Ball bearings and friction.

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MichaelG.

A machined phenolic cage has less drag over the brass/steel/plastic cages. With ceramic balls a full compliment has very little drag, despite the balls rubbing and bouncing off each other. What we have noticed in model engine bearings, is that the ceramic ball requires a different radius to be effective compared to the steel ball setup. The work I did with some bike bearings was that there is a definite gain to a ceramic ball in a bike wheel hub as long as you can keep the dirt out. We lubricated it with a pfpe oil and only 0.1cc of oil was used in each bearing. The oil is to keep the race surfaces from rusting. These were set up in October 2019 for a indoor track bike, and are still doing great. I am fortunate to have a selection of ceramic balls in some nominal sizes, and also in the plus and minus range in about 2.5 micron diameter changes. They measure the balls to 5 decimal places of millimetre. If they are too loose, they do not roll correctly and then skid. Too tight is just friction. I make the full compliment with a small groove that just allows a ball to be pushed into place. In general I use 52% of the ball diameter as the radius for the groove. Sometimes I use 51% if I want less end float on a particular bearing. This is if I am making my own races though. Most commercial races are in the 52% to 54% of ball radius , depending on the design etc for deep groove bearings.