4.2. Back suspension bracket

Possible malfunctions of a back suspension bracket, their reason and ways of elimination

Features of a design
Back suspension bracket dependent spring, with the shtangovy directing mechanism and hydraulic shock-absorbers of telescopic type of bilateral action.

Fig. 4.13. Back suspension bracket: 1 – plug expansion shock-absorber; 2 – nut; 3 – the shock-absorber is back; 4 – nut of fastening of the top bar; 5 – arm of the top bar; 6 – the bar is top; 7 – shock-absorber cover; 8 – the cover is restrictive; 9 – shock-absorber pillow; 10 – laying top springs; 11 – spring cup; 12 – spring; 13 – compression buffer; 14 – laying lower springs; 15 – the bar is cross; 16 – the bridge is back; 17 – nut; 18 – the plug is expansion; 19 – plug; 20 – the bar is lower; 21 – bolt of fastening of a bar; 22 – bolt of fastening of the shock-absorber; 23 – shock-absorber plug

The directing mechanism consists of two top bars of 6 (fig. 4.13), two lower longitudinal bars 20 and one cross bars 15 which are connected to arms of a body and the back bridge via rubber-metal hinges bolts with the self-stopped nuts.
Twisted cylindrical springs 12 with rubber laying 10 above and plastic laying 14 are below established between a body and a beam of the back bridge.
The top end of the shock-absorber 3 fastens to an internal mudguard of a sidewall through rubber pillows 9, lower – connects to an arm of the back bridge via two rubber plugs 23 and the expansion plug 1.
The course of a beam of the back bridge is limited to two rubber buffers 13 up.

Definition of technical condition
Check of technical condition of a back suspension bracket comes down to periodic surveys of bars and their rubber plugs, springs and their laying, rubber plugs and covers of shock-absorbers, compression buffers. At detection of wear of rubber plugs, destructions of buffers, gaps and cracks of covers of shock-absorbers, breakages of springs them it is necessary to replace new.
You will correct the deformed bars or replace. Wear of rubber plugs is defined as visually, and rocking of a back part of the car for identification of gaps in places of fastening of bars and shock-absorbers.

Repair of the shock-absorber
1. Disconnect the lower end of the shock-absorber from an arm, having turned off a nut 2 (see fig. 4.13) and having taken out a bolt 22.
2. Turn off a nut of the top fastening of the shock-absorber, holding a shock-absorber rod from a provorachivaniye.
3. Remove a restrictive cover 8 and a pillow of the 9th shock-absorber.
4. Take out the shock-absorber through a wheel niche.

Fig. 4.14. Installation of the shock-absorber in a vice for dismantling by a special key

5. Install the shock-absorber in a vice, having clamped a tank eye on end faces (fig. 4.14).

Fig. 4.15. A special key for a shock-absorber tank nut otvorachivaniye

Fig. 4.16. Shock-absorber of a back suspension bracket: 1 – rod; 2 – plug; 3 – the cover is restrictive; 4 – the ring is protective; 5 – laying; 6 – epiploon holder; 7 – tank epiploon; 8 – spring of the perepuskny valve; 9 – piston ring; 10 – the disk is throttle; 11 – valve disk; 12 – the plate is basic; 13 – valve spring; 14 – the washer is adjusting; 15 – valve nut; 16 – plate of the inlet valve; 17 – valve; 18 – spring of the inlet valve of compression; 19 – cup; 20 – valve case; 21 – valve spring; 22 – tank; 23 – working cylinder; 24 – piston; 25 – plate of the perepuskny valve; 26 – limiter; 27 – guide; 28 – rod epiploon; 29 – tank nut; 30 – washer

6. Extend a rod against the stop and turn off a special key (fig. 4.15) a nut of the 29th tank (fig. 4.16).
7. Take out from the tank the working cylinder 23 and a rod 1 with the details fixed on it.
8. Carefully copper hammer beat out a guide of the 27th rod from the working cylinder.
9. Take out from the cylinder the piston 24 with a rod and merge liquid.
10. Carefully copper core beat out the compression valve from the cylinder.
11. Release the tank from a vice and merge from it liquid.
12. Clamp a rod with the piston in a vice for a lyska on the top end and turn off a nut of the 15th valve of a release.
13. Remove the piston with valves (perepuskny and a release), a guide of the 27th rod, an epiploon of the 28th rod, a holder of the 6th epiploon, other details.
14. Install on a workbench the compression valve by a cup 19 up and take a cup 19, a spring of the 18th valve of compression, the valve of compression 17.
15. You carry out check and assembly of the shock-absorber in the same way as damping rack of a forward suspension bracket.
16. Install the shock-absorber upside-down. The final inhaling of nuts of fastening of shock-absorbers is carried out at full loading of the car.

Non-demountable shock-absorbers of a back suspension bracket

Fig. 4.17. Non-demountable shock-absorber of a back suspension bracket: 1 – rod; 2 – the piston with the release valve; 3 – compression valve; 4 – tank; 5 – cylinder; 6 – place of marking

The Izh-21261 cars along with folding back shock-absorbers 2123-2915006 (see fig. 4.16) are completed with shock-absorbers 2126-2915006-07 (fig. 4.17) of a non-demountable design of production of JSC Skopin Auto-Aggregate Plant.
The dimensional and adjusting sizes of new non-demountable shock-absorbers (further called "shock-absorbers") same, as old folding.
Repair of shock-absorbers comes down to their replacement. The shock-absorbers installed on the Izh-21261 cars have to meet the following requirements.
Shock-absorbers have to be painted black Pental-Amor soil-enamel of TU 2312-019-49331636-99 or black primer GF-089 of TU 6-10-883-78. Availability of paint on a surface of a rod is not allowed.
Shock-absorbers have to be tight. Tests on tightness are carried out at the stand for removal of charts like Miletto and by pumping within one minute with a frequency of 150 cycles a minute. At the same time temperature of shock-absorbers should not exceed 100 °C.
The subsequent check consists in endurance during 12 h in vertical position a rod down at a temperature of 20 °C. The rod at the same time has to be put forward to the full. In process and after tests the leak of working liquid is not allowed.
During the operation of the shock-absorber the knock, a scratch, jammings is not allowed. The puffing caused by an overflowing of damping TU 0253-048-05767924-92 TU 0253-025-00128599-2001 or GRZh-12 liquid "Lukoil EVEN" through throttle openings is allowed. Assessment of noisiness is made in comparison with control samples at the stand for removal of charts.
The effort of shift of a rod of the shock-absorber should not exceed 50 N (5 kgfs), check is made at a temperature of 20 °C. The shock-absorber is installed horizontally and fastens for the lower eye, 5 full cycles "stretching compression" are made. To a rod the dynamometer of DPU-0,1/2 of GOST 13837 fastens, and the stretching effort until the beginning of shift of a rod smoothly increases. It is allowed to make check of effort of shift of a rod by the annex to the lower eye of the control freight suspended for a rod. At the same time the weight of moving parts of the tank is accepted equal 10,29 N (1,05 kgfs). The effort of resistance of the shock-absorber at a piston stroke of 100 mm, at a temperature of 20 °C has to be equal:
– with a frequency of 100 cycles a minute of 123-165 kgfs at a release and 41–61 kgfs at compression;
– with a frequency of 80 cycles a minute of 115-150 kgfs at a release and 36–54 kgfs at compression;
– with a frequency of 30 cycles a minute of 46-85 kgfs at a release and 14–42 kgfs at compression.

Fig. 4.18. Form of the chart of non-demountable shock-absorbers of a back suspension bracket

Removal of working charts and determination of the maximum efforts of resistance of shock-absorbers at the course of a release and compression are made at dynamometer stands like Miletto or the SI-46. The form of working charts has to correspond to the data shown in fig. 4.18. Shock-absorbers have to pass bench resource tests during 2 million cycles.
Tests are carried out under following conditions:
– course of the drive of a kolebatel (80±1) of mm;
– frequency of fluctuations (235±5) cycles in a minute;
– temperature of the case of the shock-absorber (80±5) °C;
– after 2 million cycles loss of liquid should not exceed 10% of the initial volume of (250±5) cm3.

Replacement of springs of a back suspension bracket
1. Remove shock-absorbers of a back suspension bracket on both sides (see. "Repair of the shock-absorber").
2. Disconnect from an arm on a beam of the back bridge pressure regulator drive rack.
3. Disconnect from an arm on a body a cross bar 15 (see fig. 4.13).
4. Establish on both springs of the 12th device for a coupler of springs and squeeze springs a little.
5. Raise a back part of the car (at the same time wheels have to remain on the earth).
6. Take out springs.
7. Remove from springs of laying 10 and 14, a cup 11 and devices for a coupler of springs.
8. For check of draft of their springs it is triple squeeze before contact of rounds. Then springs squeeze up to the height of 205 mm (dimensional height of working rounds). At the same time the effort of compression has to be not less than 2943 N (300 kgfs). If effort of compression less, so springs "sank" and they need to be replaced. Before compression establish on springs basic washers with the screw surface corresponding to raising of trailer rounds (12,5 mm on an arch 240 °).
9. Check a condition of laying of 10 and 14 springs and if necessary replace them new.
10. Establish springs upside-down. The final inhaling of nuts of fastening of a bar and shock-absorbers is carried out at full loading of the car.