Motor Sizing for Wheel Endurance Testing

[SR71]

TL;DR

Motor sizing for wheel endurance testing

I am working with a wheel endurance testing application. I am trying to size a motor for the system. Basically, I have a drum which has to be rotated by the motor. I have different size wheels that I have to test. The motor is supposed to rotate the drum and then the wheel is pushed onto the drum with a force.

My question is when I want to find the torque (Fx perpendicular distance) do I use the radius of the drum or the radius of the wheel being tested? Currently, I am using the radius of the drum as the wheel is being pushed onto the drum but this gives me huge numbers as the wheel is pushing with 1000-2500 lbs of force.

Thank you in advance.

Link:

 

[jack action]

If the motor is on the drum then use the drum radius. If it is on the wheel then use the wheel radius.

Torque will be different in both cases but so will be the angular velocity. In both cases, the power will always be the same.

 

[Juanda]

My question is when I want to find the torque (Fx perpendicular distance) do I use the radius of the drum or the radius of the wheel being tested? Currently, I am using the radius of the drum as the wheel is being pushed onto the drum but this gives me huge numbers as the wheel is pushing with 1000-2500 lbs of force.

How is the radius of the drum or wheel relevant for this? The force is aligned with the axles so it's got no leverage. Am I misunderstanding the drawing? Or are you obtaining the tangential component due to the friction?

Since the angular velocity is constant during the test (or so I think from the video), I would say to size the motor you just need it to have enough torque to overcome the friction from the bearings and the friction due to the deformed wheel rolling.
I guess the second one should be the greatest one but I don't know how to derive it yet.

 

[Tom.G]

https://www.engineeringtoolbox.com/rolling-friction-resistance-d_1303.html

Shows that the coefficient for automotive tires is between 0.01 and 0.08, depending on the surface they are on.

Taking the two extreme conditions:
1000 lbs x 0.01 = 10 lbs
2500 lbs x 0.08 = 200 lbs

Multiply those results by your drum diameter radius to get minimum needed torque.

(above found with:
https://www.google.com/search?hl=en&q=how+to+calculate+rolling+resistance)

Cheers,
Tom

 

[Lnewqban]

Welcome, @SR71 !

Due to the different diameters of wheels to be tested, I recommend to engineer a variable velocity connection between motor and drum.
It could be a variable pulley-belt system, or a VFD (variable frequency drive), for example.
I assume each test has one or several specified angular velocities for the wheel.