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How to Build a Reciprocating Motor

Reciprocating motors use pistons to change pressure into motion. The most common form of this motor is the internal combustion engine, which powers the vast majority of automobiles. In the nineteenth century, the most common form was the steam engine, which appeared in trains and boats, as well as factory machines. Today, however, the steam engine is a curiosity, maintained in vintage locomotives for sightseeing excursions. Making a model of a reciprocating motor can create a useful teaching tool to show that pistons work.

Things You'll Need

Scrap lumber
Jigsaw
Fine-grit sandpaper
Scrap metal
Ring magnets, 1-1/2 inches in diameter
Wooden dowel, 1 inch in diameter
22-gauge wire
Steel shaft
Brass tube, to fit over steel shaft
Strong glue
12-volt battery
Carbon graphite
Scrap brass

Instructions

- 1
  Cut the following pieces out of the scrap lumber: a circle 3 inches in diameter; two rectangles, 2"x3"; a flywheel 2 inches long; a circle, 1 inch in diameter. Cut the dowel so that it is 9 inches long. Sand all pieces with fine-grit sandpaper to eliminate the risk of splinters.
- 2
  Set one of the rectangular pieces down and glue the dowel to it so that it stands vertically, about 1/4 inch from one end. Install a metal square on the rectangular piece, about an inch from the 9-inch dowel. Then, set two ring magnets on the metal so that they hold one another in place, attracted to each other and the metal.
- 3
  Slide a 1-inch brass tube onto a 2-inch steel shaft, and wrap wire around the brass tube to form a coil. Leave enough free wire on both ends so that they hang back down to the rectangular piece of wood. Attach the end of the shaft with the wire on it to a 1-inch piece of dowel using screws.
- 4
  Glue the second rectangular piece to the other end of the 9-inch dowel, so that enough of this rectangle will hang over the piston for you to be able to accommodate the motor apparatus. You'll be turning the whole assembly over, so it will all rest on this second rectangle.
- 5
  Attach the larger circle to the smaller one using the glue. Connect one end of the flywheel to the other end of the smaller circle with a bolt and nut, and the other end to the end of the 1-inch dowel that is connected to the metal shaft -- this shaft will be your piston.
- 6
  Glue a "brush," or small block of carbon graphite, to the wooden piece connecting the flywheel to the piston. Attach a small brass plate to the base rectangle -- when the brush contacts the brass, current will flow into the motor. Connect one end of the copper wire to a metal grounding piece and the other to your 12-volt battery. Run a wire from the other terminal of the battery to the ground.

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