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The motors on this look interesting — Parallax Forums

The motors on this look interesting

Martin_HMartin_H Posts: 4,051
edited 2012-12-27 11:08 in General Discussion
Take a look at this ebay item:

http://www.ebay.com/itm/4WD-Robot-Car-Chassis-Platform-in-finished-condition-compatible-with-Arduino-/320962092205?pt=Model_Kit_US&hash=item4abad4dcad

Ignoring the acrylic chassis for a moment, what I find interesting are the DC motors. They look a bit like RC servos with a center output shaft and no control electronics. Most of these China robot items are put together using off the shelf gear motors and wheels, but I've never seen motors like these before. They actually look pretty handy as they have built in mounting brackets.

Comments

  • ercoerco Posts: 20,259
    edited 2012-12-26 08:19
    But...

    The DC motor of the chassis run 210rpm at 5V

    that's way too fast and undergeared, like a Magician chassis.
  • Mark_TMark_T Posts: 1,981
    edited 2012-12-26 15:05
    The boxes are standard servo components AFAICT - convenient for packaging a motor and gears at lowest cost.
  • W9GFOW9GFO Posts: 4,010
    edited 2012-12-26 16:18
    Mark_T wrote: »
    The boxes are standard servo components AFAICT - convenient for packaging a motor and gears at lowest cost.

    I don't think so, it looks like the output shaft is in the center of the casing.
  • Martin_HMartin_H Posts: 4,051
    edited 2012-12-26 16:21
    They also have two sets of mounting brackets at 90 degree angles which servos don't have.
  • W9GFOW9GFO Posts: 4,010
    edited 2012-12-26 16:22
    erco wrote: »
    But...

    The DC motor of the chassis run 210rpm at 5V

    that's way too fast and undergeared, like a Magician chassis.

    The wheels look to be about 50mm in diameter - which would make 210 rpm equal to a little less than two feet per second. Seems okay to me, especially since there are four motors.
  • ercoerco Posts: 20,259
    edited 2012-12-26 16:38
    Then go for it. Might be fine & fun for an RC vehicle. Maybe even a bump sensor or random motion (roaming with pings) robot. But from my experience, 2 ft/sec is too fast for any useful precision robot control, and it likely also means the wheel torque is quite low, real trouble on any 4WD bot. Add that squirrelly short wheelbase, close-coupled chassis and (navigation-wise) you're just looking for a bloody nose.

    But that's just me...!
  • W9GFOW9GFO Posts: 4,010
    edited 2012-12-26 16:40
    It is called a "4WD Mini Racer Car Chassis" after all :)
  • Martin_HMartin_H Posts: 4,051
    edited 2012-12-27 08:20
    High RPM low torque motors with small wheels have a certain appeal. I have a Herbie the mousebot which uses cassette tape pinch rollers on ungeared DC motors. It works much better than you would expect.

    Update this one is funny as they forgot to remove the paper on the acrylic.

    http://www.ebay.com/itm/4WD-Robot-Car-Chassis-Android-Phone-Control-by-Arduinos-IDE-Motor-Bluetooth-/360482488009?pt=LH_DefaultDomain_0&hash=item53ee6e3ec9
  • rwgast_logicdesignrwgast_logicdesign Posts: 1,464
    edited 2012-12-27 10:40
    Id love to see a picture of your mousebot martin..

    So my bot is going to run at 240 rpm max with 4 inch wheels, that works out to 4.16 feet/per second, Is this going to be to fast to do anything accurately? Obviously im not going to accurately be using ping sensors at full speed, but I figured that Id at least be able to do accurate work with the wheel encoders/compass and maybe wiicam/lasers (as wiimotes are moved pretty quick when used properly)...

    What kind of accuracy issues do higher speeds face
  • Martin_HMartin_H Posts: 4,051
    edited 2012-12-27 11:08
    Id love to see a picture of your mousebot martin..

    It's a Solarbotics kit, so you can see their video:
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