A hit-and-miss engine is a type of four-stroke internal combustion engine

Internal combustion engine

The internal combustion engine is an engine in which the combustion of a fuel occurs with an oxidizer in a combustion chamber. In an internal combustion engine, the expansion of the high-temperature and high -pressure gases produced by combustion apply direct force to some component of the engine...

 that was conceived in the late 19th century and was produced by various companies from the 1890s through approximately the 1930s. The name comes from the method of speed control that is implemented on these engines (as opposed to the "throttle governed" method of speed control). The sound made when the engine is running is a distinctive "POP whoosh whoosh whoosh whoosh POP" as the engine fires and then coasts until the speed decreases and needs to fire again to maintain its average speed.

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 were Hercules, International Harvester

International Harvester

International Harvester Company was a United States agricultural machinery, construction equipment, vehicle, commercial truck, and household and commercial products manufacturer. In 1902, J.P...

 (McCormick Deering), John Deere

John Deere

John Deere was an American blacksmith and manufacturer who founded Deere & Company, one of the largest and leading agricultural and construction equipment manufacturers in the world...

 and Fairbanks Morse. A compilation of engine manufacturers can be found in the book American Gasoline Engines Since 1872 by C.H. Wendel. This comprehensive book lists hundreds of manufacturers of early engines including those that made the hit-and-miss type.

Construction

A hit-and-miss engine is a type of flywheel engine. A flywheel engine is an engine that has a large flywheel

Flywheel

A flywheel is a rotating mechanical device that is used to store rotational energy. Flywheels have a significant moment of inertia, and thus resist changes in rotational speed. The amount of energy stored in a flywheel is proportional to the square of its rotational speed...

 or set of flywheels connected to the crankshaft

Crankshaft

The crankshaft, sometimes casually abbreviated to crank, is the part of an engine which translates reciprocating linear piston motion into rotation...

. The flywheels maintain engine speed during engine cycles that do not produce driving mechanical forces. The flywheels store energy on the combustion stroke and supply 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 hp engine weighs approximately 1000 pounds. The engine material was mainly cast iron

Cast iron

Cast iron is derived from pig iron, and while it usually refers to gray iron, it also identifies a large group of ferrous alloys which solidify with a eutectic. The color of a fractured surface can be used to identify an alloy. White cast iron is named after its white surface when fractured, due...

 and all significant engine parts were cast from it. Small functional pieces were made of steel

Steel

Steel is an alloy that consists mostly of iron and has a carbon content between 0.2% and 2.1% by weight, depending on the grade. Carbon is the most common alloying material for iron, but various other alloying elements are used, such as manganese, chromium, vanadium, and tungsten...

 and machined to perform their function.

The fuel system of a hit-and-miss engine consists of a fuel tank, fuel line, check valve

Check valve

A check valve, clack valve, non-return valve or one-way valve is a mechanical device, a valve, which normally allows fluid to flow through it in only one direction....

 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 kerosene or diesel. 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 needle valve

Needle valve

A needle valve is a type of valve having a small port and a threaded, needle-shaped plunger. It allows precise regulation of flow, although it is generally only capable of relatively low flow rates.- Construction and operation :...

 attached to a weighted or spring-loaded piston usually in conjunction with an oil-damped dashpot

Dashpot

A dashpot is a mechanical device, a damper which resists motion via viscous friction. The resulting force is proportional to the velocity, but acts in the opposite direction, slowing the motion and absorbing energy. It is commonly used in conjunction with a spring...

.

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

Bernoulli's principle

In fluid dynamics, Bernoulli's principle states that for an inviscid flow, an increase in the speed of the fluid occurs simultaneously with a decrease in pressure or a decrease in the fluid's potential energy...

, it was self-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

Spark plug

A spark plug is an electrical device that fits into the cylinder head of some internal combustion engines and ignites compressed fuels such as aerosol, gasoline, ethanol, and liquefied petroleum gas by means of an electric spark.Spark plugs have an insulated central electrode which is connected by...

 or a device called an ignitor. When a spark plug was used, the spark was generated by either a magneto

Magneto

A magneto is a type of electrical generator.Magneto may also refer to:* Magneto , permanent magnetic alternating current rotary generator* ignition magneto, magnetos on internal combustion engines...

 or a buzz coil. A buzz coil used battery power to generate a series 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 and the ignitor contacts. 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 contacts which ignited the 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

Connecting rod

In a reciprocating piston engine, the connecting rod or conrod connects the piston to the crank or crankshaft. Together with the crank, they form a simple mechanism that converts linear motion into rotating motion....

 bearing on the crankshaft generally had a grease cup which was a small container (cup) filled with grease and a cover which screwed down on the cup. When 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 cap where lubricating oil 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 onto the ground. The drip 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 would have to apply from time 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

Crankcase

In an internal combustion engine of the reciprocating type, the crankcase is the housing for the crankshaft. The enclosure forms the largest cavity in the engine and is located below the cylinder, which in a multicylinder engine are usually integrated into one or several cylinder blocks...

. The crankshaft, connecting rod, camshaft

Camshaft

A camshaft is a shaft to which a cam is fastened or of which a cam forms an integral part.-History:An early cam was built into Hellenistic water-driven automata from the 3rd century BC. The camshaft was later described in Iraq by Al-Jazari in 1206. He employed it as part of his automata,...

, gears, governor, etc. were all completely exposed and could be viewed in operation when the engine was running. This made 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 engine malfunctions. Frequent cleaning 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 (larger engines usually 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

Cylinder head

In an internal combustion engine, the cylinder head sits above the cylinders on top of the cylinder block. It closes in the top of the cylinder, forming the combustion chamber. This joint is sealed by a head gasket...

 (most cases) and a tank mounted or 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 water in the reservoir to boil. 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 not in use and the water freezing 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 repairs are common on many of the engines that exist today.

Design

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. This is particularly true in the area of the governor

Centrifugal governor

A centrifugal governor is a specific type of governor that controls the speed of an engine by regulating the amount of fuel admitted, so as to maintain a near constant speed whatever the load or fuel supply conditions...

. 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. Patents 543,157 from 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

Throttle

A throttle is the mechanism by which the flow of a fluid is managed by constriction or obstruction. An engine's power can be increased or decreased by the restriction of inlet gases , but usually decreased. The term throttle has come to refer, informally and incorrectly, to any mechanism by which...

 the flow of the air through the intake by means of a butterfly valve; the only 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

Otto cycle

An Otto cycle is an idealized thermodynamic cycle which describes the functioning of a typical reciprocating piston engine, the thermodynamic cycle most commonly found in automobile engines....

 firing mechanism.

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 exhaust valve is closed. (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.

Usage

Hit-and-miss engines were made to produce power outputs from 1 through approximately 100 horsepower

Horsepower

Horsepower is the name of several units of measurement of power. The most common definitions equal between 735.5 and 750 watts.Horsepower was originally defined to compare the output of steam engines with the power of draft horses in continuous operation. The unit was widely adopted to measure the...

. These engines are slow speed and typically ran from 250 revolutions per minute

Revolutions per minute

Revolutions per minute is a measure of the frequency of a rotation. It annotates the number of full rotations completed in one minute around a fixed axis...

 (rpm) for large horsepower engines to 600 rpm for small horsepower engines. They were used to power pump

Pump

A pump is a device used to move fluids, such as liquids, gases or slurries.A pump displaces a volume by physical or mechanical action. Pumps fall into three major groups: direct lift, displacement, and gravity pumps...

s for cultivation, saw

Saw

A saw is a tool that uses a hard blade or wire with an abrasive edge to cut through softer materials. The cutting edge of a saw is either a serrated blade or an abrasive...

s for cutting wood, generators

Electrical generator

In electricity generation, an electric generator is a device that converts mechanical energy to electrical energy. A generator forces electric charge to flow through an external electrical circuit. It is analogous to a water pump, which causes water to flow...

 for 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 on farms, and allowed the 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 to 6 inches (152.4 mm) 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 specially made in that 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.

Later history

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. In the late 1920s International Harvester

International Harvester

International Harvester Company was a United States agricultural machinery, construction equipment, vehicle, commercial truck, and household and commercial products manufacturer. In 1902, J.P...

 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 (oil in the crankcase), 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 model LA still weighed about 150 pounds, it was far lighter than the model M 1½ HP engine, which is in the 300-350 pound range. As time passed, more engine manufacturers moved to the enclosed crankcase engine. Companies like Briggs and Stratton were also producing lightweight air-cooled engines in the 1/2 to 2 hp range and used much lighter-weight materials. These engines also ran at much higher speeds (up to approximately 2000–2500RPM) and therefore produced far more power per pound than the slow flywheel engines.

With the exception of oil field

Oil field

An oil field is a region with an abundance of oil wells extracting petroleum from below ground. Because the oil reservoirs typically extend over a large area, possibly several hundred kilometres across, full exploitation entails multiple wells scattered across the area...

 applications, flywheel engine production ceased in the 1930s.

Flywheel engines today

The Arrow Engine Company still manufactures flywheel engines, although no longer of the 'hit-and-miss' type. Mainly intended for oil field

Oil field

An oil field is a region with an abundance of oil wells extracting petroleum from below ground. Because the oil reservoirs typically extend over a large area, possibly several hundred kilometres across, full exploitation entails multiple wells scattered across the area...

 use, the 'C'-series engine is a good example of the state-of-the-art of flywheel engine design.

There is also a company in India that makes look-alikes of Lister diesel engines. These are made for use in un-developed/underdeveloped areas where reliable power is needed.

Preservation

Although thousands of out-of-use flywheel engines were scrapped in the iron and steel drives of World War II

World War II

World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...

, many survived to be restored to working order by enthusiasts. Numerous preserved hit-and-miss engines may be seen in action in the stationary engine

Stationary engine

A stationary engine is an engine whose framework does not move. It is normally used not to propel a vehicle but to drive a piece of immobile equipment such as a pump or power tool. They may be powered by steam; or oil-burning or internal combustion engines....

 section of steam fairs and vintage vehicle rallies.

External links

• Harry's Old Engine "Antique gas engine collection" – a wide variety of hit-and-miss engines (different makes, different uses), each with a detailed, illustrated description page, some including audio clips of the engines running
• Description of Novo 6HP engine (manufactured in Lansing Michigan) with video showing engine in operation
• Description of a Fairbanks Jack-of-all-trades engine
• Description of a Jaeger 2HP engine
• Description of a Reid 15HP engine
• Animation of hit-and-miss engine
• Video of large hit-and-miss engine
• Video of small hit-and-miss engine
• "International Harvester Famous 3 Horsepower Hit-Miss Engine" – Description of International Harvester Famous 3 Horsepower Hit-Miss Engine
• Gas Engine Magazine (features) – Enthusiast's magazine covering the history and preservation of hit-and-miss engines