How do I calculate torque on a shaft with a 500 lb wheel?

[cbstanfield]

I have a rather simple question but not having had physics since college, I am unable to find the solution to a problem. Given a shaft with a 500 lb wheel mounted to it how would I calculate the torque on the shaft? The wheel is 2 feet in diameter and 2 feet wide. The shaft is 2 inches in diameter and if I were to change the size of the wheel, say to double the weight and or diameter, is there an easy way to calculate the new torque value?

 

[Lsos]

Your question is akin to asking how much power is a 1000kg car using. The car is 3 meters long and 1 meter high.

The weight and size of the wheel say nothing about how much torque the shaft is transmitting.

Are you trying to spin this wheel? How fast are you trying to accelerate it? Is there a load on the shaft? These are values that are of interest.

The size of the shaft also doesn't matter.

 

[cbstanfield]

I am going to spin the wheel at 540 rpm. At first there will be no load on the shaft. Eventually I plan to put a load on the shaft so I was trying to determine what load the shaft would be able to handle without putting too much load onto the shaft. Perhaps I'm going about this the wrong way but thought calculating the torque would at least give me a starting point. If I have that I can calculate approx HP. Thanks for the help.

 

[russ_watters]

How fast do you want to accelerate it to 540 rpm? When it runs at constant rpm, there is no torque except what is lost due to friction.