Naked Science Forum

Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: thedoc on 09/05/2011 23:06:07

Title: How does a rider-less bicycle stay upright?
Post by: thedoc on 09/05/2011 23:06:07

A team working in the USA and Holland have this week come one step closer to working out how a rider-less bicycle remains upright...

Read the whole story on our  website by clicking here (http://www.thenakedscientists.com/HTML/content/news/news/2233/)

 [chapter podcast=3079 track=11.04.17/Naked_Scientists_Show_11.04.17_8365.mp3](https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fwww.thenakedscientists.com%2FHTML%2Ftypo3conf%2Fext%2Fnaksci_podcast%2Fgnome-settings-sound.gif&hash=f2b0d108dc173aeaa367f8db2e2171bd) or Listen to the Story[/chapter] or [download as MP3] (http://nakeddiscovery.com/downloads/split_individual/11.04.17/Naked_Scientists_Show_11.04.17_8365.mp3)

Title: How does a rider-less bicycle stay upright?
Post by: Airthumbs on 19/04/2011 18:00:20

What would happen if you introduced a disc into the bike frame that spins very fast on the same axis as the wheels?  The gyroscopic torque may be increased and if there is a connection the stability of a moving cycle.

Could it also be possible to use gyroscopic torque suspension by having something spinning horizontally?

Would it make it harder to accelerate and decelerate if you had something spinning 90° to the angle of movement?

Title: How does a rider-less bicycle stay upright?
Post by: Geezer on 19/04/2011 21:59:23

It's a bit hard to tell from the photo, but it looks to me as if the axis of the steering is not actually vertical.

Consequently, gravity acts to center the steering. When the steering turns, the mass of the bike is raised slightly, so as the steering attempts to turn, it encouners a force that tends to restore it to the straight ahead position.

I think they will find that if the steering axis is truly vertical, the bike will fall over.

(Hey - it's an interesting theory at least  [;D])

Title: How does a rider-less bicycle stay upright?
Post by: Geezer on 19/04/2011 23:07:52

I think I'll have to retract that! I don't think there is any tendency to elevate the mass.

Instead, as the bike tends to fall in one direction, a small torque is created that turns the steering so that the bike turns towards the direction of the fall. If the steering repositions the bike's tipping fulcrum to the "other side" of a vertical line through the bike's center of mass, the bike will start to fall in the opposite direction.

This process will continue indefinitely if the "gain" of the system is adjusted correctly, and it will appear as though the bike is travelling in a straight line, although it is actually executing a continuous series of very slight S-curves. The gain can be adjusted by positioning the height of the center of mass of the bike. The higher it is, the greater the moment of inertia. This will slow the rate of the fall, and give the steering more time to correct.

It's probably a lot more complicated than that, but I think that's the basic principle. It's really a mechanical analogue of an electronic control system that is stabilized with negative feedback.

Title: None
Post by: Cal on 25/01/2013 20:56:33

This is interesting because all the literature states that the bicycle corrects because it steers. does it? What if someone asked an engineer as this is what engineers do. apply science.