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tips for buying wheel chair motors for project? — Parallax Forums

tips for buying wheel chair motors for project?

mikeamikea Posts: 283
edited 2012-04-09 02:02 in Robotics
does anyone have any tips for buying low price easily incorporated wheel chair motors for heavy robot project should drive 100 pounds over flat but rough terrain. im trying to avoid buying the wrong motors. speed should be 5 mph but i will control it with pulse width modulation.thanks. - mike

Comments

  • Paul K.Paul K. Posts: 150
    edited 2012-04-07 19:00
    Instead of picking up brand new motors check Ebay and Craigslist for old/used motorized wheel chairs.
  • Duane DegnDuane Degn Posts: 10,588
    edited 2012-04-07 19:19
    I second Paul's advice.

    I think shipping can be a killer with those so if you can find one locally with Craig's List you should be able to save a lot of money.
  • mikeamikea Posts: 283
    edited 2012-04-07 19:55
    ok thanks guys. -mike
  • jdoleckijdolecki Posts: 726
    edited 2012-04-08 07:52
    You need to shop from Craigslist as e-bay will cost you around 150 each.

    You have to check e-bay everyday and be ready to buy the immediately.

    Search craigslist for power chair or wheel chair.
  • KMyersKMyers Posts: 433
    edited 2012-04-08 10:20
    Could also check your local med supply houses or better local chair dealers.
  • xanaduxanadu Posts: 3,347
    edited 2012-04-09 00:08
    I purchased a nice set off ebay, with the controller and tires. The controller ended up being a mistake. The controller was enormous and very durable. It looked like it could pull ten times the current the motors could. It had an inductive joystick that I spent a long time 'hacking' but a couple of safety circuits made me give up on it fairly quick. The amount of time I invested eventually led me to purchasing an MDC 2250C from roboteq. I didn't want to spend that kind of money, and in retrospect wouldn't purchase a set of motors with a chair motor controller on it again unless I knew the MCU well.

    The brakes on the motors were 24 volts and were electromagnetic solenoid type. So the clicking you hear isn't a relay it's a metal plate with a notch in it that the shaft would catch in two different places, so the motor would turn 1/2 turn before the brake set when the coil was not energized. Three things, if you're going to use the brakes you need to protect whatever you drive them with a diode across the coil just like a relay, but these coils are much larger than relay coils. The other thing is unless you have a 200lbs robot on a hill, you don't need the brakes because the gear ratio puts a lot of resistance on the shaft. Removing the brakes leaves shaft exposed at one end which is the perfect spot for a shaft encoder, which I highly recommend.

    Look for motors that have a lever to disengage them. It works out really nice when you need to move it without powering it up.

    The only other advice is see if you can find brushes for you motor before you buy it, especially if it is used. There's no odometer on these things and the brushes can be hard to find.

    Here's some pics of the mess before I broke down and got a real MCU -

    https://picasaweb.google.com/113085695335757647054/BigWheels?authkey=Gv1sRgCIe-jIfz89qE8QE .
  • jdoleckijdolecki Posts: 726
    edited 2012-04-09 02:02
    I agree the Stock Motor /Speed controller can be hacked but as you said all the redundancy makes them nearly impossible to work with

    and they are heavy. If you buy a complete chair you still can use some of the battery wiring and such.

    I usually just remove the brake altogether.

    The neutral drive leaver is a nice feature. but you can easily remove by removing the cover and taking the spring and leaver out.

    Just remember to plug the hole to keep out dirt/water.

    The Dimensional Engineering saber tooth 2x25 drive works good for me and it 140 bucks.
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