Calculate hold down force for rotating shaft

In summary, To stop a .850" diameter steel shaft from rotating under a torque of 125 ft-lbs, you will need to calculate the force required to clamp the shaft before applying the torque. This can be done by looking up the coefficient of static friction between the shaft and the clamp block and ensuring that the static frictional force acting on a radius of .425" is enough to resist the applied torque. It is also important to consider the strength of the materials involved to prevent any breakage.
  • #1
deserttech
2
0
I have a .850" diameter steel shaft that will have a torque of 125 ft-lbs put on it. I need to calculate how much down force I need to stop the shaft from rotating. I suppose we can assume that it will be steel on steel.

Going with a coefficient of friction of about .35 I tried to calculate with the typical CoF problem of a box and an incline, but I don't know how steep to make the incline.

How can I figure out how much force it will take to stop a .850" diameter shaft from rotating under a torque of 125 ft-lbs?
Thanks
 
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  • #2
deserttech said:
How can I figure out how much force it will take to stop a .850" diameter shaft from rotating under a torque of 125 ft-lbs?
Depends on how quickly you want to stop it.
 
  • #3
A.T. said:
Depends on how quickly you want to stop it.
Maybe, I didn't describe it fully. I need to know how much force it will take to clamp the shaft before I apply the torque so that it doesn't move. I'm not sure how to calculate that.
 
  • #4
deserttech said:
Maybe, I didn't describe it fully. I need to know how much force it will take to clamp the shaft before I apply the torque so that it doesn't move. I'm not sure how to calculate that.

You can get a pretty good start by looking up the coefficient of static friction between the material of the shaft and the material of the clamp block. The force that you apply to the clamp block will be the normal force generating a static frictional force; this frictional force acting on a radius of .425" has to generate enough torque to resist the 125 lb-ft that you'll be applying.

You'll want to consider the strength of everything involved to make sure nothing will break.
 
Last edited:

Related to Calculate hold down force for rotating shaft

1. How is the hold down force for a rotating shaft calculated?

The hold down force for a rotating shaft is calculated by multiplying the torque applied to the shaft by its radius. This will give you the moment of force, which can then be divided by the radius of the shaft to get the hold down force.

2. What is the unit of measurement for hold down force?

The unit of measurement for hold down force is typically expressed in Newtons (N) or pounds (lbs).

3. Is the hold down force affected by the speed of rotation?

Yes, the hold down force is affected by the speed of rotation. The faster the shaft is rotating, the greater the hold down force will be.

4. Are there any other factors that can affect the hold down force for a rotating shaft?

Yes, there are other factors that can affect the hold down force, such as the material and diameter of the shaft, as well as any additional forces acting on the shaft.

5. Why is it important to calculate the hold down force for a rotating shaft?

The hold down force is important to calculate because it helps to determine the amount of force that is needed to securely hold the shaft in place while it is rotating. This information is crucial for ensuring the safety and stability of the shaft and any attached components.

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