Watt Beam Engine

This illustration shows the general arrangement of a typical beam engine. Beam engines were used in many factories to drive machinery of all types, and were sometimes built to enormous proportions. I have omitted the valve gear in this illustration.

In most steam engines, it was important to restrict the motion of the piston and rod to a straight line in order to reduce friction and wear on the upper cylinder seal. The Watt linkage illustrated here is one of many contrivances for accomplishing this linear motion.