Why bicycles do not fall: Arend Schwab at TEDxDelft

An assistant professor in theoretical and applied mechanics who is into bicyles : Meet TEDx Delft -- 2012 performer, Arend Schwab from Delft University of Technology, Department of Mechanical Engineering.

Arend did his BSc Engineering at Dordrecht (1979) and MSc Engineering (1983) and PhD (2002) at Delft. He runs the bicycle mechanics lab and teaches mechanics. Whenever Arend comes up with an assignment for his students, the hallway of the faculty is crammed with all sorts of very strange objects that resemble bikes only slighlty. Considering bicyles constitute 40% of the Netherlands traffic making it the bicycle capital of the world, his work is very interesting not only for the dutch people but anyone who ever rode a bicycle.

Amongst his fields of interest are: Multibody Dynamics, dynamics of flexible multibody system, finite element method, legged locomotion, speed skating, and bicycle dynamics. In particular the treatment of contact phenomena like in collisions and rolling (non-holonomic constraints) is his special interest. He has given academic talks related to his area of expertise in various universities all over the world. However, the concept of TED is relatively new to him and he is very excited to present his intriguing research at such a grand platform.

In the spirit of ideas worth spreading, TEDx is a program of local, self-organized events that bring people together to share a TED-like experience. At a TEDx event, TEDTalks video and live speakers combine to spark deep discussion and connection in a small group. These local, self-organized events are branded TEDx, where x = independently organized TED event. The TED Conference provides general guidance for the TEDx program, but individual TEDx events are self-organized.* (*Subject to certain rules and regulations)

[Mswayward]

I'm disappointed by many of the comments. They are critical nit picking. What is suggested by this video is that a whole new technological bicycle may come of Arend Schwab's work. A bicycle with greater stability due to electronic stabilization. A safer safety bike. A fall resistant bike that would lower the number of people injured on bikes. I think it is great work, I applaud this work and look forward to seeing future prototypes.

[daksheshnatakala]

This is the only guy that I have actually understood. Good job for explaining it so clearly!

[kennethflorek]

wow! It was a real pleasure to be disabused of my misconceptions so convincingly. I am going to watch this a few times to catch a couple of points that went by me too fast to absorb. The remarkable thing about bicycles (I still believe) is how readily they plug into human beings innate abilities.

[TheGatoskilo]

Impressive speech! In an era in which science is devoted to come up with theories and explanations on the creation of our universe, simple everyday classic physics  phenomena such as the stability of a bicycle remain unclarified. 

[IbadassI]

Who edits these TED videos?
.
Most times the videos cut to the presenter whilst he's talking about something on the screen behind, so we miss what he's talking about!

Happens on a lot of Ted videos nowadays

[stephanematis]

Excellent review of bicycle stability and what the future could hold in improvements.

[jbibm]

I'm really glad there are people out there like this gentleman. I'm way not detail oriented enough for this type of work and it's good there are people out there like him. I'm, generally, more focused on not getting killed by a car.

[recyclespinning]

I have heard a quote: that the bike was the pinnacle of man's enginneering and all the rest of technology has been downhill from that. If you think about most everything else has increased pollution and dependency of some sort or another.

[joeshmoe]

Bicycles are by their very nature stable. Been riding since 1968 and I have never lost control due to stability issues.

[markmccormack]

I am really surprised there is no mention of wheel camber, especially given that the speaker is a professer of applied mechanics.

A single wheel rolling on it's own shows the same tendency to steer in the direction it is tilted. When a wheel that is rolling in a straight line is tilted it exerts a thrust in the same direction at the contact patch because the tilted wheel wants to follow a circular path. In effect the rolling wheel automatically moves the contact point to be under the center of gravity. This is the same principle behind a band saw blade or flat belt tracking on a crowned pulley, and also what makes a car with misaligned wheels pull to one direction.

Gyroscopic effect is negligible to nonexistent, and has been debunked, caster effect is negligible but makes steering from the handlebars more stable. I find the idea of one wheel 'falling faster' than the other highly dubious without supporting evidence.

I have a front wheel drive recumbent bike with almost zero trail/caster that will toss you onto the ground if you try to steer only with the handlebars. Instead you have to lean into a turn even at low speed and the handlebars just let you damp the oscillation or turn more agressively. ...Steering on a bicycle can be accomplished almost exclusively with camber thrust. I'm not well versed on unicycles but I tend to guess that the statement holds true for those as well.

[lalitpatnaik]

I used to think that the chief reason for the stability of bicycles was the gyroscopic effect of the fast rotating wheels. Not any longer! Thank you.

[martinhirsch]

The rear wheel imposes the trailing castor effect as well, as the rear wheel follows the path of the front wheel. Essentially, the front wheel replicates the pivot point of a castor wheel.

The key to balancing is to alter the position for the center of gravity to match the angular path of travel - alter the center of gravity to move in the direction of a desired turn, and match the turn of the wheel in proportion to the momentum and direction of an off-center center of gravity.

[esso]

Being a cyclist; first time got to know such eyes opening scientific input from Arneb !!! Kudos 👍👍👍

[Pharesm]

You are awesome :D
Much thanks for your very cool, fun and useful work.
All humans should be able to follow such amazing lines of work like this...

[ACRVasquez]

Assistant Professor vs. Mechanical Engineer:

The picture at 9:14 shows positive caster.  The device in action has positive caster.  There is no demonstration of the device working with no caster.  If his argument about tipping masses was correct, a stationary bicycle would turn toward the fall.  This does not occur in the demonstration at 4:11.  Bicycles self stabilize because of the  caster effect and the rounded rubber tire.  As the bike falls, the contact patch moves toward the side wall, and friction helps to turn the wheel toward the fall.  Metal, "pizza cutter" type wheels would rely completely on the caster effect.

[Armuotas]

The best mass/gyro/trail interaction. That would be an interesting problem to solve for AI/Neural network.

[cameronturner]

So, it's still the caster effect.
When you look at a bicycle tire in cross section it is circular. The center line of the steering axis is in line with the center of the contact patch however, as the bike leans to one side the contact patch moves to that side but the steering axis leans with the bike and so the contact patch and steering axis are no longer aligned. If the bike leans to the left the contact patch moves left of the steering axis creating a caster effect not in the line of the movement of the bike (y axis) but in the line of the lean of the bike (x axis) . This causes the steering to turn into the lean. The caster effect is in the x axis and not the y axis. Make a bike with tires that have a cross section of zero (a thin sheet of metal for example) and you will see that it is unstable. You can experience this by riding with no hands. Take a mountian bike with wide tires, ride it with no hands, then switch to very thin road tires. It will be much more difficult to ride hands free. Maybe the upward trend in accidents is due to a trend in narrower tires? Maybe a return to wider tires would help.

[timothybuse]

It doesn't sound like they considered the fact that a tilted wheel will apply a turning and stabilizing force, regardless of trail, mass distribution, and gyroscopic effects.  Lose the bike all together and slowly roll a wheel by itself,  it's stable.  As it tilts into a fall, it rolls on its radius and applies a turning motion correcting the fall.

[francischu]

amazing insight of bicycle dynamic! So many new ideas in an old machine.

[minazhou]

Good speech, now I understand how bikes balances when we ride them.