The connecting rods are of “H” section, machined all over from forgings of a special air-hardening chrome nickel steel which, after being heat treated has a tensile strength of 280,000 pounds per square inch. They are consequently very strong and yet unusually light, and being machined all over are of absolutely uniform section, which gives as nearly perfect balance as can be obtained. The big ends are lined with white metal and the small ends are bushed with phosphor bronze. The connecting rods are all alike and take their bearings side by side on the crank-pin, the cylinders being offset to permit of this arrangement. The crank-shaft is machined from the highest grade chrome nickel steel, heat treated in order to obtain the best properties of this material. It is 21⁄4 inches in diameter (57 mm.) and bored hollow throughout, insuring maximum strength with minimum weight. It is carried in three large, bronze-backed white metal bearings. A new method of producing these bearings insures a perfect bond between the two metals and eliminates breakage.
The base is cast from an aluminum alloy. Great strength and rigidity is combined with light weight. The sides extend considerably below the center line of the crank-shaft, providing an extremely deep section. At all highly stressed points, deep ribs are provided to distribute the load evenly and eliminate bending. The lower half of the base is of cast aluminum alloy of extreme lightness. This collects the lubricating oil and acts as a small reservoir for same. An oil-filtering screen of large area covers the entire surface of the sump. The propeller shaft is carried on two large annular ball bearings driven from the crank-shaft by hardened chrome nickel steel spur gears. These gears are contained within an oil-tight casing integral with the base on the opposite end from the timing gears. A ball-thrust bearing is provided on the propeller shaft to take the thrust of a propeller or tractor, as the case may be. In case of the direct drive a stub shaft is fastened direct to the crank-shaft and is fitted with a double thrust bearing.
The cam-shaft is contained within the upper half of the base between the two groups of cylinders, and is supported in six bronze bearings. It is bored hollow throughout and the cams are formed integral with the shaft and ground to the proper shape and finish. An important development in the shape of cams has resulted in a maintained increase of power at high speeds. The gears operating the cam-shaft, magneto, oil and water pumps are contained within an oil-tight casing and operate in a bath of oil.
Lubrication is of the complete forced circulating system, the oil being supplied to every bearing under high pressure by a rotary pump of large capacity. This is operated by gears from the crank-shaft. The oil passages from the pump to the main bearings are cast integral with the base, the hollow crank-shaft forming a passage through the connecting rod bearings and the hollow cam-shaft distributing the oil to the cam-shaft bearings. The entire surface of the lower half of the base is covered with a fine mesh screen through which the oil passes before reaching the pump. Approximately one gallon of oil is contained within the base and this is continually circulated through an external tank by a secondary pump operated by an eccentric on the cam-shaft. This also draws fresh oil from the external tank which can be made of any desired capacity.
SPECIFICATIONS—MODEL 5A TYPE 8
- Horse-power rating, 140 at 2,000 R. P. M.
- Bore, 4 inches = 102 mm.
- Stroke, 51⁄2 inches = 140 mm.
- Number of cylinders, 8.
- Arrangement of cylinders, “V.”
- Cooling, water. Circulation by centrifugal pump.
- Cycle, four stroke.
- Ignition (double), 2 Bosch or Splitdorf magnetos.
- Carburetor, Zenith duplex. Water jacket manifold.
- Oiling system, complete forced. Circulating gear pump.
- Normal crank-shaft speed, 2,000 R. P. M.
- Propeller shaft, 3⁄5 crank-shaft speed at normal, 1,200 R. P. M.
- Stated power at 30′′ barometer, 140 B. H. P.
- Stated weight with all accessories but without water, gasoline or oil, 514 pounds = 234 kilos.
- Weight per B. H. P., 3.7 pounds = 1.68 kilos.
- Stated weight with all accessories with water, 550 pounds = 250 kilos.
- Weight per B. H. P. with water, 3.95 pounds = 1.79 kilos.
THE CURTISS AVIATION MOTORS
The Curtiss OX motor has eight cylinders, 4-inch bore, 5-inch stroke, delivers 90 horse-power at 1,400 turns, and the weight turns out at 4.17 pounds per horse-power. This motor has cast iron cylinders with monel metal jackets, overhead inclined valves operated by means of two rocker arms, push-and-pull rods from the central cam-shaft located in the crank-case. The cam and push rod design is extremely ingenious and the whole valve construction turns out very light. This motor is an evolution from the early Curtiss type motor which was used by Glenn Curtiss when he won the Gordon Bennett Cup at Rheims. A slightly larger edition of this type motor is the OXX-5, as shown at [Figs. 231] and [232], which has cylinders 41⁄4 inches by 5 inches, delivers 100 horse-power at 1,400 turns and has the same fuel and oil consumption as the OX type motor, namely, .60 pound of fuel per brake horse-power hour and .03 pound of lubricating oil per brake horse-power hour.
