Interesting New Scientist article

[John90]

There's an article in NS last week about why bikes stay upright while rolling along. Nobody knows the complete answer apparently but the hitherto consensus view that the gyroscopic effect is essential turns out to be wrong. Nor is it down to the 'trail' (distance between the front fork if it were extended to the ground and the point where the front wheel touches the ground).

Anyway, the boffins now have sufficient understanding of the many factors at work to start designing bikes mathematically. The good/bad news is that road bikes may have evolved through trial and error to a point of near perfection and the maths will only confirm this. Most benefits are expected in the design of recumbents, bikes designed for older, less mobile riders and folding bikes.

The original article is only available if you subscribe but there is a dryer take on some of it here: bit.ly/kya4gL

 

[abo]

Heard something about this on the Naked Scientist podcast I'm sure. I'll have to dig it out

 

[mcshroom]

The answer to this was eluding me, until Kim over on yacf pointed it out: -

It's because when upright the force of the bumble bees colliding with each side is in equilibrium. As the bike starts to lean, more bees collide with the upward side. As the bees can't be there (because they're incapable of flight) this creates a pocket of low pressure, so air pressure pushes the bike upright.
As the kinetic energy of an impossible bee is proportional to the square of the relative velocity, the stabilising effect increases with the speed of the bicycle. At rest, the non-bees are too small to keep the bike upright.

Consequently, a bike cannot self-stabilise in a vacuum, as there would be no air pressure difference, and all the bees would asphyxiate.


[sub]Time for more codeine...

[/sub]
[sub]
[/sub]
[sub][/sub]

 

[400bhp]

 

[slowmotion]

Hoorah! Now I know why I'm crap at riding up hills. Those wretched Victorians got the bike design wrong, and Specialized have made the same mistake.
I particularly look forward to the improvements for "older riders"

 

[hotmetal]

Are they talking about riderless bikes remaining upright or have scientists been wondering all these years how we crazy 2-wheelers manage to balance? If the latter, they should get proper jobs!

 

[Globalti]

It's to do with steering, that's all. You steer the bike to balance it, that's why trainer bikes with no pedals are such a brilliant idea for teaching kids to ride.

 

[twozeronine]

I remember seeing a QI episode where they were talking about the science of bicycles. I remember torque being mentioned, and how it's impossible to turn left (or right) without turning the handle bars in the opposite direction first. I tried it and it's true.

 

[Globalti]

I remember seeing a QI episode where they were talking about the science of bicycles. I remember torque being mentioned, and how it's impossible to turn left (or right) without turning the handle bars in the opposite direction first. I tried it and it's true.

Sound of can of worms being opened...

It IS possible to steer a bike without first counter-steering the opposite way to displace the wheels from underneath. You can simply steer briefly, sacrificing balance in the knowledge that immediately after the movement you are going to need a wide amount of space in which to counter-steer quite heavily to get the bike upright again. It's called avoidance steering and it is a technique used a lot on mountain bikes where there's some obstacle like a rock you want to avoid. As I wrote though, it depends on there being enough trail room to recover afterwards because you will have begun deliberately to fall off your bike.

 

[twozeronine]

Sound of can of worms being opened...

It IS possible to steer a bike without first counter-steering the opposite way to displace the wheels from underneath. You can simply steer briefly, sacrificing balance in the knowledge that immediately after the movement you are going to need a wide amount of space in which to counter-steer quite heavily to get the bike upright again. It's called avoidance steering and it is a technique used a lot on mountain bikes where there's some obstacle like a rock you want to avoid. As I wrote though, it depends on there being enough trail room to recover afterwards because you will have begun deliberately to fall off your bike.

Yeah, I shouldn't have said "impossible". Like you pointed out, when I tried steering without countering it first, I lost a lot of balance.

 

[MontyVeda]

new scientist will probably have an article next year titled "its the gyroscopic effect after all"

 

[davefb]

dont they have robotic bikes then ?

just thinking, surely they must have a good idea, because otherwise how do things like that work ?


unless its all genetic algorithms........


err blimey http://video.answers...clist-516913328


ooh and a motorbike

http://videos.howstuffworks.com/wgbh-nova/2343-self-balancing-robotic-motorcycle-video.htm

not sure if i want to think too much about steering, dont wanna fall off

 

[BrumJim]

Its supposed to be all down to the Castor Effect. Personally I take that with a pinch of sugar. Or is it salt?