Backdrive with Window Motors

Hi there,

We are a very novice team trying to use the provided Denso window motor to move an arm down. I’m under the impression (and testing confirms) that these window motors do not drive backwards. While we don’t need to raise the arm after lowering it during the match, we would like a way to raise the arm again before the next match (ie the kids can lift the arm if the motor would allow it to spin backward while it is powered off but then hold it in place). We do not have a matching motor to use on the other side.

I have read online that you can remove some pins in the anti-backdrive mechanism to be able to accomplish this. Does anyone have any experience/information on this? I’ve been browsing around and haven’t found one, but if there is a good tutorial out there, please point me to it!

Thanks in advance!

Yes - they drive backwards as efficiently as forward…just reverse the polarity.

For your application, however, would some type of mechanical quick release be better?

We removed the pins you refer to for testing a year or two ago. We never did use them in competition. Older rules precluded this but I don’t know the exact current ruling on this. (There is a rule about altering integral gear trains but I think there is a comment somewhere in the current rules excluding the pins. Please check as I don’t want to accidentally lead you astray.)

I don’t have a video handy but if you start to take things apart there are a couple things that might be good to be aware of.

  1. There is a very small magnet/spacer in some motors that rests on top of the rotating sprocket “shaft” when you first take things apart. I did not even notice it the first time. I don’t know if this is on all generations of the motor.
  2. There is a one way spring clip that holds the rest of the mechanism in place. It is difficult to remove this without some damage to it. Take your time. It seemed to be okay if we put in back on with only slight damage.
  3. Once you get the clip off there is a piece holding three pins in a vertical direction. That piece has a spring behind it. It is easy to disassemble but don’t let the spring eject and loose it.

Incidentally, it is still not easy to turn. Most people must have a strong grip or get some leverage to do it. If you are raising an “arm” connected to the motor, you may have the leverage you need.

There are always alternatives but it is doable.

We bought a cheap 12v cordless drill and replaced the drill motor with wires and a connector. Place a pair of the same connectors in the wires between the Spike and the motor. Plug in the “drill” and you can drive the motor in either direction and with variable speed.
It’s very handy for testing drive systems during the build process and for positioning arms or linkages when the robot is not powered.

We did the same thing with the drill. It is VERY handy throughout the season. Here is a video showing you how to modify one. We add Anderson Powerpoles to all of our motors so we can quickly test motors.

We add Anderson Powerpoles to all of our motors so we can quickly test motors.

Those are nice auto-strippers in that clip - where did you folks get them ?

Here is one w/ pics and some other info you may need.

Good Luck and remember to keep those pins in a safe place.