4 ms·
The friction under zero load is rarely a factor in a real design. You wouldn't use a bearing as big as the one in the video unless you had thousands of pounds o
by tlb 11y ago
The friction under zero load is rarely a factor in a real design. You wouldn't use a bearing as big as the one in the video unless you had thousands of pounds of radial force, in which case it's the rolling friction that dominates. (Rolling friction is due to the balls compressing as they roll).
If you don't have large forces, you could just use a small bearing with correspondingly low friction.
Possibly there's some application that needs large bearings to handle high peak forces, but where it's otherwise spinning at high speed with near-zero forces and friction matters, but I can't think what it is.
- Glyptodon 11y agoYo-Yos maybe?
- Retric 11y agoSomething like Aircraft jet turbines might qualify. They are designed to handel a mid sized bird stike or the loss of a blade which is way outside the normal force range. Though, I suspect they are heavy enough that rolling friction still dominates.
- tim333 11y agoA lube free jet bearing could be a major plus for preventing Aerotoxic syndrome.
- FreeFull 11y agoOr have cabin air intakes that are separate from the engines.
- PhantomGremlin 11y agoThe Boeing 787 Dreamliner does this. https://en.wikipedia.org/wiki/Bleed_air#Bleedless_aircraft https://en.wikipedia.org/wiki/Bleed_air#Bleedless_aircraft
- tlb 11y agoThey're part of the engines because the air has to be compressed and heated before going into the cabin (in flight, it's 1/3 of normal pressure and -40C outside) which, it turns out, the compressor turbine is perfectly suited for.
- bluedino 11y ago>> The friction under zero load is rarely a factor in a real design. I remember as a kid I took my rollerblades apart, and 'cleaned' the bearings with WD40. The wheels spun so much faster when I simply spun the wheels on the skates. But I slowed down much faster when actually had the skates on and went down the street. Turns out re-packing the bearings with new grease fixed the problems, even though the wheels didn't free spin nearly as long.