Fifty years of Fox Engines

Model Airplane News, Nov 1997

After Ray Arden's glow plug was demonstrated with great success at the 1947 nationals, it didn't take modelers long to appreciate its simplicity and reliability when compared to the spark-ignition system. Although some spark-ignition engines ran fine with a glow plug installed, others didn't. Glowplug-equipped engines required methyl-alcohol fuels to operate properly and, because most "sparkers" ran on gasoline, problems developed.

The new plug and fuel caused catastrophic damage to several spark-ignition engine designs, including the industry leader, Ohlsson. Ohlsson engines featured an integral cylinder and head machined of alloy steel. This finned unit was "staked" to the aluminum-alloy crankcase by a unique spot-welding process, which worked satisfactorily with gasoline but not with glow fuel. Occasionally, Ohlsson engines "blew their tops" when running on glow fuel. As a 13-year-old, I had this unnerving experience with an Ohlsson .29 front rotary glow; we found the cylinder over a hundred feet away! The word got around quickly: don't stand in the line of fire when running an Ohlsson on alcohol!

Many sparkers lacked sufficient carburetor spray-bar volume to pass minimum quantities of the new fuel and were undeservedly condemned as unsatisfactory candidates for conversion to glow. Needle-valve assemblies that did have the capacity often frustrated operators with methanol's lack of economy; it required almost three times the fluid volume of gasoline to equal its run time.

The destruction of plastic fuel tanks attached to the rear of most spark-ignition engines was possibly the most galling circumstance of all. As modelers filled these tanks (intended for gasoline) with glow fuel, they watched in horror as the tank became distorted and turned to mush within seconds.

Eventually, engines were designed specifically for glow plugs and alcohol fuel. However, as with any paradigm shift, the modeling public needed an education on how to use the new technology.

About this time ('47), the Claude C. Slate Company of Los Angeles introduced their sleek-looking, lightweight, .60-class engine called the Fox "HiTorque" .59. It had a long, thin crankshaft supported by twin ball bearings, rearrotary disk induction and spark ignition. Like everyone else, its young designer, Duke Fox, was caught off guard by Arden's bombshell, Although the engine performed magnificently, it was produced at the wrong time and turned out to be the wrong size. The sensational glow-plug-inspired "baby engines" were about to be marketed by K&B (Infant .020), Anderson (Baby Spitfire .045) and Herkimer (OK Cub .049). Nevertheless, the modeling press praised Fox for his masterpiece and its companion, the "Hi-Speed," but sales were disappointing during this period of upheaval and change.

Fox, like many others in the industry, was astounded by the astronomical sales generated by these tiny engines. By talking with local modelers and reading the magazines, he carefully analyzed the postwar market. One thing was certain: the trend was toward smaller models that would fit into the family car so the wife and kids could tag along to the flying field. However, rather than try to gain a share of the 1/2A frenzy, Fox decided to explore the middle-size engine market.

After leaving the Slate Company, Fox joined forces with another modeler, forming the Arnold & Fox Engineering Co. and locating their manufacturing facility in North Hollywood, CA. In 1949, the Fox .35 Stunt engine was born. Arguably the most famous and recoanizable engine of all time (with the possible exception of the Cox Baby Bee .049), the Stunt .35 is still produced today, almost 50 years later. Here's what former Model Airplane News engine columnist Peter Chinn had to say about the engine in his June '67 review: "There are other .35's as powerful; however, none are as light or compact ... few perform with such reliability and consistency."

Although dozens of engine designs have been manufactured by Fox over the past five decades, to this columnist the milestones are represented by the following: 1947-Fox "Hi-Torque" .59.

1949-Fox .35 Stunt.

1956-Fox .29R. Known to collectors as "the bathtub intake .29," this control-line speed engine was designed to operate on high percentages of nitromethane above 20,000rpm while producing almost one brake-horsepower-very high for the period. A unique-looking engine, it featured a long, large-diameter crankshaft supported by a single ball bearing at its rear. Manufactured in two versions-a single glow-plug head and a twin-plug unit-it also sported a rear-mounted needle-valve assembly.

1957-Fox .35 Black Head Combat Special. When I replaced my Fox .35 Stunt with the new "black head" Combat Special on my Riley Wooten-designed "Quicker" control-line combat model, I was initially shocked by its unrelenting power. The combination generated speeds in excess of 110mph, and the airplane didn't seem to slow down in maneuvers. Operating on Fox "Missile Mist" fuel (16 percent nitromethane, 8 percent nitroethane, 17 percent castor oil), and crankcase pressure (metal tank), the thing was pure fun-especially when flying against a competitor with similar equipment!