I am trying to find the right motors for the following case:
I want to have a total of two motors on opposite sides of a board. The board will have a maximum weight of 150kg (330 lbs) and needs to have a maximum speed of 20km/h (12mph). Time for the motors to reach this spead is trivial, but anywhere between 5-10 seconds looks about right.
Note that those numbers can be exceeded but I need to be able to go at least this fast at peak RPM.
I am trying to find the Torque the motors will need in order to move this weight and any other specification such as Voltage and Current, in order to find the right motors.
The diameter of the wheel should be anywhere between 10 - 20 cm (4 - 8 in)
I also don't care if the motor is brushed or brushless. I would prefer to have a brushed ones since I value cost more then lifespan.
What I tried:
Horse power = kg.m/s = 150kg/2 * 20km/h = 5400kg.m/s = 72HP (sounds unreal)
which then by the use of online calculator was converted to Torque to be equal to
T = 2.57 kg.m^2/s^2 (sounds ok? or is it too small?)
[first to imperial HP = 71, then to imperial T = 18.6 - only calculators I found were using imperial]
In this scenario RPM was chosen to be 20000 since I saw a motor that had that much and since raise in RPM means decrease in torque I figured the bigger the better in order to not get a crazy high torque which I expected provided that I have 72HP
Downwards force due to the weight = m.g = 150kg.g
its split between two wheels so F at each wheel is half of that assumming weight falls in the center
F1=F2 = 75kg.g where F1 and F2 are forces at each wheel.
Torque = F1.d where d is the radius of the wheel (in m)
T = 75kg.g.0.075m = 55,2 kg.m^2/s^2
Those two numbers are very differnet though.
What should I do?