Model engine
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.
Because of the square–cube law, the behaviour of many engines does not always scale up or down at the same rate as the machine's size; usually at best causing a dramatic loss of power or efficiency, and at worst causing them not to work at all. Methanol and nitromethane are common fuels.
Overview
The fully functional, albeit small, engines vary from the most common single-cylinder
This article concerns itself with the methanol engines; gasoline-powered model engines are similar to those built for use in string trimmers, chainsaws, and other yard equipment, unless they happen to be purpose-built for aeromodeling use, being especially true for four-stroke gasoline-fueled model engines. Such engines usually use a fuel that contains a small percentage of motor oil as a two-stroke engine uses for lubrication purposes, as most model four-stroke engines — be they glow plug or spark ignition — have no built-in reservoir for motor oil in their crankcase or engine block design.
The majority of model engines have used, and continue to use, the
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 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 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.
Comparison of engines
Images of a glowplug engine and a "diesel" engine are shown below for comparison. The most obvious external difference is seen on top of the cylinder head. The glowplug engine's glow plug has a pinlike terminal for its center contact, which is an electrical connector for the glowplug. The "diesel" engine has a T-bar which is used for adjusting the compression. The cylindrical object behind the glowplug engine is an exhaust silencer or muffler.
-
Glowplug engine
-
Diesel engine
Glowplug engines
Glow plugs are used for starting as well as continuing the power cycle. The glow plug consists of a durable, mostly
Since the ignition timing is not controlled electrically, as in a
Diesel engines
Diesel engines are an alternative to methanol glow plug engines. These "diesels" run on a mixture of
Full-size diesel engines, such as those found in a
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
Model diesels are found to produce more torque than glow engines of the same displacement, and are thought to get better fuel efficiency, because the same power is produced at a lower rpm, and in a smaller displacement engine. However, the specific power may not be significantly superior to a glow engine, due to the heavier construction needed to assure that the engine can withstand the much higher compression ratio, sometimes reaching 30:1. Diesels also run significantly quieter, due to the more rapid combustion, unlike two-stroke glow engines, in which combustion may still be occurring when the exhaust ports are uncovered, causing a significant amount of noise.
Recent developments in model engineering have produced true diesel model engines, with a traditional injector and injector pump, and these engines operate in the same way as a large diesel engine.
See also
- Four-stroking
- Glow plug (model engine)
- Glow fuel
- Nitro engine
- Schnuerle porting, used on model two-stroke engines since the 1970s
Makers
- Bullitt Engines
- Cox Model Engines
- Enya Model Engines (two and four-stroke model engines)
- FOX Manufacturing
- FX Royal Racing Engines
- K&B Manufacturing http://www.mecoa.com/kb/
- Laser Engines
- LRP electronic (rebranded OS Engines)
- Mantua Models
- GAUI GPOWER
- MECOA
- Motori Cipolla
- Ninja Engine
- Novarossi
- nVision
- O.S. Engines (two and four-stroke model engines)
- OPS (engine)
- Picco Micromotori
- RB Products
- rcvengines
- Reds Racing
- Saito Seisakusho Archived 2014-02-03 at the Wayback Machine (four-stroke and model steam engine specialist)
- Team Orion
- Thunder Tiger
- Webra (out of business)
- Yamada Engines(YS) (two and four-stroke model engines)
External links
- K&B Manufacturing
- Yamada Engines
- Saito Seisakusho Archived 2014-02-03 at the Wayback Machine
- WEBRA
- FOX Manufacturing