DeveLoPMentS ContInue in CO2 power! Stefan
Gasparin has just released a “universal throttle” control, which
works with any CO2 motor (except for the very smallest, such as
the Brown A-23).
With this universal throttle, someone with an original 1947
OK CO2 motor could use it (equipped with a modern refillable
CO2 tank) to power an Old-Timer CO2 Free Flight (FF) model in
“RC Assist mode.”
This throttle control (available from the Blacksheep model club,
21410 Nashville St., Chatsworth CA 91311; Tel.: [818] 718-1685) is
somewhat expensive, but the drawing shows its intricate
construction. Considering it weighs only 2.5 grams (the same as a
dime), I can understand the reason for its price.
This new throttle offers more than just servo-controllable CO2
motor speed. Since it’s mounted away from the motor itself (the rear
of the “frost wall” makes a convenient location), that simplifies and
lightens the servo pushrod installation.
It also makes motor thrustline adjustment a bit less
bothersome than it would be with the throttle mounted directly
on the motor head.
Another advantage of the new Gasparin CO2 throttle is its added
“heat transfer” area.
Remember that CO2 motors produce their power from expansion
of the gas flowing through it—not mere pressure. We want the tank
itself to remain cool, to keep its CO2 contents liquid as much as
possible. After the gas leaves the tank, warming it helps boost power
output and duration.
That’s one reason for the apparently longer-than-necessary
metal tubing between the tank and the motor head. Airflow
past that warms the CO2 passing through it, and the new
Gasparin throttle will help add even more “ambient heat” to
the gas flow.
Speaking of keeping the CO2 tank cool in the model, in CO2-
powered FF contest events in Europe it’s long been standard
practice to chill the tanks.
For a while, competitors were using “freezing fluid” (available
from Radio Shack, for those interested in trying this technique) to
lower the CO2 tank temperature in their models as much as 60°
(F) below zero!
The idea was to maximize the amount of liquid CO2 transferred
to the tank during the “charging” operation.
Joe Wagner
T h e E n g i n e S h o p
927 Pine Ave., Ozark AL 36360
Gasparin 28BBRV, 12-gram Powerlet charge adapter. Tiny (.0018)
motor has throttle (bent wire behind head), dual ball bearings!
This new O.S. .60 FP glow engine features a long-stroke design,
rear-mounted needle valve, and a rugged, quiet muffler.
Gasparin G300BBRV (.018) motor with paintball gun Bulk CO2 Tank.
Charging adapter is below motor tank’s recharging connector.
This cross-section of the Gasparin Universal CO2 Throttle shows
the intricacy of this 21⁄2-gram device.
84 M ODEL AVIATION
May 2001 85
However, that practice was outlawed for competition, and
now CO2 tank prechilling is limited to the use of ice water. I
don’t see much need for such technique in sport flying, except in
hot weather.
The new high-efficiency Gasparin motors run for three to eight
minutes (depending on the type). If anyone needs longer running
time, it’s easy to replace the stock Gasparin CO2 tank with a larger
one (also available from the Blacksheep club), which come in 5, 13,
16, and 25cc sizes.
The stock tank for the G300BBRV motor is 13cc. That’s
enough for spinning a seven-inch high-pitch prop at roughly
3,000 rpm for nearly six minutes. A 25cc tank would almost
double that duration.
New developments have also taken place in refilling CO2 model
tanks. For the smallest-size motors, a new all-metal charging adapter
that uses the easily attainable 12-gram Powerlets provides a pocketsize
CO2 supply for small sport FF airplanes.
Earlier molded-plastic devices of this type were
troublesome; the new one (also available from the Blacksheep)
should last a lifetime.
For the large-capacity model tanks, recharging from 12-
gram CO2 capsules is neither economical nor efficient.
Paintball gun tanks are a much better choice. A good mailorder
source for these tanks is piratepaintball.com, which
advertises free shipping. (It also has a toll-free telephone order
number: [866] 777-5287.)
Piratepaintball also sells Universal Fill Adapters for the gun
tanks. These provide safety, convenient mounting for the adapter
required for recharging model airplane CO2 tanks, and essentially
leak-free bulk CO2 storage between flying sessions.
(Typical prices [January 2001] are $13 for the Universal Fill
Adapter and $20-$30 for the “bulk tanks,” depending on size.)
have you noticed my use of the word “motor” when referring to
CO2 and compressed-air model power plants?
That’s because as with electric motors, their power comes
from an “external storage supply.” In contrast, model airplane
engines develop their power by “internal combustion.”
Yet the terminology isn’t quite that rigid. Since early in the
last century, “motor” has been commonly used with reference
to “gasoline engines.” Think of motor oil, motorcycle, General
Motors, Department of Motor Vehicles, outboard motors, and
motorists.
The old-time Air Corps sergeants who chewed out rookies for
calling a Flying Fortress a “four-motored bomber,” snarling,
“This airplane has 67 ‘motors,’ but only four engines, you
knuckleheads!” were merely showing off their authority, not
conveying eternal truth.
There have also been interesting recent developments in the
model engine area. Enya has announced its re-entry into the realm
The first commercially sold model airplane engine mufflers.
Designed for use on Control Line .60s, they weren’t popular.
