Windshield Wiper Motors - Again

[Ryan Willobee]

I know this question has been beaten to death on this newsgroup, but after
several weeks of searching here and the web I still have some questions
about using these as drive motors on a 50lb or so robot.

1) Several people have recommended NOT using this motors because they are
not very efficient. Just what makes them a poor choice? Is it because of
the worm gear drive, or is it an electrical issue?

2) Do these motors generally turn at the same RPM in both directions? I'm
looking specifically at the motors available from places like All
Electronics, MECI, BG Micro, etc.

3) If these are a poor choice, does anyone know of any other cheap
(<$20-30), approx. 100 RPM, high torque motors?

Thanks for your time,

Ryan Willobee

[Sir Charles W. Shults III]

Think of it like this- windshield wiper motors are not very efficient
because they are designed to deliver high torque at a fairly low speed. It's
like driving light bulbs for your house at low voltage- there are better ways!
These motors can be used for specific things where your needs are similar to
those of windshield wipers and they will do okay. For drive motors, you really
want something that can deliver more speed and not so much torque, because then
you have a higher potential speed but a little less acceleration.
Think about driving your car on the freeway in first or second gear...

Cheers!

Chip Shults
My robotics, space and CGI web page - http://home.cfl.rr.com/aichip

[Ryan Willobee]

Sir Charles W. Shults III <aic...@cfl.rr.com> wrote in message
news:CfQb9.35134$Rx4.3...@twister.tampabay.rr.com...

> Think of it like this- windshield wiper motors are not very efficient
> because they are designed to deliver high torque at a fairly low speed.

But isn't that what I want for a robot drive motor, low speed with high
torque? How is it any different than using a high speed/low torque and
gearing it down to a lower RPM with more torque? Is it just because a
windshield wiper motor has an inefficient speed reduction design?

Thanks,

Ryan

[Sir Charles W. Shults III]

Loading these motors is part of the problem- they are most efficient at a
fairly constant speed. Robots can have wildly varying loads, where most wipers
have a pretty narrow operating range of load. Wet windshield, dry windshield-
running your wiper motors on dry glass can burn them out pretty quickly. Their
gearing is a large part of the problem.
More efficient design will generally have a much higher speed motor
internally and gear it down so that the motor does not see as large an
"instantaneous" loading.

[casey]

I have used a 24 volt windscreen motors on a robot base.
The torque is great I can push heavy furniture around
with it plus the three car batteries it carries! It will carry
a person as well.

Is efficiency an issue?

For me it was cost and availability.

It really depends what kind of robot you want. A cheap
robot with a light weight brain only needs a toy car base.

-- John

"Ryan Willobee" <will...@portup.com> wrote in message
news:nCQb9.1952$K%2.38...@newsfeed.slurp.net...

[Gordon McComb]

There are two issues with windshield wiper motors to be concerned with:

1. DC motors used in cars are made cheaply, to keep down the price.
Since there's no worry about running down the battery (because the
battery is kept charged from the engine), car makers don't bother making
these motors efficient. Now, an efficient motor on your robot may or may
not be important to you. The overall power requirements of your robot
may be low enough that it doesn't really matter.

2. Windshield wiper motors only have to go in one direction. Not all
windshield wiper motors are reversible, and those that are (just because
they happen to be) may turn more slowly in one direction or the other.
You have to test this out to determine if the motors are sufficient for
you. Some folks have resorted to re-wiring the motor to be reversible,
or using different brushes when the brush arrangement prevented
reversing.

Power window and power seat motors tend to be better suited, as they are
always reversible.

Of course, windshield wiper motors can be purchased really cheaply. The
surplus market is full of such motors intended for late-model Saturns.
These may be the ones you're looking at.

-- Gordon
Robot Builder's Bonanza, Second Edition
Robot Builder's Sourcebook - Now Out!

[Ian Juby]

Personally, I think their great for a drive train. I haven't found them to be
that bad on power but sure, there is better. Again, ye olde cordless drills
work well, fit on any sized drive shaft, have a nice gear ratio, yada
yada,....

One quick note I see hasn't been mentioned: Lots of windshield wiper motors
are worm-gear drive. Driving to high speed (especially with a heavy robot)
and then completely removing power from the motors can cause the gears to
strip. It varies, depending on the motor. I had some that you could turn by
hand, the worm gear ran so smooth. But don't count on it. On the other hand,
a worm gear that locks the wheels can be an advantage. Turn the motors off
and your robot's in "park". But again, this all depends on the motor.

Ian

Ryan Willobee wrote:

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[Venom8]

I'm using two '95 mustang wiper motors for the shoulder swing movements of
an Animatronic I'm constructing. They reverse quite nicely, with even speed.
I do how ever need two additional gear type motors to move the arms up and
down. It was mentioned in an earlier post about seat motors, does anyone
have any idea what model of vehicle I may have the best luck with? They need
to be no more that 3 inch in diameter on the drive end, as they will be
hooked directly to the shoulder axials. Power consumption is of no concern
here, as I am using the power supply from an industrial PLC panel to drive
everything. The project is basically stationary, so the need to be efficient
isn't needed for this.
"casey" <jkc...@bigpond.com> wrote in message
news:jGTb9.19269$g9.5...@newsfeeds.bigpond.com...

[BurrBeast]

AM equipment sells wiper motors in various voltage and torque
configurations and some are available in both RH and LH.
see http://www.amequipment.com

We have used their 230 model to run some bots weighing 45 kg.
We only had one team strip the gears out of the gearbox last year.
The year before we used some Mitsubishi wiper motors and stripped the gears
or burned out about 1/2 of them.

Herbach and Rademan (http://www.herbach.com) has a nice motor/wheel
assembly I just got a couple of. It is a little fast for what I want it
for but runs nice. See part number TM92ROB2188.

"Ryan Willobee" <will...@portup.com> wrote in

news:WdOb9.888$K%2.31...@newsfeed.slurp.net:

[DOC]

This sounds like Canada First!

Are you talking about Orangeville Secondary?

Are we going to have to use TWO left motors again this year?

DOC

"BurrBeast" <Your....@yourisp.com> wrote in message
news:naiA9.52532$YSz1....@news01.bloor.is.net.cable.rogers.com...

[Emil...@hotmail.com]

hey does anyone know the approximate torque of windshield wiper motor?