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Systems Operation
3406E Truck Engine
Media Number -RENR1273-07 Publication Date -01/02/2008 Date Updated -07/02/2008

i01144418

BrakeSaver
SMCS - 1155

The BrakeSaver permits the operator to control the speed reduction of the vehicle on grades and
curves. The BrakeSaver permits the operator to control the speed reduction at any time when speed
reduction is necessary but long applications of the service brakes are not desired.

BrakeSaver Components

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Illustration 1 g00292547
BrakeSaver components

(1) Flywheel housing

(2) Rotor

(3) BrakeSaver housing

(4) Flywheel

(5) Crankshaft flange

(6) Ring gear plate

(7) Stator

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BrakeSaver housing (3) is fastened directly to the rear face of flywheel housing (1). The BrakeSaver
adds approximately four inches to the length of the engine drive train. Rotor (2) and ring gear plate
(6) are installed between the rear flange of crankshaft (5) and flywheel (4). The engine can use a
standard starter motor with ring gear plate (6). The rotor turns in a space between stator (7) and
BrakeSaver housing (3).

Illustration 2 g00292548

BrakeSaver Components

(8) The rear section of the oil pump.

(9) BrakeSaver

(10) Tube

(11) Hole

(12) Bypass valve

(13) Baffle

(14) The front section of the oil pump.

(15) Engine oil pan

(16) BrakeSaver control valve

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(17) Line

(18) Line

The engine oil pump has two sections. Front section (14) of the oil pump supplies oil to the engine
for lubrication. Rear section (8) of the oil pump sends engine oil through BrakeSaver control valve
(16) to BrakeSaver (9). The rear section of the oil pump also sends oil through line (17) to the engine
oil cooler (not shown). From the oil cooler, the cool oil goes through line (18), through baffle (13)
and back into the engine oil pan (15) .

Tube (10) allows the oil in the BrakeSaver to rapidly go out of the BrakeSaver when the BrakeSaver
is turned off. This oil returns to the engine oil pan.

The oil has a high viscosity when the engine is cold (starting conditions). The high viscosity causes a
restriction to the oil flow through the oil cooler. A restriction in the oil cooler will result in an oil
pressure difference in bypass valve (12). The oil pressure difference will cause the valve to open. An
open bypass valve will cause the oil from the rear section of the oil pump to go through hole (11) in
bypass valve (12). The oil drains into engine oil pan (15) .

BrakeSaver Lubrication

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Illustration 3 g00292550
BrakeSaver lubrication

(1) Oil line

(2) Orifice

(3) Piston type ring seal

(4) Orifice

(5) Chamber

(6) Piston type ring seal

(7) Lip type seal

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(8) Lip type seal

(9) Oil drain line

Piston type ring seal (3) and piston type ring seal (6) keep pressurized oil in chamber (5) around the
rotor during operation. Lip type seal (7) and lip type seal (8) prevent oil leakage from the
BrakeSaver. Outside oil line (1) from the engine lubrication system sends engine oil to the
BrakeSaver housing.

Orifice (2) and orifice (4) in the BrakeSaver send oil to the space between the lip seals and the piston
type seals. Oil is delivered at a rate of 1.24 L/min (0.33 US gpm). The oil lubricates the seals under
all conditions of operation.

The space between the lip type seals and the piston type seals is connected to oil drain line (9). The
line allows the oil to return to the engine oil pan.

BrakeSaver Operation
The crankshaft is driven by the rear wheels during deceleration. The crankshaft is also driven by the
rear wheels during downhill operation. The speed of the vehicle is reduced by applying a braking
force to the crankshaft. The braking force is attained when the BrakeSaver converts the energy of
rotation into heat. The heat is removed by the engine cooling system.

Illustration 4 g00292551
BrakeSaver housing and rotor

(1) BrakeSaver housing

(2) Pocket

(3) Hole

(4) Pocket

(5) Rotor

Rotor (5) is fastened to the engine crankshaft. The rotor turns with the engine crankshaft. The rotor
has pockets (4) on the outer circumference of both sides. The rotor has four holes (3). The pockets
and the holes permit an equal flow of oil to both sides of the rotor.

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BrakeSaver housing (1) and the stator are fastened to the flywheel housing. The BrakeSaver housing
and the stator can not turn. Pockets (2) are located on the inside surfaces of the BrakeSaver housing
and the stator. These pockets are in alignment with pockets (4) in the rotor.

Illustration 5 g00292592

Oil flow through the BrakeSaver

(1) BrakeSaver housing

(2) Pocket

(4) Pocket

(5) Rotor

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(6) Stator

A compartment is created by stator (6) and BrakeSaver housing (1). Rotor (5) turns in the
compartment. When the BrakeSaver housing is in operation, engine oil comes into this compartment.
Oil comes into the compartment through a passage. This passage is located near the center of the
bottom of the BrakeSaver housing. Oil is thrown outward as the rotor turns with the crankshaft. As
the oil flows outward, the shape of rotor pockets (4) send the oil into pockets (2) of the stator and
BrakeSaver housing. The oil takes the shape of a spiral as the rotor turns and the oil flows around the
BrakeSaver compartment.

The oil is constantly cut by the vanes (material between the pockets) of the rotor as the oil flows
around the BrakeSaver compartment. This cutting action gives resistance to the rotor and changes
the energy of the rotor into heat in the oil. The heat is removed by the oil cooler within the engine
cooling system.

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Illustration 6 g00292593
Oil flow in the BrakeSaver

(1) BrakeSaver housing

(5) Rotor

(6) Stator

(7) Spiral flow

(8) Air pocket

More oil starts to flow in a spiral shape between the rotor and the stator when the BrakeSaver inlet
passage opens. Air pocket (8) is inside spiral flow (7) of oil. As the pressure in the rotor
compartment increases, the amount of oil in the spiral flow increases in thickness and the air pocket
has compression. The amount of oil that is cut by the rotor vanes increases as the compression in the
air pocket increases.

The level of braking can be controlled by the inlet oil pressure when the BrakeSaver is in operation.
The braking force is in direct relation to the amount of oil that is cut by the rotor vanes. The inlet
passage to the rotor compartment is closed by the control valve. There is no oil in the BrakeSaver
compartment when the BrakeSaver is not in operation.

BrakeSaver Control

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Illustration 7 g00292595
The BrakeSaver oil flow while the BrakeSaver is "OFF".

(1) BrakeSaver control lever

(2) Oil cooler

(3) Valve spool

(4) BrakeSaver control valve

(5) Oil pump

(6) BrakeSaver

(7) Line

(8) Oil pan

When BrakeSaver control lever (1) is in the "OFF" position, spring force holds valve spool (3)
against the cover at the air inlet end of BrakeSaver control valve (4). With valve spool (3) in this
position, oil pump (5) sends engine oil from oil pan (8) through BrakeSaver control valve (4) to the
oil cooler (2). From the oil cooler, the oil goes through the control valve, through line (7) and back to
the engine oil pan (8). With the BrakeSaver control valve in this position, no oil is sent to
BrakeSaver (6).

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Illustration 8 g00292596
Oil flow while the BrakeSaver is being filled.

(1) BrakeSaver control lever

(2) Oil cooler

(3) Valve spool

(4) BrakeSaver control valve

(5) Oil pump

(6) BrakeSaver

(7) Line

(8) Oil pan

When BrakeSaver control lever (1) is moved to the "ON" position, pressure air moves valve spool
(3) to the right against the spring force. With the valve spool in this position, engine oil from the oil
pump (5) is sent through BrakeSaver control valve (4) to the rotor compartment of BrakeSaver (6).
From the BrakeSaver, the oil goes through the control valve, through oil cooler (2), back through the
control valve, and back into the BrakeSaver.

The oil cannot go back to engine oil pan (8) because the passage through the control valve to line (7)
is closed by the valve spool.

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The time that is required to fill the BrakeSaver with pressurized oil to the point of maximum braking
in the BrakeSaver is approximately 1.8 seconds.

Illustration 9 g00292597
Oil flow while the BrakeSaver is in operation.

(1) BrakeSaver control lever

(2) Oil cooler

(3) Valve spool

(6) BrakeSaver

(8) Oil pan

As BrakeSaver (6) fills, the turning rotor causes an increase in the oil pressure in the BrakeSaver.
The inlet oil and the outlet oil of the BrakeSaver goes into the spring bore of valve spool (3). The oil
pressure works against the pressurized air that is on the left end of the valve spool. This force is the
average of the inlet oil pressure and the outlet oil pressure in the spring bore plus the force of the
spring. When the force of the pressurized oil plus the spring force become larger than the force of the
pressurized air the valve spool moves to the left. This movement causes a restriction in the passage
for the inlet oil. This restriction causes a decrease in oil pressure in the BrakeSaver.

A decrease in rotor speed will cause a decrease in the oil pressure in the BrakeSaver. This causes a
decrease in oil pressure in the spring bore of the valve spool. The spool will move to the right
because air pressure is exerted on the left end of the spool. This movement opens the passage for the

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inlet oil and the oil pressure in the BrakeSaver increases.

An increase in rotor speed will cause an increase in the oil pressure in the BrakeSaver. This increase
in the oil pressure will cause the valve spool to move to the left. Inlet oil is then restricted to the
BrakeSaver.

The valve spool is constantly moving. The movement of the valve spool makes adjustments to the
BrakeSaver inlet pressure in order to compensate for the changing rotor speeds. The changing rotor
speeds are caused by normal operation of the vehicle. The constant movement of the valve spool
keeps the amount of braking force in the BrakeSaver at a constant level.

During normal operation, the outlet oil from the BrakeSaver goes to oil cooler (2). From the oil
cooler, some of the oil (approximately 60 percent) goes back to the BrakeSaver inlet and the
remainder of the oil from the oil cooler goes to engine oil pan (8).

Illustration 10 g00615616
Oil flow while the BrakeSaver is being drained.

(1) BrakeSaver control lever

(2) Oil cooler

(3) Valve spool

(4) BrakeSaver control valve

(5) Oil pump

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(6) BrakeSaver

(7) Line

(8) Oil pan

When BrakeSaver control lever (1) is moved to the "OFF" position, the pressurized air on the left
end of valve spool (3) goes out of control valve (4). With no pressurized air in the valve, the
pressurized oil that is in the spring bore plus the spring force move the valve spool against the cover
at the air inlet end of the control valve. This movement closes the BrakeSaver inlet passage. The
rotor in BrakeSaver (6) pushes the oil out of the BrakeSaver. From the BrakeSaver, the oil goes
through the control valve, through line (7) and back to engine oil pan (8) .

The time that is required to remove the oil from the BrakeSaver is approximately 1.5 seconds.

With the control valve in this position, oil pump (5) sends oil through oil cooler (2) and through line
(7) back to the oil pan.

Operator Controls
Two types of controls are available for the BrakeSaver: a manual control and an automatic control.

Manual Control

Illustration 11 g00292599
Manual control diagram

(1) Pressure reducing valve

(2) Manual control valve

(3) BrakeSaver control lever

(4) Air pressure gauge

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(5) Oil temperature gauge

(6) BrakeSaver control valve

Pressurized air from the air system of the vehicle is sent to pressure reducing valve (1). The air
pressure is controlled to 345 kPa (50 psi). This controlled pressurized air goes to manual control
valve (2) .

When the operator moves BrakeSaver control lever (3) toward the "ON" position, pressurized air is
sent to BrakeSaver control valve (6). A higher pressure of air is sent to the BrakeSaver control valve
when lever (3) is moved further toward the "ON" position. An increase in air pressure that is in the
BrakeSaver control valve causes an increase in the oil pressure that is in the BrakeSaver. An increase
in the oil pressure in the BrakeSaver causes an increase in the braking force in the BrakeSaver. The
operator can give modulation to the braking force in the BrakeSaver through the movement of
BrakeSaver control lever (3) .

When the BrakeSaver is turned "OFF", the pressurized air goes out of the system through a passage
in manual control valve (2). Pressurized air is released out of the BrakeSaver control valve (6). This
removes the braking force from the BrakeSaver.

An oil temperature gauge (5) gives the operator an indication of the ability of the engine cooling
system to control the heat that is in the BrakeSaver during operation. If the gauge registers "HOT",
the operator should move the BrakeSaver control lever (3) to the "OFF" position. The operator
should use the service brakes to control the wheel speed of the vehicle. The oil temperature will
become normal again when the BrakeSaver is off. The operator can use the BrakeSaver once the
temperature returns to the normal temperature.

NOTICE
Do not manually engage the BrakeSaver and control the wheel speed
with the accelerator. The design of the cooling system is for the control
of the temperature of the oil at full engine power or full BrakeSaver
capacity. The cooling system can not handle full engine power and full
BrakeSaver capacity at the same time.

Automatic Control

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Illustration 12 g00505018
(1) Manual control valve

(2) Pressure reducing valve

(3) BrakeSaver solenoid relay

(4) "ON/OFF" switch for the BrakeSaver

(5) Circuit protection

(6) Battery

(7) Air pressure gauge

(8) Double check valve

(9) Electronic Control Module (ECM)

(10) Oil temperature gauge

(11) BrakeSaver control valve

(12) BrakeSaver solenoid valve

All the components of the manual control are in the automatic control. All the components function
in the same manner. In the automatic control, there is also a BrakeSaver solenoid valve (12), a
double check valve (8), and the ECM. When the BrakeSaver solenoid valve (12) is activated, the
BrakeSaver solenoid valve (12) sends pressurized air from pressure reducing valve (2) to BrakeSaver
control valve (11). BrakeSaver solenoid valve (12) is connected to the ECM (9) .

The mode selector switch has two positions: MANUAL and AUTOMATIC.

When the electric current opens BrakeSaver solenoid valve (12), full air pressure 345 kPa (50 psi) is
sent through the double check valve (8) to BrakeSaver control valve (11). The double check valve
keeps the pressure air from going out of the system through manual control valve (1) when the
control lever of the manual control valve (1) is not active. The double check valve also keeps the
pressurized air from going out of the system through BrakeSaver solenoid valve (12) when the

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manual control is active.

Because the solenoid valve sends full air pressure to BrakeSaver control valve (11), there is no
modulation in the "AUTOMATIC" position.

When the BrakeSaver is turned "OFF", the pressurized air goes out of the system through a passage
in manual control valve (1) or in BrakeSaver solenoid valve (12). The pressurized air is out of
BrakeSaver control valve (11) and the braking force is removed from the BrakeSaver.

Manual control valve (1) can be operated with the mode selector switch in the "AUTOMATIC"
position. During normal operation, the solenoid valve will send full air pressure to the BrakeSaver
control valve. This will remove the effect of the manual control valve. The manual control valve will
have an effect when the mode selector switch is in the "AUTOMATIC" position and there is an
electrical system failure.

Manual control valve (1) can also be operated with the engine system in the Cruise Control Mode.
Under this condition, the cruise control switch is in the "ON" position. When the Cruise Control
Mode is in operation, the air pressure is directed to BrakeSaver control valve (11) and to BrakeSaver
ON/OFF switch (4). The cruise control circuit is disabled when BrakeSaver ON/OFF switch (4)
opens.

Copyright 1993 - 2016 Caterpillar Inc. Sun Jun 5 09:50:19 UTC+0700 2016
All Rights Reserved.
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