by James Tobin
He explained the measurements of lift and drift that he and his brother had made on an actual glider in flight—the first ever made by any experimenter—and the “astonishing” implications: Lilienthal had been wrong. All the existing data about lift and drift had to be recalculated. And he and his brother meant to do the work.
Engineers who built rail trestles and sewers might not have followed the speaker through every obscure detail about centers of pressure and coefficients of lift, but they could see the pictures on the screen—a huge, cloth-and-wood contraption like a box kite, unmistakably in flight and carrying a man, this man. Plainly the fellow had done what he said ought to be done, and with remarkable success. He was an American Lilienthal—Chanute had said so—yet he, unlike the German, had not yet died.
In so many words, Will dismissed the work of Lilienthal and of Hiram Maxim. The world-renowned inventor of the machine gun had constructed wings and engines powerful enough to get an eight-thousand-pound aeroplane off the ground in 1893, Will noted. Yet Maxim had given up immediately upon realizing that he had no way of controlling its flight. So much, too, for Samuel Pierpont Langley’s ten-year pursuit of an aeronautical engine. And so much for Professor Simon Newcomb, whose measure Will apparently took during his long days of work on the paper in Dayton, and the other masters of formulas and theory who proved the impossibility of flight at their desks, with pencils.
There are two ways of learning how to ride a fractious horse. One is to get on him and learn by actual practice how each motion and trick may be best met; the other is to sit on a fence and watch the beast a while, and then retire to the house and at leisure figure out the best way of overcoming his jumps and kicks. The latter system is the safest; but the former, on the whole, turns out the larger proportion of good riders. It is very much the same in learning to ride a flying machine; if you are looking for perfect safety, you will do well to sit on a fence and watch the birds; but if you really wish to learn, you must mount a machine and become acquainted with its tricks by actual trial.
WILL’S RELATIONSHIP with Octave Chanute—until now mostly a scientific exchange through occasional letters—was deepening into personal friendship. That fall Will began to write to the older man with increasing frequency, delighted to have found a friend so eager for each new detail of the brothers’ experiments. Many of his letters stretched to several thousand words. When Will apologized for writing at such length, Chanute replied with warmth: “I am amused with your apology for writing long letters, as I find them always too brief.”
Will also felt a certain degree of pressure from Chanute, and a degree of frustration with him. It nettled him that Chanute could not yet bring himself to accept what now seemed obvious to the Wrights—that Otto Lilienthal’s hallowed calculations of lift and drift were in error. “His faith in Lilienthal’s tables is beginning to waver,” Will wrote George Spratt, “though it dies hard.”
Yet Will could not help but feel warmed by Chanute’s rising esteem. At the meeting in Chicago, among distinguished figures of his profession, the older man had treated his much younger guest as a respected peer. In their private conversations he had been very much the eager mentor, urging Will to revise his presentation (“a devilish good paper,” Chanute called it) for publication in the society’s professional journal—a badge of prestige that would certify the brothers as serious investigators. Chanute urged Will to throw off whatever doubts had snared him at Kitty Hawk, and practically begged the brothers to accept his financial aid.
Bemused, Will shrugged off the offer. This was, after all, only a hobby. The Wrights might not have wives and children to support, but they could hardly abandon their livelihood for the sake of an intellectual diversion, however fascinating. Indeed, the brothers, feeling ready at last to expand their bicycle business, were preparing for several years of intensified labor in that line. “If we did not feel that the time spent in [aeronautical] work was a dead loss in a financial sense,” Will said, “we would be unable to resist the temptation to devote more time than our business will stand.”
In spite of Will’s pleasant reception in Chicago, the brothers were not at all sure what to do next. Will had described the obstacles with admirable clarity, but the obstacles remained. Their glider was “a fractious horse” indeed, and a dangerous one, and they had little idea how to tame it.
Only one task needed to be done right away: Will had to put his talk to the engineers in shape for publication. Here Orville voiced a caution. Will had come down awfully hard on established authorities, especially Lilienthal. Now these rebukes would be committed to print. And who was Wilbur Wright? An unknown, without a degree or even much experience. Could they really be so sure of their own beliefs about puzzles they only had begun to probe? If they were going to challenge the world-famous Lilienthal—and by implication John Smeaton, whose estimates of air pressure Lilienthal had used—they ought at least to try a few experiments to confirm their hunches.
Will saw the wisdom of it. So, as the streets of West Dayton turned golden-brown with the coming of autumn in 1901, the neighbors were treated to a minor diversion—the younger Wright boys, not so young any more, taking turns on one of their black bicycles, pedaling swiftly up and down the streets and stealing frequent glances at a contraption in front at the level of the handlebars—a bicycle wheel mounted horizontally and free to spin. The brothers had affixed two metal plates on the rim, ninety degrees apart. On the left, in the nine-o’clock position, was a small, flat, metal plate set perpendicular to the air flow. In front, at the twelve-o’clock position, was a slightly larger plate, curved in an arc to match Lilienthal’s one-in-twelve curvature. When the bicycle was in motion, the air flowing over the curved plate would generate lift and turn the wheel clockwise. The air pressure against the flat plate would push the wheel counter-clockwise. The angle of incidence of the “wing” was carefully set so that it would generate just enough lift to offset the air pressure on the flat plate. If Lilienthal was right, the wheel would remain stationary. If he was wrong, the wheel would rotate. And if he was wrong in the way the Wrights suspected—that is, if his values for lift were too high—then the curved plate would generate too little lift and the wheel would rotate counter-clockwise.
With the rig in place, one or the other of the Wrights mounted the bike and started pedaling. As he glanced up and down, one eye out for horses, carts, and bicycles, the other on the experiment, the horizontal wheel turned counter-clockwise in the rushing current of air.
More attempts brought the same results. The brothers increased the angle of incidence of the curved plate until it generated enough lift to balance against the flat plate. The angle was nowhere near what Lilienthal would have predicted.
In these slight movements of a bicycle wheel, the Wrights read the auguries of a revolution. They had suspected something was wrong in Lilienthal’s tables. The wheel proved it.
Still, it was a pretty crude experiment. It had to be checked. With gathering excitement, they tore the ends off a discarded wooden starch box and fitted a fan to one of the open ends. This made a little wind tunnel of the sort they had encountered in their readings. They constructed a little wind vane that, like their bicycle rig, balanced the air pressure on a flat plate against the lift generated by wing surfaces. They placed it inside the box and switched on the fan. The wobbling vane confirmed the bicycle tests.
Working fast, they checked and rechecked results, comparing their figures to all they knew about Lilienthal’s glides. Only three weeks after his speech in Chicago, Will wrote Chanute: “I am now absolutely certain that Lilienthal’s table is very seriously in error, but that the error is not so great as I had previously estimated.” The fog was thinning. He was discerning shapes in the mist. “The results obtained, with the rough apparatus used, were so interesting in their nature, and gave evidence of such possibility of exactness . . . that we decided to construct an apparatus specially . . . for [testing] surfaces of different curvatures and different relat
ive lengths and breadths.”
They had come upon an extraordinary tool. New possibilities beckoned. A bigger and better wind tunnel would be Kitty Hawk in a box, with a perfect wind and no risk to life and limb. Instead of trudging up a giant sand hill, waiting for the wind to arrive at the proper direction and speed, guessing at angles and vectors, and laboriously tinkering with wings as long as a living room, they could insert a six-inch piece of metal in the wind tunnel, throw a switch, write a number on a page, and move on. Every test was another dot in the sketch they now could create—a sketch of a wing that really would fly.
“We have been experimenting . . . with an apparatus for measuring the pressure of air on variously curved surfaces at different angles,” Will informed his father on October 24, “and have decided to prepare a table which we are certain will be much more accurate than that of Lilienthal.”
WITH THE BISHOP AWAY on a long trip, Kate found the house on Hawthorn Street nearly as quiet in the fall as it had been in August, when her brothers were away. Every morning she caught the Third Avenue streetcar for Steele High, where she taught in the same room as the year before, the one overlooking the river, though “the pupils . . . are not so nice as they were last year.” After school, she went for bicycle rides. She saw to her father’s mail and business affairs and supervised Carrie Kayler in the housework. In the evening, she read. The only break in the routine came when her nieces and nephews dropped in, though the children were going through “not so pretty” phases that fall. Still, they touched her. “Ivonette and Milton were invited to a birthday party last evening and Uncle Orv, happening to go by the house, found baby Sister in tears because she couldn’t go, too. She would have been a sweet little guest. Uncle Orv consoled her for a few moments by producing some candy and having ‘a party’ on his lap.”
Her brothers walked in at suppertime, ate and argued, then walked out again, heading back to the shop. The house had been through a little flurry when Will went to Chicago, then dull peace returned. Now, “The boys are working every night on their ‘scientific’ (?) investigations,” she told her father. “Poor Will says he’ll have to eat crow for, after all, he has discovered by accurate tests that Lillienthal’s tables are not far off.” The weather was fine. A relative of the next-door neighbors had died. A letter of Kate’s had been discovered at the post office without a stamp. A friend of Bishop Wright’s spent the night. Apart from these events, she said, “I can’t think of any news.”
THE WALK FROM 7 Hawthorn to the bicycle shop took five minutes—one block west to South Williams, a block north to West Third, half a block farther west and across the street to 1127 West Third, between Frank Hale’s grocery and Fetters & Shank, “Undertakers & Embalmers; Coffins, Caskets & Robes of any Style or Quality Furnished at Reasonable Prices.”
Above the door at 1127 was a sign for “Wright Cycle Company.” A sign above that, at the peak, said “C. H. Webbert.” That was the building’s owner, the Wrights’ landlord and friend, Charlie Taylor’s uncle-in-law, a prosperous plumber. Inside the door was a clean-swept but sparsely furnished room with a gas stove and a cabinet full of bicycle accessories and supplies—tires, wheel rims, spokes, toe and trouser clips, foot pumps, 20th Century and Aladdin bicycle lamps; leather bicycle saddles; and jars of grease. The odors of rubber tires, gluepots, and oil mingled in the air. Through a door at the back of the room, visitors glimpsed bicycles and machinery in a warren of storage and work rooms. In those rooms, rough tables were littered with scraps of wood and sheet metal and abandoned pieces of flying toys contrived for the nieces and nephews out of paper, bamboo, and cork. Spruce shavings crackled underfoot. Racks of tools for wood-working and metal-working hung on the walls. Shelves were lined with jars of cotter pins, nuts, and nails. Overhead, long leather belts ran along the ceiling, connecting the single-cylinder natural-gas shop engine to the big power tools: a twenty-inch Barnes drill press; a fourteen-inch Putnam lathe; a bench grinder.
There was a workroom upstairs, too, where the brothers did much of their experimenting while Charlie Taylor worked on bicycles downstairs. The brothers had installed two bells to minimize interruptions. The first rang when the front door opened, the second when a customer removed the air pump from the wall—the most frequent reason for customer visits in a day of delicate tube tires. If the first bell rang, followed quickly by the second, the brothers could stay at their work; the customer only “wanted air.” If only one bell rang, then one or the other had to go downstairs and attend to business.
But November was the heart of cycling’s off-season. No more than four or five customers happened in each day, so even during business hours, the Wrights could accomplish a good deal of aeronautical work. As the days grew shorter and the wind turned cold, Wilbur and Orville went at their investigation with greater intensity than ever. With the starch-box wind tunnel, they had intended only to check their figures to support Will’s claim. But in doing so they realized they had created the means by which they could discover everything Lilienthal had died trying to find out. “We had taken up aeronautics merely as a sport,” Orville said. “We reluctantly entered upon the scientific side of it. But we soon found the work so fascinating that we were drawn into it deeper and deeper.”
If Lilienthal’s tables could not be trusted, then they must write tables of their own. And they would test not just one wing shape, as the German had, but shapes of all sorts. As Orville put it, there was “a multitude of variations [for] the pressures on squares are different from those on rectangles, circles, triangles, or ellipses; arched surfaces differ from planes, and vary among themselves according to the depth of curvature; true arcs differ from parabolas, and the latter differ among themselves; thick surfaces differ from thin, and surfaces thicker in one place than another vary in pressure when the positions of maximum thickness are different; some surfaces are most efficient at one angle, others at other angles. The shape of the edge also makes a difference, so that thousands of combinations are possible in so simple a thing as a wing.”
They constructed a wind tunnel substantially larger than their improvisation with the starch box. The new device was a wooden crate six feet long and sixteen inches square. It stood on four legs at waist height, with a fan and steel hood mounted at one end. To hold their model wing surfaces, they fashioned bicycle spokes and worn hacksaw blades into two delicate structures they called balances. They were simple but powerful mechanical computers—tiny analogs of the forces at play on the wings. With trigonometry, the Wrights could use them to analyze the performance of any wing shape they could imagine.
It appears that Will did most of the close work of fashioning the model wings. They varied in length and width, but most had exactly the same wing area, six square inches, so their performance could be easily compared. Nearly all were snipped from a sheet of steel one thirty-second of an inch thick—easier to shape than wood—and pounded into the desired testing shape. Will could cut a shape and hammer the curve he wanted in fifteen minutes. Then he would build up the leading edge to the thickness he wanted with solder and wax.
Orville, meanwhile, perfected the arrangements for the wind tunnel itself. The fan was mounted on the axle from the brothers’ old grinder. This was connected to the shop engine, which would drive the fan at some 4,000 revolutions per minute to create an experimental wind of 20 to 25 miles per hour.
They constructed the balances together. One they called the lift balance, the other the drift balance. Each was equipped with a dial and needle to register results. Experimental wing shapes were mounted not horizontally, like a bird’s wing, but vertically, so the “lift” could be measured from side to side. When they turned on the fan, wind rushed through a metal honeycomb—to keep the airflow straight—and struck the wing. This caused the entire balance to swing gently to one side, like the action of an opening gate. The dial recorded how far the gate swung. Correcting for drift and gravity, the brothers could judge the performance of each wing shape at a particular angle in a
minute or two. On the lift balance, for instance, they would affix the model wing to the balance; adjust it to the desired angle; turn on the fan; adjust the balance to correct for drift; look through the window on top of the tunnel to read the number indicated by the needle; shut off the fan; record the result; then change the wing’s angle and test again. When the full range of angles had been tried, a new wing would be attached and the cycle of lift tests would start over. Later, they tested the same wing shapes on the drift balance. Both balances measured the forces on the wings directly, eliminating the need to rely on Smeaton’s coefficient of air pressure. They found they could run dozens of tests in a single day. In four weeks they tried more than a hundred surfaces, running each through its paces at angles from zero, past thirty degrees, all the way to ninety degrees, gleaning more information in a couple of days than in two summers at Kitty Hawk. Through the window on top of the tunnel, they watched the needle respond to the wind blowing on surfaces that were flat and sharply curved, square-tipped and round-tipped. They tried tandem wing arrangements, like Langley’s; double-deckers like their own gliders; even triple-deckers. They tried surfaces of various aspect ratios—the ratio of the wing’s length to its width, or “span” to “chord”—from perfect squares to long, narrow rectangles. The tests revealed astonishing variety and unpredictability in the way surfaces responded to the flow of moving air. Their progress delighted Will’s anxiously waiting correspondent in Chicago. “It is perfectly marvelous to me how quickly you get results with your testing machine . . . ,” Chanute said. “You are evidently better equipped to test the endless variety of curved surfaces than anybody has ever been.”
