Southern California Home Shop Machinists

It is with regret we announce the passing of Peter Wood on July 2010.

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Hit N" Miss Model Engine

Here was his discussion about the engine he designed:

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HIT ‘N MISS FARM ENGINES

Before farm tractors were equipped with power takeoff pulleys in the 1930’s and before many farms had electricity, Hit ‘N Miss  engines were popular for driving hay lifts, water pumps, saw tables and just about anything  that needed a simple engine up to 10HP at constant speed that could run on kerosene or gasoline. Ignition was by impulse magneto and later by battery and high tension ignition coil.

The engine had a single cylinder with an atmospheric intake valve and a cam operated overhead exhaust valve. Constant speed was controlled by a governor that prevented the exhaust valve from closing when the governor sensed an over-speed. This made the engine misfire and also prevented fuel from being wasted during coasting. When the governor sensed an under speed condition, the exhaust valve was allowed to close and the engine resumed normal firing, hence the name Hit ‘N Miss.

This new engine is my own design started in January 2007 and first run this week.

Here are the specs:-

  Single cylinder, horizontal Hit ‘N Miss farm type engine.
  1.13in bore x 1.75in stroke.
  Swept volume 28.5cc.
  Electronic ignition with Hall sensor and rare earth magnet.
  Electronic speed control with solenoid control of exhaust valve.
  Built entirely on my 6in atlas lathe with the exception some milling of the main chassis done on my friend’s milling machine.
  No castings were used. Flywheels weigh 2 ½ lb each and are 4in diam x 1in wide.
  Piston has 2 rings from Coles Models.
  Chassis is cut from 4in x 2in rectangular steel pipe.
  Fuel tank is integral in chassis.

This engine has been both challenging and rewarding. It took me about 5 months of spare time to finish it during which time my 6 inch lathe handled some quite “innovative” set ups! When first run, it was obvious that the exhaust cam dwell angle was too long and resulted in the water jacket boiling vigorously and the engine having a “sporty” exhaust note. I reduced the dwell to open at BDC and close about 5° ATDC (crankshaft), it is much cooler and tamer now.