THE WRIGHT BROTHERS AERO ENGINE
The French manufacturer, without altering the basic design, made a number of changes of detail which seem to have greatly annoyed Wilbur Wright, although some of them could probably be listed as improvements, based on several features of later standard design. One consisted of an alteration in the position of the fuel and oil pumps, the latter being lowered to the level of the sump. The crankcase was drilled to provide forced-feed lubrication to the connecting rod big end and crankshaft main bearings. Strengthening ribs were added to the pistons running from the upper side of the pin bosses to the piston wall, and the crankcase studs holding down the cylinders were replaced with bolts having their heads inside the case. The hinged cam follower was omitted and the pushrod bore directly on the cam through a roller in its end. The magneto was moved toward the rear of the engine a considerable distance and an ignition timing control device was introduced between it and its driving gear. Instead of the magneto being mounted directly on the special bracket integral with the crankcase, a wooden board running from front to rear of the engine was used and this was fastened to the two engine support pads, the magneto bracket being omitted entirely.
Despite his criticism of the French motor and the quality of its manufacture, Wilbur was compelled to install one in his own exhibition airplane during his early French demonstrations at Le Mans after rod failure had broken his spare crankcase, and much of his subsequent demonstration flying was made with the French product.
The Eight-Cylinder Racing Engine
By 1909 regular and special air meets and races were being held and various competitions for trophies conducted. Among these the Gordon Bennett Cup Race for many years was considered a major event. For the 1910 competition it was decided to enter a Wright machine and, since this was a race with speed the sole objective, the available 4-cylinder engine, even in a version pushed to its maximum output, was deemed too small. They built for it a special 8-cylinder unit in a 90°V form. They were thus resorting to one of their 1904 concepts—modifying and enlarging a version known and proved in use—as the proper method of most quickly increasing output. Unfortunately again, there are essentially no detailed drawings available, so that the design cannot be studied.[16]
Only one engine is historically recorded as having been built, although in view of the Wrights' record of foresight and preparation it is almost certain that at least one spare unit, assembled or in parts, was provided. In any case, the airplane—it was called the Baby Grand Racer—and engine were wrecked just before the race, and no physical parts were retained, so that the sole descriptions come from external photographs, memory, and hearsay. McFarland thinks that possibly Orville Wright, particularly, was somewhat discomfited over the accident that eliminated the machine, as he had previously flown it quite successfully at a speed substantially higher than that of the ultimate winner, and he wanted to get it out of sight and mind as quickly as possible. The Air Force Museum at Wright Field, Dayton, Ohio, has an incomplete set of drawings of a 90°V, 8-cylinder Wright engine, but it is quite obvious from the basic design and individual features, as well as from at least one date on the drawings, that this conception is of a considerably later vintage than that of the Baby Grand Racer.
The racing engine was in essence a combination of two of the standard 4s on a redesigned crankcase utilizing as many of the 4-cylinder engine parts as possible. The rods were reported to have been placed side by side, and the regular 4-cylinder crankshaft, with alterations to accommodate the rods, was utilized. A single cam operated all the exhaust valves. It was compact and light, its only fundamental disadvantage being the inherent unbalance of the 90°V-8. The arrangement provided a much higher powered unit in the cheapest and quickest manner, and one that could be expected to operate satisfactorily with the least development.