BENDIX PIGGYBACK SPRING BRAKE User manual

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®
DESCRIPTION
The Bendix Piggyback Spring Brake is made up of a
conventionalbrakechamberandanemergencyorparking
spring mechanism for use on vehicles equipped with cam
foundationbrakes. TheSpringBrakeActuatorprovides: (1)
Service Braking, (2) Parking and (3) Emergency Braking.
Theactuatorcanbepipedwithvarioussystemarrangements
to be automatically or manually applied under emergency
brakingconditions.
Thespringbrakeisadiaphragmtypeactuatorwhichconverts
the energy of air pressure into mechanical force. The
diaphragm is held between the pressure plate and non-
pressure plate by a two piece clamp ring.
Different size brake chambers are identified by numbers
whichspecifytheeffectiveareaofadiaphragm.Forexample,
aType30/30SpringBrake has30square inchesofeffective
areaoneach diaphragm.
Thestandarddiaphragmmaterialisacompoundofnatural
rubberwithafabricinteriorofnylon.
FIGURE 1 - BENDIX PIGGYBACK SPRING BRAKE
Bendix Piggyback Spring Brake
SD-02-4500
PIGGYBACKCHAMBER
SERVICEPUSH-ROD
SERVICE
CHAMBER
SERVICE
DIAPHRAGM
PREVENTIVE MAINTENANCE
Important: Review the warranty policy before performing
anyintrusivemaintenanceprocedures.Anextendedwarranty
maybevoidedif intrusive maintenance isperformedduring
thisperiod.
Becauseno twovehiclesoperate underidenticalconditions,
maintenanceintervalswillvary.Experienceisavaluableguide
indeterminingthebestmaintenanceintervalfor a vehicle.
WARNING!
Piggyback Spring Brake Chambers contain a loaded
compression spring. Property damage, serious injury
or death may occur if instructions are not followed
completely.
Every300operatinghours,8,000miles, or one (1) month:
1. Check push rod travel and adjust travel at the slack
adjuster if needed. Push rod travel should be as short
aspossiblewithoutthe brakesdragging.Excessivepush
rodtravelreducesbrakingefficiency,shortensdiaphragm
life,givesslowbrakingresponseandwastes air.

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FIGURE2-PIGGYBACKSPRINGBRAKEDIAGRAM
EMERGENCY
PORT
SERVICE
PORT
MOUNTING
NUT
COTTERPIN
YOKE
LOCKNUT
SERVICE
PUSHROD
2. Checkpushrod toslackadjuster alignmentfromrelease
tofullstrokepositiontobesurethepushrodmovesout
andreturns properlywithoutbindingatthenon-pressure
plateholeorwithotherstructures.Alsochecktheangle
formedbythe slackadjusterarm and pushrod.It should
begreater than 90 degrees when thechamber is in the
releasedpositionandapproach90degreesatmaximum
readjustmentstroke.
3. Check tightness of mounting nuts. Torque on the non-
pressure plate mounting nuts should be 110 ft/lbs.
4. Check cotter pins to ensure they are in place.
5. Check all hoses and lines. They should be secure and
in good condition with sufficient length to allow for axle
movement.
Every3,600operating hours,100,000milesor one(1)year:
1. Disassemble and clean all parts. Clean all metal parts
incleaningsolvent,removingallrustandscale.Carefully
inspectallmetalparts for cracks, distortion or damage.
All diaphragm sealing surfaces should be smooth and
clean.
2. Installnewdiaphragm oranyotherparts if theyareworn
ordeteriorated. Performstepsoutlinedin"Replacingthe
Service Diaphragm". When the diaphragm, spring, or
both are replaced, they should be replaced in the
correspondingchamberonthesameaxle.
WARNING!
A piggyback spring brake chamber cannot have the
emergency diaphragm replaced. Replace the whole
piggyback spring brake chamber.
OPERATION & LEAKAGE TESTS
OPERATING TEST
1. Applybrakesand observe that the push rodsmoveout
promptlyandwithoutbinding.
2. Releasebrakesand observethatthe pushrodsreturn to
thereleasedpositionpromptlyandwithoutbinding.
3. Check push rod travel. Push rod travel should be as
shortaspossiblewithoutbrakes dragging.Adjust travel
of push rod at slack adjuster if necessary.
LEAKAGE TEST
1. Makeandhold a full brake application.
2. Usingsoapsolution,coatclampingring(s).If leakage is
detected, tighten clamping ring only enough to stop
leakage. DO NOT OVERTIGHTEN as this can distort
the sealing surface or clamping ring. Coat area around
pushrodhole(loosen boot if necessary). No leakageis
permitted. If leakage is detected, the diaphragm must
bereplaced.
WARNING! PLEASE READ AND FOLLOW
THESE INSTRUCTIONS TO AVOID
PERSONAL INJURYOR DEATH:
When working on or around a vehicle, the following
general precautions should be observed at all times.
1. Park the vehicle on a level surface, apply the park-
ing brakes, and always block the wheels. Always
wear safety glasses.
2. Stop the engine and remove ignition key when
working under or around the vehicle. When work-
ing in the engine compartment, the engine should
beshutoff and the ignition keyshould be removed.
Where circumstances require that the engine be
in operation, EXTREME CAUTION should be used
to prevent personal injury resulting from contact
with moving, rotating, leaking, heated or electri-
cally charged components.
3. Do not attempt to install, remove, disassemble or
assemble a component until you have read and
thoroughly understand the recommended proce-
dures. Use only the proper tools and observe all
precautions pertaining to use of those tools.
4. If the work is being performed on the vehicle’s air
brake system, or any auxiliary pressurized air sys-
tems, make certain to drain the air pressure from
all reservoirs before beginning ANY work on the
vehicle. If the vehicle is equipped with an AD-IS™
air dryer system or a dryer reservoir module, be
sure to drain the purge reservoir.

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FIGURE3- PIGGYBACK SPRING BRAKE CUT-AWAYVIEW
EMERGENCY
PORT
NON-PRESSURE
HOUSING PUSHROD
DIAPHRAGM
MAINSPRING
RELEASE
TOOL
SIDE
POCKET
5. Following the vehicle manufacturer’s recom-
mended procedures, deactivate the electrical sys-
tem in a manner that safely removes all electrical
power from the vehicle.
6. Never exceed manufacturer’s recommended
pressures.
7. Never connect or disconnect a hose or line con-
tainingpressure;it may whip.Neverremove a com-
ponent or plug unless you are certain all system
pressure has been depleted.
8. Use only genuine Bendix®replacement parts, com-
ponents and kits. Replacement hardware, tubing,
hose, fittings, etc. must be of equivalent size, type
and strength as original equipment and be
designed specifically for such applications and
systems.
9. Components with stripped threads or damaged
parts should be replaced rather than repaired. Do
not attempt repairs requiring machining or weld-
ing unless specifically stated and approved by the
vehicle and component manufacturer.
10. Prior to returning the vehicle to service, make
certain all components and systems are restored
to their proper operating condition.
OPERATION: GENERAL
TheBendixPiggybackSpringBrakeismadeupoftheservice
chamberandthepiggybackchamber.TheBendixPiggyback
Spring Brake provides service braking, parking, and
emergencybraking.
Thespringbrake canbemountedwith themountingboltsin
either a vertical or horizontal plane on standard mounting
studcenters.Two air lines are used: the service airlineand
theemergencyair line.
Controlledairpressure enters the servicechamberthrough
theinletport and acts uponthediaphragmmovingthe push
plateandrodassemblyforward.
When the service chamber is used to actuate cam type
brake foundation assemblies, the yoke (which is threaded
on the push rod) is connected to a slack adjuster, which in
turnisconnectedtothebrakecamshaft.Thisforwardmotion
of the push rod rotates the slack adjuster, cam shaft and
camapplyingthevehiclebrakes.
The greater air pressure admitted to the service chamber,
thegreatertheforceappliedbythepushrodand,conversely,
the less pressure applied to the service chamber the less
forceappliedbythe push rod. Push rod forceisdetermined
by multiplying the delivered air pressure by the effective
diaphragm area. For example, if 60 p.s.i. is admitted to a
type 30 service chamber, the lineal force on the end of the
push rod is approximately 1,800 lbs.
Whenairpressureisreleasedfromthebrakechamber, the
push rod return spring in combination with the brake shoe
return spring returns the diaphragm, push plate and rod
assembly, slack adjuster and brake cam to their released
positionsreleasingthebrakes.
Whenthe driveroperatestheparkingbrake, airisexhausted
fromthepiggybackchamber.Themainspringisallowedto
extend, which forces the push rod and the emergency
diaphragmforward.Thisforcestheservicediaphragmand
servicepushrodforwardwhich appliesthebrakes.
When the air pressure in the piggyback chamber drops to
below 78 p.s.i., the main spring overcomes chamber
pressureandforcesthepushrodandemergencydiaphragm
forward.
WARNING!
•Piggyback Spring Brake Chambers contain a
loaded compression spring. Property damage,
serious injury or death may occur if instructions
are not followed completely.
•When replacing the piggyback spring brake, make
sure to block the wheels to prevent vehicle
rollaway.

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FIGURE4- CAGING THE PIGGYBACK
ADAPTER
RETURN SPRING
SERVICE
RETURN SPRING
YOKE
LOCKNUT
EMERGENCY
DIAPHRAGM
SERVICE
DIAPHRAGM
RELEASETOOL
PRESSUREPLATE
MAINSPRING
•DO NOT service a piggyback spring brake
chamber if it has structural damage of any kind.
Replace the complete assembly. Dismount a
damaged piggyback spring brake by first cutting
the service push rod with an acetylene torch to
relieve any force it might have.
•Do not strike any part of a spring brake chamber
for any reason. This may cause structural
damage.
•Be careful not to drop a spring brake chamber
at anytime.
•A piggyback spring brake chamber cannot have
the emergency diaphragm replaced. Replace the
whole piggyback spring brake chamber.
•Always work from the side of the piggyback
spring brake chamber(s). Never work from the
front or back.
MECHANICAL RELEASE (CAGING) OF THE
BENDIX PIGGYBACK SPRING BRAKE
NOTE:TheBendixPiggyback Spring Brake Chamber is
not shipped caged. It must be caged prior to any work
beingdone.
1. Remove the dust cap from the keyhole in the center
ofthepiggyback spring brake chamber.
2. Remove the release tool assembly from the side
pocketof the adaptor base.
3. Inserttherelease tool(T-bolt)through thereleasetool
keyholeandintothepressure plate.
4. Turn the release tool 1/4 turn clockwise.
5. Pull on the release tool to seat it in the pressure
plate properly.
6. Put on the release washer and nut.
7. To cage the main spring, tighten the release nut with a
hand wrench and ensure the service pushrod
is retracting.
8. Donotover torquethereleasetoolassembly. Maximum
torque is 35 ft/lbs.
WARNING!
Do not use an impact wrench. An impact wrench may
over torque the release tool and cause damage to the
pressure plate.
9. The threaded portion of the release tool will extend
approximately 2.9 inches out of the nut when fully
released.
MECHANICAL RELEASE (CAGING) AND
REMOVAL OF THE PIGGYBACK SPRING BRAKE
CHAMBER TO BE REPLACED
NOTE: The piggyback spring brake chamber can be
replaced with the service brake chamber mounted to the
vehicle or removed for ease of access. To remove the
assembly from the vehicle, perform the steps outlined in
“RemovalandInstallationoftheCombinationSpring Brake.”
WARNING!
•Do not mechanically release (cage) the spring if
there is any structural damage to the brake. Caging
the spring in such a chamber may cause serious
injury or death. Replace the complete assembly.

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FIGURE5-PIGGYBACKCHAMBER
•Do not remove the Piggyback Spring Chamber
Clamps.
1. Mechanicallyreleasetheoldpiggybackspring brake by
followingtheoriginalmanufacturer’sinstructions.
2. Ensure air pressure is removed from all air reservoirs
before removing the air hoses or working on the
spring brake.
3. Remove air hoses from the Piggyback spring brake
chamber. Be sure to mark both hoses to ensure
proper reinstallation.
4. Clamp a pair of vise grips around the service pushrod
touching the non-pressure housing. This cages the
servicereturnspring.
5. Remove the clamp nuts and service clamp assembly
andcarefullyremovetheoldpiggyback chamber.
INSTALLING THE BENDIX PIGGYBACK SPRING
BRAKE CHAMBER
1. Visuallyinspecttheservicediaphragmforexcessivewear,
damage or cracks. Replace if needed. To replace the
service diaphragm, perform the steps outlined in
"ReplacingtheService Diaphragm".
2. Line up the new piggyback spring brake chamber, the
service diaphragm, and the non-pressure housing,
ensuringthattheyarecentered.
3. Reassemble the service clamp assembly. Ensure all
partsareseatedproperlyandremaincentered.
4. Torquetheclampnutsto25ft/lbs.Removethevise grips
fromtheservicepushrod.
5. Reconnect the emergency air line to the emergency
porthole and reconnect the service air line to the
service porthole.
6. Pressurizetheservice half by puttingairintotheservice
port. Do not exceed 120 psig.Test for leaks around the
clamps. No leaks are acceptable.
7. Uncagethemainspringandreturnthereleasetoolinto
the release tool side pocket.
8. Replace the dust cap in the keyhole.
WARNING!
Check for proper service and emergency operation
after servicing any part of the brake chamber(s). Check
the brake adjustment if the combination spring brake
was removed/installed (Follow vehicle manufacturer’s
instructions to adjust the brakes).
REMOVAL AND INSTALLATION OF THE
COMBINATION SPRING BRAKE
WARNING!
Do not mechanically release (cage) the spring if there
isanystructural damage to thepiggybackspring brake
chamber. Caging the spring in such a chamber may
cause serious injury or death. Replace the complete
assembly.
REMOVAL:
1. Mechanically release (cage) the old piggyback spring
brakechamberbyfollowingtheoriginalmanufacturer’s
instructions.
2. Ensure air pressure is removed from all air reservoirs
before removing the air hoses or working on the spring
brake.
3. Remove air hoses from the piggyback spring brake
chamber.Besuretomark both hoses to ensure proper
reinstallation.
4. Removetheyokepin,disconnecttheyokefromtheslack
adjuster, remove the mounting nuts, washer, and lock
washersandremovethecombinationspringbrake.While
removing, use care to prevent the combination spring
brakefromfalling.
INSTALLATION:
1. Installthecombinationspring brake using the furnished
hardware. Torque the mounting nuts to 110 ft/lbs.
Connect the yoke to the slack adjuster and install the
yoke pin and the cotter pin.
2. Reconnect the emergency air line to the emergency
portholeandreconnect the serviceairlineto the service
porthole.
3. Pressurize the service chamber by putting air into the
service port. Do not exceed 120 psig. Test for leaks
around the clamps. No leaks are acceptable.

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FIGURE6-SERVICEDIAPHRAGM
SERVICE
CLAMPRING
RELEASE
TOOL
NON-PRESSURE
HOUSING
SERVICE
DIAPHRAGM
PIGGYBACK
CHAMBER
4. Uncagethemainspringandreturnthereleasetoolinto
the release tool side pocket.
5. Replace the dust cap in the keyhole.
WARNING!
Check for proper service and emergency operation
after servicing any part of the brake chamber(s). Check
the brake adjustment if the combination spring brake
was removed/installed (Follow vehicle manufacturer’s
instructions to adjust the brakes).
REPLACING THE SERVICE DIAPHRAGM
To replace the service diaphragm, it is not necessary to
remove the complete combination spring brake from the
vehicle.However, it can be removed for ease ofaccess.To
remove the combination spring brake, perform the steps
outlined in "Removal and Installation of the Combination
Spring Brake".
WARNING!
• A piggyback spring brake chamber cannot have
the emergency diaphragm replaced. Replace the
whole piggyback spring brake chamber.
1. Protecttheservicepush rod with tape,andlockthevise
grips on the push rod close to the non-pressure plate.
(This will hold the rod in the applied position).
2. Ensure that the piggyback spring brake chamber is
caged. To cage the piggyback spring brake chamber,
performthestepsoutlinedineither"MechanicalRelease
of the Bendix Piggyback Spring Brake" or "Mechanical
Releaseof thePiggybackSpringBraketobeReplaced".
3. Mark the service clamp ring and non-pressure plate to
ensureproperalignmentofpartsduringreassembly.
4. Remove the service clamp ring assembly and the
piggyback chamber. The service clamp ring is closest
to the non-pressure plate and slack adjuster. See
providedillustrationsifindoubt.
WARNING!
Do not remove the spring chamber clamps.
5. Visuallyinspecttheservicediaphragmforexcessivewear,
damageorcracks.Replaceifneeded.
6. Lineupthepiggybackspringbrakechamber,the service
diaphragm,and thenon-pressurehousing,ensuringthat
theyarecentered.
7. Reassemble the service clamp assembly. Ensure all
partsareseatedproperlyandremaincentered.
8. Torquetheclampnutsto25ft/lbs.Removethevise grips
fromtheservicepushrod.
9. Reconnect the emergency air line to the emergency
porthole and reconnect the service air line to the
service porthole.
10. Pressurize theservicehalfbyputting airinto theservice
port. Do not exceed 120 psig.Test for leaks around the
clamps. No leaks are acceptable.
11. Uncagethemain spring and return the release tool into
the release tool side pocket.
12. Replace the dust cap in the keyhole.
WARNING!
Check for proper service and emergency operation
after servicing any part of the brake chamber(s). Check
the brake adjustment if the combination spring brake
was removed/installed (Follow vehicle manufacturer’s
instructions to adjust the brakes).
BW2106 © 2004 Bendix Commercial Vehicle Systems LLC 8/2004. All rights reserved. Printed in U.S.A.