Bendix Commercial Vehicle Systems ROTOCHAMBERS User Manual

®

Rotochambers

SD-02-1336

PUSH ROD

ASSY.

COVER

INNER

DIAPHRAGM

CLAMP

OUTER

DIAPHRAGM

CLAMP

DIAPHRAGM

GUIDE

BODY

DIAPHRAGM

SPRING

DESCRIPTION

The rotochamber is an actuator which converts the energy
of air pressure into mechanical force. The type number of
the rotochamber indicates the actuator’s diaphragm effective
area (Type 30 - 30 sq. in. of diaphragm) and the various
sizes available give a wide range of output force and length
of stroke. The rolling type diaphragm provides long life and
gives a constant output force throughout the entire stroke.

One end of the diaphragm is clamped to the inside wall of
the body by the outer clamp. The other end of the diaphragm
is clamped between the diaphragm guide and inner
diaphragm clamp. The cover is fastened to the outer body
by cap screws. Mounting studs are used to mount the
chambers. A boot retained by a boot retainer is used to
prevent entrance of moisture through the hole in the cover.
A lock nut and yoke with pin are screwed on the threaded
push rod. Most rotochambers now have 3/8 in. NPTF inlet
ports. The long stroke T ype 50 employ a 1/2 in. NPTF inlet
port.

OPERATION

Controlled air pressure enters the rotochamber through the
inlet port and acts upon the diaphragm, moving the diaphragm
guide and diaphragm forward. The diaphragm moves along
the inside wall of the cylinder body with a smooth rolling

BOOT

LOCK NUT

MOUNTING STUD

YOKE ASSY.

motion. The forward motion of the diaphragm guide and
diaphragm forces the push plate and push rod forward.

When the rotochamber is used to actuate cam type foundation
brake assemblies, the yoke is connected to a slack adjuster
which in turn is connected to the brake cam shaft. This
forward motion of the push rod rotates the slack adjuster,
cam shaft and cam applying the vehicle brakes.

The rotochamber is also used in industrial applications and
in such cases may be used in clamping or holding
operations.

The greater air pressure admitted to the rotochamber, the
greater the force applied by the push rod and, conversely ,
the less air pressure applied to the rotochamber, the less
force applied by the push rod. Push rod force is determined
by multiplying the air pressure delivered by the effective
diaphragm area. For example, if 60 psi is admitted to the
Type 30 rotochamber the lineal force on the end of the push
rod is approximately 1800 lbs.

When air pressure is released from the rotochamber the
rotochamber spring returns the slack adjuster (if applicable),
push rod, diaphragm guide and diaphragm to the released
position.

1

PREVENTIVE MAINTENANCE

A. Every month, 8,000 miles, or after 300 operating hours,

depending on type of operation:

1. Check push rod travel and adjust travel at the slack
adjuster if needed. Push rod travel should be as short
as possible without brakes dragging. Excessive push
rod travel reduces braking efficiency, shortens
diaphragm life, gives slow braking response and
wastes air.

2. Check push rod to slack adjuster alignment from
release to full stroke position to be sure push rod
moves out and returns properly without binding at
the cover hole or with other structures. Also check
the angle formed by the slack adjuster arm and push
rod. It should be 90° or greater when the chamber is
in the applied or released positions.

3. Check tightness of mounting nuts. Check cotter pins
to make sure they are in place.

4. Check all hoses and lines. They should be secure
and in good condition.

B. Every year or after each 100,000 miles or 3,600 operating

hours, depending on type of operation.

1. Disassemble and clean all parts.

2. Install new diaphragm or any other parts if they are
worn or deteriorated.

When the diaphragm, spring, or both are replaced they should
be replaced in the corresponding chamber on the same axle.

OPERATING AND LEAKAGE TESTS

A. Operating T est

1. Apply brakes and observe that the push rods move
out promptly and without binding.

2. Release brakes and observe that the push rods return
to the released position promptly and without binding.

3. Check push rod travel. Push rod travel should be as
short as possible without brakes dragging. Adjust
travel of push rod at slack adjuster if necessary .

B. Leakage T est

1. Loosen rubber boot from around push rod hole in
cover. Make and hold a full brake application.

Coat area with soap suds and check for leakage. No leakage
is permissible. If leakage is detected, the diaphragm must
be replaced.

REMOVING

1. Block vehicle wheels.

2. Disconnect line to rotochamber.

3. Remove the yoke pin.

4. Remove the rotochamber.

INSTALLING

1. Before installing chamber , check bracket for distortion,
cracks or any condition which might cause chamber
misalignment or malfunction.

2. Re-install the chamber on the bracket. Tighten the
mounting nuts securely and evenly .

3. Connect the air lines to the rotochamber and check for
leakage.

4. Insert the push rod yoke pin through the hole in the yoke
and slack adjuster. Make sure the same hole location in
the slack adjuster on each side of the axle is used.

5. The yoke should be adjusted on the push rod so that
with brakes released the angle formed by the push rod
and slack adjuster will be greater than 90° and all slack
adjusters should be at the same angle. With properly
adjusted brakes applied, the angle should still be greater
than 90°.

DISASSEMBLY

For ease in disassembly, if the rotochamber has been in
service and shows signs of rust accumulation, it is
recommended that the chamber be immersed and soaked
in the cleaning or rust dissolving solvent for 24 hours.

1. Remove yoke and lock nut from push rod.

2. Remove rubber boot.

3. Remove cap screws from cover.

4. Remove cover, springs and spring guides (if so
equipped).

5. Remove nuts from body. These nuts secure the outer
clamp to the body and are located at the air inlet end of
the rotochamber.

6. Grasp the push rod and by pulling and wiggling the
entire assembly consisting of push rod and plate,
diaphragm guide, diaphragm, inner and outer clamps
should ease out of the body .

7. Straighten the rolled diaphragm.

8. Remove outer diaphragm clamp.

9. Remove nuts from inside of diaphragm guide.

10.Disassemble inner diaphragm clamp, diaphragm and
push plate rod assembly from the diaphragm guide.

CLEANING AND INSPECTION

1. Clean all metal parts in a good cleaning solvent.

2. Carefully inspect all metal parts for cracks, distortion or
damage. Replace any parts not considered serviceable.

3. Replace diaphragm and rubber boot.

2