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• # Torque required to turn a stationary wheel

Discussion in 'Calculations' started by reversethrust, Jun 7, 2012.

1. ### reversethrustMember

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Hello! I am looking for procedure for calculating the torque required to turn a stationary wheel. It's a simple arrangeement, a bicycle like fork with a rubber tire mounted over mild steel rim and a shaft is welded over the fork. Other calculations related are simple and easily found but I am confused where to find or get an idea about calculating torque required to steer this wheel when standing. Anyone can help with finding me a source? What I know is that contact patch, the load on the tire are important in it, so is the tire-concrete interface's adhesion ratio. Anything else I am missing out ? Regards

2.
3. ### ErichWell-Known Member

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Feb 2012
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Geometry is important.

Does the axis the fork rotates on pass directly through the contact patch or is it offset?

4. ### reversethrustMember

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It passes directly through the contact patch.

5. ### MDRActive Member

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The moment of inertia of the parts about the turning axis will matter also, as will the acceleration applied.

6. ### reversethrustMember

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OK here's what I make out of your replies and my idea:

- Calculate the moment of inertia of the assembly (Solidworks would provide that)
- Determine the initial and final angular velocities, set the time required to achieve that and find angular acceleration
- Next the resistance offered by the tire-concrete interface needs to be known. Now that's a hard part as I would have to look for data in any book which provides coefficients regarding rubber-concrete interface.
- The total torque required is the torque required to overcome friction and rotate the whole assembly from rest.

7. ### Auto EngineerActive Member

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May 2012
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Ok I will keep this simple so you can calculate the coefficient of friction between the tyre and concrete, which the result only applies to the surface of the road and tyre in contact, and nothing else.

The weight of the wheel and anything attached to it like the frame I assume that you can weigh it to establish its weight. Using a load sensor if available or if not purchase yourself a spring scale which measures load something like you would use if weighing fish at the side of the river, its the cheaper alternative.

With the wheel and frame in the normal direction of movement, pull the wheel along the desired road and measure how much force is required to pull the wheel at a constant speed, record the result.

Divide this result by the weight of the wheel and frame, the result is the coefficient of friction, which is the ratio of frictional force to the force pressing the two surfaces together, the result will be (mu) i.e. 0.7 as an example.

The coefficient of friction is not dependant upon the weight of the object or put more correctly the force pressing the two surface together under test.

Auto Engineer