4 ms·

I was thinking something similar. I immediately thought, "wait, doesn't a speed change imply a force on the bearing, and wouldn't that necessarily imply frictio

I was thinking something similar. I immediately thought, "wait, doesn't a speed change imply a force on the bearing, and wouldn't that necessarily imply friction between the bearing and track?" Under load (and I've no idea how much), I just imagine this applying a subtle little ba-dump-ba-dump-ba-dump to the bearings as they spin around. Their innovation seems to suggest that this is such a small change that it has less of a bump and more of a very slight shape change effect. So there may actually be something there - I've certainly seen stranger topological results. But until I see one after a few thousand hours in a high speed motor, I'll be on the fence.

jobu 11y ago
> But until I see one after a few thousand hours in a high speed motor Add some load to that as well. It seems pretty unlikely any indentations will last very long under stress. I've replaced bearings on trailers and vehicles and they often have wear marks deeper than the indentations they showed in that video.
ars 11y ago
> doesn't a speed change imply a force on the bearing .... imply friction Not necessarily. A speed change could also be because the track is longer. That's how trains stay on the tracks, the wheels are slanted, and if they turn off the track the length of the wheel changes, which changes the speed (relative to the wheel on the other side) and steers it back onto the track. Feynman explains it: https://www.youtube.com/watch?v=y7h4OtFDnYE https://www.youtube.com/watch?v=y7h4OtFDnYE
- function_seven 11y ago
  > and if they turn off the track the length of the wheel changes But is doesn't actually change. A different part of the wheel comes into contact with the rail, but that different part always had a higher linear speed. It just wasn't in contact with the rail until the turn. But with these bearings, it appears that the balls themselves actually do speed up or slow down to maintain separation from one another. In that case, there must be a force coming from somewhere to effect those changes.

jobu 11y ago

> But until I see one after a few thousand hours in a high speed motor Add some load to that as well. It seems pretty unlikely any indentations will last very long under stress. I've replaced bearings on trailers and vehicles and they often have wear marks deeper than the indentations they showed in that video.

ars 11y ago

> doesn't a speed change imply a force on the bearing .... imply friction Not necessarily. A speed change could also be because the track is longer. That's how trains stay on the tracks, the wheels are slanted, and if they turn off the track the length of the wheel changes, which changes the speed (relative to the wheel on the other side) and steers it back onto the track. Feynman explains it: https://www.youtube.com/watch?v=y7h4OtFDnYE https://www.youtube.com/watch?v=y7h4OtFDnYE

function_seven 11y ago
> and if they turn off the track the length of the wheel changes But is doesn't actually change. A different part of the wheel comes into contact with the rail, but that different part always had a higher linear speed. It just wasn't in contact with the rail until the turn. But with these bearings, it appears that the balls themselves actually do speed up or slow down to maintain separation from one another. In that case, there must be a force coming from somewhere to effect those changes.