Operating Instructions - Section 30 03/13 OM3040 Page 30-16 DISABLED TRUCK STEERING AND BRAKING 11. If no problems are evident, proceed to move the machines. During towing, it may be necessary to steer and stop a disabled truck using hydraulic power from the tow truck. The following instructions describe the use of a "good" truck to provide the hydraulic power required to steer and stop a "disabled" truck. Travel speed should be equal to normal human walking speed. When necessary, steer the machine slowly while keeping turns at 1/4 revo- lution/second or less. Figure 30-7 illustrates a typical hookup with another HD1500-5.
Figure 30-6 shows the location of the quick disconnects on the bleeddown manifold. NOTE: Each braking application and release on the disabled truck transfers the release oil from the good truck to the disabled truck. Therefore, it is necessary to use the brakes sparingly when possible. 1. When the good truck is in position in front of the disabled truck, shut off the engine, and apply the parking brake. It may be necessary to drain oil from the dis- abled truck if the hydraulic tank inherits too much oil. 2. Bleed any pressure from the steering accumu- lators on each truck. Verify no pressure exists by attempting to steer each machine. 12.
When the trucks have reached their destination, shut the engine off, and apply the parking brake on each truck. 3. Connect the supply and return hoses to the quick disconnects on each bleeddown manifold. Route and secure the hoses in a safe fashion that will prevent hose damage during machine movement. 13. Ensure the steering accumulator pressure is bled down before removal of the hoses. Attempt to steer each truck to verify no pressure remains in the system. 4. Install pressure gauges in the brake supply cir- cuit on both trucks for verification of proper brake system pressures after machine start up. 5. Position the retarder lever on the bad truck in the OFF position.
DO NOT use the retarder lever during machine towing. 6. Turn the disabled truck keyswitch to the ON position. This prevents oil transfer between trucks from the retarder command circuit. 7. Start the good truck, and allow the engine to operate for a minimum of three minutes. 8. Verify proper brake system pressures on both trucks: 18 960 kPa (2750 psi). 9. Slowly operate the steering wheel on each truck to check steering function. Slow movement will allow any trapped air to bleed out of the system. 10. Check all hydraulic connections for leakage before machine travel. FIGURE 30-6. STEERING QUICK DISCONNECTS 1. Bleeddown Manifold 2. Supply Port 3. Return Port