I am having trouble determining the maximum weight capacity a motor can handle. I provided the specs below. The calculations are for the top row or the 580KV model.

So to start off,I'm only taking maximum values, I took the Watts and converted it to HP. About 10.06HP. Then I took this and converted it to Newtons. Around 7480N and my weight of about 725N + the vehicle at 88N so 813N. So would this motor be able to move 813N from a stand still on 27in tires? Assuming it's flat ground and no wind. If not would it be able to if already traveling at 10mph?

On a side not how fast would it be traveling if the wheel diameter is 27in, the rpm is 30,000, it's producing 7500W of power, with 82Kg of weight onboard, and the gear ratio is 1.25:1? Also acceleration? thanks

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  • 3
    $\begingroup$ you can only derive Newtons from watts at a particular speed and a particular wheel diameter. To determine what force you have to move a vehicle from standstill, you need phase current and kv to get to motor torque, and then through wheel diameter (and a possible gearbox) to get to vehicle Newtons. You have to overcome friction, and any force due to it being on a slope, before you get any acceleration. $\endgroup$
    – Neil_UK
    Dec 28, 2018 at 6:35
  • 3
    $\begingroup$ I'm voting to close this question as off-topic because the question is mainly about mechanical engineering rather than electronics. $\endgroup$
    – The Photon
    Dec 28, 2018 at 6:57

1 Answer 1

  • 27" diam= 13.5" radius
  • circumference = 84.8" = 7.0686 '
  • 10 MPH = 14.6667 fps ['/s]
  • 27"D @ 10 MPH = 2.075 revs per sec = 124.5 RPM or 12.45 RPM/MPH

  • Max RPM = 30 kRPM @ 580 RPM/V

  • yet max mechanical HP may be at 80~85% no load RPM, depending on gear or pulley losses and range.
  • Max Power = 7500 W
  • Gear ratio, G needed for max voltage,power @ X MPH
    • assume 82% of no load RPM
    • G = 0.82*20,000/(12.45 X) = 1317:1 pulley ratio ( cascaded) e.g. 131.7 for 10 MPH, 65.9 for 20 MPH
    • or G= 66 at 20 MPH @ 54V and 10 MPH @ 27Vdc

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