fly with CO2

When I started flying model powered 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 at its peak many complaints about noise began to surface leading to 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.

Some CO2 engines had started to appear in the UK by this time, Bill Brown in the US had built his first working CO2 engine in 1942, plus The American Brown, the English Shark, Telco and the Czech model, they became available, and until the early 90’s that’s how things stayed.

Enter Stefan Gasparin. Until the first ‘Interscale’ in Nottingham in 1991, this name was known to only a very few people outside of the model fraternity in then-Czechoslovakia for whom Stefan built very few tiny engines for his friends.

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 that made instruments for full-size aircraft (mostly Russian, this company at the time was suffering a sudden drop in orders) with the idea of ​​having the factory mass-produce a new engine design for him.

At Interscale, the editor of the Czech modeling magazine, Otakar Saffek, also an FAI international judge, demonstrated the Gasparin engines to a stunned group of modelers who couldn’t believe that a model airplane could fit in a 2-ounce tobacco tin, let alone have a working engine 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 staggering.

A word on how they work. 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, instead of steam. High pressure gas vapor is fed through a small tube from the tank to a chamber with a ball and seat valve in the cylinder head. When the piston, which has a top centered post, pushes the ball off the seat (at top dead center), gas rushes in and pushes the piston down. Gas escapes through the ports as the crankshaft rotates to bottom dead center. When the piston moves 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 to eliminate some problems that can arise from not following some important procedures. By following these procedures, you will get great satisfaction and fun.

Engine Maintenance: When it is necessary to open the engine to clean dirt or foreign matter from a bad landing, replace a damaged seal, etc., assemble the parts with fingers, lock nut, cylinder head, tank cap, nozzle, etc. NEVER use pliers or any type of wrench.

Lubrication: It is very important to keep your little jewel well-oiled. For the lubrication procedure, see mfg. instructions. Every six or eight flights should do it. A small amount with a needle oiler will do. Don’t overdo it with the oil. Additional oil will not harm the engine but if applied repeatedly it 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 sparkling water is cheap to buy but can be very expensive to maintain, a box of 10 bulbs only holds 80g of gas and for larger engines anyway small fills are impractical as the tank has a larger capacity than the bulb filling it. In this case the cheapest way to load the engine is to use the bulk adapter which fits a ‘Sodastream’ cylinder. They 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 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, it will be necessary to use the Gasparin deluxe charger, which accepts 8 or 12 g 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 one and exchange for a full one for less than the cost of a box of light 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 eliminate unwanted slack. The only rule to keep in mind is that the tank should not be mounted more than 45° from the vertical. It makes no difference to the motor which way it is installed.

Filling the tank can be done in two ways. With the engine filler nozzle pointing down and the magazine nozzle pointing up, a ‘gas’ charge is made, which is used for trim and flight tests and also, in very high humidity conditions. This is to prevent the gas from burning too quickly, which can lead to engine cylinder freezing and therefore very poor performance.

The other form of charge is a ‘liquid’ charge. This is with the magazine down and the engine filler nozzle up. Liquid gas is drawn into the tank and takes longer to burn than a gas charge, resulting in a much longer engine run. Beware! It is possible that if the piston pin is lifting the ball in the poppet at the time of charging, that liquefied gas could enter the cylinder. If this happens and the prop spins, the result is a blown piston ring that will have been frozen to the cylinder wall by subzero gas. Always make sure the piston is not at the top of its stroke before filling the tank.

If you’re unlucky and the ring freezes, it’s very simple to change, just unbolt the entire cylinder, lock ring and all, and lift it off the piston. You will see the ring on top of the piston, take it out and fit a new one, don’t forget to put some C02 lubricant on the ring before carefully refitting the cylinder, remember to loosen the lock ring before refitting the cylinder, put a charge of gas in the tank and screw the cylinder down moving the prop between turns until the correct speed is established, then lock with the lock ring. Simple really! AIM! If you’re trying to put a ring on one of the smaller motors, 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 on a model that should have a motor, and most of all, while they’re virtually silent, the noise they make is more realistic and won’t offend neighbors or the public when in use.

Engine speed adjustment: RPM can be changed by turning the cylinder. Loosen locknut, 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 engine with lower throttle than a smaller engine 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, you can change the seat of the aircraft in flight.

Model Weight: Light Construction. Keep wing loading down. Light models, especially at scale, look better when they fly slower.

Good luck and happy landings.