April 1957 American ModelerTable of Contents
Some things never grow old. These pages from vintage modeling magazines like American Aircraft Modeler, American Modeler, Air Trails, Flying Aces, Flying Models, Model Airplane News, & Young Men captured the era. I will be glad to scan articles for you. All copyrights are hereby acknowledged.
Babe Bee: New Member of the Cox Family
Back in the early 30's when the silence of rubber powered model flying was first shattered by the roar of the model gas engine, more flyers dreamed of owning one of these noisy monsters than could actually afford the cost. For $21.50 was a lot of money in those days and that was the cost of the engine alone.
To get the engine running you still needed an ignition system consisting of a coil, condenser and batteries, which meant an additional $5.00: Propellers weren't cheap either and they broke just as easily then as now.
Construction of a gas model became a club project with members chipping in to pay for the engine and the cost of building the model. And speaking of models, 9 and 12 foot jobs were not considered too large!
By comparison, today's model builder profiting by. the advancement of mass production methods and keen competition among engine manufacturers can own the newest member of the amazing Cox family of engines for less than the price of the outmoded ignition system alone.
The Babe Bee, one of the lowest priced model engines available today, is the result of the mass production skill of its manufacturer, L. M. Cox Mfg. Co. of Santa Ana, California.
Mass production can usually lower the cost of machining a complicated piece of equipment but simplification of design and the reduction of the number of parts necessary to do a specific job is frequently more practical.
The Babe Bee is the first engine in the Cox series with a simplification of the original induction reed design. Basic design of major components follows the Space Bug Jr. but with some modifications. which great1y change outward appearance. Aluminum crankcase although less fancy is stronger than those previously used. It is also approximately 1/8" shorter to the propeller. Fuel tank is machined from aluminum.
Forward portion of the tank forms the crankcase backplate and also houses the induction valve. This valve consists of a single extremely thin piece of flexible bronze actuated by crankcase compression. It is held in place by a steel wire snap ring which also limits its amount of travel. The rear of the tank is an aluminum casting which includes the needle valve assembly and the radial mounting lugs.
The needle valve has been moved to the top of the tank where it is exceptionally easy to get to. Air intake tube still located through the center of the tank has been redesigned to save drilling a hole through the motor mount to allow air to reach the needle valve. With the motor mounted flush to its mounting surface air can reach the needle valve via a recessed slot cast into the rear surface of the tank assembly.
The steel crankshaft is hardened and ground to a smooth finish. By relieving the center of the shaft, friction due to oil drag is kept to a minimum. Instead of the one piece crankshaft used in previous Cox engines, the Babe Bee's is internally threaded at its forward end to receive a propeller screw. This feature has been proven on many other engines to practically eliminate bent crankshafts even under the most severe crash conditions.
The steel cylinder employs the same porting design as used on the Space, Bug Jr. - a single transfer port located between the two exhaust ports. Cylinder head and glow plug unit is standard Cox design as is the design of the hardened and ground piston and its ban and socket type aluminum connecting rod.
Engine purchased for tests bears out the manufacturers claims that no break-in period is required.
Using a 5-1/2" dia. 2-1/2" pitch plastic propeller our test engine started with the very first flip and reached maximum rpm of 16,000 on the first tank of Thimble Drone fuel. No needle valve float was encountered anytime during test period; quick starts were consistent whether the engine was hot or cold.
Due to the type of fuel induction used, the Babe Bee will run in either clockwise or counter clockwise rotation. This can be an advantage as it allows the experimenter to design pusher-type models or counter-rotating multi-engined models.
Best starting method for this type engine consists of a good prime ' directly into the exhaust ports and a real snappy flip in the direction .of rotation you de-sire. It was found that a half-hearted flip resulted in starts -in the opposite direction. If you should encounter opposite starting difficulties try flipping the propeller opposite to the correct direction of rotation. We tried this idea out several times during the test and it worked perfectly.
Other Cox / Thimble-Drome Articles:
Posted January 17, 2013