Window motors....

Ok, I have a few questions related to the new(ish) smaller denso window motors:
-might anyone have a CAD file for the little buggers?
-has anyone else noticed that we weren’t given a plug in the kit to actually power them? Or are we missing them from our kit? As of now, I havent seen anything…
-Has anyone tested them this year for backdriving? If i remember they have a spur gear in the worm drive and almost completely resist backdrive.

I have an inventor file of the motor if you would like it. PM me and I can e-mail it to you. I don’t recall having a plug for them. We were using aligator clips for test purposes. They are extremely difficult to turn by hand (most likely impossible).


You actually can turn them by hand? This isn’t good.

If by backdriving you mean cranking it without the motor being on and moving it instead, then… don’t try. The last time I checked the worm gear was plastic, but that could be an older model. I have see the worm gear inside get striped teeth. :ahh: So to be on the safe side, I wouldn’t try.

Wait now I remember we made an arm with these motors, and we had to hand crank it back, but it ended up tearing up the insides. Maybe it could have been because we weren’t nice to it.

I havent been able to but I assumed it could be done…

In most automotive applications of window are not supposed to fall down as the car drives down the road. To that end, there are specs for “wind noise” which spell out how much residual torque the motors retain after the power is released as well as for “forced entry” which define how much the motors can move under various backdrive conditions.

In almost every case, automotive window motors are not intended to be backdriven. In actual fact, the motor manufacturers are walking a fine line – there is a strong correspondence between backdrive and effeciency. If they make the motors too non-backdriveable, they make the motors less effecient, which means that they need a bigger motor and more current to lift the window – neither of which their OEM customers like. On the other hand, if they make the motors too efficient, the windows creep down as the cars drive over rough roads, which drives the end users nuts with high pitched wind noise sounds.

The bottom line is that most automotive window motors CAN be backdriven if you torque them hard enough, but they don’t like it and you will probably get into trouble eventually.

Joe J.

we decided against using the window motors so we could use the Bosch motor for our robot and we were also concerned with the strippage that could occur within these motors

Virtually impossible. We’ve been using these motors (Or variations on them) for years, and never had one fail. … Except that one time we crashed the go-cart into the pole…

While performing some tests on our prototype with the new window motors, one the plastic housings cracked - Be Very careful with them!!! They are not like the window motors of previous years.

It is possible to strip the internal plastic gear but not easy.

We discovered this in 1999 when a failure cost us an easy win and eliminated us from the tournament at the Championships at EPCOT.

Do not run these motors into a brick wall at high speed.

We had an arm that lifted us off the ground. The arm used an “over center” linkage to lock our arm in place. What would happen is every time we lifted, the motor would drive this overcenter arm into a stop. We made no effort to slow the arm down, we just ran it into the stop. After a season of lifting perfectly, the motor developed a hard spot where the gear teeth were bent from repeated bashings. In our last match of the season, the robot just would not lift off the ground. Root cause analysis showed that the plastic gear was the problem. Note that a window motor would not have failed in this way because window motors are designed to be run into a brick wall at full speed – they have an internal rubber coupling that prevents the full shock load from going into the plastic worm gear.

Bottom line… …don’t run power sliding door motors into a hard stop at high speed.

Note: for a conveyor application I doubt you will have to worry at all.

Joe J.

In past years window motors, we have noticed a increase in backlash after hard use. They never failed but, then we never abused them. Our designs allowed for something else to slip instead of locking up the motor.

Just file away the white plastic connector housing and use normal fast-on connectors (terminal fully covered variety). They are a little too wide but work fine if you run the tab up the outside edge of the fast-on.

They should not turn by hand. One of the properties of a worm gear arrangement is that it will hold its position, kinda nice feature for a WINDOW motor, heh? :smiley: