Bushing Design For Cantilevered Shaft

[motoboy]

I want to support a cantilevered, high load, very low speed, 90º oscilating shaft with two bronze bushings. Don't know if PV (Pressure Velocity) calculations are valid because of possible edge loading due to cantilever. Also not sure of PV because of low speed and not a complete revolution.

Has anyone heard of bushing calculations other than PV?

 

[Philrock]

You have to respect separate P and V limitations as well as the PV limit. Manufacturers get pretty optimistic with their statements of PV capabilites, so be conservative, if possible.

Keep maximum possible spread between the bearings to minimize edge loading. If local edge loading is high due to cantilever, the bearing will wear, increasing the load bearing area, and reducing the local pressure. You just have to hope that the wear is not so damaging that it escalates in spite of the lower pressure.

 

[plasgears]

Roller element bearings would seem to fit the application. PV goes out the window with the type loading you describe.

 

[John2004]

Hi Motoboy,

You might want to check out

http://www.igus.com.

They have plastic self lubricating bushings that will take higher loads and outlast bronze bushings, and in many cases are cheaper. They also have an online computer program that will calculate bushing life, and account for edge loading and shock loads if you wish. They will also send the program to you on CD.

These plastic bushings are more compliant than bronze, and will take the edge loading better. However, the shaft clearances may be a little larger. The loads they handle, and the service life they offer, is quite impressive.

Drawn cup needle roller bearings are also fairly compact like a bushing, since they work directly on a hardened shaft, without an inner ring. They are also fairly cheap, and are forgiving to misalignment. Torrington / Timken

http://www.timken.com

has many to choose from.

Hope this helps.

John