Model Airplane Club, California, USA
Model Airplane Club, California, USA


Flying with CO2
by Otto Kuhni

With such a wonderful selection of these small (some even tiny) engines made possible by Stefan Gasparin and available through the Blacksheep, there is an opportunity to build quite a variety of small, light scale, sport, competition model aircraft, either for free flight or RC, indoor & outdoor.  You name it.  A safe, clean, and satisfying way to fly.  The power produced for their size is astonishing.

A word about how they work.  The CO2 and steam engine work on the same principal.  They are expansion engines.  The main difference, the fuel.  The CO2 engine uses gas generated from liquid CO2, as opposed to steam.  The gas vapor under high pressure is fed through a small tube from the tank to a chamber with a ball and valve seat in the cylinder head.  When the piston, which has a post centered on top, pushes the ball out of the seat (at top dead center), gas rushes in, pushing the piston down.  The gas exhausts through ports as the crankshaft swings around toward bottom dead center.  As the piston comes back up, the cycle is complete.  The engine will run either direction.

The information presented here is quite general and is intended to help the newcomer to CO2 eliminate some problems that can arise from not following a few important procedures.  By following these procedures a great deal of satisfaction and good old fun will be yours.

For advanced modelers wishing technical information, performance, charging techniques, temperatures, pressures, propellers, etc., one should read the excellent articles Fritz Muller has written on the subject.  Reprints can be obtained from Cloud 9, 4326 Andes Dr., Farifax, VA 22030.  Also follow the instructions supplied with the engines.

Servicing the engine:  When there is a need to “open” your engine to clean out dirt or foreign matter from a bad landing, replace a damaged seal, etc.,  assemble parts just finger tight, lock nut, cylinder head, tank lid, nozzle, etc.  NEVER use pliers or any kind of wrench.

Lubrication:  It’s very important to keep your little gem well oiled.  For the oiling procedure, see mfg. instructions.  Every six or eight flights should do it.  A small amount with a needle oiler will do.  Don’t over oil.  Extra oil won’t hurt the  engine but will, if done repeatedly, mess up your aircraft.

Chargers:  There are many kinds of chargers available to suit your needs.  Eight and twelve gram soda chargers, and larger tanks fitted with a valve and nozzle.  Information and parts are available from the Blacksheep.

Charging:  For a long engine run, and as a result, longer flights:  Getting  as much liquid CO2 into the onboard tank is desirable (as the liquid continues to produce gas).  To achieve this, hold the filler nozzle on the aircraft so the nozzle on the charger is pointing down.  For a shorter engine run, and shorter flights, hold so the charger nozzle is up.  Do not charge with piston at top dead center.  You can damage the piston ring.  RE:  mfg. operating instructions.

Engine speed adjustment:  RPM can be changed by rotating cylinder.  Loosen locknut, turn cylinder clockwise RPM is increased.  Counter clockwise RPM is decreased.

Selecting engine size for your model:  Refer to mfg. operating instructions.  However, it is wise to install a slightly larger engine throttled down than a smaller engine that has to be run wide open for desired performance.

Mounting tank in model:  Locate the tank on the center of balance, or slightly forward.  The weight of tank varies with the amount of liquid and if too far from the center of balance it can change the trim of aircraft in flight.

Model weight:  Build light.  Keep wing loading down.  Light models, especially scale, look better as they fly slower.

Finally it should be noted that one of the earliest pioneers of small CO2 engines for small aircraft is Bill Brown with the Campus A-100.  That was back in the 1940’s.  What he contributed over the ensuing years is immeasurable.  In addition to the number of engine types Brown made, there were also the OK’s, Telcos, Sharks, Modellas, etc. all contributing in their own right.  And now, Stefan Gasparin.  His engines are the current state of the art.  One wonders how this simple concept can keep improving so much.  Thank you Stefan, our hats are off!

Happy flying and watch those thermals.
We hate to lose these little jewels.

Mounting CO2 engines in your airplane
by Roy Hanson

In the U.S.A, small bolts, screws, dies and taps are available from:
     Micro Fasteners
     110 Hillcrest Road
     Flemington, N.J. 08822
     Phone: 908-806-4050
You will find 00-90, 0-80, and 1-72 sizes most convenient for fastening the CO2 engine to your firewall.
The firewall should be at 90o to the airplane's Horizontal Centerline, in all directions.
A loose 1/64" plywood plate, with nuts epoxed in place, will hold your nuts.
Use lots of epoxy to secure the nuts, and tap through when the epoxy is thoroughly cured.
A good starting point is 6o right thrust, 3odown.

24 hour message machine:
(818 ) 718-1685
Roy E. Hanson Jr.
21410 Nashville Street
Chatsworth, CA 91311