A round bar question!!

[cyntanada]

Dear All
I have a question about the Torque.There is a round bar(mild steel) hold by bearing at both end.If I want to roate it form static position ,how to figure out the Torque or force we need?Please see attachment.The Autocad is really size.If need more info,please tell me.Thanks for all.

[RICHARD ZASTROW]

cyntanada, Can you find the break away torgue specs for the bearings? May be available in the tech section of the bearing catalog.

Dick Z

[cam1]

Hi:
Sometimes the best way to figure this out is experimentally: wrap a thin string around the shaft, say 10 turns, and then add some weights (washers etc.) to the string.Record the mass that just allows the shaft to turn. Too many variables come into play with the theory:
1. Alignment
2. Lubrication qty, temp, viscosity etc.

The method I've described is accurate eneough for most cases.

regards

[cyntanada]

Hi Richard
The spec will be found next week.Because I don't take the catalog with me!Acorrding to you reply,the bearing's torque is one of the important event of the calculation,right?why?Thanks for you help!.

[RICHARD ZASTROW]

cyntanada, cam1 is quite correct for an existing assembly. In order to determine the torque requirement before actually building the assembly, you calculate the resistance to moving it. That will include rotating the mass and how much, if any eccentricity the mass has. Add to that the breakaway torque. Efficiency of bearings? Also, as cam1 said,type of lubrication, temperature etc. must be considered. Then add the torque required to do the work the assembly is supposed to accomplish.

Then multiply by your "fudge factor". LOL

It's a lot like pushing your automobile. Hard to start moving (breakaway). Then push it up an incline (load).

Dick Z

[cyntanada]

Hi
oh,I forgot the finally model will be put under water surface.Because this is about waterjet.I will try to make a sample to roate it by thin string!.Thanks.