[*BCM*] Re: Fwd: [phonography] Cycling recordists (Ian Thistle)

[Lee Peters]

Yea, but....

If you get going fast, the weight may not make it back to the middle.  It 
will just hang out at the rim of the wheel.  No?

----- Original Message ----- 
From: "Jason Orach" <jorach at gmail.com>
To: <list at bostoncriticalmass.org>
Sent: Sunday, January 08, 2006 1:32 PM
Subject: [*BCM*] Re: Fwd: [phonography] Cycling recordists (Ian Thistle)


I'm a senior in Mechanical Engineering at Boston University, so you
can trust me. The general idea of what Eamon Kelly (where's your
Beanpot?) wrote is correct. The best way to think about this is to
picture a seesaw. If you have a person who weighs 100lb and a person
who weighs 200lb, how can they use the seesaw? Easy! The person who
weighs 100lb sits at the end of the seesaw, and the person who weighs
200lb sits halfway between the end and the middle on the other side.

A torque or a "moment" is a force multiplied by a distance. You exert
a force on your pedals, which gets multiplied by a distance, your
crank length, to become a moment. This works against the moment of the
chain pulling on your chainring resisting motion. Back to this magnet
dynamo, there'll be a very small resistive force multiplied by how far
away from the center of the wheel the system is.

In conclusion it's a tiny magnet and your legs are pretty strong. You
might notice it when you're just starting, but I doubt it. When you're
trucking along at night you won't notice a thing.

- Jason Orach
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