Van Door Motor Worm Gear

I apologize if this is somewhere else, but I have not found it here on CD or outside on other websites. So we are still working on our arm and after opening the van door motor have decided we want to alter the worm gear. Does anybody know the specs of the current worm gear in this motor? Particularly we are looking for the pressure angle and the pitch, however, any other information would be greatly appreciated.

If i’m not mistaken, you are not allowed to alter any parts of a motor.
Are you trying to do this, though, to make it non-backdriveable?
If so, My team has the same problem; does anyone know a way to keep the van door motors from backdriving, to the extent of about 10 Nm on the shaft, in order to support a tetra on an arm? We thought about having some current running through it to keep it from moving, but then we thought that would burn it out. ANy thoughts?

It is not good to stall the motor at any amount of current. Have you tried the “brake” jumper on the Victor? That will help it hold a little more. As for altering the worm gear, I do believe that is not allowed. You should add an external worm gear or selectable (such as servo controlled) ratchet setup. One example I’ve see of a good simple ratchet was some team last year just took a sprocket and had a little lever bar that moved into the teeth to “jam” up" the system. This lever bar can be controlled by servo.

You are not allowed to alter the integral parts of a motor, or alter it physically this includes internal operational gears. Also i would recommend you not to remove the worm gear at all even just to look at it, by doing so you will alter the setup for the magnetic field and reduce the output of the motor.

To summarize rule <R31>, the only gearboxes you are allowed to modify/remove are the globe motor gearboxes and the FP gearboxes. You are not allowed to modify the gearing of the van door motor (or window motor for that matter). You are allowed to modify the output shaft. You are allowed to open the gearbox for the purposes of removing the output shaft to modify it.

Also, the worm gear is attached to the output shaft of the motor (note the difference in the context of this post between the output of the motor and that of the gearbox. Normally when referring to the output of the van door motor i would mean the output of the gearbox). Removing the worm would not effect the internal electronics or magnetics of the motor. Removing the armature of the motor can/often does have a negative effect on motor power. But, as long as you do not remove the armature, your fine from an electrical standpoint. I am not certain, but I am fairly sure that the gearbox can be removed from the van door motor with out removing the front of the motor, so that the gearbox is not integral to the operation of the motor, but put on after the motor is manufactured. But, since FIRST considers the gearbox integral to the motor, you are not allowed to modify the gearbox and shouldn’t have to worry about removing the worm anyways.

Was that convoluted enough for everyone? I hope I made sense.

It also just occurred to me. In previous years, there was a rumor that the van door motors had their own thermal breaker built in. No one could confirm this, but there were stories of the motor cutting out when being tested with nothing but jumper cables between it and the battery. Anyone have any ideas?

*edit : Upon closer inspection, a few things hit me in the head. The gearbox and motor on a van door motor are effectivly intergral. Chalk that one up to me posting way to late. The gearcase seems to act as the front of the motor can. It is possible to open up the gearcase with out removing the armature from the magnet can, with the intention of removing the output shaft. I couldn’t give an exact guide for doing so. Also, there seem to be a couple diffrent versions of the van door motor out there. They seem to differ greatly in speed, and there are at least 2 diffrent worms out there.
-Andy A.

We’re using the van door motor for the arm. Back driving was some thing we forgot about until the testing stage. A 1/4" piece of aluminum pressing on the belt and timing pulley brakes the arm. It takes very little force. A hitech servo would do it. A window motor and van door combo would also do it.