Calculate hold down force for rotating shaft
Calculate hold down force for rotating shaft
(OP)
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
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





RE: Calculate hold down force for rotating shaft
RE: Calculate hold down force for rotating shaft
Took a look at the attachment
“Do not worry about your problems with mathematics, I assure you mine are far greater.” Albert Einstein
RE: Calculate hold down force for rotating shaft
RE: Calculate hold down force for rotating shaft
RE: Calculate hold down force for rotating shaft
RE: Calculate hold down force for rotating shaft
RE: Calculate hold down force for rotating shaft
je suis charlie
RE: Calculate hold down force for rotating shaft
(125 ft-lbf *12 inches/ft) /.85 inches = 1764 lbf tangentially at the surface of the rod across the diameter of the rod.
Since the rod is slippery at .35 CoF the Normal force required is 1764 lbf/.35 = ~ 5000 lbf.
It doesn't get multiplied by two because the moment applied at each contact spot relative to that spot is zero, with the torque resisted by the force *CoF * diameter at the location opposite each contact spot.
To be sure this is a simplification as it assumes the load is actually a couple, not a torque.
RE: Calculate hold down force for rotating shaft
Regardless, the 0.85 inch dimension was stated as a diameter, and MUST be divided by 2 to get a radius.
If your interpretation of the problem involves the applied down force and an opposing reaction then go right ahead and multiply by 2.
RE: Calculate hold down force for rotating shaft
RE: Calculate hold down force for rotating shaft
I'm going with this as the original question is related to down force, not uniform radial pressure.
RE: Calculate hold down force for rotating shaft
je suis charlie
RE: Calculate hold down force for rotating shaft
RE: Calculate hold down force for rotating shaft
You will probably find useful equations in any text that includes an analysis.
Mike Halloran
Pembroke Pines, FL, USA
RE: Calculate hold down force for rotating shaft
In that case lets go straight to the pipe wrench. Self weight plus Torque/Length - say 50 lbs total?
je suis charlie