Drawbridge

Notes:

– The lifting deck is attached to the second hole of the tower by means of locknuts on 3/8”
Bolts.

– Crocheting yarn is used in the model. Tie the yarn to the top of the tower, loop it around
the respective pulleys and secure it to the 57-tooth Gear shaft by clipping it under a
Spring Clip.

– The experiment is to demonstrate the value of gears. The proper way, when turning the
Crank Handle, has the 19-tooth pinion to driving the 57 tooth gear. A ratio of 3 to 1. In
the experiment a second crank is constructed from a Bush Wheel and 11/8” Bolt and the
operating cord switched from the rod carrying the 57 tooth gear to the Crank handle. Now
by turning the Bush Wheel crank the 57-tooth Gear drives the 19-tooth Pinion. A ratio of
1 to 3. The effect of the two gears is evident. Although the deck is raised nine times
faster, it also takes nine times as much energy to raise the bridge.

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