SANY SRT95C Off-Highway Truck. Service Manual

Rear Suspension System

21 REAR SUSPENSION SYSTEM

21.1 Rear Suspension System

Fig.1 Cutaway View of Typical Rear Suspension Cylinder

1.Snap ring

10.Seal

19.plug

2.Bearing

11.Wear ring

20.Guide sleeve

3.Oil fitting

12.Retainer ring

21.Buffer seal

4.Plug

13.O ring

22.Seal-wiper

5.Charge valve

14.Ball

23.Retainer ring

6.Dust boot

15.Bolt

24.Bolt

7.Bolt

16.Cylinder tube assy.

25.Clamp

8.Plate

17.Piston

26.Piston rod

9.Retainer ring

18.Wear ring

OVERVIEW

Numbers in parentheses refer to Fig.1.
Oil/gas (nitrogen) rear suspension cylinder is
an elastic device suspending to the rear part
of mining car. It is installed to the rear part
of each longitudinal beam of frame, under
the body and above rear drive axle. The rear
suspension cylinders are used to absorb road
shocks, when the truck hits a bump on the
ground.

Rear Suspension System

OPEARATION

Numbers in parentheses refer toFig.1.
The rear suspension cylinder is composed
of two assembly. Piston rod assembly (26) is
installed to the frame through pin. Cylinder
tube assembly (16) is connected to the rear
axle. The  cylinder  is  charged  with  oil  and
compressed nitrogen. The rear suspension
cylinder works as the elastic elements and
absorber. The piston rod performs advance
and return movement in the cylinder tube to
compress nitrogen and functions as a spring;
the  function  of  absorber  can  be  realized
through  oil  flow  in  internal  and  external
oil  chambers  in  control  rear  suspension
cylinder. When the truck is kept static, the
compressed nitrogen in internal cavity may
produce sufficient force to support the truck.
If the wheels suffer impact from the ground,
the piston rod will be driven into the external
cylinder  barrel  and  thus  to  compress  the
nitrogen  and  absorb  energy.  Meanwhile,
the oil will drive ball (14) to move and open

check valve channel. The oil quickly flows into

circular cavity (cyclic annular volume formed
by piston rod external diameter and cylinder
tube internal diameter) from the main oil
chamber and through the hole on piston rod
wall and valve hole. After the impact force is
absorbed, the increased air pressure will drive
piston rod (26) to move upward to return to the
original position. Meanwhile, the oil in annular

cavity will flow back to the main oil cavity. The

oil pressure will force ball (14) to move and

close check valve channel. The oil only flows

back to the main oil cavity through hole, so as

to restrict the flow in such direction, reduce the

speed of piston rod in returning to the original
position and conduct damp and spring back

control based on flow feature difference of oil.

Fig.2 Removal and Installation of Suspension Ride Cylinder

1. Rear ride cylinder

5. Pin Assembly

2. Bolt

6. Pin Assembly

3. Lock washer

7. Dust boot

4. Washer

8. Oil fitting

REMOVAL

Numbers in parentheses refer to Fig.2.

WARNING

Pressurized cylinders. Release pressure

as described under 'Relieving Cylinder

Pressure' before removing valves or

fittings. Accidental release of pressure

will result in personal injury and property

damage.

To prevent personal injuries and property

losses, ensure that the air pressure in the

cylinder is completely released before the

suspension is dismantled. In addition, be

sure blocking and lifting equipment is of

sufficient capacity and properly secured to

2,3,4

Rear Suspension System

do the job safely.

1. Position the truck in a level work area, apply
the parking brake and switch off the
engine.
2. Turn the steering wheel in both directions
several times to relieve pressure in the
steering system. Block all road wheels.
3. Lift the rear end of the mining car, keep the
distance A between the upper pin and end cap
of guide sleeve is 517mm, and keep the tyres
away from the ground. Fasten the rear axle
assembly with proper cushion block at this
position, then lower the truck slowly to remove

the load of the suspension cylinder, and fix the

frame with cushion block at this position.
4. Release the nitrogen pressure of rear
suspension cylinders according to 'Release
suspension cylinder pressure' in this section.

5. Support the suspension with sufficient force

before  remove  the  pin.  single  suspension
cylinder weighs for more than 435kg; 19.5L oil
will be charged.
Attach a suitable lifting device or 'come-along'
to suspension cylinder (1). If a 'come-along'
is used, place a bar or heavy pipe through
both body prop pin holes in the frame. Attach
the 'come-along' to the bar or pipe. Place a
suitable strap or chain around suspension
cylinder (1) and take up the slack.
Note: Lower end of suspension cylinder (1)
must be disconnected before upper end.
6.  Remove  bolt  (2),  lock  washer  (3)  and
washer (4) used for fastening the suspension
cylinder and rear axle housing, pull out pin
assembly (5); the suspension cylinder may
apply certain pressure to pin when removing
the pin assembly.
7.  Remove  bolt  (2),  lock  washer  (3)  and
washer(4) used for fastening the upper end of
suspension cylinder and frame, then pull out
pin assembly (6).
8. Remove the rear suspension cylinder, move

Fig.3 Exploded View of Rear Suspension Cylinder

1. Snap ring

14. Bolt

2. Oil fitting

15. Guide sleeve

3. Charge valve

16. Buffer seal

4. Plug

17. Retainer ring

5. Piston rod

18. O-ring

6. Clamp

19. Wear ring

7. Dust boot

20. Bearing

8. Bolt

21. Ball

9. Plate

22. Plug

10. Retainer ring

23. Cylinder tube assy.

11. Wiper-seal

24. Bolt

12. Back-up seal

25. Piston

13. Seal

26. Wear ring

6 7

Rear Suspension System

it to a clean working area for removal; repeat
steps 5-8 to remove another suspension
cylinder if necessary.

Disassembly

Numbers in parentheses refer to Fig. 3.
1. Remove clamp(6)used for securing dust
boot (7) to piston rod (5), remove bolt (8)used
for securing dust boot (7) to guide sleeve(15),
then remove dust boot(7).
2. Remove charge valve (3) and plug(4,22)
from  cylinder.  Drain  oil  from  suspension
cylinder  into  a  suitable  container.  Do  not
disassemble charge valve (3) unless required.
3. Turn over the suspension with a crane and
proper device and fasten cylinder tube assy.
(23)  to  a  proper  position  for  disassembly.
Remove bolts (14) securing guide sleeve (15)
on cylinder tube assy. (23).
4. Install a lifting eye in the top of piston rod
(5) and attach to an adequate lifting device.
Slide piston rod (5) ,piston (25) and guide
sleeve(15)  as  an  assembly  out  from  top
of  cylinder  tube  assy.  (23).  Be  careful  not
to  damage  the  surface  of  any  component.
Place these parts on a clean workbench for
disassembly if necessary. Remove bolt (24)
securing piston(25)to piston rod (5), knock
piston (25) assembly away from the end of
piston rod (5) with a soft hammer, remove
wear ring(26) from piston (25).

WARNING

Flying metal chips. Use a soft drift and

drive to remove piston (25). Flying chips

from a hard metal drift can cause serious

personal injury.

5. Take out the ball (6) from the hole of piston
rod (5).

Note:

Take care not to misplace ball (21).

6.Place piston rod (5) assembly securely into
position in a press bed with piston rod eye
down. Press piston rod (5) out of guide sleeve
(15).Be careful not to damage the surface of
parts.

Rear Suspension System

7.Inspect,  remove  and  discard  retainer
ring(17) and O-ring (18) of guide sleeve(15)
outer groove.
8.Inspect,  remove  and  discard  steel  wire
retainer ring (10), wiper-seal (11), seal(12) and
wear ring(19) in the internal groove of guide
sleeve(15).
9.Remove  retainer  ring(1)  and  push  out
bearing (20) from piston rod (5) and cylinder
tube(23).

Inspection

Numbers in parentheses refer to Fig.3.

1.Wash all parts thoroughly in a suitable
solvent. Dry all parts with compressed air.
Check all inner and outer grooves in guide
sleeve (15) for cleanliness.
2.Inspect cylinder tube assy. (23), piston rod

(5) and piston (25) for scores, scuffing or small
ridges in the walls. Use a fine stone to smooth

out any defective areas. If damage is too
extensive, replace with a new part.
3.Check all cylinder assembly components for
signs of unusual distortion or excessive wear.
Replace defective components.
4.Inspect all plugs (4) and charging valve (3).
Check their seating positions in piston rod
(5) and cylinder tube assy. (23). If threads
in any of these parts are damaged, restore
the threads. If threads are not repairable, the
defective part must be replaced.
5.Inspect both cylinder eye surfaces for
scratches or signs of excessive wear. Check
bearings (20) and snap rings (1) for wear or
warped condition. Replace defective parts.
6.Inspect wear ring (19,26) for excessive wear
or damage. Replace if damaged.

Note:

The maintenance standard of bearings

(20) and wear ring (19,26) refer to Fig.1 and
Tab.1.

Rear Suspension System

Tab.1 Maintenance standard

No.

Check item

Criteria

Remedy

Clearance

between race

and ball of

bearing

Standard

size

Tolerance

Standard

clearance

Clearance limit

Replace

bearing

Shaft

Hole

146

0.13- 0.23

0.876

Clearance

between

piston rod

and wear

ring

200

-0.043
-0.096

+0.272
+0

0.043-0.368

0.4

Replace

bearing

Clearance

between

cylinder and

wear ring

280

-0.05

-0.296

+0.072

0.05-0.368

0.8

Replace wear

ring

Assembly

Numbers in parentheses refer to Fig.5.
1.Apply  a  light  coating  of  clean  hydraulic
oil to all components to facilitate assembly
procedure.  Make  certain  that  all  work  is
carried out in a clean area so no dirt or other
contaminants can get into the oil.
2.If removed, install snap ring (1) into cylinder
tube  assy.(23)  eye.  Use  a  hand  press  to
position bearing (2)against snap ring (1) in eye
of cylinder tube assy.(23). Retain bearing(2)
with snap ring (1). Use similar procedure to
install bearing(2) and snap rings (1) in piston
rod (5) eye end.
3.Install new snap ring (1), seal-wiper (11),
Back-up seal(12), seal(13) and wear ring(19)
into the corresponding groove of guide sleeve
(15). Before seal-wiper is installed, waterproof
glue  should  be  applied  onto  the  external
surface of frame.
4.Install new retainer ring (17) and O-ring (18)
into the corresponding groove on the external
surface of guide sleeve (15).

Rear Suspension System

5.Use a proper seal expander or similar tool
to prevent the seal ring from damage. Install
the guide sleeve (15) onto the piston rod (5)
carefully.
6.Install ball (21) into the valve seat of cylinder
piston rod(5).

Note:

Fix these balls temporarily with a little

clean grease in the rest assembly procedure.
7.Install wear ring (26) on piston (25) and
press piston assembly into position on end of
piston rod (5). Secure piston (25) assembly to
piston rod (5) with bolts (24). Tighten bolts (24)
evenly to a torque of 136 Nm.
8.Install a lifting eye in the top of piston rod
(5) and attach to an adequate lifting device.
Insert piston rod (5) ,piston (25 ) and guide
sleeve(15) as an assembly through the top of
cylinder tube assy.(23). Pushing piston rod in
until piston (25) bottoms inside the cylinder
tube. Be careful not to damage the surface of
any component.
9.Use a seal shrinker or similar product to
prevent the seal from damage. Align with each
bolt holes and install the guide sleeve (15) into
the cylinder tube assembly carefully.

Note

: Because of close tolerances, care will

have to be taken when assembling piston rod
(5) and piston(25) assembly into cylinder tube
(24).
10.Secure guide sleeve (15) to cylinder tube
assy. (23) with bolts (24). Tighten bolts to

torque of 333 N•m.

11.Install dust boot(7) on piston rod(4). Use
clamp(6) , bolt(8) and plate(9) to secure it to
piston rod (5) and guide sleeve (15).
12.Install charge valve (3) and plug(4) on
piston rod. The tighten torque of charge valve

is 50N•m, the tighten torque of charge valve
core is 0.35 - 0.45N•m, the tighten torque of
charge valve protecting cover is 4.5 - 5.5N•m.

Before installation, inspect the seal of charge
valve and plug for signs of damage, replace
them in time if they are damaged.
13.Install suspension cylinder in operation

Rear Suspension System

position and charge oil and gas into suspension
cylinder according to the requirements of the
charging procedure.

Installation

Numbers in parentheses refer to Fig.3.

WARNING

To prevent personal injury and property

damage, be sure blocking or lifting

equipment

1.Clean all parts surface of suspension
cylinder and frame to make them smooth.
2. Lift rear suspension cylinder with proper
lifting equipment or chain and make sure
the charge valve is outside the cylinder. The
weight of cylinder is 435kg; the oil capacity is
19.5L.

Note:

Lower end of suspension cylinder (1)

must be attached first.

3. Apply anti-seeze lubricant to pin assembly
(5).
4. Insert pin (5) through the rear axle housing
and the pin hole of suspension cylinder, push

it to specified position, and fasten it to the rear

axle housing with washer (4), lock washer (3)
and bolt (2).
5. Install upside of suspension cylinder to
frame, insert pin (5) through the frame and
the pin hole of suspension cylinder, push it to
specified position, and fasten it to the frame
housing with washer (4), lock washer (3) and
bolt (2).
6. Remove the lifting equipment or chain from
the rear suspension cylinder.
7.If the opposite suspension cylinder (1) was
removed, follow Steps 1 through 6 to install
the cylinder.
8. Charge the suspension cylinder according
to charging procedure. Check the operation of
suspension cylinder according to the contents

indicated in maintenance and adjustment
section.

Rear Suspension System

Frame

Stop block

Cylinder liner

upper end face

Axle housing assembly

Rear suspension cylinder

Fig.4 Check Length of the Rear Suspension Cylinder

A: Distance between centre of pin and the end cap of guide sleeve

Note

: Dimension “A” =455mm with the truck empty

Dimension “A” =366mm with the truck loaded

1. Oil fitting

3. Plug(oil fill port)

2. Nitrogen Charging Valve

4. Plug(air exhaust port)

Rear Suspension System

Fig.5 Nitrogen inflation drawing

A: Distance between the center of pin and cap of guide sleeve.

1. Charge valve

3. Nitrogen joint

5. Nitrogen cylinder

2. Plug

4. Cut-off valve

6. Pressure regulator

7. Pressure gauge

The user provides the nitrogen cylinder,

pressure regulator and instruments.

Cut-off valve

Only one side is

controlled when

charging one

suspension cylinder.

Rear Suspension System

Maintenance and adjustment

Periodic maintenance includes the following
steps:
1. Clean the device. Check the signs of wear,
damage or oil-gas leakage. Pay special
attention to the exposed part of piston rod

and inflation valve. Repair or replace them as

required.

Note:

The dust boot is equipped with zipper

which  can  be  replaced  without  remove
suspension cylinder or pin.
2.  Check  all  parts  for  signs  of  wear  or
looseness. In case of any looseness, repair or
replace them if necessary.
3. Inspect the exterior of suspension cylinder
for  signs  of  oil  leakage.  Repair  or  replace
according to the requirements and add oil
again according to the method described in
the instructions.

Note

: Refer to following procedure in this part

for detailed instructions of oil level inspections.
4. Check the relevant operating conditions of
suspension cylinder according to the following
method:
1)Run the truck and make that two suspension
cylinder can achieve a balance at the normal
operating temperature.
2) Position the empty truck on a flat ground.
Measure the distance A between the center
of pin and the end cap of guide sleeve as
shown in Fig.8. The value obtained should
be  approximately  455mm  (with  the  error
not exceeding 10mm; refer to Fig. 8). If the
distance  is  not  in  this  range,  check  and
adjust the nitrogen pressure according to the
procedure below this part. The following signs
indicate that it is necessary to maintain the
interior of suspension:
a.  There  is  sign  of  oil  leakage  in  the
surrounding of suspension cylinder.
b. The gas column height changes frequently.
It is required to charge nitrogen.

Note 1

: The reduction in the gas column

height is usually accompanied by the loss of
gas.

Note 2

: At the circumstance of normal gas

column height, the offset of gas height
indicates that the oil is losing.

Note 3

: The traveling or excessive elasticity

of gas will lead to repeated operation of
suspension cylinder.
3) After the suspension cylinder is inflated
to the correct height, apply the rated load,
park the truck on a flat ground, the distance
A between the center of pin and the end cap
of guide sleeve should be equal to 366mm
or higher. (If A is less than 366mm, check the
truck is overloaded or not. If not, deflate and

add oil, inflate gas again ).

Note 4:

The unsmooth traveling or excessive

elasticity of gas column will lead to repeated
operation of suspension at its travel terminal.

Charging rear suspension cylinder

WARNING

Lifting heavy parts or machines. To prevent

personal injury and property damage, be

sure blocking or lifting equipment is of

sufficient capacity and properly secured to

do the job safely.

WARNING

Pressurized cylinders. Release pressure

as described under 'Relieving Cylinder

Pressure' before removing valves or

fittings. Accidental release of pressure

will result in personal injury and property

damage.

To prevent personal injuries and property

losses, ensure that the air pressure in the

cylinder is completely released before the

Rear Suspension System

suspension is dismantled. In addition, be

sure blocking and lifting equipment is of

sufficient capacity and properly secured to

do the job safely.

Relieving Cylinder Pressure

Note:

Truck must be unload and on a level

surface prior to relieving suspension cylinder
pressure.
1.Support the frame near the suspension with
blocking and/or a hydraulic jack with adequate
capacity.
2.Place a 35mm cushion block between the
frame  and  oscillation  stopper  to  facilitate
charging procedure.
3.Remove  the  cap  from  nitrogen  charging
valve at the top of the cylinder. Turn the hex
out  on  the  valve  1/4  to  1/2  turn  counter-
clockwise and depress the valve core. If no
gas escapes, continue to turn the hex nut in
1/4 turn increments until the nitrogen releases
as the valve core is depressed.
4.Remove blocking or release pressure on the
hydraulic jack and allow the truck’s weight to
fully retract the suspension cylinder rod.
5.Depress nitrogen charging valve core again
to be sure all pressure has been relieved.

Note

:Nitrogen leaving the cylinder will often

carry oil with it. This results form foaming
of the oil in the cylinder. The foaming takes
place as nitrogen which was dissolved in the
oil at high pressure expands at atmospheric
pressure. The oil lost in this operation must be
replaced in the charging operation. The longer
the oil is allowed to stand at atmospheric
pressure after discharging cylinder, the easier
it will be to purge cylinder of bubbles in the oil
when recharging.

WARNING

Pressurized cylinders. Keep valve core

depressed until all gas is bled from

cylinder. Failure to release air pressure

may result in personal injury or property

damage.

Charging Instructions

Note1:

This procedure should be performed

after the suspension cylinder is installed
on mining truck. If it is not installed, the
suspension cylinder should be placed with a
proper supporting form and fastness before
this procedure is operated.

Note2:

To ensure that both suspension

cylinders  will  be  equally  charged  to  the
required  height  specifications  and  equal
pressures, both cylinders should be charged
simultaneously. Also when front suspension
cylinders  are  being  charged,  both  rear
suspension  cylinders  should  be  extended
equally. This can be accomplished by placing
equal  thickness  blocks  between  axle  and
frame at the bump stops. It may be necessary
to raise frame slightly to install spacers. Be
sure  to  remove  spacers  when  charging  is
complete.

Note3:

The pressure of a confined gas varies

directly with its temperature. Hence, extreme
changes in suspension cylinder ambient
temperature will change its nitrogen charge
volume and,consequently, its operating height.
It might be necessary, therefore, to add or
remove nitrogen to maintain proper cylinder
height as ambient temperature changes.

WARNING

Pressurized cylinders. Release pressure

as described under 'Relieving Cylinder

Pressure', before removing valves or

Rear Suspension System

SANY SRT95C Off-Highway Truck. Service Manual - page 25