The earliest internal-combustion engine designers learned quickly that a mechanism to regulate engine speed was necessary in order to free the operator from constant attention to the engine. The most demanding of this speed regulation is needed when generating electric power, in which case a variation of just 1 or 2 percent in engine speed is proven to be unsatisfactory.
If the engine needed to be left unattended for long periods of time, such as would be the case in the oil field, an additional safety consideration was addressed for over-speed control to prevent a 'runaway.' The oil field engine didn't require the accuracy of speed control - as needed to generate electricity - but it did need a reliable governor that could be left unattended and reasonably hold a safe speed. It was a necessary consideration for the oil man.
One of the simplest governors ever designed is the inertia or pendulum type. Generally, a governor of these types is attached to the exhaust pushrod, or a rod attached to an eccentric, and usually a tipping (inertia) or swinging (pendulum) weight balances in a manner that when the engine speed (and rod motion) increases, a latch catches onto a valve of some sort to initiate a miss stroke on a four-cycle, or to close off the transfer ports on a two-cycle-type engine.
Some early forms of the pendulum governor closely resemble a metronome, which is commonly used by musicians. By adjusting a tensioning spring, the motion of the governor weight can be made to latch onto or release as needed. These governor types eliminated many of the moving parts and belt drives that were used on the traditional steam engine-type centrifugal governors.
The simple design and the ease of maintenance on these oil field governors were advantageous to an engine that might be checked on only once each day. Accurate speed would not have been a major issue in the oil field, and the rugged, simple construction of these governor types probably worked well in the power house.
A point of interest the modern-day oil field engine enthusiasts might notice is that - as with any large engine of this type - they were intended to be operated while bolted to a substantial concrete base. Any movement while running on a display trailer has a direct effect on the proper operation of an inertia or pendulum governor. Care should be taken that trailers are blocked or solidly jacked, and the gas cock is weaned down to prevent shall we say an uncomfortable rate of speed.
I'd like to thank Tom Winland, Hank Tomey and "Uncle Bob" Elsoton for their assistance in compiling information and photos for this month's column.
Inertia and pendulum governors always catch my eye and tend to have a hypnotic effect. I like to think of them as "mechanical beauty."
Oil field engine manufacturers that used inertia- or pendulum-type governors include:
- Pattin Bros. Co.
- Kootz & Stroehman
- S.M. Jones (Acme Gas Engine)