Garage Tinkering That Changed The World
The Wright Brothers' Wind Tunnel
Everyone knows about the Wright Brothers' invention of the first sustained-flight airplane. Few people know, however, that there was an awful lot of science behind it, and that the science of flight started with a fan, a couple of boards, a piece of hacksaw blade and a bicycle spoke. Here, in the actual words of Wilbur Wright, is a description of the wind tunnel they built to try out more than 200 models before they built one and actually tried to fly it. The wind tunnel they built had an accuracy which rivaled modern wind tunnels.
"My brother Orville and I built a rectangle-shaped open-ended wind tunnel out of a wooden box. It was 16 inches wide by 16 inches tall by 6 feet long. Inside of it we placed an aerodynamic measuring device made from an old hacksaw blade and bicycle-spoke wire. We directed the air current from an old fan in the back shop room into the opening of the wooden box. In fact, we sometimes referred to one of the two open ends of the wind tunnel as the "goesinta" and the other end as the "goesouta." An old one-cylinder gasoline engine (that also turned other tools in the shop, such as our lathe) supplied the power to turn the fan. This was because there was no electricity in our shop. In fact, even the lights were gas lights.
"It took us about a month of experimenting with the wind tunnel we had built to learn how to use it effectively. Eventually we learned how to operate it so that it gave us results that varied less than one-tenth of a degree. Occasionally I had to yell at my brother to keep him from moving even just a little in the room because it would disturb the air flow and destroy the accuracy of the test.
Over a two month period we tested more than two hundred models of different types of wings. All of the models were three to nine inches long. Altogether we measured monoplane wing designs (airplanes with one wing), biplanes, triplanes and even an aircraft design with one wing behind the other like Professor Langley proposed. Professor Langley was the director of the Smithsonian Museum at the time and also trying to invent the first airplane. On each little aircraft wing design we tested we located the center of pressure and made measurements for lift and drift. We also measured the lift produced by wings of different "aspect ratios." An aspect ratio is the ratio or comparison of how long a wing is left to right (the wing span) compared to the length from the front to the back of the wing (the wing chord). Sometimes we got results that were just hard to believe, especially when compared to the earlier aerodynamic lift numbers supplied by the German Lillienthal. His numbers were being used by most of the early aviation inventors and they proved to be full of errors. Lillienthal didn't use a wind tunnel like Orville and I did to obtain and test our data.
"We finally stopped our wind tunnel experiments just before Christmas, 1901. We really concluded them rather reluctantly because we had a bicycle business to run and a lot of work to do for that as well.
"It is difficult to underestimate the value of that very laborious work we did over that homemade wind tunnel. It was, in fact, the first wind tunnel in which small models of wings were tested and their lifting properties accurately noted. From all the data that Orville and I accumulated into tables, an accurate and reliable wing could finally be built. Even modern wind tunnel data with the most sophisticated equipment varies comparatively little from what we first discovered. In fact, the accurate wind tunnel data we developed was so important, it is doubtful if anyone would have ever developed a flyable wing without first developing this data. Sometimes the non-glamorous lab work is absolutely crucial to the success of a project.
"In any case, as famous as we became for our "Flyer" and its system of control, it all would never have happened if we had not developed our own wind tunnel and derived our own correct aerodynamic data."
Wind tunnels today come in many types, from low-speed wind (for use in designing cars) to those which generate hypersonic wind speeds (for testing beyond-mach speed planes).
One major development was the "choking down" of the actual area where the wind passes over the model, in order to make the wind go faster there. Another major development which helped is the "closed-return" system which takes the "goesouta" wind, already moving at top speed, and funnels it back around to the "goesinta" end for added efficiency. Both these improvements are shown in the diagram, below:
For information on how to build your own wind tunnel, click here .