Glen's Machine Shop

Bearing calculator

This program will tell you if your crankshaft bearings are suitable. You can calculate the load on a main or rod bearing.
This will tell you if a bearing size will provide acceptable performance in your engine.
This program assumes that all bearings are made from 932 (SAE 660) bearing bronze.
Suggested loads are :
Main bearings : 500 - 700 PSI
Rod bearings : 1500 - 2500 PSI
These calculations are for pressure feed oiling, if pressure feed oiling is not used, you may want to consider keeping the bearing under a lesser load.
All fields are required, except the width of the oil groove, which is only required if you specify an oil groove

Most of the information used to create this program is from Machinery's Handbook,
except for the info on pressure/velocity.

The piston diameter and compression ratio is used to calculate the load on the bearing.

For a main bearing of .500 dia, a minimum oil groove of .030 wide, and .015 deep is suggested

Here are 2 PDF files that I found while searching for information on bearings. They have very little info pertaining to engine design. I don't remember where I got these files from, but I make them available here:
Bearing Design Guide (PDF)
Sleeve bearings (PDF)

NOTE: When using this program, please keep in mind that this is not a final word on bearings. This will help you to size your bearings, but there are many things in bearing design that are not addressed here. I made this for my own use and will not be responsible for your use (or mis-use) of it.

Enter the piston diameter in inches:
This is a rod bearing
This is a main bearing
Select one for main bearings only:
This crank is supported by 1 bearing
This crank is supported by 2 bearings
This bearing has an oil hole
This bearing has an oil groove
Enter the width of the oil groove (inches):
Enter the compression ratio (ex. for 6:1 enter 6):
Enter the max engine speed in RPM:
Enter the length of the bearing (inches):
Enter the bore of the bearing (inches):

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