I wanted to know if anyone had ever used this constraint, because for me it is lacking.
Let me explain: if I put two teeth in contact and then I do this constraint it will work in one direction but not in the other i.e. there must be a little play between the teeth so when returning for a period of time the two gears must not touch each other put there it doesn't do it.
Before I was told that this question has already been asked, yes I have already looked but it does not answer my question.
I used this feature for the first time last week, and obviously it's not done to manage a game catch-up. It just allows you to manage a rotational speed ratio between 2 sprockets. You must first have your sprockets in a "0" position and then activate this constraint.
And at times, the teeth shift, especially when you continue the constraints a little further (in the case of a cascade of pinions in this case). So I found no other solution than to deactivate the gear constraint, put my sprockets back in the "0" position and reactivate the gear constraint!
Benoit LF is right: this constraint only serves to give a rotational speed ratio between 2 cylinders: if the first one turns at a speed X, the second will turn with a speed equal to X x Gear ratio.
The position of the teeth is not taken into account. If the teeth are well placed initially, the simulation of the gear should be correct (a priori this is not the case given the previous comments).
So this constraint can be used for other things than gear simulation: I used it to simulate universal shafts for example, but it can be used for systems with belts, chains, .....