Small engine

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Briggs & Stratton Vanguard V-twin engine in a portable generator Portable electrical generator side.jpg
Briggs & Stratton Vanguard V-twin engine in a portable generator


A small engine is the general term for a wide range of small-displacement, low-powered internal combustion engines used to power lawn mowers, generators, concrete mixers and many other machines that require independent power sources. [1] These engines often have simple designs, for example an air-cooled single-cylinder petrol engine with a pull-cord starter, capacitor discharge ignition and a gravity-fed carburettor.

Contents

Engines of similar design and displacement are also used in smaller vehicles such as motorcycles, motor scooters, all-terrain vehicles, and go-karts.

Characteristics

The engines are small in both physical dimensions and power output, relative to larger automobile engines. Power outputs are typically less than 11 kW (15 hp). The smallest of all are used in handheld garden machinery, such as string trimmers and chainsaws, which have a displacement as small as 24 cc (1.5 cu in). [2] Production cost is often a key consideration for small engines, resulting in relatively simple designs (compared with automotive engines, for example).

The most common configuration is a single-cylinder engines that is air-cooled. The combustion cycle can be either two-stroke (which results in a lighter engine for a given power output) [3] [4] or four-stroke (which produce lower levels of exhaust gas emissions). [5] [6] The fuel is usually either petrol or diesel. [7]

In 1973, a small Wankel (rotary) engine manufactured by NSU was used in a lawn mower. [8]

Design

Electrical system

When a manual starter system is used (such as a recoil starter with a pull-cord), only a basic electrical system is required, since the system's only purpose is to power the spark plug. Older engines used a magneto to achieve this, while newer engines often use a capacitor discharge ignition (CDI) system with an ignition coil. [9] These systems do not require a battery or charging system. [10]

Before the invention of the recoil starter, a notched pulley was attached to the engine's flywheel; the operator would manually wind a rope around the pulley then jerk the rope to rotate the engine so that it would start. Following the introduction of the sprag clutch in the 1960s, the "impulse" or "wind-up" starter was popular for a brief period. [11] These used a heavy spring which the operator placed under tension using a rotating crank handle. [12] However, these systems were potentially dangerous as it was possible to leave the starter wound up and ready to start the engine unintentionally, even long after the crank was wound up.

Electric starting, which has become more common over time, requires a more complex electrical system. These engines also require a starter motor, a battery to power it and an alternator to keep a battery charged.

Fuel system

Petrol engines often use simple fuel systems consisting of a float-type carburetor with a fuel tank located above it (so that the fuel is delivered by gravity, avoiding the need for a fuel pump). Sometimes, the fuel tank is located below the carburetor and fuel is delivered using engine vacuum or crankcase pressure pulsations.

Diesel engines use fuel injection. [13]

Governor

Most small engines use a governor to maintain a constant engine speed under varying loads. Some engines also have a mechanism for the user to adjust the engine speed. Rather than directly controlling the opening of the carburetor throttle, this is usually achieved by adjusting the governor, which in turn regulates the engine speed higher or lower.

Valvetrain

The most common design is an overhead valve configuration, as used by the Honda GX range since the 1980s for example. [14]

A sidevalve configuration is used instead by some engines, owing to its simplicity for both manufacture and basic maintenance.[ citation needed ] Some engines in recent years, for example the Honda GC series, now use an overhead cam configuration. [15]

Crankshaft

Small engines can have the crankshaft oriented either horizontally or vertically, according to the intended application. Vertical axis engines were originally developed for rotary lawnmowers, but the size of this large market has encouraged a supply of cheap engines and they are now also used for other purposes such as generators.

Manufacturers

The four largest manufacturers of small engines for power equipment in 2019 were Briggs & Stratton, Honda, Kawasaki and Kohler. Other major players include: Kubota, Yamaha and Liquid Combustion Technology. [16]

Repairs/maintenance

The repairing of small engines in a vocational occupation. While often touted as a separate job by commercial education institutions, it may also be a skill someone uses as part of a larger job, such as an automotive or agricultural mechanic. Various safety precautions need to be taken when working on small engines. [17]

Emissions

Small engines, because of their simple designs and lack of emission control systems used on larger engines, emit disproportionately large amounts of air pollution, particularly volatile organic compounds and carbon monoxide. It is estimated that over 10% of US carbon monoxide pollution in 2011 was from small engines. [18]

In response to this, some jurisdictions, notably the US state of California, have imposed increasingly strict emissions regulations for small engines. In 2021, California effectively banned the sale of small engines used in garden equipment from January 1, 2024. [19]

The major alternative to small engines is the use of electric motors powered by rechargeable batteries.

See also

Related Research Articles

<span class="mw-page-title-main">Diesel engine</span> Type of internal combustion engine

The diesel engine, named after Rudolf Diesel, is an internal combustion engine in which ignition of the fuel is caused by the elevated temperature of the air in the cylinder due to mechanical compression; thus, the diesel engine is called a compression-ignition engine. This contrasts with engines using spark plug-ignition of the air-fuel mixture, such as a petrol engine or a gas engine.

<span class="mw-page-title-main">Reciprocating engine</span> Engine utilising one or more reciprocating pistons

A reciprocating engine, also often known as a piston engine, is typically a heat engine that uses one or more reciprocating pistons to convert high temperature and high pressure into a rotating motion. This article describes the common features of all types. The main types are: the internal combustion engine, used extensively in motor vehicles; the steam engine, the mainstay of the Industrial Revolution; and the Stirling engine for niche applications. Internal combustion engines are further classified in two ways: either a spark-ignition (SI) engine, where the spark plug initiates the combustion; or a compression-ignition (CI) engine, where the air within the cylinder is compressed, thus heating it, so that the heated air ignites fuel that is injected then or earlier.

<span class="mw-page-title-main">Fuel injection</span> Feature of internal combustion engines

Fuel injection is the introduction of fuel in an internal combustion engine, most commonly automotive engines, by the means of an injector. This article focuses on fuel injection in reciprocating piston and Wankel rotary engines.

<span class="mw-page-title-main">Carburetor</span> Component of internal combustion engines which mixes air and fuel in a controlled ratio

A carburetor is a device used by a gasoline internal combustion engine to control and mix air and fuel entering the engine. The primary method of adding fuel to the intake air is through the Venturi tube in the main metering circuit, though various other components are also used to provide extra fuel or air in specific circumstances.

<span class="mw-page-title-main">Two-stroke engine</span> Internal combustion engine type

A two-strokeengine is a type of internal combustion engine that completes a power cycle with two strokes of the piston in one revolution of the crankshaft. A four-stroke engine requires four strokes of the piston to complete a power cycle in two crankshaft revolutions. In a two-stroke engine, the end of the combustion stroke and the beginning of the compression stroke happen simultaneously, with the intake and exhaust functions occurring at the same time.

A stratified charge engine describes a certain type of internal combustion engine, usually spark ignition (SI) engine that can be used in trucks, automobiles, portable and stationary equipment. The term "stratified charge" refers to the working fluids and fuel vapors entering the cylinder. Usually the fuel is injected into the cylinder or enters as a fuel rich vapor where a spark or other means are used to initiate ignition where the fuel rich zone interacts with the air to promote complete combustion. A stratified charge can allow for slightly higher compression ratios without "knock," and leaner air/fuel ratio than in conventional internal combustion engines.

<span class="mw-page-title-main">Petrol engine</span> Internal combustion engine designed to run on gasoline

A petrol engine is an internal combustion engine designed to run on petrol (gasoline). Petrol engines can often be adapted to also run on fuels such as liquefied petroleum gas and ethanol blends.

<span class="mw-page-title-main">Four-stroke engine</span> Internal combustion engine type

A four-strokeengine is an internal combustion (IC) engine in which the piston completes four separate strokes while turning the crankshaft. A stroke refers to the full travel of the piston along the cylinder, in either direction. The four separate strokes are termed:

  1. Intake: Also known as induction or suction. This stroke of the piston begins at top dead center (T.D.C.) and ends at bottom dead center (B.D.C.). In this stroke the intake valve must be in the open position while the piston pulls an air-fuel mixture into the cylinder by producing a partial vacuum in the cylinder through its downward motion.
  2. Compression: This stroke begins at B.D.C, or just at the end of the suction stroke, and ends at T.D.C. In this stroke the piston compresses the air-fuel mixture in preparation for ignition during the power stroke (below). Both the intake and exhaust valves are closed during this stage.
  3. Combustion: Also known as power or ignition. This is the start of the second revolution of the four stroke cycle. At this point the crankshaft has completed a full 360 degree revolution. While the piston is at T.D.C. the compressed air-fuel mixture is ignited by a spark plug or by heat generated by high compression, forcefully returning the piston to B.D.C. This stroke produces mechanical work from the engine to turn the crankshaft.
  4. Exhaust: Also known as outlet. During the exhaust stroke, the piston, once again, returns from B.D.C. to T.D.C. while the exhaust valve is open. This action expels the spent air-fuel mixture through the exhaust port.

The straight-five engine is a piston engine with five cylinders mounted in a straight line along the crankshaft.

<span class="mw-page-title-main">Lawn mower</span> Grass cutting device

A lawn mower is a device utilizing one or more revolving blades to cut a grass surface to an even height. The height of the cut grass may be fixed by the design of the mower but generally is adjustable by the operator, typically by a single master lever or by a mechanism on each of the machine's wheels. The blades may be powered by manual force, with wheels mechanically connected to the cutting blades so that the blades spin when the mower is pushed forward, or the machine may have a battery-powered or plug-in electric motor. The most common self-contained power source for lawn mowers is a small 4-stroke internal combustion engine. Smaller mowers often lack any form of self-propulsion, requiring human power to move over a surface; "walk-behind" mowers are self-propelled, requiring a human only to walk behind and guide them. Larger lawn mowers are usually either self-propelled "walk-behind" types or, more often, are "ride-on" mowers that the operator can sit on and control. A robotic lawn mower is designed to operate either entirely on its own or less commonly by an operator on a remote control.

<span class="mw-page-title-main">CVCC</span> Reduced-emissions engine by Honda

CVCC, or Compound Vortex Controlled Combustion, is an internal combustion engine technology developed and trademarked by the Honda Motor Company.

Manifold vacuum, or engine vacuum in an internal combustion engine is the difference in air pressure between the engine's intake manifold and Earth's atmosphere.

<span class="mw-page-title-main">Motorcycle engine</span> Engine that powers a motorcycle

A motorcycle engine is an engine that powers a motorcycle. Motorcycle engines are typically two-stroke or four-stroke internal combustion engines, but other engine types, such as Wankels and electric motors, have been used.

<span class="mw-page-title-main">Single-cylinder engine</span> Piston engine with one cylinder

A single-cylinder engine, sometimes called a thumper, is a piston engine with one cylinder. This engine is often used for motorcycles, motor scooters, go-karts, all-terrain vehicles, radio-controlled vehicles, power tools and garden machinery. Single-cylinder engines are made both as 4-strokes and 2-strokes.

<span class="mw-page-title-main">Model engine</span>

A model engine is a small internal combustion engine typically used to power a radio-controlled aircraft, radio-controlled car, radio-controlled boat, free flight, control line aircraft, or ground-running tether car model.

<span class="mw-page-title-main">Push start</span> Method of starting a motor vehicle

Push starting, also known as bump starting, roll starting, clutch starting, popping the clutch or crash starting, is a method of starting a motor vehicle with an internal combustion engine that has a manual transmission, a mechanical fuel pump, and a mechanically driven generator or alternator. By pushing or letting the vehicle roll downhill then engaging the clutch at the appropriate speed the engine will turn over and start. The technique is most commonly employed when other starting methods are unavailable.

Internal combustion engines date back to between the 10th and 13th centuries, when the first rocket engines were invented in China. Following the first commercial steam engine in 1698, various efforts were made during the 18th century to develop equivalent internal combustion engines. In 1791, the English inventor John Barber patented a gas turbine. In 1794, Thomas Mead patented a gas engine. Also in 1794, Robert Street patented an internal-combustion engine, which was also the first to use liquid fuel (petroleum) and built an engine around that time. In 1798, John Stevens designed the first American internal combustion engine. In 1807, French engineers Nicéphore and Claude Niépce ran a prototype internal combustion engine, using controlled dust explosions, the Pyréolophore. This engine powered a boat on the river in France. The same year, the Swiss engineer François Isaac de Rivaz built and patented a hydrogen and oxygen-powered internal-combustion engine. Fitted to a crude four-wheeled wagon, François Isaac de Rivaz first drove it 100 metres in 1813, thus making history as the first car-like vehicle known to have been powered by an internal-combustion engine.

<span class="mw-page-title-main">Hesselman engine</span>

The Hesselman engine is a hybrid between a petrol engine and a diesel engine. It was designed and introduced in 1925 by Swedish engineer Jonas Hesselman.

Internal combustion engines come in a wide variety of types, but have certain family resemblances, and thus share many common types of components.

<span class="mw-page-title-main">Internal combustion engine</span> Engine in which the combustion of a fuel occurs with an oxidizer in a combustion chamber

An internal combustion engine is a heat engine in which the combustion of a fuel occurs with an oxidizer in a combustion chamber that is an integral part of the working fluid flow circuit. In an internal combustion engine, the expansion of the high-temperature and high-pressure gases produced by combustion applies direct force to some component of the engine. The force is typically applied to pistons, turbine blades, a rotor, or a nozzle. This force moves the component over a distance, transforming chemical energy into kinetic energy which is used to propel, move or power whatever the engine is attached to.

References

  1. ↑ Curt Wayne; J.H. Bishop (1991). Small Engine Repair Manual. Haynes. ISBN   1-85010-755-6.
  2. ↑ "Chainsaw Buying Guide". www.chainsawjournal.com. 28 August 2014. Retrieved 19 July 2019.
  3. ↑ "How Two-stroke Engines Work". www.howstuffworks.com. 1 April 2000. Retrieved 19 July 2019.
  4. ↑ "The Lighter, Better, More Efficient Two-Stroke Engine". Popular Mechanics. 3 October 2011. Retrieved 19 July 2019.
  5. ↑ Potera, C. (2004). "Air Pollution: Asia's Two-Stroke Engine Dilemma". Environmental Health Perspectives. 112 (11): A613. doi:10.1289/ehp.112-a613a. PMC   1247506 . PMID   15309754.
  6. ↑ "How Two-stroke Engines Work". www.howstuffworks.com. 1 April 2000. Retrieved 19 July 2019.
  7. ↑ One-cylinder Diesel engines
  8. ↑ "Now You Can 'Mow' with a Wankel!" Popular Science, July 1973 p. 18
  9. ↑ "How to test and repair ignition system problems?". www.briggsandstratton.com. Retrieved 22 July 2019.
  10. ↑ "How does a magneto work?". www.howstuffworks.com. 8 May 2000. Retrieved 22 July 2019.
  11. ↑ "History of the Starter Motor". www.crankshift.com. 1 October 2013. Retrieved 22 July 2019.
  12. ↑ "Your were asking: Impulse starters". www.classicmotorcycle.co.uk. 26 May 2017. Retrieved 22 July 2019.
  13. ↑ "B-Series, small diesel engine, single cylinder engine". www.hatz-diesel.com. Retrieved 23 July 2019.
  14. ↑ "Honda GX160 engine". Honda.
  15. ↑ "GC160 4-Stroke Engine- Features, Specs, and Model Info". www.honda.com. Retrieved 21 July 2019.
  16. ↑ "Small Engine Industry Comprehensive Study". Lawn Manual. Retrieved 18 June 2022.
  17. ↑ "Notes on the Troubleshooting and Repair of small Gasoline Engines and Rotary Lawn Mowers". www.repairfaq.org. Retrieved 10 August 2019.
  18. ↑ Banks, Jamie L; McConnell, Robert (April 16, 2015). "National Emissions from Lawn and Garden Equipment" (PDF). Environmental Protection Agency – via 2016 International Emissions Inventory Conference, San Diego.
  19. ↑ "2021 Amendments to the Small Off-Road Engine Regulations | California Air Resources Board". ww2.arb.ca.gov. Retrieved 2024-04-05.
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