What was the mechanical function of the Parallel Motion linkage developed by Watt and his team?
Allowing the piston rod to move vertically while connecting to the beam driving rotary motion without binding
As Watt integrated rotary motion into his engine design, a significant mechanical challenge arose regarding how to connect the purely vertical movement of the piston rod to the oscillating beam used to drive the rotary gears. If a rigid connection were used, the required pivot point would lead to the piston rod binding or putting undue stress on the cylinder walls as the beam moved in an arc. Parallel motion was an ingenious linkage system designed to solve this geometrical problem. It ensured that the piston rod maintained a nearly perfectly straight vertical path throughout its travel, even as it connected to the beam undergoing angular movement, thereby maintaining mechanical integrity and reducing wear.
