Model engine - AbsoluteAstronomy.com

For the band (previously known as Black Eyed Sceva), see Model Engine
Model Engine
Model Engine was an alternative rock band based in Santa Barbara, California. Prior to 1997 the trio, consisting of Jeremy Post, Brad McCarter and Brent Nims were known as Black Eyed Sceva. Confusion over the meaning of the name and its constant mispronunciation led the band to change its moniker...

.

In radio-controlled model

Radio-controlled model

A radio-controlled model is a model that is steerable with the use of radio control. All types of vehicles imaginable have had RC systems installed in them, including cars, boats, planes, and even helicopters and scale railway locomotives....

ing, a model engine is an 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...

used to power a radio-controlled aircraft

Radio-controlled aircraft

A radio-controlled aircraft is controlled remotely by a hand-held transmitter and a receiver within the craft...

, radio-controlled car

Radio-controlled car

Radio-controlled cars are self-powered model cars or trucks that can be controlled from a distance using a specialized transmitter...

, radio-controlled boat

Radio-controlled boat

- Fun Sport :Electric Sport boats are the most common type of boat amongst casual hobbyists. Hobby quality boat speed generally start at around 20MPH and go up from there, and can be just as fast or faster than their internal combustion counterparts, with the latest in Lithium Polymer and Brushless...

, free flight

Free flight (model aircraft)

The segment of model aviation known as free flight is the original form of the aeromodeling hobby, extending back centuries.- Description :...

and control line

Control line

Control line is a simple and light way of controlling a flying model aircraft. The aircraft is connected to the operator by a pair of lines, attached to a handle, that work the elevator of the model. This allows the model to be controlled in the pitch axis...

aircraft, and tether car

Tether car

Tether Cars are model racing cars powered by miniature internal combustion engines and tethered to a central post. Unlike radio control cars, the driver has no remote control over the model's speed or steering.-Basics:...

models also use these engines.
Because of the square-cube law

Square-cube law

The square-cube law is a principle, drawn from the mathematics of proportion, that is applied in engineering and biomechanics. It was first demonstrated in 1638 in Galileo's Two New Sciences...

, the behaviour of many machines does not always scale up or down at the same rate as the machine's size (and often not even in a linear way), usually at best causing a dramatic loss of power or efficiency, and at worst causing them not to work at all.
Methanol

Methanol

Methanol, also known as methyl alcohol, wood alcohol, wood naphtha or wood spirits, is a chemical with the formula CH3OH . It is the simplest alcohol, and is a light, volatile, colorless, flammable liquid with a distinctive odor very similar to, but slightly sweeter than, ethanol...

and nitromethane

Nitromethane

Nitromethane is an organic compound with the chemical formula . It is the simplest organic nitro compound. It is a slightly viscous, highly polar liquid commonly used as a solvent in a variety of industrial applications such as in extractions, as a reaction medium, and as a cleaning solvent...

are proven solutions to enhance the power of an automobile engine (Top Fuel

Top Fuel

Top Fuel racing is a class of drag racing in which the cars are run on a mix of approximately 90% nitromethane and 10% methanol rather than gasoline or simply methanol. The cars are purpose-built for drag racing, with an exaggerated layout that in some ways resembles open-wheel circuit racing...

)
and they can even get these small engines running.

Overview

The fully functional, albeit small, engines vary from the most common single-cylinder two-stroke to the exotic single and multiple-cylinder four-stroke, the latter taking shape in boxer

Flat engine

A flat engine is an internal combustion engine with multiple pistons that move in a horizontal plane. Typically, the layout has cylinders arranged in two banks on either side of a single crankshaft and is sometimes known as the boxer, or horizontally opposed engine. The concept was patented in 1896...

, v-twin

V-twin

A V-twin engine is a two-cylinder internal combustion engine where the cylinders are arranged in a V configuration.- Crankshaft configuration :Most V-twin engines have a single crankpin, which is shared by both connecting rods...

, inline

Straight engine

Usually found in four- and six-cylinder configurations, the straight engine, or inline engine is an internal-combustion engine with all cylinders aligned in one row, with no offset...

and radial

Radial engine

The radial engine is a reciprocating type internal combustion engine configuration in which the cylinders point outward from a central crankshaft like the spokes on a wheel...

form, a few Wankel engine

Wankel engine

The Wankel engine is a type of internal combustion engine using an eccentric rotary design to convert pressure into a rotating motion instead of using reciprocating pistons. Its four-stroke cycle takes place in a space between the inside of an oval-like epitrochoid-shaped housing and a rotor that...

designs are also used. Most model engines run on a blend of methanol

Methanol

, nitromethane

Nitromethane

, and lubricant (either castor

Castor oil

Castor oil is a vegetable oil obtained from the castor bean . Castor oil is a colorless to very pale yellow liquid with mild or no odor or taste. Its boiling point is and its density is 961 kg/m3...

or synthetic oil

Synthetic oil

Synthetic oil is a lubricant consisting of chemical compounds that are artificially made . Synthetic lubricants can be manufactured using chemically modified petroleum components rather than whole crude oil, but can also be synthesized from other raw materials...

). Two-stroke model engines, most often designed since 1970 with Schnuerle porting for best performance, range in typical size from .12 cubic inches (2 cubic centimeters) to 1.2 ci (19.6 cc) and generate between .5 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...

(370 watt

Watt

The watt is a derived unit of power in the International System of Units , named after the Scottish engineer James Watt . The unit, defined as one joule per second, measures the rate of energy conversion.-Definition:...

s) to 5 hp (3.7 kW), can get as small as .010 ci (.16 cc) and as large as 3-4 ci (49–66 cc). Four-stroke model engines have been made in sizes as small as 0.20 in3 (3.3 cm3) for the smallest single-cylinder models, all the way up to 3.05 in3 (50 cm3) for the largest size for single-cylinder units, with twin- and multi-cylinder engines on the market being as small as 10 cm3 for opposed-cylinder twins, while going somewhat larger in size than 50 cm3, and even upwards to well above 200 cm3 for some model radial engine

Radial engine

The radial engine is a reciprocating type internal combustion engine configuration in which the cylinders point outward from a central crankshaft like the spokes on a wheel...

s. While the methanol and nitromethane blended "glow fuel

Glow fuel

Glow fuel is a generic term used to describe a fuel source used in model engines -- generally the same or similar fuels can be used in model airplanes, helicopters, cars and boats. Glow fuel can be burned by very simple two stroke engines or by more complicated four stroke engines and these...

" engines are the most common, many larger (especially above 15 cm3/0.90 cu.in. displacement) model engines, both two-stroke and a few four-stroke examples, are spark ignition, and are fueled with gasoline. This article concerns itself with the methanol engines; gasoline-powered model engines are similar to those built for use in string trimmer

String trimmer

A string trimmer, also known as a strimmer, line trimmer, weed whacker, weed whip, weed eater, weedy, or whipper snipper, is a powered handheld device that uses a flexible monofilament line instead of a blade for cutting grass and other plants near objects...

s, chainsaw

Chainsaw

A chainsaw is a portable mechanical saw, powered by electricity, compressed air, hydraulic power, or most commonly a two-stroke engine...

s, and other yard equipment.

The majority of model engines have used, and continue to use, the two-stroke cycle

Two-stroke cycle

A two-stroke engine is an internal combustion engine that completes the process cycle in one revolution of the crankshaft...

principle to avoid needing valves in the combustion chamber

Combustion chamber

A combustion chamber is the part of an engine in which fuel is burned.-Internal combustion engine:The hot gases produced by the combustion occupy a far greater volume than the original fuel, thus creating an increase in pressure within the limited volume of the chamber...

, but a growing number of model engines use the four-stroke cycle

Four-stroke cycle

A four-stroke engine, also known as four-cycle, is an internal combustion engine in which the piston completes four separate strokes—intake, compression, power, and exhaust—during two separate revolutions of the engine's crankshaft, and one single thermodynamic cycle.There are two...

design instead. Both reed valve

Reed valve

Reed valves are a type of check valve which restrict the flow of fluids to a single direction, opening and closing under changing pressure on each face...

and rotary valve

Rotary valve

A rotary valve is a type of valve in which the rotation of a passage or passages in a transverse plug regulates the flow of liquid or gas through the attached pipes. The common stopcock is the simplest form of rotary valve...

-type two-strokes are common, with four-stroke model engines using either conventional poppet valve

Poppet valve

A poppet valve is a valve consisting of a hole, usually round or oval, and a tapered plug, usually a disk shape on the end of a shaft also called a valve stem. The shaft guides the plug portion by sliding through a valve guide...

, and rotary valve formats for induction and exhaust.

The engine shown to the right has its carburetor in the center of the zinc alloy casting to the left. (It uses a flow restriction, like the choke on an old car engine, because the venturi effect

Venturi effect

The Venturi effect is the reduction in fluid pressure that results when a fluid flows through a constricted section of pipe. The Venturi effect is named after Giovanni Battista Venturi , an Italian physicist.-Background:...

is not effective on such a small scale.) The valve reed, cross shaped above its retainer spring, is still beryllium copper alloy, in this old engine. The glow plug is built into the cylinder head. Large production volume makes it possible to use a machined cylinder and an extruded crank case (cut away by hand in the example shown). These Cox

Cox Models

Cox Models, a former division of Estes Industries of Penrose, Colorado, was a multimillion-dollar hobby company, is one of the hobby industry's oldest companies and is noted for its production of miniature model internal-combustion engines....

Bee reed valve engines are notable for their low cost and ability to survive crashes. The components of the engine shown come from several different engines.

Glowplug engines

Glow plugs

Glow plug (model engine)

A glow plug is a device, similar to a spark plug, used to help ignite the fuel in the very small internal combustion engines typically used in model aircraft, model cars and similar applications...

are used for starting as well as continuing the power cycle. The glow plug consists of a
durable, mostly platinum

Platinum

Platinum is a chemical element with the chemical symbol Pt and an atomic number of 78. Its name is derived from the Spanish term platina del Pinto, which is literally translated into "little silver of the Pinto River." It is a dense, malleable, ductile, precious, gray-white transition metal...

, helically wound wire filament

Heating element

A heating element converts electricity into heat through the process of Joule heating. Electric current through the element encounters resistance, resulting in heating of the element....

, within a cylindrical pocket in the plug body, exposed to the combustion chamber

Combustion chamber

. A small direct current

Direct current

Direct current is the unidirectional flow of electric charge. Direct current is produced by such sources as batteries, thermocouples, solar cells, and commutator-type electric machines of the dynamo type. Direct current may flow in a conductor such as a wire, but can also flow through...

voltage

Voltage

Voltage, otherwise known as electrical potential difference or electric tension is the difference in electric potential between two points — or the difference in electric potential energy per unit charge between two points...

(around 1.5 volts) is applied to the glow plug, the engine is then started, and the voltage is removed. The burning of the fuel/air mixture

Air-fuel ratio

Air–fuel ratio is the mass ratio of air to fuel present in an internal combustion engine. If exactly enough air is provided to completely burn all of the fuel, the ratio is known as the stoichiometric mixture, often abbreviated to stoich...

in a glow-plug model engine, which requires methanol

Methanol

for the glow plug to work in the first place, and sometimes with the use of nitromethane

Nitromethane

for greater power output and steadier idle, occurs due to the catalytic

Catalysis

Catalysis is the change in rate of a chemical reaction due to the participation of a substance called a catalyst. Unlike other reagents that participate in the chemical reaction, a catalyst is not consumed by the reaction itself. A catalyst may participate in multiple chemical transformations....

reaction of the methanol vapor to the presence of the platinum in the filament, thus causing the ignition. This keeps the plug's filament glowing hot, and allows it to ignite the next charge. Since the ignition timing is not controlled electrically, as in a spark ignition engine or by fuel injection

Fuel injection

Fuel injection is a system for admitting fuel into an internal combustion engine. It has become the primary fuel delivery system used in automotive petrol engines, having almost completely replaced carburetors in the late 1980s....

, as in an ordinary diesel

Diesel engine

A diesel engine is an internal combustion engine that uses the heat of compression to initiate ignition to burn the fuel, which is injected into the combustion chamber...

, it must be adjusted by the richness of the mixture, the ratio of nitromethane to methanol, the compression ratio

Compression ratio

The 'compression ratio' of an internal-combustion engine or external combustion engine is a value that represents the ratio of the volume of its combustion chamber from its largest capacity to its smallest capacity...

, the cooling of 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...

, the type of glow plug, etc. A richer mixture will tend to cool the filament and so retard ignition, slowing the engine, and a rich mixture also eases starting. After starting the engine can easily be leaned (by adjusting 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 :...

in the spraybar) to obtain maximum power. Glowplug engines are also known as nitro engines. Nitro engines require a 1.5 volt ignitor to light the glow plug in the heat sink

Heat sink

A heat sink is a term for a component or assembly that transfers heat generated within a solid material to a fluid medium, such as air or a liquid. Examples of heat sinks are the heat exchangers used in refrigeration and air conditioning systems and the radiator in a car...

. Once primed, pulling the starter with the ignitor in will start the engine.

Diesel engines

Diesel engines are an alternative to methanol glow plug engines. These "diesels" run on a mixture of kerosene

Kerosene

Kerosene, sometimes spelled kerosine in scientific and industrial usage, also known as paraffin or paraffin oil in the United Kingdom, Hong Kong, Ireland and South Africa, is a combustible hydrocarbon liquid. The name is derived from Greek keros...

, ether

Ether

Ethers are a class of organic compounds that contain an ether group — an oxygen atom connected to two alkyl or aryl groups — of general formula R–O–R'. A typical example is the solvent and anesthetic diethyl ether, commonly referred to simply as "ether"...

, castor oil

Castor oil

Castor oil is a vegetable oil obtained from the castor bean . Castor oil is a colorless to very pale yellow liquid with mild or no odor or taste. Its boiling point is and its density is 961 kg/m3...

or vegetable oil, and Amsoil

Amsoil

AMSOIL Inc. is a corporation based in Superior, Wisconsin that primarily formulates and packages synthetic lubricants and filters. The company's advertising slogan is The First in Synthetics.-History:...

cetane

Cetane number

Cetane number or CN is a measurement of the combustion quality of diesel fuel during compression ignition. It is a significant expression of diesel fuel quality among a number of other measurements that determine overall diesel fuel quality.- Definition :...

or amyl nitrate

Amyl nitrate

Amyl nitrate is the chemical compound with the formula CH34ONO2. This molecule consists of the 5-carbon amyl group attached to a nitrate functional group. It is the ester of amyl alcohol and nitric acid.-Applications:...

booster. Despite their name, their use of compression ignition, and the use of a kerosene fuel that is similar to diesel, model diesels share very little with full-size diesel engine

Diesel engine

A diesel engine is an internal combustion engine that uses the heat of compression to initiate ignition to burn the fuel, which is injected into the combustion chamber...

s.

Full-size diesel engines, such as those found in a truck

Truck

A truck or lorry is a motor vehicle designed to transport cargo. Trucks vary greatly in size, power, and configuration, with the smallest being mechanically similar to an automobile...

, are fuel injected

Fuel injection

and either two-stroke or four-stroke. They use compression ignition to ignite the mixture: the compression within the cylinder heats the inlet charge sufficiently to cause ignition, without requiring an applied ignition source. A fundamental feature of such engines, unlike petrol (gasoline) engines, is that they draw in air alone and the fuel is only mixed by being injected into the combustion chamber separately. Model diesel engines are instead a carbureted two-stroke using the crankcase for compression. Their carburettor supplies a mixture of fuel and air into the engine, with the proportions kept fairly constant and their total volume throttled to control the engine power. Apart from sharing the diesel's use of compression ignition, their construction has more in common with a small two-stroke motorcycle or lawnmower engine. In addition to this, model diesels have variable compression ratio

Compression ratio

s. This variable compression is achieved by a "contra-piston," at the top of the cylinder, which can be adjusted by a screwed "T-bar". The swept volume of the engine remains the same, but as the volume of the combustion chamber at top dead centre is changed by adjusting the contra-piston, the compression ratio (swept volume + combustion chamber / combustion chamber) changes accordingly.

Model diesels are found to produce more torque

Torque

Torque, moment or moment of force , is the tendency of a force to rotate an object about an axis, fulcrum, or pivot. Just as a force is a push or a pull, a torque can be thought of as a twist....

than glow engines of the same displacement

Engine displacement

Engine displacement is the volume swept by all the pistons inside the cylinders of an internal combustion engine in a single movement from top dead centre to bottom dead centre . It is commonly specified in cubic centimeters , litres , or cubic inches...

, and are thought to get better fuel efficiency

Fuel efficiency

Fuel efficiency is a form of thermal efficiency, meaning the efficiency of a process that converts chemical potential energy contained in a carrier fuel into kinetic energy or work. Overall fuel efficiency may vary per device, which in turn may vary per application, and this spectrum of variance is...

, because the same power is produced at a lower RPM, and in a smaller displacement engine. However, the specific power

Specific power

In physics and engineering, surface power density or sometimes simply specific power is power per unit area.-Applications:* The intensity of electromagnetic radiation can be expressed in W/m2...

may not be significantly superior to a glow engine, due to overbuilding, to assure that the engine can withstand the much higher compression, sometimes reaching ratio

Ratio

In mathematics, a ratio is a relationship between two numbers of the same kind , usually expressed as "a to b" or a:b, sometimes expressed arithmetically as a dimensionless quotient of the two which explicitly indicates how many times the first number contains the second In mathematics, a ratio is...

s of as high as 30:1. Diesels also run significantly quieter, due to the more rapid combustion, unlike glow engines, in which combustion may still be occurring when the exhaust ports are uncovered, causing a significant amount of noise.

Overview

Glowplug engines

Diesel engines

See also