Compression Trivia

[Bob Bidonde]

Compression loading on rod and crankshaft bearings due to compression ratio of the cylinder head is not the design limit loading for babbitt bearings.

Raising the compression ratio significantly increases the combustion pressure loading on the bearings, so combustion pressure loading is the design loading condition of the engine.

In the case of the Model A & Model B engines, I calculate pressure loading during combustion to be in the neighborhood of 9000 to 10,000 lbs per square inch.

In addition to the pressure loading, the babbitts must endure inertial loads due to the motion of the reciprocating and rotating parts.

Connecting rod babbitts are the weak link.