Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Motor necessary to power a small cart

Tags:
  1. May 15, 2016 #1
  2. jcsd
  3. May 15, 2016 #2
    Right offhand I'd say no. It looks like the RPM is 200, and I'm assuming the torque is 6.5 kg-cm(?). So available torque at 1:1 ratio on a 25 cm diameter tire would be about half that, or 3.25 kg-cm. To get to 6 km/hr with the same tire you would need about 3:1 speed increase, which would reduce the torque to about 1.1 kg-cm. With all the other considerations (rolling resistance, elevation increases in common roads, even flat ones) I don't see it working.

    Anyone else?
     
  4. May 16, 2016 #3

    CWatters

    User Avatar
    Science Advisor
    Homework Helper

    Power = Torque * angular velocity
    Power in Watts
    Torque in Nm
    angular velocity in rads/s

    200rpm = 200*2*pi/60 = 21rads/s
    6.5 kg.cm = 0.64 Nm

    So that motor develops....

    Power = 21 * 0.64 = 13W

    Google says Kids carts typically use 500W motors and adult carts 1500W.

    So way too small.
     
  5. May 16, 2016 #4

    CWatters

    User Avatar
    Science Advisor
    Homework Helper

  6. May 16, 2016 #5

    jack action

    User Avatar
    Science Advisor
    Gold Member

    What is important is the power rating of the motor. As @CWatters calculated, there is a 13 W output (it is actually 9.4 W, since the rated RPM is 140 rpm and not 200 rpm). This is a replacement motor for a ride-on of this kind and it is rated at 170 W; so a lot more. And it is cheaper than yours!
     
  7. May 19, 2016 #6
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted