# Torque on a shaft connecting to a wheel

1. Apr 25, 2012

### zuq

hi guys

Lets say I have a wheel that is driven by a shaft connected straight to a motor.

Wheel raidus is 0.0762m while shaft raidus is 8mm.

If I know the torque acting on the wheel, say 20Nm , what would be the torque on the shaft?

Thanks

2. Apr 25, 2012

### Pkruse

Exactly the same.

3. Apr 25, 2012

### xxChrisxx

It's an abiguously worded question.
Is the 20Nm applied by the motor? Or applied at the wheel (as a brake), or is it a net torque?

A torque acts about an axis.
If the axis of the wheel and the shaft axis are colinear, they are the same.

4. Apr 25, 2012

### zuq

Thanks Pkurse and xxChrisxx

@xxChrisxx

My background is in electrical, so bare with me please.
This is for a kart where say 50Newtons of drag force is opposing the karts movement. In terms of torque at wheels, for a radius of 0.5m say it becomes 25Nm.

Now if the motor is directly coupled to the wheel, with shaft radius of say 0.25m (overly exaggerating) will the torque produced by motor be 25Nm in steady state conditions?..i.e. not accelerating and keeping at a constant velocity.

And offcourse the motor and wheel will have same RPM.

5. Apr 25, 2012

### Pkruse

If motor shaft is directly coupled to the wheel, then they see the same torque. Assuming one wheel drive, r at .25, drag at 50, then torque is 12.5.