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Unread 24-01-2006, 00:39
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Re: Window motors....

Quote:
Originally Posted by sanddrag
You actually can turn them by hand? This isn't good.
I havent been able to but I assumed it could be done...
ERic
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Unread 24-01-2006, 08:45
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Re: Window motors....

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.
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Last edited by Joe Johnson : 24-01-2006 at 08:48.
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Unread 24-01-2006, 21:53
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Re: Window motors....

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
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Unread 24-01-2006, 21:58
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Re: Window 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...
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Unread 24-01-2006, 22:43
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Re: Window motors....

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.
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Unread 25-01-2006, 08:12
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Re: Window motors....

Quote:
Originally Posted by Leo 1529
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
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.

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Unread 25-01-2006, 09:58
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Re: Window motors....

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.
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