Assessing Lubrication Adequacy in Cam Shaft and Lifter Design

[ksw100]

I am designing a camshaft and lifter system for a slow-moving (100 to 1000 rpm cam speed) valve control system, similar in design to a typical internal combustion engine valve train. What formulas are used to determine if the spring forces and speeds are within the lubrication (oil or grease) capabilities?

I am familiar with the basic bearing PV (Pressure and Velocity) equation, but it does not seem applicable here. The equation seems inapplicable because calculating pressure requires knowing the contact area. However, in this case, the contact area is nearly zero: a convex curved cam lobe presses against a flat lifter (i.e., follower or tappet), making the contact area theoretically near zero thus pressure (P) becomes unrealistically high.

 

[enginesrus]

This is the transmission section. So this post should be in the engine section.

 

[SwinnyGG]

You need to use one of the Moes equations for a problem like this. They are available online, and they are intricate.

There are also calculators out there which will spit out the Moes parameters and the actual final film thickness, such as:

https://www.tribonet.org/central-film-thickness-calculator-line-contact/

I would personally only use these as a general guide, I wouldn't build anything without having done the detailed calculation to ensure accuracy before you spend money.