Bronze Bushing Design
Bronze Bushing Design
(OP)
Can anyone recommend a good reference source, where I can find information on bronze bushing design?
I have an application with (4) four 158" DIA sheave with a pressed-in bronze bushing, rotating on a steel shaft. One sheave is fixed and the remaining (3) three are floating. The problem is with the recommended operating clearances (max, min)? The sheaves were purchased about 10 years ago and there is very little information available and the supplier is not willing to give out any recommended running clearances or original (as purchased) clearances. The operating parameters are as follows:
RPM - 90 max
Sheave Weight - 5000lb
Applied Load - 14,000 lb
Shaft OD - 9in to 11in (Can't measure directly)
Bushing Material - SAE 65, Bronze (Best Guess)
Shaft Material - 4140 (Best Guess)
Lubrication - Synthetic Grease
Any help or additional insights are appreciated.
I have an application with (4) four 158" DIA sheave with a pressed-in bronze bushing, rotating on a steel shaft. One sheave is fixed and the remaining (3) three are floating. The problem is with the recommended operating clearances (max, min)? The sheaves were purchased about 10 years ago and there is very little information available and the supplier is not willing to give out any recommended running clearances or original (as purchased) clearances. The operating parameters are as follows:
RPM - 90 max
Sheave Weight - 5000lb
Applied Load - 14,000 lb
Shaft OD - 9in to 11in (Can't measure directly)
Bushing Material - SAE 65, Bronze (Best Guess)
Shaft Material - 4140 (Best Guess)
Lubrication - Synthetic Grease
Any help or additional insights are appreciated.





RE: Bronze Bushing Design
Best Regards,
Mike
mike@usmech.net
RE: Bronze Bushing Design
RE: Bronze Bushing Design
Any "older" Boston Gear book as a great section on bushings
eddie
www.geocities.com/motorworksnf/123
RE: Bronze Bushing Design
Any "older" Boston Gear book has a great section on bushings
eddie
www.geocities.com/motorworksnf/123
RE: Bronze Bushing Design
As far as my application noted above, I recently measured the clearances in the bushings amd found the three floating bushings to have a clearance of around .014" to .015". In my search for allowable recommended tolerances, I turned to a few machinists for a little insight into my problem. Their rule was 0.001" on the diameter per inch of shaft diameter but made no comment limiting this to specific size? As well, one vendor who had previously quoted on a similar application had a running clearance of .009" to .010" with a similar shaft, but I wanted to double check to make sure.
The next question I have yet to answer is, when are they considered worn out? There must be a recommended max clearance rule somewhere but the problem is finding it or are they worn out when they stop doing their intended job?
Thanks,
Tyroneous
RE: Bronze Bushing Design
They give .005/0.010 for "RC5" in this size range & 0.005/0.013 for "RC6" "Medium Running Fits" "higher running speeds or heavy jnl. pressures, or both"
RC7 "Free Running Fits" 0.008/0.016 'where accuracy is not essential" or "large temp. variations" or both
RC8 [0.012/0.025]& RC9[0.018/0.038] "Loose running Fits" "intended for use where wide commercial tolerances may be necessary, together with an allowance, on the external member"
RE: Bronze Bushing Design
Does the sheave wander or act erratically??? probably last a lifetime at that speed...
RE: Bronze Bushing Design
Due to the time required to measure the bronze journal bearings with the machine disassembled, I had to measure the clearances with the sheaves on the shaft. I was unable to determine if the bearing was belled but I accounted for eccentricity by taking clearances at three different angular locations ( 0°, 144° & 288°). I measured the clearances to be relatively consistent, within .002" to .003" on all three bearings indicating a relatively consistent wear pattern. As well, the sheaves don't wander or act erratically but they do have a vibration issue which is the result of no static balancing during original manufacturing, but that's another issue. The sheave with the greatest imbalance did not show signs of increased wear so the vibrations doesn't seem to increase the wear of the bronze bearings.
Thanks,
Tyroneous
RE: Bronze Bushing Design
The running clearances also depend on the operating enviroment. If foreign particles, e.g. sand, metal chips, are present then large clearance is preferable. If the bushings are meant for sealing purposes then you might think of using a smaller clearance. At the speed of 90 rpm I think your bushings probably will last for a very long time without wear even with some vibrations.