Simple Machines

Most gears are wheel and axles with teeth. Other simple machines can be found in the design of apple parers. Paring arms are third or first class levers; many push-offs are first class levers (right). Blades and forks are wedges. Some early wooden parers have belt-drive systems that may be classified as pulley systems. Clamps are the most obvious use of the screw. The threaded-shaft that carries the fork in many lathe parers is a screw.

The Oriole and Jersey lathe parers make a more subtle use of the screw. A large wheel is fitted with a screw thread, which advances through teeth as the machine is cranked (left).

Maxam’s Patent Automatic Scroll Wheel Apple Parer may exhibit the most interesting use of the screw. The hub (right) of the hand-driven gear is molded into a screw. The threads of the screw push a first class lever connected to a gear system that rotates the paring arm.