| Although today, the technological advancement of | | | | displacement or the interior volume swept by the |
| airplane powerplant specially on the electric | | | | piston in making its stroke up and down the |
| motors which now uses Lithium Polymer batteries, | | | | cylinder (swept volume) In the case of diesels, |
| we should also learn the internal combustion type | | | | displacement is always quoted in cubic |
| since the development of those miniature | | | | centimeters or cc (mainly because the model |
| airplanes and helicopters owe so much. There are | | | | diesel originated in Continental Europe). In the case |
| two main types of model airplane engine - glow | | | | of glow engines, displacement is (nearly) always |
| engines and diesels. Although the ignition type is | | | | quoted in cubic inches or cubic inches (because |
| popular on big birds (1/4 scale), we will | | | | this type originated in the United States) |
| concentrate on the 'standard' model engines. Glow | | | | Manufacturer produce glow engine in a more or |
| engine are by far the more numerous and | | | | less standard range of sizes, originally representing |
| popular, faster revving and generally more | | | | logical steps in power output. These are 0.049 |
| powerful size for size. They are suitable for | | | | cubic inch (also known as 1/2A); 0.09 cubic inch |
| powering all types of model aircraft and are | | | | (also known as Class A); 0.19 cubic inch, 0.29cubic |
| produced in three general categories - standard | | | | inch, 0.35cubic inch, 0.49 cubic inch and 0.60 cubic |
| engines for general use; racing engines for | | | | inch Quite often the cubic inch is dropped and just |
| competition models; and RC engines for radio | | | | the figures quoted 049, 09, 19, etc.Some |
| controlled aircraft. Standard engines may also be | | | | manufacturers produce additional sizes, e.g. smaller |
| used for radio controlled models fitted with a | | | | than- 0.049 cubic inch for powering tiny models, |
| throttle control or RC carburetor. This applies | | | | and intermediate sizes to cater for a particular |
| particularly to smaller engine sizes. Larger RC | | | | size or type of model, such as 0.40 cubic inch for |
| engines are generally specially designed to produce | | | | RC models. The need for intermediate sizes is |
| maximum power at more moderate revs than | | | | rather more commercial than realistic however. |
| either standard or racing engines.Glow engines | | | | Classification of porting nearly all present day |
| have three particular disadvantages, although | | | | model airplane engine are of similar layout, the |
| these are outweighed by the simplicity of | | | | main differences being in the method of inducting |
| operation and general flexibility of the type. First | | | | the fuel/air mixture into the crankcase and then |
| they need a special type of ignition plug, known as | | | | transferring it to the top of the cylinder. Induction |
| a glow plug, which can burn out and need | | | | is controlled by a rotary valve, either a hole |
| replacement. They also need a battery connected | | | | opening into a hollow section of the crankshaft, or |
| to the plug for starting (and if the battery is 'flat' | | | | a disc with a hole, driven by the crankshaft. In |
| the engine will not start!), and special alcohol-base | | | | either case, sheathe hole in the crankshaft (or |
| fuels which are a little more costly than diesel | | | | disc) comes opposite the end of the carburetor |
| fuels and also attack paints and cellulose dope | | | | tube the intake port is opened and then closed by |
| finishes. For this reason, model aircraft powered | | | | subsequent rotation of the crankshaft. The |
| by glow engines must be finished in fuel proof | | | | circumferential length of this hole determines the |
| dopes, or given a final coat of special fuel proof | | | | intake timing.When induction takes place in front |
| paint.Diesels are self-contained engines that they | | | | of the cylinder (through the crankshaft), the |
| need only a supply of suitable fuel to run. They | | | | layout is known as front rotary (readily |
| are generally heavier and more robust than glow | | | | distinguished by the carburetor, or strictly |
| engines, so they are usually longer lasting. They | | | | speaking, the intake tube) coming in front of the |
| vibrate more and are less responsive to throttle | | | | cylinder. With rear rotary engines the intake tube |
| control than glow engines, so are not generally | | | | attaches directly to the back of the crankcase. |
| recommended for powering radio controlled | | | | Transfer of fuel and air mixture drawn into the |
| models. They cannot rev as fast as a racing glow | | | | crankcase to the top of the cylinder is controlled |
| engine, so are less competitive in this respect. On | | | | by piston movement opening the top of a |
| the other hand they can be excellent power units | | | | transfer port (or ports) formed in the side of the |
| for small and modest: size free fight 'sports' | | | | cylinder. This porting may be conventional, or |
| models and certain types of control-line models. | | | | specially arranged to give a 'boost' to the charge |
| Diesels are produced in a much more restored | | | | to fill the cylinder head in the most effective |
| range of sizes than glow engines. Very small | | | | manner. The latter is a relatively new |
| diesels (smaller than 0.5cc) are difficult (and costly) | | | | development with model airplane engine and is |
| to produce and can prove tricky to start and | | | | known as schnuerle porting. It is now a feature of |
| adjust. At the other end of the scale, diesels | | | | many high performance glow engines.Manolito |
| larger than about 3.5cc generally prove | | | | Montala was a RC model airplane enthusiast and |
| disappointing in performance. Thus diesel | | | | he also have a degree in Aeronautical Engineering. |
| production is virtually limited to a size range from | | | | He is also a CAD Engineer and a webmaster. You |
| 0.5 to 3.5cc with the 1cc and 1.5cc sizes being by | | | | will find many more topics on model airplane |
| far the most popular.Engine sizes - and how they | | | | engine by visiting Model Aeronautics For Dodos. |
| are specified.Engine sizes are specified by | | | | |