Re: Questions for those who really know their physics . . .

Wildepad wrote: 
On Thu, 29 Dec 2005 03:00:47 GMT, throopw@xxxxxxxxx (Wayne Throop)
wrote:

: Wildepad <noreplies@>

: This is just different enough from the elevator scenario that I
: suspect it can only be proven one way or another by experimentation.

Shrug. The escalator steps are in uniform, linear motion. 

Except that they're not, really.

They can be idealized as that, but in reality a graph of the speed of
anything driven directly by an electric motor is a sine wave, not a
flat line. 

There is a constant cycle of acceleration and deceleration as the
armature of the motor changes its position relative to the field.

Also, in the real world, motors cannot adjust instantaneously to
varying loads -- the shock of something hitting a step slows the
escalator's motion, then the escalator speeds up under the new load to
return to its average speed.

While these factors don't noticeably affect the performance of a
normal escalator because they use a motor whose rpm is high compared
to the speed of the steps, a desktop model of one would surely have to
use a stepper motor which would aggravate the effects.

Oh, pooh. So use a Homopolar motor (true DC, no cogging) with enough mass in the rotor to smooth out any load-driven variations to indetectability.

  Mark L. Fergerson

.

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