A 1926 Mercedes-Benz transport vehicle in Northern China was driving on the highway after traveling about 2,000 km. The two rear wheels suddenly locked. I got off the vehicle to observe and occasionally heard the sound of ignition and smelled the strange smell of burning plastic. The engine was working normally, but the vehicle could not drive.
Fault inspection and analysis: After the engine was turned off, I drilled into the bottom of the cab to observe and found that the insulation of the starter live wire had been worn through the frame. The live wire copper wire directly interfered with the frame, forming a short circuit and then discharging to produce sparks, burning the hand brake air pipe. Use an open-end wrench to manually unscrew the bolts at the tail of the composite brake cylinder to make the spring energy storage system of the composite brake cylinder inoperative, and then tow the car to the repair shop.
The 1926 Mercedes-Benz transport vehicle in Northern China has a trough frame. Because the starter live wire is too long and not properly bundled, the starter live wire is bent above the trough frame. Due to the action of gravity and inertia, the starter live wire and the trough frame produce interference friction. Since the plate of the groove frame is stamped and the edge of the frame is not chamfered, the starter live wire and the groove frame will interfere with each other as long as the car is driving. Over time, the insulation of the starter live wire is worn through by the groove frame, and the starter live wire copper wire is in direct contact with the frame. The body and frame of the vehicle are generally used as negative poles in the design of the whole vehicle. In the absence of any load, the positive pole of the starter live wire directly contacts the negative pole of the frame, which will generate a large current, release a large amount of sparks and heat, and the hand brake air pipe pipeline just passes through the inside of the groove frame, causing the hand brake air pipe pipeline to be burned through. After the hand brake air pipe pipeline is burned through, the hand brake pipeline gas leaks, causing the composite brake cylinder to move the brake air chamber push rod forward under the action of the diaphragm spring, forming a braking state, and the car cannot move forward.
Troubleshooting: Replace a hand brake hose and a matching starter live wire and tie them firmly, and test drive, everything is normal.