Hello everyone,
I need a motor for my project, but I´m not quite sure if my calculations are correct.
I need a motor to move a 500 kg horizontally (linear motion), where the friction constant is 0.8. The speed should be around 0.3 m/s
To calculate the force required to move the object:
F = m * g *u , F = force, m = mass of object, g = gravity constant, u = friction.
F = 500 kg * 9,82m/s2 * 0.8 F = 3924 N to push the object. That must be right.
Calculating the motors torque:
T = F * d, where T = torque, F = force, d = radius of wheel
T = 3924 N * 0.101 m
T = 396.324 Nm
Are my calculations alright? Since the torque calculated is the torque that will be needed to overcome friction i will obviously need a little higher torque to account for acceleration. Will selecting a motor of 420 Nm be alright? with 4 motors I would need 105 Nm motor for each wheel.
Do i need to use a gearbox motor for this purpose? Kindly correct me if I did any mistakes in the previous steps, and how to approach this forward as well. TIA
Kind Regards,
Khuzaim Khan
Please check again the friction coefficient, it may be too high if you are using the wheels...
Another suggestion is to see the system from a dynamic point of view: which acceleration will be required for the car movement? And when you answer this question the gearbox necessity will be justified.
I have some suggestions.
1) If you want to use four wheels and motors, to carry 500kg weight, you have to find out the power rating of single motor.
2) To get the exact motor rating, first you need to calculate exact mass of the whole system. In your calculation, you did not consider,
a) mass of the wheels
b) mass of the motor itself
c) mass of the carrier or trolley
3) In your calculation, you calculated the effect of friction one time, but for four wheeler you need count this effect four times, or simply calculate the force for a single motor.
4) If we consider the weight of other things except 500kg load is 100kg (I don't have idea about the actual weight of the motor), then total weight of the system = 600 kg-weight.
Weight over a single motor = 600/4=150kg-weight
Total frictional force= 150*9.8*0.8= 1176 N= f(k)
Remember, to start your carrier, you have accelerate at from 0 velocity. And to accelerate the car, you need to apply greater force than f(k).
Let you want to speed up your carrier to 1m/s for 0m/s within 20s. Then the acceleration is=(1-0)/20=0.05m/s2
Now, the required force for a single motor will be= f(k)+ma =1176N+150*0.05=1183.5N
Then the torque will be = F*d = 1183.5*0.101=119.5335=120Nm approximately.
Now, you need to calculate the required power of the motor by using this formula
P=wT; where w=2*pi*N/t
Your calculations are ok, few points you should consider before proceeding.
1. Friction coefficient you considered is too high. I don't know your application but for any application, this has to be reduced.
2. Your motor's operational rotational speed will come around 30 RPM considering 0.3m/s and 0.101 Radius. so, you must use a gearbox with a minimum of 10 to 15 gear ratio.
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