All wheels of the wheel tractor-scraper are equipped with air brakes. The air brakes are actuated by air pressure when the service brake pedal (1) is pushed by the operator. The braking force increases as the pedal pressure is increased.
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| Illustration 1 | g00315249 |
The service brakes on wheel tractor-scrapers are designed to stop the machine. The service brakes should not be used repeatedly to slow the machine partially during retarder operation.
All four wheels of the wheel tractor-scraper are equipped with spring applied parking brakes. The parking brakes and service brakes use the same brake actuator to activate the brakes.
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| Illustration 2 | g00315251 |
Pull the parking and the secondary brake control (2) outward. This will release the air pressure and the springs will be allowed to apply the parking brakes.
If the brake air pressure drops below
The action alarm will also sound if the transmission control is moved out of the NEUTRAL position during engagement of the parking brake.
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| Illustration 3 | g00315250 |
The retarder is a fluid coupling that is mounted at the engine flywheel housing. Engage the retarder (3) in order to slow the machine ground speed. The transmission must be in gear in order to drive the retarder impeller.
Use the retarder on a downgrade to prevent engine overspeed.
Use the retarder to help to stop the machine. The retarder will not completely stop the machine and the retarder will not hold the machine stationary.
Note: Use the retarder at least one time during each work day to keep the seals lubricated.
The speed selection is very important because a lower speed increases the effective force of the retarder. Generally, the speed that is used to negotiate an empty machine on an upgrade should be used for driving a loaded machine on a downgrade of the same slope. Readjust the speed after a trial run.
Before you approach a downgrade, slow the machine. Anticipate the need to use the retarder. Move the retarder control lever in order to engage. The retarder will usually engage in less than four seconds. Downshift the transmission to the necessary lower speed.
Select the proper transmission speed that will allow the retarder to maintain a safe ground speed with little use of the service brakes.
To ensure maximum cooling and the best retarding effect, select the proper transmission speed that will keep the engine speed above 1800 rpm. Do not allow the engine speed to exceed 2300 rpm. Do not allow the converter/retarder oil temperature to exceed
Travel at the best average speed. Always reduce the engine speed when applying the service brakes. Do not attempt all of the braking at the bottom of a hill. Keep braking steady while the ground speed is under control.
Attempting to stay in a lower speed on a long downgrade by using the retarder can be unsuccessful. Engine speed may increase beyond the green operating range.
Use the service brakes until the speed is reduced. If additional braking is needed, pull the parking and secondary brake control outward in order to add more braking force. If proper conditions exist, you can drag the scraper bowl in order to slow the machine.
Use the retarder when you are entering a cut or a dump area. This will allow the transmission to downshift.
Important Conditions During Retarding
The ground speed must be suitable for the operating conditions. Operate the machine at a rate that will not cause retarder overheating.
Braking should be steady. Do not try to brake in a short distance while you operate at a fast speed.
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Engine overspeed may cause serious damage. Keep the tachometer indicator in the green operating range. |