Choosing of Motor

Hi there, i am doing a school project to build a car(4 wheels) that can carry a payload with a weight up to 9 kg(Total) with gear motors(4 Motors in total)

Based on my calculations, assuming there is no friction:
Force required to move= Mass* Acceleration
= 9kg* 9.81m/s-2
= 88.29 N

Torque required to move wheels = Force * Radius of wheels(120mm Diameter wheels)
= 88.92N * 0.06m
= 5.3352Nm
Torque required per motor = 1.3338Nm = 188.881990814 = 13.60097480898 kgcm

After browsing the 25D gear motors, do i choose this motor for my project?


9kg sounds heavy for those gearmotors and would probably strain the components of the gear motor mechanically. For comparison, the 6WD Dagu Wild Thumper has a recommended max payload of 5kg and uses 6 gearmotors of that size. You should probably consider using larger more powerful gearmotors. I do not have a recommendation for a more powerful motor.

- Grant

This suggests that you plan for the cart to accelerate as if it were in free fall, which is unrealistic.

An acceleration of 1 m/s/s would be more realistic. Starting from zero, after just 1 second the cart would be moving 1 m/s (a walking pace). After two seconds, it would already be moving faster than most people can comfortably walk.