In this groove is a steel roller upon a pin attached to the bell crank operating the main valve stem.
The ash pan is provided with two dampers, one at each end, and the front one is operated by the bell crank a c.
First block the bell crank by using a "U" bolt (which should be provided) in the holes placed in the gear frame for this purpose.
Throwing reverse lever in mid-gear will help to get bell crank in position to block.
What is to be done should the vertical arm or bell crank break?
If break is near the top and below the jaw, first block the bell crank and wire the connection rod fast to radius bars.