Alt-BEAM Archive
Message #09167
To: beam@sgiblab.sgi.com
From: Bob Shannon bshannon@tiac.net
Date: Thu, 13 Jan 2000 20:58:22 -0500
Subject: [alt-beam] Re: Photovore Performance?
David Perry wrote:
> mine are nimkiki pager motors which are shorter and fatter than solarbotics
> ones so this restricts somewhat how you can mount it, that means i need
> bigger wheels.
>
> David Perry
Not so easy with pager motors. As Dave wrote earlier, pager motors are designed
to deliver low torque at high speed without drawing a heck of a lot of power.
But when the SE fires, we have to accelerate the resting deadweight of the whole
photovore and overcome the stiction (not friction). This takes torque, not
speed.
Using a motor that has lower 'spec sheet' efficiency, but that is designed to
deliver more torque at a lower speed than the pager motor can get that photovore
up and moving with LESS energy drawn from the cap.
This is really important, becuase the energy needed to keep the photovore
rolling along is far far less than the startup acceleration energy. One good
strategy is to accelerate quickly, and spend a lot of time coasting along as the
capacitor voltage drops, using the inertia stored in the moving 'vore. A big
key here is to use a small roller to support the chassis rather than using the
belly-dragger design of the photopopper or Chiu's free form tutorial.
People race sollar rollers, why not race photovores?
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