

Unrideable bricycle - bromagosa
https://www.youtube.com/watch?v=rvmJ_R4psdo

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Isamu
Abstract from paper:

A bicycle with compliant training wheels, half way between a bicycle and a
tricycle, is uncontrollable

ANDY RUINA, Cornell University, Mechanical Engineering

We have built and tested a vehicle that can balance and steer like a bicycle,
a tricycle, or anything in between. A bricycle is essentially a bicycle with
springy training wheels. The stiﬀness of the training wheel suspension can be
varied from inﬁnite, when the bricycle is a tricycle, to zero, when it is a
bicycle. One might expect a smooth transition from tricycle to bicycle as the
stiﬀness is varied, in terms of handling, balance and feel. But the situation
is more complicated. Rather, the controllability of a bicycle depends on
gravity. Without gravity, lean and direction cannot be controlled
independently. Springy training wheels eﬀectively reduce or even negate
gravity. Indeed, experiments with the bricycle show problems when the total
eﬀective gravity is about zero. People can then still balance easily but can
no longer turn the brike. The theory and experiment show a qualitative
diﬀerence between bicycles and tricycles. A diﬀerence that cannot be met
halfway.

Related:
[http://ruina.tam.cornell.edu/research/topics/bicycle_mechani...](http://ruina.tam.cornell.edu/research/topics/bicycle_mechanics/overview.php)

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wgeorgecook
This is probably one of those things where we have no idea what a practical
application is until it pops up on something.

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bromagosa
I was thinking exactly the same thing! What kind of stuff would you want to
keep on a straight trajectory and prevent from steering?

Many studies that seem unpractical or even stupid at first sight become genius
when somebody finds a problem to which they are an elegant and obvious
solution.

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DEinspanjer
Okay, I'll burn my karma for it...

Chuck Norris could steer a bricycle!

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ZeroGravitas
That was much better than I expected from the initial still.

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wgeorgecook
Username is relevant

