Why should wheels be round?

[unixronin]

Discussions can lead to funny places.  For instance, as a result of an ad in Car & Driver, I was explaining to Goose the concept of "form follows function", and some of the features that a bicycle MUST have, as part of its form, in order to fulfil its function.  (For instance: there must be a place for the rider, a way to make it go, a way to make it stop, and a way to steer it.)  But beyond that, there's a lot of flexibility.

For instance, a bicycle doesn't have to have round wheels.

Yes, that is exactly what I meant.  If you build it correctly, you can build a bicycle whose wheels are not circular — not even elliptical — but which will nevertheless still work on an ordinary road.

Consider a bicycle whose wheels are constant-diameter polygons.  You can't just put them into a regular bicycle, because although their diameter is constant, their radius certainly isn't.  But suppose you attach each axle to a free-floating fork which is free to move vertically in the frame, and which does not actually support the frame.  Now, attach rollers to the frame which ride on top of the wheel, and which support the frame.

It'll look pretty strange, especially when in motion, as the axles and forks will be constantly working up and down as the bike moves.  But it'll work.  (In fact, it should give a smoother ride than a conventional bicycle with fixed forks, because in effect each tire is being used twice, giving close to twice as much shock/bump absorbtion for a given size tire.)

(I swear I did not front-load the music.  It's just what was up when I restarted my playlist.)

Comments

[radarrider.livejournal.com]

Not only that, but you can connect the forks to the source of motive power and have them *drive* the wheels. A downward force is applied when the forks are moving down and an upward force when they're moving up. The ideal form of the wheels would be a circle with the forks attached off-center.

Think of how the steam piston on an old steam locomotive drives the wheels. The difference is that the wheels on a locomotive are still on an axle in the center that holds it in place. On your hypothetical bicycle, the rollers that ride on the wheel and support the frame would hold it in place.

I can't see how this could in any way be close to as efficient as a standard bicycle but it would work.

[unixronin.livejournal.com]

Yup, you could indeed do that. It neatly solves the problem of converting reciprocating motion to linear DOH! I meant ROTARY motion, too, although torque would probably be poor.

[dirtynumbangel.livejournal.com]

You do know you're an enormous geek, yes?

And that is precisely what we all love so very much about you?

[unixronin.livejournal.com]

Thank you. :)

[cymrullewes.livejournal.com]

s/that/the way you think

:-) (at least for myself. You can love him for being an enormous geek.)

[arasirsul.livejournal.com]

I'm having trouble envisioning a wheel of constant diameter that isn't either a) a circle, or b) concave at some point, making it not possible for the part that's recessed to actually touch the ground.

On the other hand, I'm having no problems envisioning a square wheel with a traditional fork-attached-to-axle sort of device. It just needs to exist in three dimensions. Bend all the corners correctly and you can get what's basically a circle, looking at it from the side, but obviously not one from the top...

[rbos.livejournal.com]

A triangle with its sides bulged out will have this property.

[unixronin.livejournal.com]

I'm having trouble envisioning a wheel of constant diameter that isn't either a) a circle, or b) concave at some point, making it not possible for the part that's recessed to actually touch the ground.

Probably the best-known example of a constant-diameter polygon is the English 50-penny piece introduced when UK currency went metric in the early 70s. It was designed to have a constant diameter (and therefore work in coin-operated machines), and be the same diameter as the ten-penny coin (formerly the two-shilling piece, or florin), but be readily distinguishable from it by both touch and feel.

It became popularly known as the "Wilson", after Labor-party Prime Minister Harold Wilson, because it was said that like him, it had many sides and two faces.

[otherbill.livejournal.com]

The same concept has been used in two dimensions to develop a drill press that drills square holes. The drill bit has the cross-section of a constant-radius triangle, and the rest is left as an exercise for the reader. :-)

[unixronin.livejournal.com]

That's a slightly different principle, I think. But there are conceptual similarities. (If memory serves, the square hole drill press operates on a principle closer to the technique of using a synchronized-speed rotating cutter to turn square or hexagonal shafts on a lathe.)