BRAKING R2900.pdf

CATERPILLAR ELPHINSTONE PTY. LTD.

Page 1

R2900 LHDR2900 LHDR2900 LHDR2900 LHDR2900 LHDBRAKING SYSTEMBRAKING SYSTEMBRAKING SYSTEMBRAKING SYSTEMBRAKING SYSTEM

MODULEMODULEMODULEMODULEMODULEFORM NO. 9EL9203-00FOR USE IN SERVICE TRAINING GUIDE:-CEPL R2900 LHD - July 1998

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Service Training ModuleR2900 Brake Module


List of ContentsCaterpillar Elphinstone Machine

List of Contents .......................................................................................................................................... 2Important Safety Notice ............................................................................................................................. 3R2900 Braking System Overview .............................................................................................................. 4Introduction ................................................................................................................................................ 5Braking System Block Schematic ............................................................................................................. 6Braking System Component Location ........................................................................................................ 7Location of Brake System Components ..................................................................................................... 8Accumulator Charging Valve (Accumulator Fully Charged - Cut-Out Cycle) ............................................. 9Accumulator Charging Valve (Accumulator Being Charged - Cut-In Cycle) ............................................ 10Location of Brake System Components ................................................................................................... 11Service Brake Control Valve (Released Position) .................................................................................... 13Service Brake Accumulator ...................................................................................................................... 15Wheel Brake (Parking Brake Released) ................................................................................................... 16Wheel Brake (Parking Brake Released - Service Brake Applied) ............................................................ 17System Operation (Parking Brake Engaged) ........................................................................................... 18System Operation (Parking Brake Released) .......................................................................................... 20System Operation (Service Brakes Applied) ............................................................................................ 21Towing Brake Release System ................................................................................................................ 22Towing Brake Release System Operation (Towing Brake Release Activated) ......................................... 23Brake Pressure Test Points ...................................................................................................................... 25Brake Electrical System ........................................................................................................................... 26System Operation (Power Supply) ........................................................................................................... 28System Operation (Relay Latched and Parking Brake Engaged) ............................................................ 29System Operation (Parking Brake Released) .......................................................................................... 30Parking Brake CMS Component Location ............................................................................................... 31System Operation CMS (Parking Brake Released) ................................................................................. 33Stop Light and Residual Brake Pressure Light Circuit Components ........................................................ 34System Operation (Stop Light/Residual Brake Pressure Circuit) ............................................................. 35Electric Brake Release System ................................................................................................................ 36System Operation (Electric Brake Release) ............................................................................................ 37Practical Tasks ......................................................................................................................................... 38Theory Assessment ................................................................................................................................. 39Theory Assessment Answers .................................................................................................................. 41Theory Assessment ................................................................................................................................. 42Theory Assessment Answers .................................................................................................................. 44Servicemans Handouts ........................................................................................................................... 45



IMPORTANT SAFETY NOTICEThe course content and subject matter is currentat the time of publication. Specifications,torques, pressure settings, measurements,adjustments, illustrations and other items canchange at any time. Always refer to the machinespecific service manual, parts book and updatesprior to performing repairs and adjustments.Caterpillar Elphinstone Pty Ltd cannot anticipateevery possible circumstance that might involvea potential hazard. The warnings in this moduleare therefore not inclusive. If a procedure, tool,device or work method not specificallyrecommended by Caterpillar Elphinstone Pty Ltdis to be used, you must satisfy yourself that it issafe for yourself and others. You should alsoensure that the machine will not be damaged ormade unsafe by the procedures you choose.



Aims:The aim of this training module is to provide participants with the operational knowledge and diagnostic skills necessary totroubleshoot the R2900 Braking System.

Nominal Duration:The module is designed so that most of the trainees will acquire the knowledge in one 4 hour session. The length of timeactually taken to complete the module will vary depending on factors such as the teaching method used, the traineesknowledge and skills at entry, and the individual trainees ability.

Pre-Requisites:Mechanical tradesman - should have completed a Basic Hydraulic and Electrical Training Program (preferred but notessential).

Learning Outcomes:As a result of studying this module, participants should be able to:1.1.1.1.1. Demonstrate an understanding of the function and operation of the braking system and its components.2.2.2.2.2. Use and understand the braking system schematic.3.3.3.3.3. Trace the oil flow through the braking system during all modes of operation.4.4.4.4.4. Apply this operational knowledge to troubleshoot a series of braking system problems.5.5.5.5.5. Use the Service Manual and Parts Book to assist with troubleshooting.

Assessment:Tasks:Part A:Part A:Part A:Part A:Part A: Practical Tests.Part B:Part B:Part B:Part B:Part B: Theory Assessment (True/False Test).

Resource Requirements: R2900 LHD. Fully equipped classroom with white board and overhead projector. Training Module and handout material. Hydraulic pressure gauges. Service Manual. Parts Book. Tools for practical tasks.

Module Description

R2900 Braking System Overview



1

Introduction

Introduction:

Schematic colour code:

Testing & Adjustingprocedures:

Servicemans Handouts:

This presentation discusses the system operation and adjustingprocedures for the R1600 LHD Braking System.

Graphical symbols and sectional view drawings will be used whendiscussing systems operations. Systems will be explained by tracingoil flow from the tank, through the system, and back to the tank.

The colour codes for hydraulic oil used throughout this presentation areas follows:RedRedRedRedRed - System or high pressure.OrangeOrangeOrangeOrangeOrange - Pilot pressure.Blue Blue Blue Blue Blue - Blocked or trapped oil.Green Green Green Green Green - Tank or return oil

NOTE:NOTE:NOTE:NOTE:NOTE: Always follow the procedures in the Service Manual when Always follow the procedures in the Service Manual when Always follow the procedures in the Service Manual when Always follow the procedures in the Service Manual when Always follow the procedures in the Service Manual whentesting and/or adjusting the machine braking system.testing and/or adjusting the machine braking system.testing and/or adjusting the machine braking system.testing and/or adjusting the machine braking system.testing and/or adjusting the machine braking system.

Give each trainee a copy of the relevant servicemans handouts,supplied with this training module.



2

Braking System Block Schematic

This block schematic of the R2900 LHD braking system shows thecomponents and oil flow. There are two brake control systems on themachine: the parking brake system and the service brake system. Anoptional feature of the brake system is the towing brake releasesystem.

The brake and pilot pump oil (red) flows to the accumulator chargingvalve. The valve divides the oil flow of the brake and pilot pump, priorityis given to the service brake circuit. When the parking brake controlvalve is activated, pump oil is directed into the parking brake section ofthe wheel brakes to release the brakes.

Brake and pilot pump oil flows through the accumulator charging valveto the service brake accumulator. When the service brake control valveis activated, accumulator oil goes to the service brake section of thewheel brakes. The wheel brakes are dual-piston, outboard, wet-discbrakes located in the wheel ends. Each wheel brake has a parkingbrake piston and a service brake piston. The parking brake is springengaged and hydraulically released. The service brake is hydraulicallyapplied.

Block Schematic- Parking brake system- Service brake system

Other Brake System Features:- Towing brake release system

The pump draws oil (green)from the tank and sends flow(red) to the various controlvalves

The parking brake is springengaged and hydraulicallyreleased

The service brake ishydraulically applied

BRAKE ANDPILOT PUMP

ACCUMULATORCHARGING

VALVE

PARKINGBRAKE CONTROL

VALVE

PILOTRELIEFVALVE

SERVICEBRAKE

CONTROLVALVE

TANK

SERVICE BRAKEACCUMULATOR

WHEELBRAKE

FILTER

ACCUMULATORCHARGE RELIEFVALVE



3

Braking System Component Location

The hydraulic brake system consists of: hydraulic tank (1), parkingbrake control valve (2), service brake accumulator (3), accumulatorcharge relief valve (4), pilot oil filter (5), pilot relief valve (6), front wheelbrakes (7), service brake control valve (8), rear wheel brakes (9),accumulator charging valve (10), brake and pilot pump (11) and electricbrake release pump (12) .

There are four wheel brakes on the machine. Each wheel brake hastwo sections; a parking brake section and a service brake section. Theparking brake is oil pressure released and spring applied. The servicebrake is oil pressure applied and spring released. The service brakecan be used when the brake is released.

Identify components(1) Hydraulic tank(2) Parking brake control

valve(3) Service brake

accumulator(4) Accumulator charge

relief valve(5) Pilot oil filter(6) Pilot relief valve(7) Front wheel brakes(8) Service brake control

valve(9) Rear wheel brakes(10) Accumulator charging

valve(11) Brake and pilot pump(12) Electric brake release

pump

1 2 3 4 5 6

7 8 9 10 11 12



4

Location of Brake System Components

The hydraulic tank (1) is located on the right hand side of the machine.The hydraulic oil filters (2) are mounted inside the hydraulic tank. Thereis a bypass valve for the filter elements. Whenever the restrictionthrough the filters is too high, the bypass valve will open.

The brake and pilot pump (3) is part of a two section pump, which ismounted on the left hand rear of the torque converter updrive transferhousing. The brake and pilot pump (3) supplies oil to the pilot steeringsystem, brake system and pilot hydraulic system. The accumulatorcharging valve (4) is located on the left hand inside wall of the rearframe. The valve divides the oil flow from the brake and pilot pump,priority is given to the brake circuit.

The pilot system relief valve (5) is mounted on the rear frame crossbeam. The pilot oil filter (6) is mounted behind the relief valve manifold.The pilot relief valve controls the pressure in the pilot oil system. Thepilot oil filter (6), filters the pilot oil and is fitted with a bypass valve whichwill open whenever the resistance to the flow of oil through the filter istoo high.

Hydraulic filters are mountedinside the hydraulic tank

Brake and pilot pump is partof a two section gear typepump

Accumulator charging valvedivides oil flow with prioritygiven to the braking system

Pilot relief valve controls thepressure in the pilot system

Pilot oil filter is fitted with abypass valve

1. Hydraulic tank.2. Hydraulic oil filters. 3. Brake and pilot pump.

4. Accumulator charging valve.5. Pilot relief valve.6. Pilot oil filter.

1

2

3

4

5

6



5

Accumulator Charging Valve (Accumulator Fully Charged - Cut-Out Cycle)

With the engine running, oil from the brake pump goes into theaccumulator charging valve (ACV). If the brake accumulator does notneed oil, the ACV directs all oil from the brake pump to the pilot circuit.When the brake accumulator needs oil, the ACV divides the pump flow.The ACV will direct a percentage of pump oil to the accumulator. Theremainder of the pump oil will flow to the pilot circuit.

When the oil pressure in the accumulator reaches the cut out pressureof the accumulator charging valve, the accumulator is fully chargedwith oil.

Oil from the brake and pilot pump enters the ACV. This oil passesthrough a drilled passage in valve spool (9) to chamber (8). Pressurewill increase in chamber (8) and move valve spool (9) to the right. Thevalve spool (9) is now held against spool stop (11) and pump oil will flowto the pilot circuit.

Oil pressure in the accumulator moves check valve (4) to the rightagainst pilot valve spool (1). Oil pressure in the accumulator is retainedby check balls (4) and (5).

Accumulator charging valve(accumulator fully charged -cut-out cycle)(1) Pilot valve spool(2) Upper limit check ball(3) Pilot valve spring(4) Lower limit check ball(5) Check valve(6) Orifice(7) Passage(8) Chamber(9) Charging valve spool(10) Spring(11) Spool stop

Accumulator charging valvein CUT-OUT cycle:

Accumulator does not needoil; the ACV directs all pumpoil to the pilot circuit

7

3

12

4

81110

9

6

5



6

Accumulator Charging Valve (Accumulator Being Charged - Cut-In Cycle)

Brake application will cause the oil pressure in the accumulator todecrease. When the pressure decreases to the cut-in pressure, pilotvalve spring (3) will unseat check ball (4). At the same time, check ball(2) seats. Pilot valve spool (1) allows only one of these check balls to beseated at a time.

When check ball (4) is unseated, pressure from the accumulator flowsthrough passage (7). The oil enters the chamber behind valve spool (9).The spring (10) and the accumulator oil pressure balance the pumppressure in chamber (8) acting on the opposite end of valve spool (9).This means that the pump pressure is always higher than theaccumulator pressure. Pump pressure flows through orifice (6), pastcheck valve (5), and out to the accumulator.

When the accumulator is fully charged, the oil pressure in theaccumulator will seat check ball (4). The pilot valve spool (1) will unseatcheck ball (2) and allow pressure in the chamber behind valve spool (9)to return to tank. Valve spool (9) will now move to the right and directbrake charge pump oil to the pilot circuit.

Accumulator charging valve(accumulator being charged -cut-in cycle)(1) Pilot valve spool(2) Upper limit check ball(3) Pilot valve spring(4) Lower limit check ball(5) Check valve(6) Orifice(7) Passage(8) Chamber(9) Charging valve spool(10) Spring(11) Spool stop

Accumulator needs oil; theACV divides pump flow toaccumulator and pilot circuit

Accumulator will charge untilCUT-OUT pressure is reached

7

3

12

4

5

6

8

910 11



7

Location of Brake System Components

The parking brake control valve (1) is located on the left hand inside wallof the rear frame.

When the parking brake control knob (in operators station) is moved tothe released position, the solenoids of the parking brake control valveare energised. Oil flows to the parking brake sections of the wheelbrakes. Oil pressure then releases the parking brake.

The accumulator charge relief valve (2) is mounted on the left handinside wall of the rear frame. The relief valve protects the service brakesystem if the accumulator charging valve fails.

The brake control pedals (3) regulate the pressure at the brakes. Asthe position of the pedal changes, the pressure at the brakes alsochanges.

The service brake accumulator (4) is mounted on the inside left handwall of the rear frame. The accumulator stores hydraulic oil underpressure and supplies oil at a constant pressure range to the servicebrake system.

Parking brake control valvesolenoids are energised torelease the parking brake

Accumulator charge reliefvalve protects the servicebrake system if theaccumulator charging valvefails

Brake pedals regulate thepressure at the wheel brakes

Service brake accumulatorsupplies oil at a constantpressure to the servicebrakes

1. Parking brake control valve. 2. Accumulator charge relief valve.

3. Brake control pedals. 4. Service brake accumulator.

2

1

433

Continued



The brake pedal is connected to the service brake control valve. Theservice brake control valve is supplied with oil from the service brakeaccumulator. The service brake control valve will modulate this pressuredepending on the position of the pedals.

NNNNNOTEOTEOTEOTEOTE:::::The brake and transmission neutraliser control pedal (left side pedal)applies the brake first then neutralises the transmission.

Service brake control valvemodulates the pressure to thewheel brakes, depending onposition of the pedals

Left pedal applies the brakesfirst then neutralises thetransmission



8

Service Brake Control Valve (Released Position)

The service brake control valve is a dual pressure reducing valve withtwo independent output pressures. The valve is directly below theservice brake pedal.

The service brake control valve modulates pressurised oil from theaccumulator to the service brake section of the wheel brakes. Theposition of the brake pedal causes a specific pressure at the brakes.As the position of the pedal changes, the pressure at the servicebrakes also change.

If one braking circuit fails, the second braking circuit remains functionaldue to the mechanical contact between the two spools (4) and (5).

With the engine running, oil flows from the service brake accumulatorto service brake control valve (1) through two inlet ports. When theoperator pushes on the brake pedal, springs (2) cause spools (4) and(5) to overcome the force of spring (6) and move down.

Service Brake Control Valve:(1) Service brake control

valve(2) Springs(3) Return port(4) Spool(5) Spool(6) Spring

The service brake controlvalve modulates (regulates)the pressure to the servicebrake

The further the pedal isdepressed, the greater thepressure at the service brake

TO WHEELTO WHEELTO WHEELTO WHEELTO WHEELBRAKESBRAKESBRAKESBRAKESBRAKES

FROMFROMFROMFROMFROMACCUMULAACCUMULAACCUMULAACCUMULAACCUMULATORTORTORTORTOR

TO WHEELTO WHEELTO WHEELTO WHEELTO WHEELBRAKESBRAKESBRAKESBRAKESBRAKES

FROMFROMFROMFROMFROMACCUMULAACCUMULAACCUMULAACCUMULAACCUMULATORTORTORTORTOR

AccumulatorOil Pressure

Tank Oil

Regulated OilPressure

TTTTTANKANKANKANKANK

5

4

3

1

6

2

Continued



When spool (4) moves down, oil from the accumulator port flows pastthe spool to the front brake port. The oil flows into the oil line to thefront service brakes and applies the front brakes.

Spool (4) is on top of spool (5) and as spool (4) moves down it causesspool (5) to also move down. As spool (5) moves down, oil from theaccumulator port flows past the spool to the rear brake port. The oilflows into the oil line to the rear service brakes and applies the rearbrakes.

Internal metering passages reduce oil pressure to each axle. Theservice brake control valve meters oil to the rear brakes at a higherpressure than the front brakes.

When the operator releases the brake pedal, spring (6) forces spools(4) and (5) up. Now the oil flowing from the accumulators is blocked atthe spool.

When the spools move up, the return ports are open. The oil in theservice brake ports can now flow into the return ports. Oil in the frontand rear brake oil lines is now vented back to the hydraulic tank.

When the control spoolsmove down, accumulatorpressure oil flows to thewheel brakes

The service brake controlvalve reduces (modulates)the oil pressure to the wheelbrakes



9

Service Brake Accumulator

The service brake accumulator supplies oil under pressure to theservice brake control valve. There is a nitrogen charge in theaccumulator.

The accumulator has a sealed piston (3) that moves up and downinside the bore of the accumulator. The chamber (4) above the pistonhas a charge of dry nitrogen gas. The charge of dry nitrogen gas is putinto the accumulator through valve (2).

Oil from the pump and accumulator charging valve comes through port(6) into chamber (5). When the pressure in the accumulator reachesthe cut-out pressure of the accumulator charging valve, the supply ofoil to the accumulator is stopped by the accumulator charging valve.

Service Brake Accumulator(1) Accumulator(2) Nitrogen charging valve(3) Piston(4) Nitrogen gas chamber(5) Pressure oil chamber(6) Oil pressure outlet

The accumulator suppliesoil under pressure to theservice brakes

The gas chamber above thepiston has a charge of drynitrogen gas

Pump oil pushes the pistonup and causescompression of the drynitrogen gas

Pressure Oil

1

3

6

2

4

5

Nitrogen Gas



10

Wheel Brake (Parking Brake Released)

The outer casing (3) is bolted to the axle housing which does not turn.There are splines on the inside of the outer casing (3). Splines on thecircumference of the steel plates (7) fit in the splines of the outer casing(3). This keeps the steel plates (7) stationary.

The wheel hub (outer housing of the final drive) (5) has splines on itsouter circumference. These splines fit into the splines on the inside offriction discs (8). Both wheel hub (5) and friction discs (8) turn together.

When the parking brake is released, oil flows through a port in the endplate to annular passage (6). The oil pressure moves parking piston (1)to the left, compressing springs (4), until the piston contacts the endplate. This relieves the pressure from the brake pack. Friction discs (8)and wheel hub (5) are free to rotate.

When the parking brake is engaged, the oil in the annular passage (6) isdumped to tank. When the oil pressure drops, the parking piston ismoved to the right by springs (4) until it contacts service piston (2) andforces it into contact with brake pack (9). This holds the rotating discsto the stationary plates and locks wheel hub (5) to the axle housing.

Wheel Brake (parking brakereleased)(1) Parking piston(2) Service piston(3) Outer casing(4) Springs(5) Wheel hub(6) Annular passage(7) Steel plates(8) Friction discs(9) Brake pack

When the parking brake isreleased, oil pressuremoves the parking pistonto the left away from thebrake pack

When the parking brake isapplied, springs move theparking piston to the rightagainst the brake pack

Parking BrakeOil Pressure

1 2 35

4

6

987



11

Wheel Brake (Parking Brake Released - Service Brake Applied)

When the service brake pedal is depressed, oil under pressure flowsthrough a port in the end plate into annular passage (6). The pressureof the oil moves service piston (2) to the right against the brake pack (9).Springs (4) are tensioned by pull rods (5) as the service piston moves.

This causes friction between the steel plates (7), which are heldstationary by outer casing (3), and friction discs (8) which turn with therotation of the wheels. This friction causes the wheels to turn slower orstop. The amount of brake application depends on the position of thebrake pedal.

Grooves cut in the faces of the friction discs (8) allow cooling oil to flowbetween the plates and discs. The cooling oil will constantly flowbetween the plates and discs in either the service brake applied orreleased positions.

Wheel Brake(1) Parking piston(2) Service piston(3) Outer casing(4) Springs(5) Pull rods(6) Annular passage(7) Steel plates(8) Friction discs(9) Brake pack

When the service brake isapplied, the service pistonmoves to the right against thebrake pack

Cooling oil will constantlyflow between the brake packin both the brake applied andbrake released position

Parking BrakeOil PressureServiceBrake OilPressure

1 2 3

4

5

7 8

96



12

System Operation (Parking Brake Engaged)

TANK

SERVICE BRAKECONTROL VALVE

PARKING BRAKECONTROL VALVE

REAR WHEELBRAKES

FRONT WHEELBRAKES


BRAKE ANDPILOT PUMP

TO P

ILO

TSY

STEM

ACCUMULATORCHARGING VALVE

PILOTRELIEF VALVE

STEERINGPUMP

ACCUMULATORCHARGE RELIEF

VALVE

This schematic shows the braking system with the engine running, theparking brake engaged and the service brake released.

Oil from the brake and pilot pump flows to the accumulator chargingvalve and the pilot relief valve. The accumulator charging valve keepsthe pressure in the service brake accumulator within a constant range.The pilot relief valve controls the pilot oil pressure to the parking brakecircuit. The brake and pilot pump also supplies oil to the hydraulicimplement and steering pilot systems.

The pump oil flows through the accumulator charging valve to theservice brake accumulator. A piston in the service brake accumulatoris held against the oil intake end by dry nitrogen gas. The service brakeaccumulator stores hydraulic oil pressure for operation of the servicebrakes. When the service brake accumulator is fully charged, theaccumulator charging valve directs its pump oil flow to tank. Oil flow isblocked by the service brake control valve.

Braking system shown withengine running, parking brakeapplied and service brakesreleased

The brake and pilot pumpsupplies oil to theaccumulator charging valveand pilot system

The accumulator chargingvalve keeps the pressure inthe service brakeaccumulator within aconstant range

The service brakeaccumulator stores oilpressure for operation of theservice brakes

Continued



The parking brake control valve consists of two solenoid control valves.When the solenoids are de-energised, pump oil is blocked at thecontrol valves.

The parking brake section of the wheel brakes is open to tank throughthe parking brake control valve. The parking brakes are applied byspring pressure.

Two solenoid control valvescontrol the operation of theparking brake



13

System Operation (Parking Brake Released)

TANK



REAR WHEELBRAKES

FRONT WHEELBRAKES


BRAKE ANDPILOT PUMP

TO P

ILO

TSY

STEM


PILOTRELIEF VALVE

STEERINGPUMP


VALVE

When the parking brake control in the cab is moved to the releasedposition, power is sent to energise the parking brake solenoid controlvalves.

Oil from the brake and pilot pump flows through the pilot relief valve tothe parking brake control valve. The pilot relief valve controls themaximum pressure in the parking brake circuit.

Oil flows to the parking brake section of the wheel brakes. The oilpressure causes the parking brake piston to retract, releasing theparking brake.

Braking system shown withengine running, parkingbrake released and servicebrakes released

The pilot relief valvecontrols the oil pressure inthe parking brake circuit

When the parking brakecontrol is moved to thereleased position, theparking brake solenoidcontrol valves areenergised

Pressure oil is sent to theparking brake section ofthe wheel brakes



14

System Operation (Service Brakes Applied)

TANK



REAR WHEELBRAKES

FRONT WHEELBRAKES


BRAKE ANDPILOT PUMP

TO P

ILO

TSY

STEM


PILOTRELIEF VALVE

STEERINGPUMP


VALVE

Oil from the brake and pilot pump flows through the accumulatorcharging valve to the service brake accumulator. The service brakeaccumulator stores hydraulic oil pressure for the operation of theservice brakes. When the service brake accumulator is fully chargedwith oil, the accumulator charging valve sends the pump oil flow totank.

The service brake control valve is in the circuit from the service brakeaccumulator to the service brakes. When the brake pedal is pushed,oil from the service brake accumulator goes to the service brakesection of the wheel brakes. The service brake control valve is atandem type valve providing split system braking. In the event of afailure in either the front or rear brake system, the other portion of thevalve will continue to function.

After the service brakes have been activated several times, the volumeof oil in the service brake accumulator is reduced. The piston in theservice brake accumulator moves down towards the oil end until thereis a decrease in pressure. The accumulator charging valve cuts insending oil from the brake and pilot pump to the accumulator.

Braking system shown withengine running, parking brakereleased and service brakesapplied

The accumulator chargingvalve charges the servicebrake accumulator withpressure oil

When the brake pedal isdepressed, pressure oilmoves the service brakepiston to apply the brakes

The further the pedal isdepressed, the greater thepressure at the wheel brakes



15

Towing Brake Release System

The towing brake release system allows the operator to release theparking brakes if the brakes are applied due to a machine fault. Whenthe brakes are released, the machine can be towed to a service area.The system is activated by a towing hook (5) compressing the towingbrake release piston in the machine towing bar.

The towing brake release system must only be activated by aThe towing brake release system must only be activated by aThe towing brake release system must only be activated by aThe towing brake release system must only be activated by aThe towing brake release system must only be activated by atowing hook securely attached to the recovery machine. Thetowing hook securely attached to the recovery machine. Thetowing hook securely attached to the recovery machine. Thetowing hook securely attached to the recovery machine. Thetowing hook securely attached to the recovery machine. Thetowing hook must be securely attached to the towing bar of thetowing hook must be securely attached to the towing bar of thetowing hook must be securely attached to the towing bar of thetowing hook must be securely attached to the towing bar of thetowing hook must be securely attached to the towing bar of theinoperative machine prior to activating the release system. Failureinoperative machine prior to activating the release system. Failureinoperative machine prior to activating the release system. Failureinoperative machine prior to activating the release system. Failureinoperative machine prior to activating the release system. Failureto do so may result in the towed machine moving, causing seriousto do so may result in the towed machine moving, causing seriousto do so may result in the towed machine moving, causing seriousto do so may result in the towed machine moving, causing seriousto do so may result in the towed machine moving, causing seriouspersonal injury or death.personal injury or death.personal injury or death.personal injury or death.personal injury or death.When the machine has been towed to a safe place, ensure that it isWhen the machine has been towed to a safe place, ensure that it isWhen the machine has been towed to a safe place, ensure that it isWhen the machine has been towed to a safe place, ensure that it isWhen the machine has been towed to a safe place, ensure that it isparked on a level surface and that the wheels are blocked securelyparked on a level surface and that the wheels are blocked securelyparked on a level surface and that the wheels are blocked securelyparked on a level surface and that the wheels are blocked securelyparked on a level surface and that the wheels are blocked securelyso the machine can not move prior to any service work beingso the machine can not move prior to any service work beingso the machine can not move prior to any service work beingso the machine can not move prior to any service work beingso the machine can not move prior to any service work beingperformed on the machine.performed on the machine.performed on the machine.performed on the machine.performed on the machine.Ensure the inoperative machine can not move before disconnectingEnsure the inoperative machine can not move before disconnectingEnsure the inoperative machine can not move before disconnectingEnsure the inoperative machine can not move before disconnectingEnsure the inoperative machine can not move before disconnectingthe towing hook.the towing hook.the towing hook.the towing hook.the towing hook.

Towing brake release systemcomponents:(1) Brake release cylinder(2) Towing brake release

sequence valve(3) Shuttle valves(4) Check valve(5) Towing hook

The towing brake releasesystem allows release of theparking brake in the event ofa machine fault

The towing brake releasesystem is activated when thetowing brake release cylinderpiston is moved up

1. Brake release cylinder.2. Brake release sequence valve.3. Shuttle valves.

1

3

2

5

4. Check valve. 5. Towing hook.

4



16

System Operation (Towing Brake Release Activated)

TANK


REAR WHEEL BRAKES

FRONT WHEEL BRAKES


BRAKE ANDPILOT PUMP

TO P

ILO

TSY

STEM


PILOTRELIEF VALVE

STEERINGPUMP

TOW BRAKERELEASECYLINDER

BRAKE RELEASESEQUENCE VALVE

SHUTTLEVALVE

EXTE

RNAL

FORC

E


VALVE


The towing brake release system is an attachment of the parking brakecircuit.

When the towing brake release system is activated, the piston in thetowing brake release cylinder is compressed against spring pressure.The piston moves up and covers the tank port. Movement of the pistonnow creates oil pressure which is directed, via a shuttle valve, to theparking brake section of the wheel brakes to release the brakes.

When the towing brake release cylinder piston is released, the springmoves the piston down. The oil pressure in the wheel brakes decreasesand the parking brakes apply.

During normal operation, when the operator releases the parkingbrake, the parking brake control valve sends oil pressure to the wheelbrakes. The oil pressure also activates the brake release sequencevalve. The sequence valve opens the towing brake release cylinder totank.

The towing brake releasesystem is activated by thetowing brake releasecylinder piston

The piston creates oilpressure as it moves upand this pressure releasesthe parking brake sectionof the wheel brakes

When the towing brakepiston moves down, theparking brakes apply

Continued



With the brake release sequence valve open to tank the towing brakerelease system is disabled during normal machine operation.

The check valve replenishes oil in the brake release system whenrequired.

When the towing brake release cylinder is in the deactivated position,the spring chamber is connected to the hydraulic tank port. Thisprevents a pressure increase (hydraulic lock) behind the shuttle valvesso the parking brakes can be released.

Brake release sequence valvedisables towing releasesystem during normalmachine operation

Check valve replenishes oil inthe brake system whenrequired

Tank port prevents hydrauliclock between shuttles anddeactivated piston



17

Brake Pressure Test Points

The pilot pressure test point (1) is located on the pilot oil filter. The testpoint is used for checking the pilot pressure in the parking brake,steering and implement hydraulic system.

The pressure point (2) located in the pressure manifold, below thebrake accumulator is for checking the CUT- IN, CUT- OUT pressures ofthe accumulator charging valve.

The accumulator charge relief valve (3) can only be tested and set on atest bench.

Identify components(1) Pilot pressure test point(2) Accumulator charging

valve pressure test point(3) Accumulator charge relief

valve

Testing & adjustingprocedures

1. Pilot pressure test point.

3

Always follow the procedures in the Service Manual when testing andadjusting the machine

12

12

2. Accumulator charging valve pressure test point.3. Accumulator charge relief valve.



18

Brake Electrical System

The parking brake system is controlled by parking brake control switch(1) in the cab. The standard parking brake control switch is a pull-to-apply type. When the switch is pulled out, the brakes will apply.Certain mining regulations require machines to be equipped with apush-to-apply parking brake control switch. When the switch is pushedin, the brakes are applied.

When the service brake oil pressure is in the operating range, servicebrake low oil pressure switches (2) and (3) will close. Switch (3) willprovide an earth for parking brake relay (4). If the park brake controlswitch is in the engaged position, the relay (4) will energise and latch.

If the engine is started with parking brake control switch (1) in therelease position, the brakes will not release as the parking brake relaywill not be latched. The switch must be moved to the engaged positionto latch the relay.

When the parking brake control switch is moved to the release position,power is supplied to park brake solenoid control valves (5) to release

The parking brake is engagedand released by the parkingbrake control switch

When the service brake oilpressure is in the operatingrange, the parking brake canbe released

If service brake oil pressurefalls below the operatingrange, the parking brake willapply

1. Parking brake control switch.2. Service brake oil low pressure switch (CMS).3. Service brake oil low pressure switch (B.A).

4. Parking brake relay.

5. Solenoids.6. Parking brake low oil pressure switch.7. Parking brake pressure switch (remotes).

Continued

1 3

2

4

76

55



If service brake oil pressure falls below the operating range, switch (3)will open. The parking brake relay will open and interrupt power tosolenoids (5). The parking brake will apply.

Service brake low oil pressure switch (2) is for the Caterpillar MonitoringSystem. When brake oil pressure falls below the normal operatingrange, the switch will open, causing a category three warning. TheCaterpillar Monitoring System alert indicator will come on, the fault lightwill flash and the fault alarm will sound.

The parking brake low oil pressure switch (6) is an input of the electronictransmission control. When the parking brake is engaged, the switchsends a signal to the transmission control. The control shifts thetransmission to neutral. The transmission control also sends theparking brake status to the Caterpillar Monitoring System over the datalink. When the parking brake is engaged, the alert indicator for theparking brake flashes on the Caterpillar Monitoring System. If theoperator selects FORWARD or REVERSE while the parking brake isengaged, the Caterpillar Monitoring System initiates a category 3warning.

Parking brake pressure switch (7) is part of the optional remote controlsystem.

The Caterpillar MonitoringSystem monitors the servicebrake oil pressure

If the service brake oilpressure falls below thenormal operating range, theCaterpillar Monitoring Systemwill initiate a category 3warning

The parking brake low oilpressure switch is an input ofthe transmission electroniccontrol - the signal tells thecontrol when the parkingbrake is engaged

The transmission electroniccontrol sends the parkingbrake low oil pressure switchsignal to the CaterpillarMonitoring System over theCat data link



19

System Operation (Power Supply)

+ 24v

10 A

10 A

272228183738

BCA

81413

123

123

123

10 1

12

12

PARKING BRAKERELAY

PARKING BRAKECONTROL SWITCH

REMOTE CONTROLSWITCH

SERVICE BRAKE LOWOIL PRESSURE SWITCH

TRANSMISSION PRESSURESWITCH ABA

PARKING BRAKESOLENOIDS

REMOTE CONTROL

BRAKE CONTROL

POWER SUPPLY FROM REMOTECONTROL CIRCUIT BREAKER

POWER SUPPLY FROMBRAKE CONTROL CIRCUIT BREAKER

GROUND CIRCUIT

87 30

This schematic shows the wires that have battery voltage with the keyswitch in the on position, and the parking brake control switch in thebrake engaged position (engine off).

Power is then supplied from the brake control circuit breaker to theparking brake control switch. With the switch in the engaged positionpower is available at the parking brake relay which cannot be energisedbecause with the engine off there is no system pressure. The servicebrake low oil pressure switch and the ABA switch (Automatic BrakeApplication) contacts are therefore open, interrupting the ground circuitfor the parking brake relay.

NOTE:NOTE:NOTE:NOTE:NOTE:If the ABA transmission oil pressure switch (optional) is not fitted a loopwire is fitted to the three pin plug to complete the circuit to the brakecharge pressure switch (as shown).

Power is supplied to terminal 30 on the parking brake relay through theremote control switch (optional) from the remote control system circuitbreaker.

Key on engine not running

Power is supplied from brakecontrol circuit breaker toparking brake relay

Loop wire fitted whenoptional impending brakeapplication is not required

Power supplied to terminal 30on brake relay from remotecontrol circuit breaker



20

System Operation (Relay Latched and Parking Brake Engaged)

+ 24v

10 A

10 A

272228183738

BCA

81413

123

123

123

10 1

12

12

PARKINGBRAKE RELAY





REMOTE CONTROL

BRAKE CONTROL



GROUND CIRCUIT

87 30


With the engine running the transmission oil pressure will rise. Thetransmission pressure (ABA) switch (if fitted) will close.

At the same time the brake oil pressure will increase. The service brakelow oil pressure switch will close. With both switches in the closedposition the parking brake relay circuit is completed to ground and theparking brake relay will latch.

With engine runningtransmission and brake oilpressure will increase

With both switches closedthe parking brake relay willlatch



21

System Operation (Parking Brake Released)

+ 24v

10 A

10 A

272228183738

BCA

81413

123

123

123

10 1

12

12

PARKING BRAKERELAY





REMOTE CONTROL

BRAKE CONTROL


POWER SUPPLY TO ENERGISEPARK BRAKE SOLENOIDS

GROUND CIRCUITTRANSMISSION PRESSURESWITCH ABA

87 30

Power is supplied from the remote circuit breaker to latch the parkingbrake relay.

Once the parking brake relay is latched and the parking brake switch ismoved to the released position, power is directed to parking brakesolenoids. The parking brake solenoids are energised and the parkingbrakes are released.

Parking brake relay islatched by power fromremote circuit breaker

Once relay is latched,parking brake can bereleased



22

Parking Brake CMS Component Location

The display area of the CMS shows the operator the condition of themachine systems and alerts the operator to any abnormal machineconditions that may exist.

In the CMS electrical brake system three switches and alert indicatorsare used.a. Parking brake low oil pressure switch.b. Service brake low oil pressure switch.c. Impending brake application.The parking brake pressure switch (1) is located below the brakerelease control valve on the left hand inside wall of the rear frame.

The parking brake pressure switch via the electronic transmissioncontrol module, activates the alert indicator (4) on the CMS panel whenthe parking brake is engaged.

When the parking brake is released the park brake pressure switch willopen. The parking brake light on the CMS panel will then go out.

CMS display area alerts theoperator to any abnormalmachine conditions

Brake system uses threeswitches and alert indicators

Parking brake pressureswitch activates the parkingbrake alert indicator on theCMS dash when parkingbrakes are applied.

1. Parking brake low oil pressure switch.

4. Parking brake low oil pressure alert indicator.5. Service brake low oil pressure alert indicator.6. Impending brake application alert indicator.

1

2. Impending brake application switch.

2

4

6

5

3. Service brake low oil pressure switch (C.M.S).

3

Continued



The parking brake pressure switch sends a signal to the transmissioncontrol module. When the emergency /parking brake is applied, thisswitch will close, causing the transmission to neutralise. When theparking brake is released, the transmission will resume normaloperation.

The service brake low oil pressure switch (3) is located on the left handinside wall of the rear frame.

When the machine is started the brake system oil pressure increases.When the pressure reaches the setting of switch (3) its contacts willclose causing the low brake oil pressure light (5) on the CMS panel togo out. The parking brake can now be released.

If the service brake oil pressure decreases to below the setting ofswitch (3) its contacts will open and the service brake low oil pressurelight on the CMS panel will come on, warning the operator of lowservice brake oil pressure.

The impending brake application switch (2) (optional) is located onback of the hydraulic pilot filter housing above the torque converter.

If the transmission oil pressure falls below the setting of switch (2), theimpending brake application light (6) on the dash will illuminate warningthe operator of the abnormal condition.

Park/ing brake released,switch will open and parkbrake alert indicator willdeactivate

The parking brake pressureswitch sends a signal to thetransmission control module.

Service brake low oilpressure switch.

Switch for impending brakeapplication light. (IBA)



23

System Operation CMS (Parking Brake Released)

PARKING BRAKE LOWOIL PRESSURE SWITCH

SERVICE BRAKE LOW OIL PRESSURE SWITCH CMS

IBA CMSSWITCH CAT DATA LINK CIRCUIT

SERVICE BRAKE LOW OILPRESSURE SWITCH CMSCIRCUIT

IMPENDING BRAKEAPPLICATION CIRCUIT

PARKING BRAKE LOW OILPRESSURE SWITCH CIRCUIT

123

123

123

CBA

1011

2736395

1234

PARK BRAKE SWITCH N.CPARKBRAKE SWITCH N.OCAT DATA LINK -CAT DATA LINK +GROUND

232435332

CAT DATA LINK +CAT DATA LINK -BRAKE OIL PRESSUREIMPENDING BRAKE APP.GROUND

ELECTRONIC TRANSMISSIONCONTROL

COMPUTERISED MONITORINGSYSTEM

The parking brake cannot be released until the brake and transmissionoil pressure increases. This increase in pressure will cause the servicebrake low oil pressure switch and impending brake application (I.B.A.)switch (if fitted) to close, causing the alert indicators on the CMS dashto go out.

When the parking brakes are released the parking brake low oil pressureswitch closes sending a signal to the electronic transmission control.This signal is then communicated to the CMS on the CAT control datalink causing the parking brake light to go out.

The CAT data link is bidirectional, allowing the transmission control toreceive and send information. The purpose of the data link is to enablethe transmission control to communicate with the ComputerisedMonitoring System (CMS). The data link is not a single visiblecomponent as it consists of internal control circuits and connectingwiring harness.

NOTE:NOTE:NOTE:NOTE:NOTE:When the impending brake application is not fitted a loop wire is fittedto complete the circuit to ground (as shown above).

Parking brake can not bereleased until brake andtransmission have systempressure

CAT Data Link allows thetransmission control toreceive and send informationto the computerisedmonitoring system

Loop wire fitted whenoptional impending brakeapplication is not fitted



24

Stop Light and Residual Brake Pressure Light Circuit Components

The components of this circuit are; stop light switch (1), stop light (2),rear brake pressure switch (3) and residual brake pressure light (4).

The stop light switch (1) is mounted in the front brake circuit at theoutlet of the brake control valve.

If the machine is equipped with a residual brake pressure option a rearbrake pressure switch (3) is also fitted.

When the service brakes are applied the stop light (2) will illuminate.

NOTE:NOTE:NOTE:NOTE:NOTE:Operating the machine with residual pressure will cause overheating ofthe brakes and may severely shorten the service life of brakecomponents.

Identify components:(1) Stop light switch(2) Stop light(3) Residual brake pressure

switch(4) Residual brake pressure

light

Operating the machine withthe residual pressure willcause overheating of thebrakes and may severelyshorten the service life ofbrake components

1. Stop light switch. 2. Stop light.

3. Rear brake pressure switch. 4. Residual brake pressure light.

21

3

4



25

System Operation (Stop Light/Residual Brake Pressure Circuit)

312

3 1 2

12

915A

TS

TO FRONTLIGHT SWITCH

STOP/TAILLAMP

CAB

FRONT BRAKEPRESSURE SWITCH

REAR BRAKEPRESSURE SWITCH

+24V

POWER SUPPLY

STOP LIGHT CIRCUITRESIDUAL BRAKEPRESSURE LIGHT

When the service brakes are applied oil pressure will close the brakepressure switches and completes the circuit to the stop/tail lampPower will now be supplied to illuminate the stop light.If the machine is equipped with a residual brake pressure circuit a rearbrake pressure switch is also fitted (as shown).

When the service brake is applied the brake oil pressure rises abovethe setting of residual brake pressure switches. The switches will closecompleting the circuit to the residual brake pressure light. Power willnow be supplied to illuminate residual brake pressure light.

If the residual brake oil pressure remains in the wheel brakes above thesetting of the switches after the brakes have been released, the lightwill remain illuminated. Also the rear brake light will illuminate.

When the service brakes areapplied will close the brakepressure switches andcompletes the circuit to thestop/tail light

Machine equipped with aresidual brake pressurecircuit are fitted with a rearbrake pressure switch andlight



26

Electric Brake Release System

The electric brake release circuit allows the operator to release theparking brake if the brake is applied due to a machine fault. When thebrakes are released, the machine can be towed to a service area.

The electric brake release circuit is controlled by a switch located onthe circuit breaker board in the operators station.

The electric brake release circuit uses an electric hydraulic pump tosupply oil to the parking brake circuit and the service brake circuit.

When the brake system is fully charged, the operator must use theparking brake control switch to release the brakes.

Because the service brake circuit is charged with oil, the service brakecan be used to stop the machine during towing, etc.

Brake Release CircuitComponents:(1) Brake release pump(2) Brake release pump

relay(3) Brake release switch(4) Park brake control

switch

The brake release circuitallows the operator to releasethe parking brake

The pump is activated by aswitch located on the circuitbreaker board.

An electric hydraulic pumpcharges the parking brakecircuit and service brakecircuit

1. Brake release pump.

1

2. Brake release pump solenoid.

3. Brake release pump switch.

3

2

4

4. Park brake control switch.



27

System Operation (Electric Brake Release)

BRAKE RELEASEMOTOR

POS NEG

GS

MOTOR

MTRBAT

MOTOR

15A

675A

POS NEG

6

BRAKECONTROL

BRAKE RELEASESWITCH BRAKE RELEASE

RELAY

FUSE

DISCONNECT SWITCH

12 VOLTBATTERIES

+24V

RELAY POWER SUPPLYBRAKE RELEASE MOTOR CIRCUIT

The above electrical schematic shows the brake release pumpactivated.

When the brake release toggle switch is held in the on position, powerfrom the brake control circuit breaker energises the brake release relay.Then power is supplied from the 675 amp fuse to activate the brakerelease pumps electrical motor.

Explain operation



28

Practical Tasks

Task 1Task 1Task 1Task 1Task 1: Each trainee will be required to successfully bleed down the oilpressure in the brake system.1. Find the procedure in Service Manual.2. Follow the procedure and successfully complete the task.

Task 2Task 2Task 2Task 2Task 2: Trainer to place a series of electrical faults on the machine.1. Place a faulty parking brake relay in the circuit.2. Remove wire EL332-BR from parking brake control switch.Each trainee will be required to successfully

1. Fault find the electrical faults, using the electrical schematic and service manual.2. Rectify the faults, test and start machine.

Always check the Service Manual for the correct adjusting procedureand specifications.Always follow the procedures contained in the Service Manual whentesting and/or adjusting the machine.

Bleed down oil pressure inthe brake system

Electrical Faults.

Service manual.

1. Electrical faults. 1. Bleed down oil pressure.



Q.1.Q.1.Q.1.Q.1.Q.1. Each wheel brake has:Each wheel brake has:Each wheel brake has:Each wheel brake has:Each wheel brake has:

A. One sectionB. Two sectionsC. Four sectionsD. Nine sections

Q.2.Q.2.Q.2.Q.2.Q.2. The parking brake is:The parking brake is:The parking brake is:The parking brake is:The parking brake is:

A. Oil applied and spring releasedB. Oil applied and releasedC. Oil released and spring appliedD. Pedal controlled

Q.3.Q.3.Q.3.Q.3.Q.3. The brake and pilot pump is a:The brake and pilot pump is a:The brake and pilot pump is a:The brake and pilot pump is a:The brake and pilot pump is a:

A. Centrifugal pumpB. Piston pumpC. Vane pumpD. Gear pump

Q.4.Q.4.Q.4.Q.4.Q.4. The accumulator charging valve divides the oil flow between the:The accumulator charging valve divides the oil flow between the:The accumulator charging valve divides the oil flow between the:The accumulator charging valve divides the oil flow between the:The accumulator charging valve divides the oil flow between the:

A. Pilot and transmission systemsB. Brake and pilot systemsC. Brake and hydraulic systemsD. Pilot and oil cooling systems

Q.5.Q.5.Q.5.Q.5.Q.5. The accumulator charge rThe accumulator charge rThe accumulator charge rThe accumulator charge rThe accumulator charge relief valve limits maximum oil prelief valve limits maximum oil prelief valve limits maximum oil prelief valve limits maximum oil prelief valve limits maximum oil pressuressuressuressuressure in the :e in the :e in the :e in the :e in the :

A. Pilot systemB. Parking brake systemC. Accumulator charging circuitD. Main hydraulic circuit

R2900 LHD Braking System

Theory Assessment

Directions: Multiple Choice.Read each statement carefully and circle the letter(s) of the correct answer(s)* Reference to notes and other literature is allowed.

Continued



Q.6.Q.6.Q.6.Q.6.Q.6. The service brake accumulator supplies oil under prThe service brake accumulator supplies oil under prThe service brake accumulator supplies oil under prThe service brake accumulator supplies oil under prThe service brake accumulator supplies oil under pressuressuressuressuressure to:e to:e to:e to:e to:

A. The parking brake control valveB. The service brake control valveC. The accumulator charging valveD. The pilot relief valve

Q.7.Q.7.Q.7.Q.7.Q.7. The service brake contrThe service brake contrThe service brake contrThe service brake contrThe service brake control valve is operated by a:ol valve is operated by a:ol valve is operated by a:ol valve is operated by a:ol valve is operated by a:

A. LeverB. SwitchC. PedalD. Solenoid

Q.8.Q.8.Q.8.Q.8.Q.8. The service brakes arThe service brakes arThe service brakes arThe service brakes arThe service brakes are:e:e:e:e:

A. Electronically appliedB. Spring applied and oil releasedC. Oil applied and releasedD. Oil applied and spring released

Q.9.Q.9.Q.9.Q.9.Q.9. The accumulator charging valve gives priority oil flow to:The accumulator charging valve gives priority oil flow to:The accumulator charging valve gives priority oil flow to:The accumulator charging valve gives priority oil flow to:The accumulator charging valve gives priority oil flow to:

A. The brake systemB. The brake and pilot systemsC. The hydraulic systemD. The transmission control valve

Q.10. The service brake accumulator is charged with:Q.10. The service brake accumulator is charged with:Q.10. The service brake accumulator is charged with:Q.10. The service brake accumulator is charged with:Q.10. The service brake accumulator is charged with:

A. Compressed airB. OxygenC. HydrogenD. Dry nitrogen



Q.1. B.

Q.2. C.

Q.3. D.

Q.4. B.

Q.5. C.

Q.6. B.

Q.7. C.

Q.8. D.

Q.9. A.

Q.10. D.

R2900 Braking System

Theory Assessment Answers



Q.1.Q.1.Q.1.Q.1.Q.1. The parking brake is contrThe parking brake is contrThe parking brake is contrThe parking brake is contrThe parking brake is controlled by:olled by:olled by:olled by:olled by:

A. A switch on the pilot control valveB. A switch on the main dash panelC. A switch on the circuit breaker boardD. The transmission electronic control module

Q.2.Q.2.Q.2.Q.2.Q.2. When the parking brake switch is moved to the engaged position:When the parking brake switch is moved to the engaged position:When the parking brake switch is moved to the engaged position:When the parking brake switch is moved to the engaged position:When the parking brake switch is moved to the engaged position:

A. The front wheel brakes releaseB. The rear parking brakes releaseC. The service brakes applyD. All the wheel brakes are activated

Q.3.Q.3.Q.3.Q.3.Q.3. The brake oil prThe brake oil prThe brake oil prThe brake oil prThe brake oil pressuressuressuressuressure switches are switches are switches are switches are switches are located on:e located on:e located on:e located on:e located on:

A. The inside left wall of the rear frameB. The inside right wall of the rear frameC. The radiator guardD. The right wall of the front frame

Q.4.Q.4.Q.4.Q.4.Q.4. The parking brake rThe parking brake rThe parking brake rThe parking brake rThe parking brake relay is located:elay is located:elay is located:elay is located:elay is located:

A. Behind the pilot control valveB. Under the STIC steer control valveC. Behind the CMS dashD. Under the operators seat

Q.5.Q.5.Q.5.Q.5.Q.5. The parking brake rThe parking brake rThe parking brake rThe parking brake rThe parking brake relay contrelay contrelay contrelay contrelay controls the:ols the:ols the:ols the:ols the:

A. Service brake applicationB. Release of the parking brakeC. Release of the service brakesD. Transmission gear selection

R2900 LHD Brake Electrical System

Theory Assessment

Directions: Multiple Choice.Read each statement carefully and circle the letter(s) of the correct answer(s)* Reference to notes and other literature is allowed.

Continued



Q.6.Q.6.Q.6.Q.6.Q.6. The parking brake solenoids arThe parking brake solenoids arThe parking brake solenoids arThe parking brake solenoids arThe parking brake solenoids are mounted on the:e mounted on the:e mounted on the:e mounted on the:e mounted on the:

A. Main implement control valveB. Brake system relief valveC. Transmission hydraulic controlsD. Hydraulic brake release control valve

Q.7.Q.7.Q.7.Q.7.Q.7. When rWhen rWhen rWhen rWhen remote contremote contremote contremote contremote control is fitted to the machine:ol is fitted to the machine:ol is fitted to the machine:ol is fitted to the machine:ol is fitted to the machine:

A. Two extra solenoid control valves are fittedB. One extra solenoid control valve is fittedC. Three extra solenoid control valves are fittedD. Five extra solenoid control valves are fitted

Q.8.Q.8.Q.8.Q.8.Q.8. When the transmission oil prWhen the transmission oil prWhen the transmission oil prWhen the transmission oil prWhen the transmission oil pressuressuressuressuressure rises the:e rises the:e rises the:e rises the:e rises the:

A. Parking brake switch will openB. ABA switch (if fitted) will openC. ABA switch (if fitted) will closeD. Parking brake switch will close

Q.9.Q.9.Q.9.Q.9.Q.9. When the service brake oil prWhen the service brake oil prWhen the service brake oil prWhen the service brake oil prWhen the service brake oil pressuressuressuressuressure incre incre incre incre increases to working preases to working preases to working preases to working preases to working pressuressuressuressuressure:e:e:e:e:

A. The brake charge pressure switch will closeB. The parking brake relay will unlatchC. The brake charge pressure switch will openD. The service brakes will apply

Q.10.Q.10.Q.10.Q.10.Q.10.The electric brake rThe electric brake rThe electric brake rThe electric brake rThe electric brake release pump is activated by:elease pump is activated by:elease pump is activated by:elease pump is activated by:elease pump is activated by:

A. The remote controlsB. The parking brake switchC. A toggle switch mounted on the dashD. A toggle switch mounted on the circuit breaker board



Q.1. B.

Q.2. D.

Q.3. A.

Q.4. C.

Q.5. B.

Q.6. D.

Q.7. B.

Q.8. C.

Q.9. A.

Q.10. D.

R2900 Brake Electrical System

Theory Assessment Answers



?

Servicemans Handout No. 1Braking System Component Location

(1) Brake and pilot pump(2) Accumulator charging valve(3) Pilot oil filter(4) Pilot relief valve(5) Brake system relief valve(6) Accumulator(7) Service brake control valve(8) Wheel brakes(9) Parking brake release solenoid(10) Hydraulic tank(11) Electric pump

3



5

Servicemans Handout No. 2Accumulator Charging Valve (Component Location)

(1) Spring(2) Check valve(3) Spool stop(4) Pilot valve spool(5) Pilot valve spring(6) Chamber(7) Charging valve spool(8) Orifice(9) Upper limit check ball(10) Lower limit check ball(11) Passage

11

7

3

8

6

5

4

21

9

10



10

Wheel Brake (Parking Brake Released)Servicemans Handout No.3

(1) Parking piston(2) Service piston(3) Outer casing(4) Springs(5) Wheel hub(6) Annular passage(7) Steel plates(8) Friction discs(9) Brake pack

Park BrakeOil Pressure



12

Servicemans Handout No. 4System Operation (Parkimg Brake Engaged)

TANK



REAR WHEELBRAKES

FRONT WHEELBRAKES


BRAKE ANDPILOT PUMP

TO P

ILO

TSY

STEM


PILOTRELIEF VALVE

STEERINGPUMP


VALVE

(1) Pressure oil(2) Pilot oil(3) Tank oil



13

Servicemans Handout No. 5System Operation (Parking Brake Released)

TANK



REAR WHEELBRAKES

FRONT WHEELBRAKES


BRAKE ANDPILOT PUMP

TO P

ILO

TSY

STEM


PILOTRELIEF VALVE

STEERINGPUMP


VALVE




14

Servicemans Handout No. 6System Operation (Service Brakes Applied)

TANK



REAR WHEELBRAKES

FRONT WHEELBRAKES


BRAKE ANDPILOT PUMP

TO P

ILO

TSY

STEM


PILOTRELIEF VALVE

STEERINGPUMP


VALVE




16

Servicemans Handout No. 7System Operation (Towing Brake Release Activated)

TANK


REAR WHEEL BRAKES

FRONT WHEEL BRAKES


BRAKE ANDPILOT PUMP

TO P

ILO

TSY

STEM


PILOTRELIEF VALVE

STEERINGPUMP

TOW BRAKERELEASECYLINDER

BRAKE RELEASESEQUENCE VALVE

SHUTTLEVALVE

EXTE

RNAL

FORC

E


VALVE





19

Servicemans Handout No 9System Operation (Power Supply)

+ 24v

10 A

10 A

272228183738

BCA

81413

123

123

123

10 1

12

12

PARKING BRAKERELAY



SERVICE BRAKE LOW0IL PRESSURE SWITCH

PARK BRAKESOLENOIDS

REMOTECONTROL

BRAKE CONTROL

POWER SUPPLY FROMREMOTE CONTROL CIRCUIT BREAKER


GROUND CIRCUIT

87 30




20

Servicemans Handout No. 10System Operation (Relay Latched and Parking Brake Engaged)

+ 24v

10 A

10 A

272228183738

BCA

81413

123

123

123

10 1

12

12

PARKING BRAKERELAY



SERVICE BRAKE LOW0IL PRESSURE SWITCH

PARK BRAKESOLENOIDS

REMOTECONTROL

BRAKE CONTROL

POWER SUPPLY FROMREMOTE CONTROL CIRCUIT BREAKER


GROUND CIRCUIT

87 30




21

Servicemans Handout No. 11System Operation CMS (Parking Brake Released)

PARKING BRAKEPRESSURE SWITCH

SERVICE BRAKE LOW OILPRESSURE SWITCH CMS

IBA CMSSWITCH CAT DATA LINK CIRCUIT

SERVICE BRAKE LOW OILPRESSURE SWITCH CMSCIRCUIT

IMPENDING BRAKEAPP, CIRCUIT

PARKING BRAKE LOW OILPRESSURE SWITCH CIRCUIT

123

123

123

CBA

1011

2736395

1234

PARK BRAKE SWITCH N.CPARKBRAKE SWITCH N.OCAT DATA LINK -CAT DATA LINK +GROUND

232435332

CAT DATA LINK +CAT DATA LINK -BRAKE OIL PRESSUREIMPENDING BRAKE APP.GROUND

ELECTRONIC TRANSMISSIONCONTROL

COMPUTERISED MONITORINGSYSTEM



25

Servicemans Handout No. 12System Operation (Stop Light and Residual Brake Circuit)

312

3 1 2

12

915A

TS

TO FRONTLIGHT SWITCH

STOP/TAILLAMP

CAB

FRONT BRAKEPRESSURE SWITCH

REAR BRAKEPRESSURE SWITCH

+24V

POWER SUPPLY

STOP LIGHT CIRCUITRESIDUAL BRAKEPRESSURE LIGHT



27

Servicemans Handout No. 13System Operation (Electric Brake Release)

BRAKE RELEASEMOTOR

POS NEG

GS

MOTOR

MTRBAT

MOTOR

15A

675A

POS NEG

6

BRAKECONTROL

BRAKE RELEASESWITCH BRAKE RELEASE

RELAY

FUSE

DISCONNECT SWITCH

12 VOLTBATTERIES

+24V

RELAY POWER SUPPLYBRAKE RELEASE MOTOR CIRCUIT

List of Contents Important Safety Notice R2900 Braking System Overview Introduction Braking System Block Schematic Braking System Component Location Location of Brake System Components Accumulator Charging Valve (Accumulator Fully Charged - Cut-Out Cycle) Accumulator Charging Valve (Accumulator Being Charged - Cut-In Cycle) Location of Brake System Components Service Brake Control Valve (Released Position) Service Brake Accumulator Wheel Brake (Parking Brake Released) Wheel Brake (Parking Brake Released - Service Brake Applied) System Operation (Parking Brake Engaged) System Operation (Parking Brake Released) System Operation (Service Brakes Applied) Towing Brake Release System Towing Brake Release System Operation (Towing Brake Release Activated) Brake Pressure Test Points Brake Electrical System System Operation (Power Supply) System Operation (Relay Latched and Parking Brake Engaged) System Operation (Parking Brake Released) Parking Brake CMS Component Location System Operation CMS (Parking Brake Released) Stop Light and Residual Brake Pressure Light Circuit Components System Operation (Stop Light/Residual Brake Pressure Circuit) Electric Brake Release System System Operation (Electric Brake Release) Practical Tasks Theory Assessment Theory Assessment Answers Theory Assessment Theory Assessment Answers Serviceman's Handouts

TEXT: USE TOOLBAR CONTROLS

Documents

BRAKING R2900.pdf