Steam Engine Build/Piston Head

Steam Engine Build Instructions

=Description=

The piston head converts energy stored in steam pressure to motion. As steam in the cylinder expands, it pushes against the piston head, which is connected to a connecting rod, and then to a crank on a crankshaft. The crankshaft converts linear motion in rotary motion. The piston is built from two pieces: the piston head and the piston stem, welded together. On the face of the piston head are two threaded holes that receive the bump valve pins (see Steam Engine Build/Bump Valve Pin). A series of holes are bored in the piston head from the bottom to reduce weight. Two rectangular grooves are turned into the piston face to receive piston rings.

=CAD=

Piston Stem

Piston Head

Piston Head Assembly

Full Piston Assembly with Rings and Pins

=Drawing=



=Instructions=

Piston Head


 * 1) Mount a 4.0" cast iron rod in a lathe.
 * 2) Reduce the outside diameter to 3.75".
 * 3) Cut two piston ring grooves at 0.5" (center) offset from the top and bottom of piston (width and depth are TBD).
 * 4) Cut off the piston head to a length of 2.0"
 * 5) On the top of the piston head, drill two 0.25" holes, 1.25" from the center (Holes A in drawing).
 * 6) From the bottom of the piston head, bore the following holes:
 * 7) 4 Holes B:  1.0" dia to a depth of 1.5" (weight reduction).
 * 8) 4 Holes C:  0.5" dia to a depth of 1.0" (weight reduction).
 * 9) 1 Hole D:  0.5" dia to a depth of 1.0" (piston stem receiving hole).

Piston Stem


 * 1) Use 0.5" steel rod stock.
 * 2) Cut off 0.2" on either side, 0.5" in from end.
 * 3) Round off the end (0.5" dia.)
 * 4) Drill a 0.25" dia hole

Assembly


 * 1) Insert completed piston stem into piston stem receiving hole (Hole D).
 * 2) Weld around to secure it.