|If you missed no questions, great - you probably are very familiar with your governor, and a safe engine operator.
If you missed more than one, please read the following, and always consider safety first - we want you around to restore more engines!
|Hit & Miss Governor Operation explained:
The governors on most antique and "hit and miss" engines are mechanical flyweight type governors that operate by locking the exhaust valve open when they reach rated or set speed.
The set or governed speed is determined by balancing the force of spring tension against that of "spinning" weights. Some have levers to adjust the spring tension, and position of the locking arm, others have spring anchors that may be lengthened or shortened.
As an engine's speed increases, weights move outward due to inertia, or their desire to move in a straight line. A spring, or pair of springs is attached that tries to keep them from moving out. The tighter the springs are set, the faster the weights, and thus the engine, must rotate to overcome the force of the springs and to move outward. Looser springs means that the weights can move outward more easily, at lower speeds, allowing the engine to run more slowly. Spring tenstion determines governed speed.
As the weights move outward, they usually also move a sliding pin or collar that in turn moves a lever which locks the exhaust valve push-rod in the open, or extended position. When the valve is held open, the engine cannot develop any 'vacuum' on the intake stroke, so it cannot draw a fresh charge of fuel - it cannot fire again.
As the engine speeds up, the weights move outward against spring pressure. As they move outward, they push on or slide a collar or pin, which in turn pushes a lever that will move into or against a latch on the push-rod of the exhaust valve, locking it open, and preventing it's moving back to closed position.
As engine speed decreases, the weights move back inward, also allowing the lever, or latch to move away from the exhaust push-rod, allowing the valve to close again, allowing the engine to draw a fresh charge of fuel, and fire again.
The governor can only determine the fastest engine speed, it cannot determine the minimum for obvious reasons - minimum speed is determined by such as overloading, poor mechanical condition, overheating, poor state of tuneup, among other things.
You can see how the governor on your engine works by moving the weights outward by hand, and watching the attached collars and levers. You should be able to easily move all parts by hand, they should not be so tight as to bind, but should not have excessive wear or slop. A worn governor can fail as easily as one that is binding or too tight. Wear means that parts may not properly line up and be able to lock the valve as needed.
One that is too tight may bind or seize and fail to be able to lock the exhaust valve to control the engine.
Make sure weights are free to move, and that the latch or lever that moves to lock the exhaust push-rod is easily moved into latch position - test it by moving the lever inward toward the push-rod and making sure that it will indeed hold the valve open.
If you paint your engine, be sure that no paint is on the pins that governor parts pivot on - it may get gummy and inhibit free movement. I usually sand paint off of all pivot points to insure free movement. Also make sure that no parts are "painted in position" - try all parts for free movement after the engine is dry.
Loose flywheels can have mixed results - if the flyweights of your governor are on the flywheel, a loose flywheel can have varied results. For example, if the flywheel were to slide outward on a 1.5 hp Fairbanks Morse, or a Chapman engine, the weight will no longer line up with the governor latch arm, making the engine "run away". The reverse is true of most Rock Island and Alamo engines, a flywheel sliding off just a small amount will cause the governor weights to pull the sliding cone or collar with it, and lock the exhaust open, slowing or even stopping the engine. On the other hand, what if it pulled enough to break the latch arm - the result could be a runaway engine with a loose flywheel!
Please pay close, careful attention to the restoration of the governor parts. Granted, an engine that won't run isn't much fun, but one that runs too fast can end your fun for good.
1. b The governor sets the maximum engine speed. Load and engine condition determine minimum speed.
2. c Hit & Miss governed gas engines used mechanical flyweight governors
3. d As engine speed increases, weights move outward.
4. a When engines reaches rated speed, exhaust valve is locked open, allowing it to "coast".
5. b Loosening the springs holding the weights will slow the engine.
6. c The balance of spring tension against the outward forces of the governor weights determines the governed speed.
7. False Leaving an engine unattended can be dangerous as a governor can fail allowing engine to overspeed and self destruct.
8. False Governors can malfunction totally, allowing uncontrolled speeds.
9. a Governor parts should move freely when checked by hand, so they will not bind or "stick".
10. False Governor weights may be on flywheel, or on a separate gear driven by the cam, or other gear on engine. One example is the John Deere type 'E' engine with an internal governor system.