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The Compound Gear Train This Gear-Train model kit is a great way to demonstrate how compound gear ratios can reduce or increase torque and the effects that has on power and speed.
   $24.95  more info

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Perpetual Motion Machine The classic "overbalanced wheel" perpetual motion machine, as designed by French Architect Villiard De Honnecourt in about 1235, and studied extensively by Leonardo Da Vinci in the late 1400's.
   $98.00  more info

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The Lever Paradox When discussing levers, Archimedes said: "Equal weights at unequal distances are not at equilibrium." unfortunately, Archimedes never saw our Lever Paradox, where equal weights at unequal distances do balance!
   $24.95  more info