April 1969 American Aircraft Modeler
[Table of Contents]
Aeromodeling has seen significant changes over the decades both in technology and preferences. Magazines
like American Aircraft Modeler,
American Modeler, and
Air Trails were the best venues for capturing snapshots of the
status quo of the day. All copyrights are hereby acknowledged.
the authors of this article had a crystal ball to see into the future,
they would have been disappointed to learn that their prediction for
a resurgence of CO2-powered model aircraft was not going to come true.
Today it is difficult to get a CO2 engine other than to buy a used one
See the "Fizz-Wizz
article from the March 1962 American Modeler
and the "Push-Air
" article from the February 1970 American
. Here is a link to my
CO2 Power is Coming
Return of once popular CO2 flying brings improved and lighter engines
and all-new compressed-gas jet- here used on the Micro-Jet Delta.
Howard Mc Entee and Bill Brown Jr.
This is an old 005 engine modified by McEntee for convenient
top-of-cylinder refilling. New engine not yet in production.
OLD-TIMERS who remember the late 1940's will recall the interest in
CO2-powered (CO2 in this article means carbon dioxide) model planes,
for sport flying and competition (there was at least one AMA class).
These remarkable powerplants were developed by Bill Brown Jr., already
famed for the development of the Brown Junior gas engine (that's gas,
not glow!) which revolutionized model aviation, and brought on the continuing
development of tiny model glow engines which have reached such perfection
Never one to rest on his laurels, Bill then dabbled with
CO2 power. In the post-war 1940's he perfected three sizes of these
engines. One was a rather large job (relative to his others), which
turned an 8" prop with lots of power. It used an entire Sparklet CO2
cartridge for each flight. These cartridges were used then, as they
are now, for specially equipped bottles that turned plain tap water
into "soda water" for drink mixing. This engine had a displacement of
.018 cu. in. Really interested in much smaller units, Bill sold all
rights to the big engine to Herkimer Tool & Model Works, who marketed
the engine under their "OK" label as late as the early '60's.
Larger engine, an 018 Herkimer OK, is shown with the 005 mill
and its light-weight aluminum supply tank. Note aspirin tablet!
Next came Bill's favorite - the tiny A-100. The complete powerplant,
less prop, weighed about ¼ oz. A low-pitch 4"-dia. prop was recommended.
It flew planes ranging from 1-2 feet span, which weighed about 1½ oz.
maximum. It was flown very successfully in tiny all-balsa scale planes
of 12" or so. The displacement was only .0015 cu. in.! The final engine
in the series was the "B," with a displacement of .005 cu. in. and total
plant weight (including tank but less prop) of about .65 oz., for planes
up to 30" span. Production on both of the smaller engines ceased around
Those of us who were active with CO2 had a high regard
for Bill Brown's developments, but we (and Bill, too) freely conceded
that some detail improvements were needed. Tank filling was a bit unhandy.
You screwed the cartridge holder into a valve in the tank, a simple
but fussy operation. The A-I00 crankshaft bearings wore rapidly. Some
of us put in brass bushings - but this thinned the crankcase nose so
that it broke easily. Basically, the plants worked fine, and the incentive
for improvement came when the late Jim Walker became interested in them.
With such backing, Brown developed a much simpler, faster and more
convenient filling system. The tank is fueled through a tiny nipple
on the engine cylinder head. Crankshaft bearings were greatly improved
and the case beefed up considerably. A much better valve material was
found for the engine. CO2 gas is admitted to the cylinder through a
tiny ball valve. Great things were looked for with the improved design
but Jim's death brought a halt to CO2 progress.
Over the years,
Bill Brown Jr. has run his machine-tool business in central Pennsylvania
for a living- but continued to dream of marketing better CO2 powerplant.
We're happy to report that such marketing may not be too far off. Bill
has refined designs for three engines, with .001, .005 and .02 cu. in.
Jet is easily filled through outlet nozzle using CO2 cartridge
and holder - which has pressure fitting. This fitting also is
the launch-release device. Thrust nozzle adjustable for power
output and duration. Delta is exciting fun job. Jet can be mounted
in dime-store, 29c gliders.
There is also a tiny jet engine. Due to its relative simplicity, it
doubtless will be marketed first. However, all components of this plant
will be worked into the piston powerplant to come later. We show here
with a little delta profile jet plane Bill has been flying. Thrust doesn't
last long-about 5 seconds (replaceable nozzles with different-sized
orifices will be offered for varying thrust)-but the plane gets high
enough for a fine glide.
Brown has chosen the middle-sized .005
engine as his first piston job of the new series to be marketed, but
its difference from the old "B" is amazing. About the only similarity
is the .005 cu. in. displacement. The plant will weigh little more than
the old A-100, and the engine itself isn't much bigger than the A-100
engine (which was only about 7/8" from top to bottom) . This engine
will be marketed with the same tank used for the jet engine (larger
or smaller tanks may be used, however). The jet engine itself (with
proper nozzle to act as a filler valve) may be employed to "gas up"
the piston plant, if you want to bury the engine in an inaccessible
spot - inside a scale plane cowling, for example.
While the .005
and .02 engines offer ample power to fly outdoor F IF models of all
types, the .001 job sounds ideal for the tiniest indoor designs! All
the engines can be adjusted easily for thrust. Thus, the .005 should
do fine indoors. Furthermore, with the very tiny and light gear we have
today - it sounds like a natural for indoor R/C flying. Just think of
the possibilities: No smoke, no smell, very little noise, no fire hazard,
instant starting every time, low fuel cost (we used to get up to six
flights from a single Sparklet cartridge). Larger cartridges that are
refillable reduce even this cost, allow many dozens of flights before
refilling. You can even recharge these larger cartridges yourself, from
the CO2 fire extinguishers and tire inflators sold in some garages (and
these too are rechargeable for a nominal fee).
We wish to emphasize
that these CO2 power units are not on the market yet - so don't write
and. ask where you can get them. We don't know where - or exactly when.
But it appears that Bill Brown Jr.'s long wait to market perfected tiny
CO2 powerplants is about to end. You can be sure we'll keep you posted
as to when he has something ready to sell. It shouldn't be long now!
Micro-Jet Delta: Full-sized plans for this tiny speedster aren't necessary.
Just use the dimensions noted on our reduced plan. Be sure to use the
lightest 3"-wide Contest balsa throughout. You can fudge a tiny bit
when laying out the wing, even though when scaled to full-size, our
plans show that 3½" wide sheet is required for the rear portion of the
wing. Cement the three sections of wing sheet together first on a flat
surface, then slip the sanded assembly into the fuselage slot and cement
firmly. Note there is a slight curvature in the wing; the center (at
about the CG point) is 1/8" lower than the leading and trailing edges.
Bill just drew a radius for a very large circle for the wing section.
You can probably eyeball this. The exact curve isn't vital, just as
long as there is 3/32" to 1/8" difference, as noted.
The tank must be cemented firmly in place. Feed tube to the jet
engine is shown going into the fuselage slot, but could just as well
be under the wing. It is vital to have the jet nozzle pointed correctly.
This might require adjustment. The jet unit must be cemented to the
fuselage firmly, since the entire plane is supported by the jet nozzle,
when you are charging the tank.
The "Load-N-Launch" filler holds
the CO2 cartridge, and has what appears to be a small knurled "chuck"
at the forward end. The knurled portion is turned until the filler is
a snug, but not tight, fit on the jet nozzle. Once this adjustment is
made, you will not have to repeat it. The filler can be slipped on and
off the nozzle with light pressure.
The special filler for the
jet engine has a further sliding tip that fits over the chuck end. After
you have charged the tank in the plane, you point the whole works up
at a moderate angle, holding the filler with one hand, the sliding tip
piece with the other. The plane is supported entirely by the jet nozzle
fit in the filler chuck. Now push the sliding tip piece smartly forward.
This disengages the jet nozzle from the filler chuck, and gives the
little jet a launching shove, whereupon the CO2 takes over to provide
No finish is needed on the plane. Remember,
there is no oil or dirty fuel involved. Keep it light for the best results.
Note that as this is written we do not have information on exactly when
the jet units will be marketed, or what the price will be. But when
they reach the hobby shops, you can be all ready to fly one with this
simple delta. Bill Brown has found it to be a fine flier, and you should