Puzzle Description:

A man on a bicycle. About the title: The gyroscopic effect assist the biker in stability. If you tilt to one side, the rotating wheels create a force which help you stand straight.

#1: J.C. Anderson (jc.noserdna) on Nov 15, 2007

Well done. Clear, concise image with few pixels. Iconic Rocks!

Nice small puzzle. Easy, but still required some thinking.

I like this puzzle a lot. Some of the early reviewers thought it required guessing to solve, but it doesn't. Getting started does require some tricky work, but not guessing.

Great puzzle, but the physics isn't entirely right. A spinning bicycle wheel does generate quite a lot of gyroscopic force, as you can tell if you hold a dismounted while by the axles and spin it, but the force doesn't turn out to be anywhere near enough to hold a bicycle upright. You could build a bike with roller skate-sized wheels, which would generate no significant gyroscopic effect, and you'd still find it easy to ride on (well, easy to coast on, I can't imagine how you'd attach a chain to such a small wheel).

On the other hand, if you lock the steering wheel of a bicycle so that it can't be turned, you'll find that nobody can ride it without falling over, not even in a straight line. A bicycle is balanced by constant steering. If you look at the tracks of a bicycle that has ridden through a puddle, you'll be able to see that the track of the front wheel swerves in a sine wave around the track of the back wheel, even if the rider thinks he was riding in a straight line. If try riding very slowly, you'll find you have to do this steering in a much more extreme way to keep balanced.

This constant steering isn't entirely a clever stunt by the rider. Bicycles are engineered to do some of this steering automatically. The front fork is swept forward a bit so that the point of contact of the wheel with the road is slightly forward of the line the front fork pivots on. Because of this, when the bicycle starts to tip to one side, the handlebars naturally turn in the direction that causes the bike turn in the direction it is leaning, which tends to bring the wheels back under the bike (if it is moving) and thus rights it again. This is why you can ride a bike no handed. You can ride a bike without a swept fork, but it is harder and it would be completely impossible to ride it no-handed.

Oops, I haven't thought about this stuff in decades and got a few bits wrong. The point of contact of the wheel with the pavement is behind the line the fork pivots on, not in front, and this is due to the angle at which the fork is attached to the frame, not the sweep of the fork.

Here's some Berkeley dude's essay on bike physics: http://socrates.berkeley.edu/~fajans/Teaching/Steering.htm

Thank you for the clarification!
Well, I've just said it helps anyway.
However after verification, it seems centrifugal force provides the most for stability : http://hyperphysics.phy-astr.gsu.edu/hbase/mechanics/bicycle.html

I'll just pinpoint that the gyroscopic effect try to do the steering Jan explained too.

Bicycle physics is extremely complex. Notice that the main reference for your page was a paper published in the American Journal of Physics in 1982. So physicists were still finding new things to say about this as recently as 25 years ago. The centrifugal force referred to here is not due to the rotation of the wheel, but due to the turning of the bicycle as the rider steers to keep the bike balanced. It's a different oversimplification than the one I used (actually there is no such thing as centrifugal force).

There's a classic old two-volume book on the physics of bicycles that I once read, but I can't remember the title or author. Oh well.

See guys! PBN is educational!

Oh, my head hurts. lol

Thanks for the puzzle Hirameki!

My head hurt after doing the puzzle. It REALLY hurts after reading all this stuff! :D

Very nice image for its size. I love how it looks good and recognizable, even without anything other than the wheels to represent the entire bike.

Very nice image and nice solve. Thanks!

This is a nice little puzzle with just enough detail to show the object without getting messy. The solve was good, but what I like most is the discussion it sparked.

Like many (if not most) people who've heard the over-simplified gyroscope explanation, I didn't bother to think more about it. So I found the discussion of bicycle physics very interesting. Here's my take on it:

If there's one thing we humanoid primates are good at, it's staying erect on flimsy supports. (Either two skinny wheels, or two feet way down there.) The gyroscopic effect of the wheels giving us sideways pressure when the angle moves coupled with our innate vertical sense give us the necessary inputs to stay erect. The trailing spot of contact of the front wheel enhances this with some steering correction, but it is our balance that keeps us erect.

Look at the way children learn. Slow = bad. A child will never learn if they always try to move slowly. The steering is just too difficult, and the auto-steering doesn't kick in. Then suddenly, the child gets up the nerve to go faster and of they go - zoom! Until ... a turn! Crash.

The practice that needs to be done is not in moving in a straight line - physics and our natural balance take care of that. It's the turns - specifically the counter-intuitive steering in the wrong direction to start a turn. If you just turn in the direction you want to go, centrifugal force will throw you off the bike. If you want to turn right, you must steer slightly left to get the bike to lean to the right before you turn to the right.

Once a kid incorporates this quirk of balance into their brain, they will never forget how to ride a bike.

When I first saw this puzzle, I was planning to comment that at this size the extra empty columns to make even fives really doesn't seem necessary. (Although on large puzzles it can really help.) Silly me to jump to such a conclusion, here the extra space is a great part of the image, giving the bicycle and rider a place to go! Nice puzzle!

http://www.straightdope.com/columns/read/2015/why-is-it-easier-to-balance-on-a-moving-bike-than-a-non-moving-one-revisited
This is an article I had read on how a bicycle works that I had found interesting.

Simply put, when you lean a bit to the left, say, the gyroscopic effect causes the front wheel to turn to the left, which does help the rider stay up by putting the wheel a bit more under him than if it turned right or didn't try to turn either way. That's really all there is to it.

https://www.youtube.com/watch?v=I2RwzIJTx3A

Interesting. I just thought it was called balance.

This video just showed up. It is full of interesting things, like the fact that bicycles keep themselves upright, and they do it through several different methods

https://www.youtube.com/watch?v=9cNmUNHSBac

I knew what the video was going to be before I clicked on it :D

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