The Bishop's Boys (37 page)
Authors: Tom D. Crouch
He would raise the issue carefully. All too often, he suspected, his older brother reacted against his suggestions on principle. This time Wilbur listened as Orv explained the notion at breakfast the next morning. He understood immediately, but was reluctant to add yet another control to befuddle the pilot. The movable rudder was a fine idea, but why not link it directly to the wing-warping cradle, so that the rudder would automatically move to counter the warp-induced drag? To simplify matters, a single vane could be substituted for the double surface of the fixed rudder. They began work on the new rudder later that day.
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The camp was crowded now. Lorin appeared unexpectedly on September 30, having come down to see for himself what his brothers were up to. He struck up an immediate friendship with Spratt, who arrived the next day. Chanute and Herring appeared four days later, in the midst of yet another rainstorm. Six bunks were squeezed into the narrow quarters up in the rafters, and the sound of Orv’s mandolin accompanying a chorus of voices could be heard far into the night.
Herring set to work assembling both the “multi-wing” glider and the Lamson “oscillating wing machine.” He abandoned the Lamson craft after only two days of testing. Working together, the entire team was unable to pull it into the air with a pilot on board. When tested separately as kites, the wings flew at an angle of almost 20 degrees in a 30-mile per hour wind.
Wilbur attributed the problem to structural weakness. “I noted that when there was not even enough wind for support, the surfaces were badly distorted, twisting so that, while the wind at one end was on the underside, often at the other extreme it was on top. Mr. Chanute,” he concluded, “seems much disappointed in the way it works.”
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Herring’s own machine was no more successful. An altered version of the original Chanute-Herring triplane of 1896, the wings were free to rock back and forth in response to changes in the center of pressure. Herring made several faltering glides with the craft on October 13, the only day on which it was flown. His best distance was just under fifty feet.
For Herring, the whole experience was humiliating. A proud, self-confident man, he considered himself the leading American flying-machine experimenter. He had struggled for years, unfairly put upon—as he saw it—by fate and the whim of men like Chanute and Langley who gave him money, but not the freedom to develop his own ideas. He saw the 1902 Wright glider in the air on only two or three days while he was in camp. It was enough. Clearly, these newcomers had swept past him and were threatening to wrest the prize from his grasp.
The camp began to break up with Lorin’s departure on October 14. Chanute and Herring left for Washington the following afternoon. Both men hoped to see Samuel Langley. Chanute did spend a few minutes with him on October 16; he described the extraordinary progress of the Wrights, and urged Langley to go to the Outer Banks to see for himself. “After seeing you,” Langley wrote the next day, “I almost decided to go, or send someone, to see the remarkable experiments that you told me of by the Wright brothers.” In fact Langley wired Kitty Hawk requesting permission to visit the camp, but Wilbur and Orville replied that there would scarcely be time before the close of the season.
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On October 10, Wilbur was up again with a new rudder that turned to counteract the retarding effect of wing warping.
Herring, unable to see Langley, left a note, desperate either for a job or a small grant that would enable him to set off in pursuit of the Wrights. But Langley, far less forgiving than Chanute, had no intention of becoming involved with Herring ever again.
Conditions at the Kill Devil Hills were “so much easier” after Herring and Chanute’s departure. The Wrights were in the air from dawn to dusk. “In two days,” Orv boasted to Katharine,
we made over 250 glides, or more than we had made all together up to the time Lorin left. We have gained considerable proficiency in the handling of the machine now, so that we are able to take it out in any kind of weather. Day before yesterday [October 21] we had a wind of 16 meters per second or about 30 miles per hour, and glided in it without any trouble. That was the highest wind a gliding machine was ever in, so that we now hold all the records! The largest machine that we handled in any kind [of weather], made the longest distance glide (American), the longest time in the air, the smallest angle of descent, and the highest wind!!! Well, I’ll leave the rest of the “blow” till we get home.
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Glides in excess of 550 feet were commonplace. The best flights of the season came on October 23, their next-to-last day in the air. Will set the record for both time and distance with a single glide covering 622.5 feet in 26 seconds. Orv was not far behind with a flight of 615.5 feet in just over 21 seconds.
They spent their days in the air, and their nights in serious discussion. After three seasons at Kitty Hawk, they had achieved their original goals. The 1902 glider was proof that they had solved the basic problems of flight. They were ready for the next step—the construction of a powered airplane.
The basic calculations for its design were run while still in camp. They solved the lift equation as usual, but the drag formula was now especially important. Gravity had powered their earlier machines, supplying the force necessary to overcome drag and achieve flying speed. This time they would not have that advantage. Their powered machine would take off from a dead stop on level ground. Whatever combination of engine and propellers they chose would have to provide sufficient thrust to achieve flying speed and sustain them in the air.
The answers were clear. They would need some 520 square feet of wing to lift a machine with a total weight of no more than 625 pounds, including the engine and pilot. A suitable airframe of that size would weigh perhaps 290 pounds. The addition of a 140-pound pilot left 200 pounds as the upper limit for the weight of the engine, propellers, and transmission. An engine generating 8–9 horsepower would produce the thrust required to get such a machine off the ground in a reasonable headwind.
With everything going so well, the Wrights would have liked to continue flying until the end of the month, but that was not possible. Bill Tate needed to prepare his fishing boat and crew for the coming season—without his assistance, the brothers could not launch their machine. They left camp for the last time at dawn on October 28 and walked the four miles to Kitty Hawk in a cold drizzle to catch the boat for Elizabeth City—and home. They left their own glider and the two Chanute machines behind, packed away in the rafters of the shed where they would remain until the camp reopened in 1903.
November 1902~August 1903
T
he Wrights scarcely paused after returning from Kitty Hawk. Orville went to work on a new wind tunnel and a final check of the lift and drag figures. Wilbur wrote to ten manufacturers of gasoline engines, asking about prices and delivery times for an engine that would weigh no more than 180 pounds and deliver 8–9 horsepower.
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In December, they turned their attention to the other half of the propulsion problem—the propeller. Langley, Maxim, Ader, and others had given little thought to propeller efficiency, relying on angled blades to pull their machines through the air like a screw drilling into wood. That would not do for the Wrights. They set out to engineer their propellers, just as they had their wings, achieving a specific thrust calculated in advance. Anything less would be a surrender to guesswork.
“We had thought of getting the theory of the screw propeller from the marine engineers,” Orv wrote in 1908, “and then, by applying our tables of air pressures to their formulas, of designing air propellers suitable for our purpose.”
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They discovered that there was no theoretical base for the design of ship propellers. A century after the introduction of the marine screw, engineers continued to follow empirical practice of no value to the Wrights.
Reasoning their way along, the Wrights made another fundamental breakthrough. “It was apparent,” Orville recalled in 1913, “that a propeller was simply an aeroplane [wing] traveling in a spiral course.” A propeller was not a screw, it was a rotary wing. Instead of being driven against the air to provide lift, it was spun, generating thrust. The formulas and coefficients used in wing design could also be applied to propellers. At first glance, as Orville pointed out in a later article, this did not seem to be a problem,
but on further consideration it is hard to find even a point from which to make a start; for nothing about a propeller, or the medium in which it acts, stands still for a moment. The thrust depends upon the speed and the angle at which the blade strikes the air; the angle at which the blade strikes the air depends upon the speed at which the propeller is turning, the speed at which the machine is traveling forward, and the speed at which the air is slipping backward; the slip of the air backward depends upon the thrust exerted by the propeller, and the amount of air acted upon. When any of these changes, it changes all the rest, as they are all interdependent upon one another. But these are only a few of the many factors that must be considered and determined in calculating and designing propellers.
3
The longer they studied it, the more complex the problem became.
With the machine moving forward, the air flying backward, the propellers turning sidewise, and nothing standing still, it seemed impossible to find a starting point from which to trace the various simultaneous reactions. Contemplation of it was confusing. After long arguments we often found ourselves in the ludicrous position of each having been converted to the other’s side, with no more agreement than when the discussion began.
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Charlie Taylor witnessed those discussions. “Both boys had tempers,” he recalled. “They would shout at one another something terrible. I don’t think they really got mad, but they sure got awfully hot.”
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The arguments that shocked Charlie in fact allowed them to explore every facet of a problem. Their ability to defend a point of view with real passion, while at the same time listening to the other fellow’s opinion, was an essential part of the process.
The elements of a propeller theory were falling into place by early March 1903. The answers did not come in a brilliant flash of insight but were reasoned through step by step.
The design of the transmission system arose directly out of their cycling experience. Rather than bolting a single propeller directly to the crankshaft, they linked twin pusher propellers to the engine with a set of chains, achieving maximum performance with the propellers revolving at a relatively slow speed. To avoid the excessive torque resulting from two propellers spinning in the same direction, the blades were contrarotating—they simply crossed one of the hollow guide tubes protecting the propeller drive chains.
The power plant remained a problem. None of the established engine manufacturers had the slightest interest in constructing an aircraft power plant. Fortunately, the Wrights had Charlie Taylor. Charlie had never built an engine, but he had worked on them, and he was a first-class machinist. Will and Orv also had some direct experience with internal-combustion engines, having designed and built the motor that drove the line shaft in the bicycle shop.
The world’s first aircraft engine would have to meet three basic requirements: it must produce 8–9 horsepower, weigh no more than two hundred pounds, and run smoothly. The least vibration or roughness would place an impossible strain on the transmission chains.
To save weight, they would cast the crankcase from aluminum. It was a chancy decision. Casting such material into the size of an engine block was work for professional foundrymen.
Construction was
en bloc
, as the French said, with the crankcase and four cylinders cast as a single unit. It was water-cooled, with a separate radiator and a waterjacket cast into the block. An air-cooled engine would be lighter, but could only be run for short periods without potentially catastrophic overheating. The savings in weight would be of little use if the finished engine refused to run.
Fuel was gravity-fed from a can mounted several feet above the engine on an inboard wing strut. There was no carburetor. Gasoline was vaporized in a beaded steel can through which air passed on its way into the engine. The resulting mixture was circulated across the hot crankcase to vaporize any remaining liquid gasoline, then run directly past the intake valves in the manifold. Ignition was make or break, with the contacts operated by cams. A battery was required for starting. A low-tension magneto driven by the flywheel provided the spark once the engine was running.
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Orv and Charlie began work on the engine in late December. “We didn’t make any drawings,” Taylor commented. “One of us would sketch out the part we were talking about on a piece of scratch paper and I’d tack the sketch over my bench.”
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