Mechanical governors have been used with most engines since they were first developed until electronic devices took over the task relatively recently . Governors based on rotation were used to control the distance between wind-driven millstones in the 17th Century. Later, with the advent of factories, regulated rotary motion was needed In the late 18th century, and, James Watt invented what he called a conical pendulum, which operated on a principal similar to governors to follow—balls attached to a rotating rod which was driven by the speed of the machine. As the speed increased, the balls tended to fly out (origin of the term “balls out”) which would cause levers to decrease the amount of steam entering the machine. A rough drawing is below.
Governors were primarily to guarantee a controlled output. You do not want the power in your machine (car, tractor, train, etc) to fluctuate with the fuel flow. You want to select the desired speed and make sure that the machine speed stays constant. They are sometimes thought to be speed limiters, and, in a way, they do stop excess speed, but they are much different than speed limiters contained in modern vehicles and other machines where limiting the top speed is required. Oddly enough, humans with political charge of states are called governors, and in a sense they are, in that they are supposed to smooth out the behavior of the state, but mechanical governors were not meant to cause radical change, as some human governors want to do. That was to be left to the humans in control of the machine—perhaps the analogue is the voters in the state.
I recently restored a Pickering Governor, shown in the photo to the right. Thomas Pickering was both the inventor and the name of the business he began in Portland, Connecticut, that was based on this governor. It was used widely on rotating steam machines in the U.S. for many years, and it still in use. It was a dominant fixture on steam locomotives, factory machines, and all manner of other steam-powered devices. And in fact, before electronics came along, devices operating on the same principal were installed in automobiles, trucks, tractors, and other machines powered by hydrocarbons.
As you can see from the photograph, the Pickering Governor has three balls mounted on spring segments, the bottom end of each being fastened to a collar that rotates but can not move up the central shaft, and the other end fastened to one that can move. As the speed of this unit (which is driven by a belt from the machine) increases, the balls tend to move out, which pulls the top collar down. This movement is somewhat resisted by the coil spring shown in the photo. The upper collar pushes on a rod that runs the length of the shaft, and moves a sliding gate in the piping ,which controls the amount of steam entering the machine. More speed results in less steam, and less results in more. Voila, constant motion, with speed controllable by compression in the coil spring. A drawing is below, if you want more detail. But in spite of the complexity of the drawing, the operation of the governor is extremely simple—few moving parts, no tricky mechanisms, an elegant, reliable, and affordable product, which served our species well over many years, and could be understood and maintained by people with a minimum of training—A very good product indeed.
Why did I restore this governor? As you know by now, I love to restore old machines, especially if they were good products. In fact, I can hardly stand seeing such elegant and historical machines die on scrap heaps.
What am I going to do with it? Easy. I am going to put it on my desk beside my computer. It not only will represent a good contrast in modern and old technology, but will remind me that several large projects I have under way (writing books, etc) will proceed better if I work on them a bit every day. I tend to work on them in bursts, ending when I can’t stand to do so any more, and then ignore them, during which time I lose track of what I have done and where I am going, which in turn requires that I spend time reviewing what I have done and trying to recall hot ideas I had which I can’t quite remember. I need a better internal governor, and maybe this beautiful historic old external one will remind me. Also it is a more interesting object to look at than my computer (when the computer is simply showing me my desktop) and will not require constant upgrading and deleting of unwanted messages and advertisements.