Hit-and-miss engines were made by a multitude of engine manufacturers during their peak usage which was from approximately 1910 through the early 1930s when they began to be replaced by more modern designs. Some of the largest engine manufacturers wereStover,Hercules,International Harvester (McCormick Deering), John Deere and Fairbanks Morse.
This is a video montage of the Otto engines running at the Western Minnesota Steam Threshers Reunion (WMSTR), in Rollag, Minnesota. It is a type of hit-and-miss engine.(2min 16sec, 320x240, 340kbit/s video)A hit-and-miss engine is a type of flywheel engine.Aflywheelengine is an engine that has a large flywheel or set of flywheels connected to the crankshaft. The flywheels maintain engine speed during engine cycles that do not produce driving mechanical forces. The flywheels store energy on the combustionstrokeandsupply the stored energy to the mechanical load on the other three strokes of the piston. When these engines were designed technology was not nearly as advanced as today and all parts were made very large. A typical 6 horsepower (4.5 kW) engineweighsapproximately1000 pounds (454 kg). The engine material was mainly cast iron and all significant engine parts were cast from it. Small functional pieces were made of steel and machined to perform their function.
The fuel system of a hit-and-miss engine consists of a fuel tank, fuel line, check valve and fuel mixer. The fuel tank most typically held gasoline but many users would start the engines with gasoline and then switch over to a cheaper fuel such as keroseneordiesel.The fuel line connected the fuel tank to the mixer. Inserted into the fuel line was a check valve which kept the fuel from running back to the tank between combustion strokes. The mixer created the correct fuel/air mixture by means of a needlevalveattachedto a weighted or spring-loaded piston usually in conjunction with an oil-damped dashpot.
Mixer operation was simple, it contained only one moving part, that being the needle valve. While there were exceptions, a mixer did not store fuel in a bowl of any kind. Fuel was simply fed to the mixer, where due to the effect of Bernoulli's principle,itwasself-metered in the venturi created below the weighted piston by the action of the attached needle valve, the method used to this day in the SU carburetor.
Sparks to ignite the fuel mixture are created by either a spark plug or a device called an ignitor. When a spark plug was used, the spark was generated by either a magneto or else a trembler (or 'buzz') coil. A buzz coil used battery power to generateacontinuousseries of high voltage pulses which were fed to the spark plug. For ignitor ignition, either a battery and coil was used or a "low tension" magneto was used. With battery and coil ignition, a battery was wired in series with a wire coil andtheignitorcontacts. When the contacts of the ignitor were closed (the contacts reside inside the combustion chamber), electricity flowed through the circuit. When the contacts were opened by the timing mechanism, a spark was generated across the contactswhichignitedthe mixture. When a low tension magneto (really a low-voltage high-current generator) was used, the output of the magneto was fed directly to the ignitor points and the spark was generated as with a battery and coil.
Lubrication on these early engines was almost always manual (except for very large engines). Main crankshaft bearings and the connecting rod bearing on the crankshaft generally had a grease cup which was a small container (cup) filled with grease andacoverwhich screwed down on the cup.
A typical engine oilerThis is one made by LunkenheimerWhen the cover was screwed down tighter grease was forced out of the bottom of the cup and into the bearing. On very early engines there may have been just a hole in the casting of the bearing capwherelubricatingoil would be squirted while the engine was running. The piston was lubricated by a drip oiler that continuously fed drips of oil onto the piston. The excess oil from the piston ran out of the cylinder onto the engine and eventually ontotheground. Thedrip oiler could be adjusted to drip faster or slower depending on the need for lubrication, dictated by how hard the engine was working. The rest of the moving engine components were all lubricated by oil that the engine operator wouldhaveto apply fromtime to time while the engine was running.
Virtually all hit-and-miss engines were of the "open crank" style, that is, there was no enclosed crankcase. The crankshaft, connecting rod, camshaft, gears, governor, etc. were all completely exposed and could be viewed in operation when the engine wasrunning.Thismade for a messy environment as oil and sometimes grease was thrown from the engine as well as oil running onto the ground. Another disadvantage was that dirt and dust could get on all moving engine parts, causing excessive wear and enginemalfunctions.Frequentcleaning of the engine was therefore required to keep it in proper operating condition.
Cooling of the majority of hit-and-miss engines was by water in a reservoir. There were a small portion of small and fractional horsepower engines that were air-cooled with the aid of an incorporated fan. The water-cooled engine had a built in reservoir(largerenginesusually did not have a reservoir and required connection to a large external tank for cooling water via pipe connections on the cylinder). The water reservoir included the area around the cylinder as well as the cylinder head (most cases)and atank mountedor cast above the cylinder. When the engine ran it heated the water. Cooling was accomplished by the water steaming off and removing heat from the engine. When an engine ran under load for a period of time is was common for the waterin thereservoir toboil. Replacement of lost water was needed from time to time. A danger of the water-cooled design was freezing in cold weather. Many engines were ruined by the forgetful operator neglecting to drain the water when the engine was notin useand the waterfreezing and breaking the cast iron engine pieces. However, New Holland patented a v-shaped reservoir, so that expanding ice pushed itself up and into a larger space, so that the ice wouldn't break the reservoir. Water jacket repairsarecommon on manyof the engines that exist today.
These were simple engines compared to modern engine design. However, they incorporated some very clever designs in several areas, many times because the designer was attempting to circumvent infringing a patent for a particular part of the engine. Thisisparticularlytrue in the area of the governor. Governors were centrifugal, swinging arm, pivot arm, and many others. The actuator mechanism to govern speed was also varied depending on patents existing and the governor used. See, for example, U.S.Patents543,157from 1895 or 980,658 from 1911. However accomplished, the governor had one job - to control the speed of the engine. In modern engines, power output is controlled by throttling the flow of the air through the intake by means of abutterflyvalve; theonly exception to this being in diesels and Valvetronic petrol engines. On hit-and-miss engines, the governor holds the exhaust valve open whenever the engine is operating above its set speed, thus interrupting the Otto cycle firingmechanism.
The intake valve on hit-and-miss engines has no actuator. It has a light spring that holds it closed until it can be drawn open when a vacuum occurs in the cylinder. Such a vacuum can only occur when the piston is in a down-stroke and when the exhaustvalveisclosed. (Therefore, when the governor holds the exhaust valve open, the intake valve will not open.) This vacuum causes the intake valve to open, which allows the fuel-air mixture to enter.
Hit-and-miss engines were made to produce power outputs from 1 through approximately 100 horsepower (.75 - 75 kW). These engines are slow speed and typically ran from 250 revolutions per minute (rpm) for large horsepower engines to 600 rpm for small horsepowerengines.
A Jaeger Trash Pump used for pumping dirty (trashy) water. It has a Hercules 2½ HP (1.9 kW) engine on it. This is an example of an integrated function of hit-and-miss engines (i.e. not belted)They were used to power pumps for cultivation, saws for cuttingwood,generatorsfor electricity in rural areas, running farm equipment and many other stationary applications. Some were mounted on cement mixers. These engines also ran some of the early washing machines. They were used as a labour-saving device onfarms,and allowedthe farmer to accomplish much more than he was previously able to do.
The engine was typically belted to the device being powered by a wide flat belt, typically from 2 - 6 inches (5 - 15 cm) wide. The flat belt was driven by a pulley on the engine that attached either to a flywheel or to the crankshaft. The pulley was speciallymadeinthat its circumference was slightly tapered from the middle to each edge (like an over-inflated car tyre) so that the middle of the pulley was a slightly larger diameter. This design kept the flat belt in the centre of the pulley.
By the 1930s, more-advanced types of engines were being designed and produced. Flywheel engines were extremely heavy for the power produced, ran at very slow speeds, required a lot of maintenance, and could not easily be incorporated into mobile applications.Inthelate 1920s International Harvester already had the model M engine which was an enclosed version of a flywheel engine. Their next step was the model LA which was a totally enclosed engine (except for the valve system) featuring self-lubrication(oilin thecrankcase), reliable spark plug ignition, faster-speed operation (up to about 750-800 RPM) and most of all, light in weight compared to earlier generations. While the 1½ HP (1.1 kW) model LA still weighed about 150 pounds (68 kg), it was farlighterthanthe model M 1½ HP engine, which is in the 300-350 pound (136 - 159 kg) range. Later a slightly improved LA, the LB was produced. The models M, LA and LB were throttle governed. As time passed, more engine manufacturers moved to the enclosedcrankcaseengine.Companies like Briggs and Stratton were also producing lightweight air-cooled engines in the 1/2 to 2 HP (.37 - 1.5 kW) range and used much lighter-weight materials. These engines also ran at much higher speeds (up to approximately 2000–2500RPM)and thereforeproduced far more power per pound than the slow flywheel engines.
With the exception of oil field applications, flywheel engine production ceased in the 1940s.
Although thousands of out-of-use flywheel engines were scrapped in the iron and steel drives of World War II, many survived to be restored to working order by enthusiasts. However in recent years engines with original paint have become more desireabletomanycollectors than repainted engines. Numerous preserved hit-and-miss engines may be seen in action at shows dedicated to antique engines (many have antique tractors too) as well as in the stationary engine section of steam fairs and vintage vehicle rallies.