The cylinders are secured to the side plates of the crank case so that when those side plates are removed, the cylinders are removed with them. The pipes are detachable at their centers; small pipes running to the heads of the cylinders extending into the larger pipes which run to the valve chamber. This arrangement is shown in the end view of the engine. A 17″ propeller is used in connection with this engine.
GASOLINE ENGINES
THE JOPSON 1 H. P. GASOLINE ENGINE FOR MODEL AËROPLANES
During the past few years several attempts have been made, both in this country and abroad, to produce a reliable gasoline engine for model aëroplane work, but mostly without any degree of success. The reason for this inability, no doubt, is due to the scarcity of small working parts sufficiently light and at the same time reliable. The engine described herewith, designed by Mr. W. G. Jopson, a member of the Manchester Aëro Club, England, is one of the few that have been made to work satisfactorily.
The interesting horizontal-opposed Jopson gasoline engine for model aëroplanes. The top photograph shows the half-speed shaft and the arrangement of the valve mechanism. This engine is air cooled, develops 1 h.p. at 1,500 r.p.m., and weighs 7¹⁄₂ lbs., including gasoline tank and propeller. The bottom view shows the engine with propeller in situ. Courtesy Flight.
As the accompanying diagrams [19] and [20] and [photograph] show, the engine is of the four-cycle, horizontal opposed type, having two cast-iron cylinders of 1¹⁄₄″ bore and 1³⁄₈″ stroke. Each cylinder is cast in one piece, and as the engine is air cooled, they are cast with radiating fins. One h.p. is developed at 1500 r.p.m. The total weight of the engine, gasoline tank and propeller is 7¹⁄₂ lbs. In preparing the design of this engine, the designs of similar full-sized aëro engines were followed as far as possible. The pistons are similar to those used on large aëro engines and are fitted with two rings; the crankshaft is turned out of two inch special bar steel, and is carried in two phosphor-bronze bearings. There is no special feature about the connecting rods, these being of the standard type, but very strong and light. To enable the two cylinders to be exactly opposite one another, the connecting-rods are offset in the pistons and are connected to the latter by gudgeonpins. The aluminum crank case is extremely simple, being cylindrical and vertically divided. The inlet valves are automatic, the exhaust valves being mechanically operated; the camshaft is driven from the main shaft by two-to-one gearing.
Diagram 19
Sectional elevation of the 1 h.p. Jopson gasoline engine for models. The disposition of the gasoline tank and wick carburettor is particularly noteworthy. It will be seen that metal journals are provided for the crankshaft, which is turned out of 2-inch bar steel. Courtesy Flight.