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Wednesday, October 2, 2013

"Success Assured" - Part 4 of "First to What?"

With the airplane now fairly well understood, the Wrights knew all that they had to do was to add an engine to their existing design.  By 1903, there were many different companies building internal combustion engines for cars, motorcycles and other uses, and the Wrights had always assumed they could purchase what they needed.  In December 1902, fresh from their successful flying in North Carolina, they contacted several of them asking for an engine that could deliver 8 or 9 HP and would weigh less than 180 lbs.  Ten firms responded, but none could deliver such an engine, or would do so for a reasonable price.

Now they turned to one of their employees for help, mechanic Charles Taylor, after deciding to build their own.  With Charles' help and mechanical expertise, they designed and built a small 4-cylinder engine weighing only 179 lbs.  To save weight, they greatly simplified the engine, which lacked sophisticated cooling, carburetor and spark plugs.  The engine was cooled by evaporation of water from a cooling jacket, and would overheat once that water was gone.  Fuel dripped into the inlet manifold from a small 1 qt fuel tank fed by gravity.  Ignition was mechanical driven by a battery (not on the airplane) for starting and a simple magneto to keep it running.  When cold the engine delivered 16 HP, but quickly dropped to 12 HP as it heated up.  It took them 6 weeks from concept to bench tests.

The Wright Brother's Engine, built by Charles Taylor
 The main technological advance that the Wrights were responsible for in 1903 was the propeller design.  Up till then, airplane propellers had been thought of as being like fans, with flat blades, or like screws, with curved blades.  The Wrights believed that propellers were a well understood technology, but as they researched naval design, they found little or no real empirical understanding of how this 100 year old design actually worked.  The two brothers began addressing the problem in their usual style, each arguing from a point of view until they had both convinced each other that the other person was right.  After several months, they hit on the answer that suddenly seemed obvious - a propeller was an airfoil, just like a wing - only one that rotated and moved through the air in a spiral and generated its lift horizontally.

The innovative propeller design and bicycle chain drive
 With that revelation, they could use their tables of airfoil designs and wind tunnel test to build a twisted airfoil shape for their propeller.  They mounted the engine and used bicycle chains connecting sprocket wheels of various sizes to gear the rotation down to the optimal speed for the propeller.  Each propeller was 8.5 feet in diameter, made of spruce, and twisted along its length so that the airfoil met the oncoming air at the best angle of attack.  The Wrights used gear ratio of 23 to 8, so that for every 23 revolutions of the engine, the propellers rotated 8 times.

Now the Wrights designed and engineered their 1903 airplane, knowing their engine power and weight, pilot weight, lift coefficient and target speed - they had all the components needed to calculate the lift, drag weight and trust needed to design their airplane.  They also submitted their first patent application for a "flying machine", which was awarded in 1906, and focused on the 3 axis control.  Using their experience of flying the 1902 glider they developed a padded hip cradle to control the wing warping and inter-connected vertical rudder, and a simple wooden lever that controlled the moveable elevator (still on the front, canard-style).  They mounted an anemometer to measure airspeed, a rev counter to monitor the engine speed, and on-off switches for fuel flow.  In September, the Wrights packed up their Flyer and headed for Kitty Hawk.

The 1903 Flyer's controls - hip cradle for the prone pilot, elevator lever and engine controls

Bad weather delayed their progress as they assembled their machine, a full 700 lbs in weight - twice as heavy as the 1902 glider, 21 ft long and with 40 ft wingspan.  It was massive.  Due to it's size and weight, the airplane couldn't be hand launched like previous designs, so the Wright built a simple 60 ft launching rail after calculating the needed take off run.  Although the brothers experienced issues with the sprocket wheels coming loose and a damaged propeller that had to be sent back to Dayton for repair, on December 14th they were ready.  They flipped a coin to see who would make the first flight (Wilbur won).  Giving full power to engine, the Flyer accelerated down the track, until after 40 ft it suddenly reared skyward, stalled at 15 ft and smashed into the sand damaging the left wing.

Undismayed, the brothers began to repair their aircraft, wrote home "There is now no question of final success",  and in a telegram "Success Assured.  Keep Quiet".  This one statement, "Success Assured", is I think the most telling - they had designed, tested and engineered the airplane - they KNEW it would work.  They were also totally unworried about competitors who were trying their own designs around this time, such as Samuel Langley and Augustus Herring.  They knew their aircraft would work, the others wouldn't.

On December 17th, with the airplane repaired and the weather cooperating, it was Orville's turn.  Forewarned by Wilbur about the overly-sensitive elevator, Orville started his take off run with Wilbur running alongside.
One of the most famous photos ever taken - Orville at the controls, Wilbur running on December 17th, 1903


Karlene Petitt said...

Another fabulous post. One thing that resonated throughout... brothers working together. Isn't it amazing what we can accomplish together? So much more than alone. Thanks for a great post and sharing more or our history.

Chris said...

A really well-done post, D.B.! Have you had the opportunity to visit Kill Devil Hills? For me, something about being there really brought the history to life.