Why does a moving bicycle not fall over? TU Delft casts aside some old theories

Delft University of Technology ^ | April 14, 2011 | M&C

[decimon]

Given sufficient forward speed, a bicycle pushed sideways, will not fall over. Scientists have been trying to find a conclusive explanation for this remarkable characteristic for over a century. This week, researchers at TU Delft have thrown new light on the question in a publication in Science.

Staying stable

The research at TU Delft, in collaboration with scientists from Cornell University (USA), centred on the following intriguing question: why is a bicycle self stable, above a certain speed? You add speed to a bike and can then give it a sideways push without it falling over.

Rotating wheels

Scientists have long been poring over this complicated question, even from as far back as the nineteenth century. Until recently, the consensus within the scientific community was that the stability was very closely related to two factors. First, the rotating wheels of the bicycle were supposed to provide stability through gyroscopic effects. Secondly, it was thought that the ‘trail’ played an important part. Trail is the distance by which the contact point of the front wheel trails behind the steering axis.

Predicting

The publication by TU Delft in Science puts paid to this old notion once and for all. 'We have known for years that the generally accepted explanation for the stability of the bicycle was too simple,' says researcher Dr Arend Schwab of the 3mE faculty at TU Delft. 'Gyroscopic effects and trail do help, but are not essential for stability.' Dr Schwab and a number of colleagues brought out a publication several years ago on the theory behind the stability of the bicycle (in 2007 in Proceedings of the Royal Society, doi:10.1098/rspa.2007.1857).

[decimon]

Back-pedaling ping.

[edpc]

You add speed to a bike and can then give it a sideways push without it falling over.

Let's test the theory.

[babble-on]

the department doing the study is literally run by Professor Boneshaker

[battlecry]

I guess they were too lazy to look up Vittore Cossalter’s work.

[ThomasThomas]

http://www.youtube.com/watch?v=PCXcLkKZbVI&feature=related

Bikes fall over.

[decimon]

the department doing the study is literally run by Professor Boneshaker

Boneschansker, if that's the same.

[oh8eleven]

Scientists have been trying to find a conclusive explanation for this remarkable characteristic for over a century.
Government grant heaven. And when they do find an answer, WTF are they going to do with it?

[decimon]

Yeah, I tried that ramp thing once. Just once.

[decimon]

And when they do find an answer, WTF are they going to do with it?

Build TF a better bicycle?

[Daffynition]

[Krankor]

I think it has something to do with a bumblebee.

[Attention Surplus Disorder]

Sweet!

[decimon]

That Mary Poppins thing really doesn’t work.

[JudgemAll]

I’m confused, this is nothing new. Every engineers knows it is because of the inertia of the wheel as tethered to the center which causes rigidity in space. It’s similar to the effect of rolling a ball of playdoh into a stable cylinder which cannot be tilted left or right, but it is done dynamicaly so with a thin wheel bicycle.

[knarf]

I had a pretty good idea, without fancy thoughts nor words .. by the time I was 10.

[Retired Greyhound]

LOL, I’m never riding a bicycle again after seeing that.

They all seemed to face plant.

[JudgemAll]

Congrats: that is a beautiful picture of a gyroscope demonstration.

[BenLurkin]

[Calvin Locke]

In one of my college physics lectures, the prof had a weighted bicycle
wheel with handles that he pulled the rip cord to spin up, picked it
up, and sat down on a stool, and demonstrated the various forces
and effects.