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Aviation History
1925
1925 - 0828.PDF
^j * ^ 3 w= ^ ^ ^ DECEMBER 17, 192S THE RICKENBACKER COMMERCIAL AERO ENGINE A New Air-Cooled Radial of American Design DURING the New York Air Races, which were held at MitchelField, New York, last October, a number of aeronautical exhibits were on view in one of the hangars, and one of theseexhibits, which attracted a considerable amount of interest, was the new Rickenbacker commercial aero engine, developedby Capt. Eddie Rickenbacker—one of America's well-known " Aces " in the Great War. This engine has been designed and developed to fill the needfor a simple, light, durable and inexpensive engine for com- mercial aircraft. The engine is a five-cylinder of the air-cooled, radial type,and develops 60 to 80 h.p. It weighs less than 175 lbs., and is under 30 in. in overall diameter. It has less parts thanthe average motor-car engine, and may be repaired by a mechanic of ordinary ability. The cost of construction iscomparatively low, due to the extreme simplicity of the motor. The selection of the air-cooled, radial type for theattainment of the desired features is the result of several years of study of all parts of aircraft engines by Capt.Rickenbacker. In the opinion of Capt. Rickenbacker, although radial The Rickenbacker Commercial Aero Engine : This is an American air-cooled radial developing 60-80 h.p.and weighing about 175 lbs. engines are not new, their development has never progressed very far, and the more conventional, vertical and Vee-types were naturally chosen for military aeroplanes during the war when emergency demanded quick production. The features of the radial type for aeroplanes were, how- ever, appreciated even during the war, as evidenced by the fact that a great deal of work had already been done on developing this type of motor before hostilities ended. This work has continued, but mainly for military purposes, and with but little—in comparison—thought of commercial aviation. Capt. Rickenbacker has developed his new engine on the basis of this past experience, and with the added consideration given to simplicity and durability for practical commercial use. The engine has been tested for six months, and has proved even better than Capt. Rickenbacker, himself, expected. However, he is making no elaborate claims as regards per- formance until it has shown its qualities in the air. It is not expected that this engine will greatly exceed others in its category in regard to power output per cubic inch piston displacement, nor will it be the lightest possible weight for its power output. It will, however, be economical in the consumption of fuel and oil, and will continue to run satis- factorily many hours after a lighter-weight engine of approxi- mately the same horse-power would demand overhauling. The cylinders are cast individually from the best grade of cylinder-iron—the cooling fins of the circumferential type being cast integral. Single inlet and exhaust valves are placed directly in the spherical-shaped combustion head ; their axes being inclined to the axis of the cylinder, so as to obtain the best possible conditions for cooling. Two spark plugs are provided for each cylinder. The valves are operated through push rods by rockers, which are supported on the valve port flanges. The flanges with rocker arms attached may each be removed as a unit. The valve tappet clearances may be adjusted at the outer ends of the duralumin push rods. The crankcase is a simple barrel-shaped aluminium casting which contains a cored passage serving as an inlet manifold. Directly back of each cylinder, there is attached to the crankcase a flange with a pipe leading to the inlet valve of that particular cylinder. The crankcase has one transverse wall containing a boss for supporting the rear crankshaft bearing. To the rear of this wall are the radially- disposed bosses receiving the guides for the cam followers, as well as bosses for the engine support studs, and a studded flange for supporting the gear-case. Forward from the transverse wall are the flanges and openings for attaching the cylinders, besides the carburettor flange and oil-drain con- nection located on the bottom. The crankcase has a large opening in front which is sufficient in size to permit the crankshaft and connecting rods being inserted as a unit. Hence the connecting rods and crankshaft counterweights can be fitted before final assembly with the saving of considerable time. This large opening in front is covered by a plate which carries the ball bearing receiving the propeller thrust. Thus, simplicity and rugged construction is the feature of the crankcase. The crankshaft lias a single throw with a counterweight attached at each side. It is supported on two ball bearings ; the forward bearing, as stated above, carries the thrust of the propeller. The usual taper and key joint for the propeller hub is provided in front, while at the rear is a driving slot receiving the shaft which drives the cam and other units. The crankshaft is simple and light, weighing only slightly over ten pounds. It is, nevertheless, ruggedly designed and made from a suitable drop-forged alloy steel and heat-treated to obtain the best physical properties. The counterweights are securely attached and their use gives almost perfect balance to the rotating and reciprocating parts. The drop-forged duraluminum connecting rods are of the articulated type—that is, for the top or number one cylinder, the rod and cap have full bearing on the crankpin and to these are attached the four linked rods of the other cylinders. The shanks of the rods have the usual H section and the master rod and cap are held together by four bolts which also locate and secure the pins supporting the inner ends of the linked rods. The bearing on the crankpin is of ample proportions and under full pressure lubrication. To begin with, the rods are of light weight and the loads are comparatively low, and since the babbitt is applied directly to the master rod and cap, the heat dissipating qualities of the bearing are oi the best. The pistons are made from permanent mold aluminium alloy castings and provided with cooling ribs underneath the head. There are three rings per piston, the lower one serving as an oil scraper, and the piston pins float in both rods and pistons. The pistons are assembled after the crankshaft with con- necting rods are positioned in the crankcase—thereupon the cylinders can be attached to the crankcase. The aluminium gear case, which is attached to the rear oi the crankcase, supports the cam ring and the oil pump, as well as all gears for driving same. The gear-case may be re- moved and replaced without affecting the valve timing in the least, therefore when the engine has once been timed there need be no fear of getting it out of adjustment during inspection or while making repairs. One of the unique features of this design is the single ring of three cams which operates all ten valves. In this feature alone, the construction has been greatly simplified and cost of production reduced to a marked degree. The timing of the cam may be very easily and quickly effected after the reai cover or breather has been removed. This rear cover sup- 828
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