Why is a bicycle easier to balance at speed? | James May's Q&A | Head Squeeze

Why is riding a bike at speed easier than falling off one?

Taken from James May's Q&A Ep 32

Welcome to BBC Earth Science! Here we answer all your curious questions about science in the world around you (and further afield too). If there's a question you have that we haven't yet answered let us know in the comments on any of our videos and it could be answered by one of our Earth Science experts.

[DrRPR]

Try to hold a spinning hard drive and tilt your wrist. You will feel the hard drive resisting.

[BR]

I actually took a class at my university last semester called "The Joy of Physics on a Bicycle".

Best. Class. Ever.

The ability to balance has a lot to do with steering inputs. A good test to prove this is to weld the handlebars so that the front wheel remains straight. You'll only be able to ride about 20 feet before falling over. The info presented by James about caster and the wheel automatically turning to correct lean is spot on.

[synchronyJEM]

Clearly it must work since so many channels do it. Having James May asking to subscribe easily has a bigger effect than the viewers exploring the content and/or subscribing with the usual method. And that's how the channel makes his revenue, by having as much subscribers as possible.

Also, James May makes it with class and humor, in my opinion.

[kyle]

It's actually very simple. The trail makes it so that the wheel turns into the direction you fall. Your momentum, however, is in the opposite direction, and balances out your falling. You become more stable at speed because these forces increase.

The effect even still works with no rider. You can give a bike with nobody on it a running push and it'll keep upright until it runs out of speed.

There's also the matter of your own learned ability to use these effects to your advantage, without even thinking of it.

[RDL]

Loved the Hitchhikers Guide to the Galaxy Reference at the end. When Arthur flies...
 

[ReachAndTouch]

You are brilliant HS, and James is a natural communicator.

[WyvernApalis]

Despite knowing how it works, I still want to watch because it's James May

[BlueCosmology]

There's also a reason fictitious forces are more often called inertial forces. Because some people seem to think that because of what it is called it isn't a real thing, as if for some reason a name changes what it is, and inertial force adds a bit of information. As it is a force that is caused by the mass.

[aph]

There were some scholarly articles on this from 2011 talking about self-stabilizing bicycles. There are videos with a brief explanation and examples of trail-less and gyro-less stable bicycles. search for "TMS Bicycle, stable without gyros or trail"

[TwoWheelWarrior]

Every cyclist is a hero. Helping save the world. One pedal revolution at a time...

[cebax]

In a way your right though. The weaving motion made by people riding bikes is not so much the reason the bikes stay upright, but a biproduct of the riders balance and the corrections he has to make in order to keep gravity & or Wind from overpowering forward momentum.

[akshayisr]

It exists in the frame of reference of the rider because it is an accelerating frame. And it is opposite to the direction of the acceleration of the frame which is in the opposite direction of centripetal force which exist in an external observers frame. If you want to apply laws of motion in the riders frame of reference then you will have to consider centrifugal force.

[BBCEarthScience]

Sorry our Q&A video was later than usual today guys, we've been busy on #GeekWeek business! Enjoy!

[LoafPuff]

Centrifugal force (Latin for "center fleeing") describes the tendency of an object following a curved path to fly outwards, away from the center of the curve. It's not really a force; it results from inertia i.e. the tendency of an object to resist any change in its state of rest or motion. Centripetal force is a "real" force that counteracts the centrifugal force and prevents the object from "flying out", keeping it moving instead with a uniform speed along a circular path. nearly there James, nearly there.

[Muck]

A "physical process" is easier to manage when you "pour energy into it". Balancing a broom on your hand is easier if you are moving forward, because the directions in which the broom can fall are narrowed down a bit compared to the full 360° while standing still.

[BeastOfTraal]

I've seen a bicycle that turns the opposite way of the handle bars. It was called the impossible to ride bike. Trying to ride on that bike was like getting on a bicycle for the first time.

[andrewince]

When setting up a BMX most people use forks with a 35mm offset. This definitely increases stability. There's a possible case that human balance is the key to bike stability. Trials riders can keep a bike upright when stationary by using small rocking movements. If you feel like trashing a bike you can try doing something often referred to as a "ghosty". While moving simply dismount, the bike will carry on until it slows too much and topples.

[kght]

you might be surprised at how easy it is if you were to try, adults who have never ridden a bike generally figure it out in about 5 minutes on their own just because they have seen other people do it. only little kids have to be taught. as james may said, it is just natural.

[thesecondislander]

It does exist, both as a fictitious force and a reaction to centripetal force. The first case describes a "Nonexistant" force stemming from difference in frame of reference, the other a very real force.

[deano]

i think the answer is in Wikipedia somewhere. Basically computer simulations were used to show that a bike is always falling over, which means the center of gravity is off to one side of the bike, so you steer in that direction and then the center of gravity moves to the other side and you start falling the other way, repeat the process and the bike weaves down the road constantly falling in opposite directions. The faster you go the longer the wavelength of the weave and so the less you need to move the handlebar to stop if falling over, so it feels easier to control. Factors like trail, angle of the forks, offset of the handlebars from the steering axis etc makes correcting the fall easier or harder. The idea is that a bike is fundamentally unstable, but an effective mechanism for controlling the fall is present. Interestingly the Wright brothers (previously bicycle builders) wrote that their success in developing the aeroplane was to use the same principle of a naturally unstable platform but that had effective control surfaces so the pilot could constantly counteract the tendency of the plane to crash. According to them prior to this the focus of plane design had been to produce self-stable designs, which didn't work.