@DeepCut @Peterea, 21,000 RPM that's crazy fast, i may have to get some of those myself. 21,000 RPM is fairly high however I have brushless RC helicopter motors that max out at 70,000 RPM in which case the bearings must be as small as possible because the linear speed of each ball bearing is a function of the inner diameter of the race in relation to the ball bearing diameter. One of my pulse motors uses ball bearings with an outside diameter of 1/4" which is quite small and has very little friction as well I have some ball bearings with an outside diameter of 1/8" which is very small. The best bearing for larger applications that I have found are ceramic skate-board ball bearings which have the lowest friction I have yet to measure other than my magnetic bearings which of course have basically no friction at any speed. It is important to remember that the friction increases drastically with load and RPM as such a bearing may feel as if it has no friction on the bench but have a great deal of friction at max speed under load. I like to do a comparison test because it is hard to grasp just how much friction standard bearings actually have until we compare it to a high quality bearing, for instance a standard ball bearing will make 8 revolutions on a spin test and a magnetic bearing will make 70+ revolutions in the same test. In any case the best quality off the shelf bearings I have found are usually high end, application specific, bearings made for RC helicopters or skate boards. I should also mention that my thoughts concerning bearing technology led to a little insight concerning other technologies. That is we can never know which setup is best until we have seen the best and make a relative comparison. As such I think it is silly that some people may say spinning a magnet past a coil of wire must always produce the same results, you see the technology we have is not the best way of doing things but the worst. Imagine that, what if we were doing everything wrong but this was the only way we knew of doing things -- how would we know?. I have found there is always a better way of doing things however we have to think for ourselves instead of following others and their popular opinion of the way things are. Regards AC
« Last Edit: 2011-05-28, 16:42:04 by allcanadian »
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Comprehend and Copy Nature... Viktor Schauberger
“The first principle is that you must not fool yourself and you are the easiest person to fool.”― Richard P. Feynman
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