When I started flying powered model airplanes in the 1950’s we only had the ic engine generally available, articles appeared in the model press from time to time in the 1960’s about the use of CO2 engines,
Unfortunately the ic engines had some drawbacks mainly in the fact that they were noisy, there were no mufflers for them in those days and as control line flying was in full swing a lot of noise complaints started to come in which caused the loss of several flight sites. Manufacturers began to produce mufflers for many of the larger engines, and there were attempts to produce the first electric aircraft. The drawback was that these proved very heavy due to the batteries, the size of the motor and the radio equipment at the time.
Some CO2 engines had started to appear in the UK by this time, Bill Brown in the US had built his first CO2 engine which ran in 1942, plus The American Brown, the English Shark, Telco and the model Czech, they were available, and until the early 90’s that’s how things stayed,
Stefan Gasparin enters. Until the first ‘Interscale’ in Nottingham in 1991 this name was known only to a few people outside of the model fraternity in then Czechoslovakia for whom Stefan built very few tiny engines for friends of his.
The advent of the Velvet revolution allowed him to consider selling his engines to the West and with this in mind he teamed up with a small company making instruments for full size aircraft (mostly Russian, this company at the time was suffering from a sudden drop in orders) the idea is for the factory to mass-produce a new engine design for it.
At Interscale, the editor of the Czech model magazine, Otakar Saffek, also an FAI international judge, showed the Gasparin engines to a stunned group of modellers who couldn’t believe that a model aircraft could only fit into a tobacco tin. 2 ounces, while still having a working motor installed in it that actually worked.
Therefore, today there is an opportunity to build a wide variety of competition, sport, small-scale and light aircraft models, whether for free flight or RC, indoors and outdoors. You say it. A safe, clean and satisfying way to fly. The power produced for its size is amazing.
A word on how they work. The CO2 and the steam engine work on the same principle. They are engines of expansion. The main difference, the fuel. The CO2 engine uses gas generated from liquid CO2, rather than steam. High-pressure gas vapor is fed through a small tube from the tank into a chamber with a ball and valve seat in the cylinder head. When the piston, which has a centered post at the top, pushes the ball off the seat (at top dead center), the gas rushes in and pushes the piston down. Gas escapes through the ports as the crankshaft rotates toward bottom dead center. When the piston goes back up, the cycle is complete. The motor will run in either direction.
The information presented here is quite general and is intended to help newcomers to CO2 eliminate some problems that can arise from not following some important procedures. By following these procedures, you will get great satisfaction and fun.
Motor maintenance: when it is necessary to open the motor to clean dirt or foreign matter from a bad landing, replace a damaged seal, etc. etc. NEVER use pliers or any type of wrench.
Lubrication: It is very important to keep your little jewel well oiled. For lubrication procedure, see mfg. instructions. Every six or eight flights you should do it. A small amount with a needle oiler will do. Don’t go overboard with the oil. Additional oil will not damage the engine, but repeated application will damage the aircraft.
Chargers for C02 Engines.
There are currently 5 types of charger available.
In the UK we generally use just 2. The simple ‘spartlet’ type using the 8g bulb used to make soda water is cheap to buy but can be very expensive to run, a box of 10 bulbs only contains 80 g of gas, and anyway, for larger engines, small fills are impractical as the tank has a larger capacity than the bulb that fills it. In this case the cheapest way to charge the engine is to use the bulk adapter which fits a ‘Sodastream’ cylinder. These are usually available in some form around the world, but if you are using a non-Sodastream cylinder, make sure the pressure release valve is on the side of the cylinder and is NOT built into the main valve.
In countries where ‘Sodastream’ cylinders are not available, it is often possible to obtain 12g bulbs, usually used in airguns. To use this size of bulb, you will need to use the Gasparin deluxe charger, which accepts 8 or 12g bulbs.
In the UK the ‘Sodastream’ cylinder can be obtained from Boots, Tesco etc, you only need to buy the cylinder once, thereafter return the empty and exchange for a full one for less than the cost of a box of bulbs Each cylinder contains 250 gms of gas and can last for years. Installation of C02 engines is quite simple, the tube from the engine to the tank can be gently bent to almost any shape required, in the case of the Gasparin tube it can be wrapped around a pencil to remove any slack. desired. The only rule to keep in mind is that the tank should not be mounted more than 45° from vertical. It makes no difference to the motor which way it is installed.
The filling of the tank can be done in two ways. With the engine filler nozzle down and the charger nozzle up, a ‘gas’ charge is made, this is used for trim and flight testing and also in very high humidity conditions. This is to prevent the gas from burning too quickly which can lead to freezing of the engine cylinder and therefore very poor performance.
The other form of cargo is a ‘liquid’ cargo. This is with the magazine down and the engine fill nozzle up. Liquid gas is drawn into the tank and takes longer to burn than a gas charge, resulting in the engine running much longer. Beware! It is possible that if the piston pin is lifting the ball in the overhead valve at the time of loading, that liquid gas could enter the cylinder. If this happens and the propeller turns, the result is a ruined piston ring that will have been frozen into the cylinder wall by the sub-zero gas. Always make sure the piston is not at the top of its travel before filling the tank.
If you get unlucky and freeze up the ring, it’s very easy to change, just unscrew the entire cylinder, lock ring and all, and lift it off the piston. You will see the ring at the top of the piston, take it out and put a new one on, don’t forget to put some C02 lube on the ring before carefully refitting the cylinder, remember to loosen the locking ring before refitting the cylinder , place a charge of gas in the tank and screw the cylinder down moving the strut between turns until the correct speed is established, then lock with the lock ring. Simple really! TARGET! If you’re trying to put a ring on one of the smaller engines, G24 down, I recommend wearing jeweler’s glasses so you can see what you’re doing!
C02 engines are now reliable and relatively inexpensive to purchase. They look good in a model that should have a motor and above all, although they are practically silent, the noise they make is more realistic and will not offend neighbors or the public when in use.
Engine speed adjustment: RPM can be changed by turning the cylinder. Loosen lock nut, turn cylinder clockwise RPM increases. RPM is reduced counterclockwise.
Selecting the motor size for your model: See mfg. operating instructions. However, it is advisable to install a slightly larger motor with lower throttle than a smaller motor that must run wide open to get the desired performance.
Mounting the tank on the model: Position the tank at the center of balance, or slightly forward. The weight of the tank varies with the amount of liquid and if it is too far from the center of balance, it can change the seat of the aircraft in flight.
Model Weight: Lightweight Construction Keep the wing load down. Lightweight models, especially scale ones, look better when they fly slower.
Good luck and happy landings