OM3223 Operation - Section 32 Operator Cab and Controls Page 32-7 Hoist Control Lever Hoist control (4, Figure 32-7) is a four position hand- operated lever located between the operator seat and the center console. Retard Speed Control (RSC) Adjust Dial RSC adjust dial (5, Figure 32-7) allows the operator to vary the downhill truck speed that the retard speed control system will maintain when descending a grade. To Raise Dump Body 1. Pull the lever to the rear to actuate the hoist cir- cuit.
(Releasing the lever anytime while raisin gthe body will place the body in HOLD at that position.) When the dial is rotated counterclockwise toward this symbol, the truck will descend a grade at lower speeds. When the dial is rotated clockwise toward this symbol, the truck speed will increase. 2. Raise the engine rpm to increase hoist speed. 3. Reduce engine rpm as the last stage of the hoist cylinders begin to extend and then let the engine go to low idle as the last stage reaches half-extension. Throttle pedal position will override the RSC setting.
If the operator depresses the throttle pedal to increase truck speed, dynamic retarding will not come on unless truck overspeed setting is reached or the foot operated retard pedal is used. When the throttle pedal is released and the RSC switch is ON, dynamic retarding will come on at, or above, the RSC dialed speed and will adjust truck speed to, and maintain, the dialed speed. 4. Release the hoist lever as the last stage reaches full extension. 5. After the material being dumped clears the body, lower the body to frame. Refer to operating instructions, dumping for more complete details concerning this control.
To adjust the RSC control, pull switch (6) on and start with dial (5) rotated toward fastest speed while driv- ing the truck at the desired maximum speed. Relax the throttle pedal to let the truck coast and turn RSC adjusting dial slowly counterclockwise until dynamic retarding is activated. Dynamic retarding will now be activated automatically anytime the set speed is reached, the RSC switch is ON, and throttle pedal is released. With the RSC switch ON and dial adjusted, the sys- tem will function as follows: As truck speed increases to the set speed and the throttle pedal released, dynamic retarding will apply.
As truck speed tries to increase, the amount of retarding effort will automati- cally adjust to keep the selected speed. When truck speed decreases, the retarding effort is reduced to maintain the selected speed. If truck speed continues to decrease to approximately 4.8 kph (3 mph) below set speed, dynamic retarding will turn off automati- cally. If truck speed must be reduced further, the operator can turn the adjust dial to a new setting or depress the foot operated retard pedal. FIGURE 32-8. HOIST CONTROL LEVER To Lower Dump Body Move the hoist lever forward to the DOWN position and release.
Releasing the lever places the hoist control valve in the FLOAT position allowing the body to return to the frame. If the operator depresses the foot operated retard pedal and the retard effort called for is greater than that from the automatic system, the foot pedal retard will override RSC.