Tiziano Bortolai of Italy did this “full house” setup (above left) on an MVVS .61 diesel. He’s had great contest success in Europe flying this engine on the nose of a big Lanzo Bomber. He uses a 16-inch propeller as opposed to the 14-inch propeller normally used on an MVVS 61 for typical R/C flying. This open rocker
slow the engine down; and 3. Restrict or “strangle” the engine air intake. Terry O’Meara had a good deal of contest success in the 1980s with a seven-foot wing span Scram powered by a Cannon .30. He not only had the big plane/small engine com- bo, but he “strangled” the engine by putting a piece of half round wooden dowel in the in- take. The engine was hard to start, but once he got it started, it seemed to run all day on its fuel allotment.
The Cox engines used in Half-A Texaco F/F offered engineering opportunities as well. The 8 cc (big) Cox reed valve tanks were made with venturi diameters ranging from .058 to .092. Cox also made ten differ- ent cylinders for the .049. Competitive en- gines used a tank with a small venturi, a cylinder with a single bypass port, head shims to reduce compression, and the biggest propeller that would turn fast enough to get your airplane off the ground. A Goldberg 3⁄32-inch wheel collar made a per- fect bushing for the 5–40 machine screw used to hold the prop on. A favorite propeller
OS .60 four-stroke (above right) has been converted to ignition for use in the R/C Texaco event. It’s got a Cox .049 needle valve assembly. Dale Tower reportedly got a 20-plus minute motor run using such an OS .60 ignition conversion at this year’s Southwest Regionals at Eloy, Arizona.
for the event was the black Cox 9–2, al- though I’ve seen 10–4s get a ship off the ground. Intake restrictions on larger engines are a field of dreams for backyard engineers. Dave Harding’s Ohlsson .60 used a Cox 15 venturi and spray bar in the intake. It has a very fine taper and click stops. Since there’s a ¼–20 thread at the bottom, Dave machined a series of different sized intake restrictors for the venturi. The OS .60 four-stroke shown in the pictures has a Cox .049 NVA with a .095-inch throat. That throat yields an intake area that’s just 25% of the normal intake area for the engine. Tiziano Bortolai of Italy modified a diesel MVVS .61 (shown in the pictures) with the full packet. He’s got a restricted venturi, a uniflow tank and a 16-inch propeller.
Texaco is a fuel economy event, so of course people will tinker with fuel mixes. Some of the classes require the use of “com- mercially available” glow fuels. Other class- es allow more “creativity”. Spark ignition motors will run on either methanol or gaso-
line based fuels. On a volumetric basis, there’s more energy in either gasoline or kerosene than there is in methanol. You can juggle the gasoline/oil ratio a bit on fuel for a spark ignition engine, but lubrication re- quirements impose some limits. I’m told that Bortolai has as many as four different “diesel fuel” mixes, varying the ether/ kerosene/lubricant mix to suit the atmos- pheric conditions of the contest day. I’m about out of space, and I want to men- tion Hal Cover’s 1911 Peoli Racer. The New York Times reported on rubber powered model airplane contests in Central Park in 1907 and 1908. The contests were scored on the longest straight line distance covered. The Racer is typical of the designs used in such contests. I saw Hal fly the Racer in a twin pusher contest in June. The Racer went up like a rocket, but once the motors were exhausted, the relatively small wing area meant the competition thermalled away, and the Racer returned to ground. Still hors- es for courses—and the Racer would have been a winner in those 1908 contests.
Steve Evans holds his ½A Texaco Free Flight sized Bomber (above left). The 630 square inch Leisure Bomberkit for electric F/F has frequently been used. A collection of Half-A Texaco engines (above center). Left middle is the 5.1 cc R/C ½A Texaco engine. Right middle is a Cox “Texaco” engine with an 8 cc tank. Bottom left is a Sal Taibi high capacity tank for Half-A Texaco. Bottom right is a Big Mig Norvel .049 with a uniflow tank mount. The propellers are all bushed and range from 7–4 to 10–6. For ½A Texaco Hal Cover holds his 1911 PeoliRacer(at right) at a twin pusher contest at Perris in June. It got higher than all the other competition on the motor run, but came down fast.
FLYING MODELS 47
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