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Paths of 800 unmanned bicycles being pushed until they fall over (lemmy.ml)

submitted 4 days ago by qaz@lemmy.world to c/dataisbeautiful@lemmy.ml

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[–] orbituary@lemmy.dbzer0.com 3 points 3 days ago (1 children)

It's entirely expected. The anomalies are going to be on the furthest left and right; Bikes that fall down right away or ones that stay up longest. The average would be the densest area - bikes that performed "okay." The symmetry is also an expected function with the only options for the wheel to turn being left or right.

If these were not standardized releases, meaning, the energy used to push the bike varied from one to the next - say, because a person was pushing them and not a machine with a defined load - then it explains the short vs. long distances, however that would be normalized even with a predefined load and look similar to this... just bigger distances.

[–] usualsuspect191@lemmy.ca 2 points 3 days ago (1 children)

Bikes aren't symmetrical though, with the drive-train to one side, so you'd think there'd be a more noticeable bias in one direction. Guess it's a very minor effect.

[–] shiny_idea@aussie.zone 19 points 3 days ago (1 children)

I dug up the actual paper (Cook, 2004) and it turns out the bicycle was symmetrical... and, in fact, entirely virtual.

The virtual bicycle used for simulation

It's a plot of a computer simulation, rather than records from a real-world physical experiment.

A bicycle is composed of four rigid bodies: the two wheels, the frame, the front fork (the steering column). Each adjacent pair of parts is connected with a joint that allows rotation along a defined axis, and the wheels are connected to the ground by requiring that their lowest point must have zero height and no horizontal motion (no sliding).

So the simulation has a lot of simplifications from reality, and the picture tells us more about the simulation model than it tells us about the real world. It is a pretty picture, though.

Here's the paper reference:

Cook, M. 2004. It takes two neurons to ride a bicycle.

(I couldn't get it from the Cook's Caltech site, but I found a copy elsewhere.)

[–] Eh_I@lemmy.world 2 points 3 days ago (1 children)

The interesting thing in this situation is that it curved at all.

[–] Sims@lemmy.ml 3 points 1 day ago* (last edited 1 day ago)

The fork is bend so the bike automatically counter-steers against gravity. As long as the speed is high and the wheels are spinning (centripetal/symmetry forces), it will tend to steer in a straight line. So the spinning wheel and the bend, makes the bike run upright. The bend has a name, but I forgot..