Calculating Torque on Clutch

[George1985]

I am looking at installing an 'anti-reverse rotation' clutch on the fan shaft. The purpose is to prevent the shaft from rotating backwards. The cause of reverse rotation is the wind. The clutch is said to be rated for 829 ft-lbs. What sort of calculation do I need to do to verify that this is adequate?

It seems to me that 829 ft-lb rated clutch would be adequate because a person can easily stop the reverse rotation with their hand, but I know that there is probably lots of inertia associated with the fan. Thanks.

 

[zekeman]

I suppose one way of getting it empirically would be to reverse rotate the fan and plot the torque vs the reverse CFM and the corresponding velocity. Then from data on the maximum possible wind velocity you find the corresponding torque from your data.

 

[SnTMan]

leist22,

there is probably lots of inertia associated with the fan

In stopping the fan with your hand you are countering the intertia effects.

If it is NOT moving, inertia is in your favor, it will have to overcome to accelerate it.

Regards,

Mike

 

[DLite30]

I think that you already know that the static holding torque of the clutch is adequate. What you probably need to figure out is what forces from the torque produced from the deceleration of the the fan, that the structure and fan itself can handle.

If the fan is easily enough stoped with your hand, then engaging a high torque clutch as you have chosen, you can probably imagine imaging how fast the fan will stop, and probably tear the blade off the hub, or twist the structure.

So the main issues i see is: how quickly can the fan be decelerated without causing damage to it or the structure, and then how to control this rate of deceleration. Or how do you keep the fan from back-spinning at all.

One option you may want to consider is a "sprag" clutch, which you can google for more info, but it essentially allows free shaft rotation in one direction, but clutches the shaft to an outer housing in the reverse direction.