1203cent.qxd 11/13/03 2:19 PM Page 1 n a chilly North Carolina edge. It is likely that this informa- Omorning 100 years ago, two tion became the basis for the design brothers from Dayton, Ohio, at- of their early gliders. It also led them tempted a feat others considered im- to contact Octave Chanute, an possible, and their success changed American engineer who was the world. leading the way for experiments in Today we take air travel for aeronautics. granted, and rarely give a second thought to our capability to fly liter- Three problems ally anywhere in the world. But one The Wrights realized from the be- hundred years ago, the endeavors ginning that they had to solve three of the Wrights and other aeronau- problems: tical pioneers were widely viewed • Balance and control. as foolhardy. Although some of the THE WRIGHT • Wing shape and resulting lift. world’s most creative minds were • Application of power to the converging on a solution to the flight structure. problem, well-respected scientists STUFF: Of the three, they correctly recog- such as Lord Kelvin thought flight Materials in the Wright Flyer nized that balance and control were impossible. the least understood and probably In fact, Simon Newcomb, pro- The flight of the Wright Flyer was the most critical. To solve that fessor of mathematics and as- the “first in the history of the world problem, they turned to gliding ex- tronomy at Johns Hopkins Univer- periments. sity and vice-president of the in which a machine carrying a man National Academy of Sciences, had had raised itself by its own power The 1900 glider declared only 18 months before the into the air in full flight, had sailed After a few preliminary experi- successful flight at Kitty Hawk, forward without reduction of speed, ments with small kites, they built “Flight by machines heavier than air and had finally landed at a point as their first glider in 1900. It was a bi- is unpractical and insignificant, if not high as that at which it started.” plane with a wingspan of 16 feet, a utterly impossible.” horizontal elevator in the front, no Sometimes it is important to not — Orville Wright tail, and wing tips that could be know what is impossible. Orville warped to provide control. The and Wilbur Wright, bicycle me- Walter M. Griffith glider was essentially a kite with ash chanics and builders by trade, first Materials and Manufacturing Directorate ribs, metal connections, and cloth became seriously interested in flight Air Force Research Laboratory coverings. The total cost of the glider in the 1890’s. They were aware of the Wright-Patterson Air Force Base was about $15. gliding experiments of German en- Dayton, Ohio Realizing that they needed a more gineer Otto Lilienthal from pub- constant wind than possible in lished accounts, some in popular magazines of the day. Dayton, they sought guidance from the Weather Bureau They were shocked by his death in 1896 in a gliding acci- in Washington, D.C. Based on information about constant dent. Also aware of Samuel Langley’s experiments in the strong winds, they traveled to Kitty Hawk, North Carolina, United States, Wilbur wrote to the Smithsonian in 1899 for at the end of the bicycling season. Experiments during this a list of literature references that would further his knowl- trip convinced them that their wing warping concept was “Four men, two boys and a dog” look on at Kitty Hawk on December 14, 1903, moments before the first unsuccessful flight trial. (Photo courtesy Wright State University Library Special Collections) ADVANCED MATERIALS & PROCESSES/DECEMBER 2003 21 1203cent.qxd 11/13/03 2:20 PM Page 2 homemade wind tunnel and glides, some covering more than 600 tested more than 200 wing feet. By the time they returned to shapes. The data compiled Dayton, they had solved the major during these experiments pro- problems of control in the air. Full of vided the Wrights with more ad- new confidence, all they needed was vanced aeronautical under- an engine, a problem they viewed as standing than anyone else in relatively easy to solve. history. They realized that the ta- bles of lift and drag coefficients Engine trouble published by Lilienthal were ap- The brothers wrote to a number of plicable only in special cases. automotive companies in search of an Based on the corrected data, internal combustion engine capable of they designed a new wing. It providing 8 horsepower and weighing adequate to provide control, but oth- was less curved and had an aspect less than 180 pounds. To their sur- erwise the gliding results were less ratio (wing length:chord length) of prise, no such engine was available successful than they had hoped. 6:1, and wing warping provided (although some believe a few compa- more control. The glider maintained nies did not want to be associated with The glider wing a forward elevator, but fixed vertical attempts at manned flight). Not to be The brothers returned to North Car- fins were added in the rear. denied, they designed their own en- olina in the Fall of 1901 with a larger Excited by the new design, the gine and built it, with the able assis- glider of similar design, with a 22-foot Wrights left for Kitty Hawk in Sep- tance of their mechanic, Charles wing span, but the poor gliding results tember 1902, even before the bicycle Taylor. made them question the published season ended. The new wing design The engine had four water-cooled scientific data on which their wing was validated: the glider flew mag- cylinders. Cast iron cylinders were designs were based. Back in their nificently. fitted into a single cast-aluminum Dayton bicycle shop in early 1902, During the following two months, crankcase. Buckeye Iron and Brass they experimented extensively with a the Wright brothers made almost 1000 Foundry in Dayton cast the crankcase. The Al-9Cu alloy, designated Alloy A, had a tensile strength of 18,000 psi. The radiator was made from lengths of tin speaking tube, like the tubing used in apartment buildings for in- tercom systems. The crankshaft was rough cut from a slab of high-carbon steel, and lathe-turned to provide pre- cise size and smoothness. Pistons and cylinder barrels were made of cast iron. Taylor did all the machining in the bicycle shop, and completed the basic engine in six weeks. Gasoline was fed by gravity from a small tank just below the upper wing. Two valves in the copper fuel line were used for metering the flow and for shutoff to stop the engine. Raw gasoline entered a chamber next to the cylinders, mixing with incoming air. A coil and four dry-cell batteries pro- vided the initial spark for starting. A twenty-six-pound flywheel drove a low-tension magneto to supply the current while the engine was running. By retarding or advancing the timing of the spark, the speed could be con- trolled somewhat. The 1903 engine provided 16 horse- The Wright Brothers’ bicycle shop in Dayton, Ohio, was the site of most of the experimenta- power immediately after starting, but tion and development of the first airplane. The shop is currently at Greenfield Village in Michigan. that dropped to 12 horsepower after On the research done here, Fred Kelly writes in his biography of the Wrights (pp 45-46): “…it is doubtful if the difficulties and full value of the Wrights’ scientific researches within their bicycle a few minutes. The basic engine shop are yet appreciated. The world knows they were the first to build a machine capable of sus- weighed about 140 pounds, less than tained flight and the first to actually fly, but it is not fully aware of all the tedious, grueling scien- the 180 pounds originally specified. tific laboratory work they had to do before flight was possible.” (Photo courtesy Wright State Uni- Taking advantage of the extra power versity Library Special Collections) and lower weight, they added struc- 22 ADVANCED MATERIALS & PROCESSES/DECEMBER 2003 1203cent.qxd 11/13/03 2:20 PM Page 3 tural reinforcement to the air- Summary of materials in the 1903 Wright Flyer frame. Their total investment in the engine was about $300. White spruce Spars, ribs, struts, rear rudder, forward elevataor, Straight grain and kiln dried engine support, propellers Spruce propellers Ash Ribs, end bows (steam bent) The Wrights had assumed that Straight grain and kiln dried the technology of propellers was Steel wire Wing and truss wire (0.091 inches diameter, #13 W&M well established, since they had Hand drawn gage); Trailing edge wire (0.054 inches diameter, been used in marine applications #17 W&M gage) for a long time. However, a quick Aluminum alloy Al-9Cu Engine crankcase study of the literature, their usual High-carbon steel Crankshaft (machined from a 100 lb block), approach to any problem, miscellaneous hardware showed that the theory was not developed sufficiently. Their re- Steel tubing Connecting rods, 1 1/8 inch with cast bronze ends search demonstrated that the Platinum Contacts in engine cylinders for spark generation problem was more intricate than Tin tubing Radiator originally thought. After months Unbleached muslin Wing covers, “Pride of the West” trade name, with of calculations and discussions 108 threads per inch with each other, they concluded Note 1: In early experiments, pine was substituted for spruce, but it failed in hard landings. that that propellers were essen- Note 2: Why Spruce and Ash? tially rotary wings generating From a May, 2003, interview with Nick Engler, University of Cincinnati: “Mankind had been working wood for thrust aerodynamically.