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Magnifying Wheel<br />
Athin wire attached to the magnifying lever pulls<br />
_on the inner hub of a magnifying wheel. This magnifying<br />
wheel is a pulley comprised of two coaxial wheels<br />
that rotate together: a small inner wheel (the hub) and a<br />
larger outer wheel. The wheel oscillates as the operator<br />
turns the crank; its circular motion mirrors the peaks and<br />
valleys of the output. A separate wire is wrapped around<br />
the larger wheel and attaches to the pen mechanism. The<br />
diameter of the outer wheel is five times the diameter of<br />
the inner wheel (100 mm versus 20 mm) and so the motion<br />
from the end of the magnifying lever is magnified<br />
by a constant factor of five. This wire attaches to the top<br />
of the post holding the machine’s pen so that the wheel’s<br />
rocking turns into an up and down motion of the pen.<br />
To set up the machine an operator first wraps the outer<br />
wire around the hub, holding it in place while looping<br />
another wire around the inner hub. If not done carefully<br />
the wheel unwinds causing the wires to fly off the hubs<br />
and the pen to drop.<br />
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