valve 6 closed, the opening value of valve 5 is changed (throttled by air pressure) until the required air pressure value is established on pressure gauge 7. After this, tap 6 is opened and the column is connected to the valve of the inflated tire. As soon as the tire reaches the air pressure set by the pressure gauge, excess pressure will arise under the regulator diaphragm, unbalanced by the spring; in this case, the diaphragm, bending upward, will compress the spring and release valve 5, which will shut off the air supply from the line.

Plan - outline

industrial training lesson

Topic: Car maintenance.

Lesson topic: Maintenance of mechanisms and parts of vehicle chassis.

Purpose of the lesson: to form in students the basic concepts of maintenance of mechanisms and chassis parts of automobiles.

Educational goal: instill in students conscientious attitude to study the material presented.

Type of activity – a lesson in presenting new material.

2. Main part of the lesson – 70 min.

Study questions:

Basic malfunctions of mechanisms and parts of the chassis of cars.

The main work performed during the maintenance of mechanisms and parts of the chassis of automobiles.

1. Chassis malfunctions .

As a result of overload and careless driving, the frame may bend, cracks may appear in it and rivets may become loose. The frame is repaired in the workshop, the bent frame is straightened, loose rivets and frame parts with cracks are replaced.

The main malfunctions of the front and rear axles include: bent front axle, wear of kingpins and kingpin bushings, incorrect adjustment or wear of bearings, bearing breakage, development of bearing race mounting locations, and breakage of axle shaft stud threads. A bent front axle, worn kingpins and bushings, improper alignment, or worn wheel bearings will result in improper wheel alignment, making the vehicle difficult to control and

Tire wear increases, which negatively affects driving safety, a bent axle must be corrected, worn pins, bushings and wheel bearings must be replaced.

The front wheel bearings are adjusted in the following sequence: lift the front axle and install it on the trestles, remove the wheel, unscrew the cap, unscrew and unscrew the nuts, remove the hubs, wash and inspect the bearings (if there is a crack or significant wear, replace the bearings), fill the hub with lubricant and put in place, install the washer and tighten the nut until it stops, and then unscrew it 1 / 8 turnover. The wheel should rotate freely, without jamming and have no play. After checking, the nut is cottered and the cap is screwed on.

On trucks, the rear wheel bearings are adjusted in the same sequence, except that instead of the cap, you need to unscrew the axle stud nuts and remove the axle shafts, and instead of removing the cotter pin, you need to unscrew the lock nut and remove the lock washer. Defective wheel hubs are repaired or replaced with new ones. Driving with faulty hubs can lead to an accident.

As a result of prolonged operation, the spring leaves partially lose their elasticity, and the pins and bushings wear out. If you drive carelessly, the spring leaves break. Springs that have lost their elasticity sag more than usual, causing the tires to rub against the body and quickly wear out. In addition, such springs break easily.

Driving a car with a broken spring can cause the axle to skew and make it difficult to control. Springs that have lost elasticity or have broken leaves are replaced.

The shock absorber's seals, joints, valves and springs wear out. As a result of wear of the seals, fluid leaks out and the performance of the shock absorber deteriorates sharply. A faulty shock absorber must be sent in for repair.

As a result of careless driving, the wheels or rims may be bent. If the wheel studs and nuts are not tightened, the disk holes for the fastening studs wear out and the disks become unusable. Defective wheels are sent in for repair. Driving with faulty tires is dangerous.

Malfunctions tires Holes or punctures of tires with sharp objects, delamination of the frame, peeling of the tread, destruction of the bead ring, puncture or rupture of the tubes - all these defects are usually the result of careless driving, non-compliance with air pressure standards in tires and failure to comply with the rules for servicing automobile studs To repair tires on the road The car must have a first aid kit.

The damaged tire must be removed and thoroughly inspected. Stuck nails and other objects must be removed. If there are large holes in the tire, it is necessary to install a cuff made from two or three layers of a piece of a scrap tire frame or from a piece of rim tape. Upon returning to the garage, the damaged tire must be sent in for repair. To restore the tread, tires that do not have carcass delamination and through holes are accepted. To detect small punctures in the chamber, it is inflated with air and immersed in water. Air bubbles will come out at the damage site.

Punctures or minor damage along the way can be repaired with a rubber patch. The area of ​​the chamber within a radius of 20...30 mm around the damage is cleaned with a rasp or steel brush and patches of raw rubber are applied, a cup with a vulcanizing briquette is applied and clamped with a clamp (Fig. 1). The briquette is loosened and lit, after complete combustion of the briquette, after 10... 15 minutes, unscrew the clamp screw and remove the chamber.

Temporary sealing of chamber punctures in the absence of vulcanization briquettes can be done with a patch from a scrap chamber using rubber glue.The edges of the patch are cut to a cone. The patch and the chamber area around the damage are thoroughly cleaned with a rasp or steel brush, dust is removed, washed with gasoline and dried, then coated twice with rubber glue and dried after each coat for 15...20 minutes. After drying, the patch is applied to the damaged area and rolled.

Malfunctions in the external or internal threads of the valve are corrected with a die or tap, and the faulty spool is replaced.The valve must be closed with a cap to prevent dirt from entering.

2. Basic work By chassis maintenance.

EO. Inspect the condition of the frame, springs, suspension, shock absorbers, and wheels.

TO-1. Check and, if necessary, adjust the wheel hub bearings; check and, if necessary, secure stepladders, spring pins and wheel nuts. Lubricate (according to the lubrication schedule) the spring pins and the pivot pins of the steering axles. Check the condition of the car's front suspension.

TO-2. Inspect the condition of the front axle beam. Check and, if necessary, adjust the amount of toe-in

front wheels. If tires wear heavily, check the angle of the king pins and the steering angle of the front wheels. Check for misalignment of the front and rear axles (visually).

Check the condition of the frameAndtowing device, condition of springs, secure spring clamps, stepladders, spring pins.

Check the condition of shock absorbers, discs and wheel rims.

Lubricate (according to the lubrication schedule) the pivot pins and spring pins. Remove the hubs, wash, check the condition of the bearings and, after replacing the lubricant, adjust the wheel bearings.

Wheel alignment is checked using a ruler or on a stand. To check wheel alignment with a ruler, the car is placed on an inspection ditch so that the position of the wheels corresponds to movement in a straight line. Use a ruler to measure the distance between the tires or wheel rims at the rear of the front axle; The ruler is placed below the wheel axis (at the height of the ruler chains) and the points of contact are marked with chalk. Then the car is rolled so that the points marked with chalk are at the same height in front, and measured again. A number indicating the difference between the firstAndThe second measurement is the wheel toe value.

During inspection, maintenance and repair of the chassis, safety regulations must be followed. When installing springs, do not check the alignment of the holes in the spring and the bracket ears with your fingers, as this can lead to injury. When assembling the spring after lubrication, it must be properly secured in a vice so thatthe sheets, when straightened, did not cause injury,

Basic technical work service tires

EO. Clean the tires from dirt and check their condition.

TO-1. Check the condition of the tires, remove foreign objects stuck in the tread and between the dual tires, the air pressure in the tires and, if necessary, pump air into them.

TO-2. Inspect the tires, removing any stuck objects in the tread. Check the air pressure and bring it to normal. Rearrange the wheels according to the diagram. Send damaged tires for repair. Tire serviceability is a prerequisite for the driver’s safe work on the line. The absence of a tread pattern impairs the braking capabilities of the vehicle, so it is prohibited to use tires with a worn tread pattern.

Tire reliability is also a prerequisite for vehicle operation. Holes, as well as a rotten frame, can lead to a tire rupture while the vehicle is moving and an accident. Driving on half-flat tires, in addition to their rapid wear, is dangerous due to the car pulling to the side.

Control questions.

List the main frame faults.

List the main faults of springs.

List the main malfunctions of shock absorbers.

List the main malfunctions of wheels and tires.

List the main work carried out during the EO of the chassis of cars.

List the main work carried out during maintenance - 1 of the chassis of cars.

List the main work carried out during maintenance of the 2nd chassis of cars.

List the main work carried out during maintenance, maintenance - 1 and maintenance - 2 of car tires.