Assignment
The old overrun brakes had one serious disadvantage. Whenever one wanted to drive in reverse, someone else had to operate the handbrake on the trailer. Then the towing vehicle was driven a small distance, so
that at the rear, a spring-loaded shackle could snap into place. After releasing the handbrake nothing more stood in the way of reversing. If one then pulled off forwards a little more vigorously, the shackle could return
to its initial position or perhaps not …
Function
Today, the mechanism has come a lot further. One now makes use of the difference between braking and reversing. Even when braking, the drum - compared with the anchor-plate - always turns in the same
direction. The above drawing should make the principle clear. As long as braking takes place when driving forwards, both brake-shoes remain in this position. Also the center of rotation of the right, running-off shoe,
does not change.Should however, the brake-drum turn backwards, a braking action is triggered, which together with the rotation of the brake-drum, causes the right brake-shoe to be pushed against a spring found
nearer to the center of rotation. Using an increased amount of effort, the trailer can be pushed backwards. The effort, due to the remaining friction of the brake-pads is necessary to keep the spring under tension. If the
tension decreases, the right brake-shoe returns to its initial center of rotation. 05/10
