Measured Specs on 12V DC Gearmotor (Windshield Wiper Motor)

I purchased a couple of these new windshield wiper motors from ebay.
They are not the common Saturn type of motor, but similar.  They have
only 2 wires, and the negative is isolated from the housing (unlike
the Saturn motors).  I did not like the Saturn motors because of the
chassis gnd.  If used as a servo, the chassis would be hot in one
direction.

I took some torque and current measurements using a Fluke 337 clamp
meter and a 50lbs fishing scale.  I made a simple jig to mount the
motor solid to the bench, then attached a 12" steel tube arm to the
shaft.  I then attached my fishing scale exactly 12" away from the
center of the shaft and mounted it solid to the bench.

I used a 12V 7.5ah sla battery fully charged to 12.6V.  This battery
can source 72A for < 10s, so there was plenty of current for my quick
tests.

Results:

Stall Current: 45A  (voltage drop to around 10V)
Stall Torque: 23 ft. lbs.

No load Current: 2A (motor running)

In Rush Current: 8.3A (no load)

All results were very similar in both directions.

Unfortunately, the motors have no markings on them, but they look just
like most of the motors that are sold at surplus stores for around
$20.00.  They have 3 - 6mm mounting bolts and run at around 60rpm no
load.

I plan on using these motors for my RC land speed car project.  One
for the steering, and one for the hydraulic brake.  After measuring
them it looks like they may be a bit overkill, but it can't hurt.
I'll just need to make sure I set up my servo drivers properly (end
limits) and have some good mechanical stops to avoid breaking
anything!

Terry

Depends on the application, I suppose, but I don't usually like
to use this type of motor because:
- the main gear often gets shot if someone applies too much
  torque to it.
- the motors draw a lot of current.

For applications in this class (inexpensive, no special
operating parameters) I prefer to use cordless drill motors
with the built in planetary gears.

Lots to choose from. And prices vary depending on
quality.

DOC


Terry wrote:

Yes, I have used some of the 18V cordless drill motors for the drive
system on a robot I was building a while back.  I think I would still
need to gear it down further to be used for steering.  I could also
reduce the voltage, but then I would be loosing some torque.  I'll
have to check them out and see how strong the ones I have are.

Ya, I am a little worried about the gears on those worm drive motors.
For the brakes, I don't think it will be a problem at all.

Thanks for the input.

Nuther point that might help...

I put together something recently where I made a small spring loaded
clutch.

It was also for steering. In my case a tricycle. And I needed to
build
an aditional gear box as well.

Takes a little bit of machining and you need to get the spring
pressure about right for the job.

But you avoid the limit switches problem.

DOC


Buy my junk!  http://www3.sympatico.ca/doc/robotone/for-sale.html