Engine Governors

Engine governors were the mechanical solution to speed control


| September 2012



Engine Governors

This photo of the governor on a John Deere tractor shows the linkage from the governor to the carburetor. 

Imagine driving a tractor without an engine governor. You’d soon discover why governors are sometimes referred to as speed regulators. Without a governor, the engine would lug down every time you went up a hill and would rev up the minute you went down the other side. As a result, you’d constantly be adjusting the throttle.  

The same thing would happen when the tractor encountered a load while pulling an implement. You’d have to give it more throttle to compensate, only to slow down in lighter soil. Fortunately, inventive minds found a solution to the problem long before internal combustion engines were even invented.  

By most accounts, an engine governor is described as a mechanism that uses a rotating mass applied against a spring to adjust the carburetor throttle shaft to regulate the engine speed around a set point established by the throttle lever position. In other words, you set the throttle for the speed you want to travel and the governor’s job is to maintain that speed. 

In nearly all cases, the governor is driven by the timing gear or by a drive coming off the magneto or distributor drive shaft and interconnected with the hand throttle linkage and the carburetor throttle plate. The rotating mass, meanwhile, is usually a set of flyweights or cams with weights at the end. However, in some cases, such as the governor used on Ford 9N, 2N and 8N tractors, a set of steel balls within a pair of races is used.  

Time-honored invention 

Engine governors are hardly unique to modern internal combustion engines, though. According to historians, centrifugal governors were used to regulate the distance and pressure between millstones in windmills as early as the 17th century.  

Even as governors were developed for early steam engines, they were less than precise. However, that wasn’t as important then, since many early engines were used to pump water — an application that could tolerate variations in the working speed. A constant operating speed did not become necessary until Scottish engineer James Watt introduced the rotative steam engine used to drive factory machinery.