[*BCM*] Fwd: [phonography] Cycling recordists

[Eamonn Kelly]

yes! time for a physics lesson from an unqualified dude who hasn't taken any physics in 3 years! 
it does indeed make the wheel harder to turn, as stomv says.  think of any given point on a rotating wheel.  at any instant, that point is travelling outward in a direction paralell to the curve of the wheel at that given point.  but as the wheel rotates, that point will resist a change in direction b/c it's momentum is in that particular direction.  thus, the heavier the wheel, the more momentum any particular point has, and the more resistance it will offer to changing direction, i.e. to rotation.  TA DA!  this episode of mr. wizard has been brought to you by ovaltine.

any real science people wanna corroboate that for me?

eamonn

p.s. it still sounds like a cool idea and may in fact be more efficient for powering a light.


 |  On Sat, 7 Jan 2006 14:52:08 -0500
 |  Ian Thistle <idiotkid at gmail.com> wrote:
 |  My physics are rusty, or weren't that great to begin with, but I believe
 |  it's harder to power extra mass when it is on your wheel as opposed to on
 |  your bike somewhere else.  There are specific terms for this I'm forgetting.
 |  
 |  On 1/7/06, Thomas John Vitolo <tjvitolo at bu.edu> wrote:
 |  >
 |  > I stumbled on this while looking up ways to
 |  > > generate power.    http://www.freelights.co.uk/   it seems to be a
 |  > > nice way to make your bike visible without making it more difficult
 |  > > to
 |  > > ride (friction and so on).  The key is the magnet tumbles past one
 |  > > of
 |  > > the magnets on the spokes and thereby creates electrical current.
 |  > > No
 |  > > physical turbine gets cranked, which seems amazing to me not being
 |  > > much of an electrician.
 |  >
 |  > It still makes it more difficult to ride.  After all, you've now got to
 |  > (1) work
 |  > harder because you've added weight to your wheel and have to "lift" it,
 |  > and (2)
 |  > the magnetic force of when the moving magnet approaches the generator
 |  > results in
 |  > resistance.  Think of pushing a magnet toward another like magnet.  Sure,
 |  > it's
 |  > not much resistance in either case, and you get the added bonus of
 |  > recovering
 |  > nearly all of the force when (1) the magnets get to "fall" and (2) the
 |  > generator
 |  > pushes the magnet away once it's past.
 |  >
 |  > But, no machine is perfectly efficient, so there is a 100% chance that
 |  > this
 |  > frictionless dynamo system makes it harder to pedal than no dynamo system
 |  > at
 |  > all.  How much harder to pedal?  Probably not much.
 |  >
 |  > - stomv
 |  >
 |  > P.S.  Since your cycle will have more mass with the dynamo system on, you
 |  > will
 |  > face more rolling friction when you ride, it's just that the friction
 |  > isn't on
 |  > the dynamo, it's between your wheels and the road.
 |  > Support a few technologists in Washington.  Go to:
 |  > http://actblue.com/list/stomv
 |  > _______________________________________________
 |  > Boston Critical Mass mailing list
 |  > list at bostoncriticalmass.org
 |  > http://bostoncriticalmass.org/list
 |  > To unsubscribe email list-unsubscribe at bostoncriticalmass.org
 |  >