The "comeback can"

[scott]

I have been thinking lately about the "comeback can." It is a child's toy that you roll away from yourself, and then it comes back on it's own to where it was first rolled from:

http://madprofessor.net/can.html

The comeback can is also used in physics classrooms to demonstrate the conservation of energy.

I've been thinking about them because comeback cans seem to "have a mind of their own;" that is, they want to move themselves independently once they are wound up.

Imagine if each of the cylindical weights in a wheel were an individual comeback can. During one part of the wheel's revolution, a can would be wound up, and during another part of the revolution, it would move itself into an off-balance position.

I have tried but so far failed to come up with such an arrangement... :-) The problem seems to be the same one that usually occurs when attempting to employ springs to optimally position a weight in a wheel.

But a comeback can seems to be a little more independent of the wheel (it rolls on a surface rather than being directly attached by a spring.) This makes me wonder if the same ordinary limitations of springs might not necessarily apply in all cases when employing a comeback can...
??
Just thinking out loud...

Best,
Scott

[Jonathan]

That's very interesting, I've never heard of it before.

The problem seems to be the same one that usually occurs when attempting to employ springs to optimally position a weight in a wheel.

As I try to avoid springs (but will think about this now that you've brought it up) in the hope that there is some alternative, what problem is that?

[Neo]

Hi Scott,

I think you should check out this Donald F. Wilkes: Rolamite on www.rexresearch.com it may give you a different spin on your ideas...read all the articles...

[Patrick]

Hi Scott;
I saw a site that showed kids on a video working with that/similar idea.

http://wings.avkids.com/Curriculums/For ... howto.html

I am not sure how one could implement but looks like an area for further study.
--Patrick