6 ms·
The mechanics of turning are one of those things that seem simple and mundane at first but become increasingly more interesting the more you analyze them. For
by erikig 7y ago
The mechanics of turning are one of those things that seem simple and mundane at first but become increasingly more interesting the more you analyze them.
For instance:
How do trains turn if the outside wheels can't spin faster than the interior wheels?
- https://www.youtube.com/watch?v=Ku8BOBwD4hc https://www.youtube.com/watch?v=Ku8BOBwD4hc
How do you create stable train wheels?
- https://www.youtube.com/watch?v=agd8B-31bjE https://www.youtube.com/watch?v=agd8B-31bjE
How do automotive differentials work?
- https://www.youtube.com/watch?v=85CA4_cgZ5U https://www.youtube.com/watch?v=85CA4_cgZ5U
How do 6 wheel truck differentials work?
- https://youtu.be/LwZBnMQ40rI?t=261 https://youtu.be/LwZBnMQ40rI?t=261
And on and on down the rabbit hole
- auxym 7y agoGreat video from 1937 on differentials: https://www.youtube.com/watch?v=yYAw79386WI https://www.youtube.com/watch?v=yYAw79386WI
- userbinator 7y agoI think it's been discussed a few times on HN before. The fact that it's over 80 years old yet easier to understand than newer material is amazing.
- salty_biscuits 7y agoActually train stability is way more subtle than that. Even the "stable" one has a critical speed at which it will become unstable. This is called Klingel motion or "hunting". It is caused by the effective damping from the contact reducing as train speed increases. https://en.wikipedia.org/wiki/Hunting_oscillation https://en.wikipedia.org/wiki/Hunting_oscillation
- dsfyu404ed 7y agoThe answer to all your questions is "with a nonzero but acceptable amount of scrub" ;)
- jcampbell1 7y agoCaster and trail are interesting concepts which make it so the steering automatically returns to straight. It is confusing that the casters on office chairs use trail, not caster. It should be intuitive why one can ride a bike hands free, but good luck on a bird/lime.
- taneq 7y agoThe 6-wheel diff video starts a bit late and misses some details. They first start talking about 6-wheel diffs here: https://youtu.be/LwZBnMQ40rI?t=248 https://youtu.be/LwZBnMQ40rI?t=248 The question about train wheels reminds me of one of my all-time favourite videos, where Feynman explains how trains follow their tracks: https://youtu.be/q5PAJ4tEIsM https://youtu.be/q5PAJ4tEIsM
- mc32 7y agoImagine those Soviet icbm trucks with two front turning axles and three rear axles. Or even worse the MZKT 79221[1] which was like eight axles. [1]https://en.m.wikipedia.org/wiki/Missile_vehicle https://en.m.wikipedia.org/wiki/Missile_vehicle