Guide Bars

Guide Bars, in a steam-engine, gas-engine, or other similar motor, are parallel bars along which the cross-head of the piston-rod may slide. The rectilinear motion of the piston-rod is to be converted into a rotatory motion of the shaft by means of the connecting rod. One end of this must travel in a straight line, the other end in a circle. The guide-bars provide the constraint in the first case, the crank the constraint in the second.