Bronze Bearing Allowables

[smjmitchell]

Hi All,

I have a bronze bearing through which a chrome plated steel tube slides (actually the lower bearing in a telescopic landing gear leg for a light aircraft). The bearing is a hollow cylinder approx 1.25" high with a bore of approx 2" and is pressed into the outer tube of the leg and retained with a circlip.

The loads on the bearing is mainly a intermittant radial load (i.e. during landing impacts) and is applied concurrently with the inner tube sliding through the bearing.

The bearing is fitted with a scaper and 'O' rings to keep out dirt etc and to keep hyraulic pressure inside the leg.

I have searched through a lot of data on plain bearing design and I am left with two unanswered questions.

1. What is the best bronze alloy for use in a bearing of this type.

2. What allowable bearing stresses should be used for final sizing of the bearing.

Any info or suggestions of references to consult would be appreciated.

Thanks,

Steve

 

[plasgears]

I don't know about solid bronze as a bearing, but you can get good guidance from Keystone (Marysville, PA) on PM bearings of various compositions. Iron rich PM bearings are emerging as strong, durable bearings, and they are cost effective, too.

 

[rnd2]

On the assumption the sliding surfaces are properly lubricated with grease, for this application, the choice would be more for structural than lubricative reasons.
The addition of tin and or lead in a bronze alloy improves lubricity and aluminium and zinc detracts. The choice of grease and its distribution on the sliding surface would be far more important. As plasgears infers, a sintered bearing filled with oil is worth considering if it is mechanically robust enough for the application.

 

[smjmitchell]

Yes the bearings are well greased.

 

[rnd2]

thread821-62340 may help you