Hyperbolic Worm Gears

Worm gears find many uses in engineering applications due to their compact size and high gear reduction ratios. A disadvantage of this type of gear set is that only one tooth on the spur gear is engaged (or "in mesh") with the worm gear at any time. This causes high contact stresses which can accelerate wear.

This thing is a demonstration model of a hyperbolic (also known as an enveloping) worm gear. Both the worm gear and the spur gear teeth are cut from hyperbolic surfaces. This allows multiple teeth on the spur gear to engage the worm simultaneously. This reduces the contact stress between the gears, and allows higher torques to be transmitted through the gearset. A video showing the motion of the hyperbolic worm gears is shown here: http://youtu.be/O-MFFjBNCb8.

In this design 12 teeth on the spur are theoretically in constant mesh with the worm gear, although manufacturing tolerances result in less-than-perfect contact. The gear reduction is 72:1 (72 revolutions of the worm g