1. If the Column wheel chrono movt has a flyback function then you can reset the chrono to zero without stopping it then resetting it.1. Is it true that column wheel mechanism will prevent you from resetting to zero while chrono is running?
2. What about cam/lever operated chronos such as 7750?
3. what happens if you reset it by mistake while it was running?
The Valjoux 7733, 7750 and the Lemania 5100 are cam operated chronographs. The cam on these performs the same function as the castellated wheel on a column wheel chronograph. The column/cam sequences the actions of the chronograph so that operating the pushers out of order will not harm the mechanism. Separate actions of the buttons are required to start/stop the chronograph and reset, and the reset is inoperative when the chronograph is running.
The only difference between a cam operated movement and a column wheel movement is the castellated wheel (the column wheel) rotates in only one direction, so after several pushes it completes a revolution. In cam operation, the cam switches between two positions, back and forth.
There is a third type of chronograph, the lever action. In this type the action is controlled by levers, and through careful arrangement of them, pushing them out of sequence does not harm the movement either. The Heuer 11/12 and the Valjoux 7740 are examples of the lever action movement.
Any of the three can be modified to be flybacks, all that is required is the reset pusher be designed to lift the slider gear off the chronograph second wheel and force the reset hammers down against a spring (the hammer spring operates in the opposite direction it normally would), releasing the reset button allows the reset hammers to return to the up position and drops the slider gear back into engagement, if the chronograph is still in the running mode. If, with the flyback, the chronograph is stopped, the reset functions the same as before.