1. General. The propel system allows the roller to move either forward or backward. When the engine is started,
oil under pressure oil from the charge (control) circuit flows to the propel control valves. When the propel
control lever (which is connected to the propel control valves) is in the forward or reverse position, oil is sent
to the propel hydraulic pump. The further the lever is pushed, the higher the oil pressure sent to the hydraulic
pump. The more pressure there is, the faster the roller will move. The hydraulic pump pushes oil through
hydraulic lines until the oil enters the propel motors. The front and rear propel motors turn the propel
gearboxes which turn the roller drums. Inside each propel gearbox is a brake. This brake is always engaged
unless pressure from the brake/shift manifold is present. This pressure is controlled by the propel control
If the roller needs to move while the engine is not able to supply the pump with power, there is a manual
brake release pump on the roller. This manual brake release pump pressurized the hydraulic lines releasing
the brakes. Also, there are brake and neutral start relays in the system which prevent movement of the roller
during the starting procedure.
2. Fuel/Hydraulic Pump. The fuel/hydraulic oil tank consists of the hydraulic tank (located on the right-side)
and the fuel tank (located on the right-side). Although the tanks are welded together, they are separate in
their function. The CB534B Roller hydraulic oil tank holds 15.5 gal (59 Liters) of hydraulic oil. The CB534C
Roller hydraulic oil tank holds 24 gal (91 Liters) of hydraulic oil.
3. Propel Hydraulic Pump. The propel hydraulic pump is a variable displacement, piston-type pump mounted
in tandem with the vibratory hydraulic pump to the engine. Both run at engine speed and rotate clockwise
as seen from the drive end of the pump.
4. Propel Motors. The hydraulic propel motors are located on the left-side of the front drum and the right-side
of the rear drum. The front motors is a fixed displacement axial piston-type motor. The rear motor is a variable
displacement axial piston-type motor.
5. Propel Control Lever and Valve. The propel control lever controls the direction of the roller. If the lever is
pushed forward, the control valve, which is connected to the lever, directs fluid to the propel hydraulic pump
in such a way that the hydraulic pump sends oil to the propel motor to turn forward. This propel pump sends
fluid the opposite direction if the control lever is pulled backward. The further the lever is pulled, the higher
the oil pressure being sent from the control valve is. The more control valve pressure, the more volume of
fluid the pump sends to the motors and the faster the roller travels.
6. Parking Brake Switch. The parking brake switch keeps the roller from moving by interrupting the inputs
from the control valve. The hydraulic pump will not send oil to the motors that the brake will not disengage
while the parking brake is on . The parking brake switch glows red when parking brake is engaged.
7. Brake and Neutral Start Relays. The brake and neutral start relays are safety devices that interrupt the
electrical signal to the starter if the control lever is not in the neutral, or center position. This ensures that
the roller will not move while the engine is being started.
8. Steering Pump. The steering pump provides a charge pressure to the propel system. This charge pressure
sends source pressure to the brake/shift valves. The charge pressure is used to supply the propel control
valve with signal oil, and to disengage the brakes.
9. Brake/Shift Valves. The brake/shift valves distribute the charge pressure to the propel control valve and
the brakes. When pressure is sent from the control valve, the brake/shift valve sends pressure to release
the brakes. The brakes/shift valves also control the speed range of the roller operates. The operator controls
the speed range by an electrical switch that operates the valve solenoid. This solenoid either opens or closes
the brake/shift valve changing the fluid pressure to propel control valve which effectively changes the speed