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Model Aeroplanes and Their Engines: A Practical Book for Beginners cover

Model Aeroplanes and Their Engines: A Practical Book for Beginners

Chapter 27: COMPRESSED AIR ENGINES
By George Anthony Cavanagh
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About This Book

This practical guide introduces model aeroplane hobbyists to the history, materials, and step-by-step construction techniques needed to build and fly models. It explains propeller design and carving, wing and frame construction, assembly, launching methods, chassis and pontoon fabrication, and includes measured diagrams and photographs. Sections survey powerplants and propulsion — rubber, compressed-air, gasoline, steam, and carbonic gas engines — and offer simple engine plans and performance data. The work also presents notable record models and flight examples, practical advice on forming clubs and competitions, and a concise dictionary of aeronautical terms for beginners.

COMPRESSED AIR ENGINES

THE WISE COMPRESSED AIR ENGINE

Although of peculiar construction, the Wise rotary compressed air engine offers a very interesting design from a viewpoint of ingenuity. This engine embodies a number of novel features not hitherto employed in the construction of compressed air engines, and in view of the fact that the majority of compressed air engines are made on the principle of the opposed type, this engine suggests many possibilities for the rotary type engine.

The engine consists of five cylinders and weighs four ounces, including the propeller and mounting frame. On a pressure of 15 lbs. the engine will revolve at a speed of 1000 r.p.m. The connecting rods are fastened to the crankshaft by means of segments and are held by two rings, making it possible to remove any one piston without disturbing the others. This is done by simply removing a nut and one ring. The crank case is made from seamless brass tubing, into which the cylinders are brazed. The valve cage and cylinder heads are also turned separately and brazed. One ring only is used in connection with the pistons. The cylinders have a bore of ¹¹⁄₃₂″, with a piston stroke of ⁷⁄₁₆″. In view of the fact that pull rods show a greater tendency to overcome centrifugal force, they are used instead of push rods to operate the valves. The crankshaft has but one post, which is uncovered in turn by each inlet pipe as the engine revolves. The “overhang” method is used to mount this engine to the model. With the exception of the valve springs, the entire engine, including the mounting frame and tank, is made of brass.