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power window motor as generator?


By strider3700, Section Hydro
Posted on Wed Sep 14, 2005 at 09:56:08 PM MST
I've got a spare power window motor will it work?

Ok in a previous post we worked out that I can produce 75 or so watts of power from my current water system.  Since this is very little but will still be fun to play with I've been looking into finding a small motor/generator for really cheap.  A couple of days ago while digging through my old car parts I came across a power window motor.  Looking online I found  similar motors with the following specs
  1. Working voltage: 12V
  2. No load speed: 74rpm
  3. No load current: <2.8A
  4. Stall torque: 7.5 - 12nm
  5. Stall current: <30A
  6. Rated load: 2.94nm
  7. Rated current: <13A
and
  1. Working voltage: 12V
  2. No load speed: 79rpm
  3. No load current: <2.5A
  4. Stall torque: 6.5 - 11nm
  5. Stall current: <26A
  6. Rated load: 2.94nm
  7. Rated current: <12A
now I'm just guessing here,  but rated current of 12 amps at 12v would produce 144 watts at something less then the no load speed of 80 rpm?

Or am I completely wrong here?   I have no idea how to hook this up to the turbine at the moment anyways but figure I should try.
power window motor as generator? | 6 comments (6 topical)

Re: power window motor as generator? (3.00 / 0) (#1)
by veewee77 on Wed Sep 14, 2005 at 04:46:41 PM MST

You will not get any kind of performance from that motor because it is a gearmotor and most of the energy will be lost in the gears.  This is likely a worm gear motor anyway, and will be very hard to turn from the output (normally) shaft.  they are designed to make a lot of torque at low output rpm, and inversely will require a LOT of torque on the output shaft to turn it and since it is a worm gear motor, you may not even be able to turn it from the output shaft.

Doug



Re: power window motor as generator? (3.00 / 0) (#2)
by maker of toys on Wed Sep 14, 2005 at 05:20:25 PM MST

 your power window motor is likely to have a worm-reduction gearbox on it.  that type of reduction gear is 'non reversable' and won't work as a generator without some serious modification.  Not that it can't be done, just that you're looking at some quality time with your power tools. I seem to remember a couple of threads on the matter recently, one that I was involved in was:

http://www.fieldlines.com/story/2005/8/19/12236/5371

sorry, you'll have to dig for the others.

 the upshot is that a (rewound) heater fan motor would probably be better, but a window motor could be used with mods.  In my comment, i forgot to mention that the motor itself (as opposed to the motor/gearbox combination) will turn more like 4000 no load rpm.  (that's right, a worm reduction can easily be 50:1 or more.)

Note that it is pretty much unheard of to get nameplate volts/amps out of a motor thats been converted to a generator; i'd be really happy to get 1/4 the nameplate numbers into an actual load, while spinning the gen at 'rated' rpm.

see if you can nobble a tape-drive motor or a treadmill motor. . .  Junk stores and Ebay.  Or you can go the rewind route.



It's not a case of 'Save the planet,' it's a case of 'Save the humans.'



Re: power window motor as generator? (3.00 / 0) (#3)
by jlt on Thu Sep 15, 2005 at 09:09:28 AM MST

you might try looling for electric string trimmer moter i have used these for small wind gens they will put out 12volts without any mods at aprox 600rpm .


Re: power window motor as generator? (3.00 / 0) (#4)
by SpirckleM on Thu Sep 15, 2005 at 10:01:58 AM MST

jlt

By "electric string trimmer" motor, do you mean an electric weed eater motor?  That's what I took it as at first and thought "cool" I have an old one tucked away in storage, but then I reread and now I'm not sure if that is exactly what you mean.

--------
Using the best of today's thinking to create the problems of tomorrow

[ Parent ]



Re: power window motor as generator? (3.00 / 0) (#5)
by jlt on Fri Sep 16, 2005 at 06:17:13 AM MST

yes a weed eater moter.they are two pole dc moter. there mst be some diods. in there to make them work. i dont know . as i have only used just the moters.mine was 11amp model. with 44in2 blade prop on it. worked pretty good but was a little slow to start turning. I mounted a 14in 6 blade fan off of a cooling fan on it and it started much sooner. didnt seem to hurt outpu t . I run it for a year before a wind storm. got it.made some larger gennis after that as tip back gov on them.to save them from those violent storms that blow down trees remove roofs.and wind gens



Re: power window motor as generator? (3.00 / 0) (#6)
by strider3700 on Fri Sep 16, 2005 at 12:12:58 PM MST

Thanks for the info guys.  I do have an old weedeater that for some reason does nothing when I pull the trigger.  I'll strip it and see what I can do with it's motor.

[ Parent ]


power window motor as generator? | 6 comments (6 topical)
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