Figure 2-3.Cylinder, piston, connecting rod, and crankshaft for a one-cylinder engine.
because it is attached to the crankshaft, it must also
move in a circle.
When the piston of the engine slides downward
because of the pressure of the expanding gases in the
cylinder, the upper end of the connecting rod moves
downward with the piston in a straight line. The lower
end of the connecting rod moves down and in a circular
motion at the same time. This moves the throw and, in
turn, the throw rotates the crankshaft; this rotation is the
desired result. So remember, the crankshaft and
connecting rod combination is a mechanism for the
purpose of changing straight line, or reciprocating
motion to circular, or rotary motion.
Each movement of the piston from top to bottom or
from bottom to top is called a stroke. The piston takes
two strokes (an up stroke and a down stroke), as the
crankshaft makes one complete revolution Figure 2-4
Figure 2-4.Piston stroke technology.