While there were spark plug and distributor ignition systems available during the Wrights’ era, they chose to use what was called a “make-and-break” system which basically meant a separate set of contact points located in each cylinder head. Their choice was mainly due to the amount of oil present in each cylinder which quickly fouled most spark plugs. Platinum faces were installed on the spring-loaded ignition points which were governed by a bar stock camshaft mounted half way between the exhaust valve camshaft and the valve “box.” It was run by a spur gear attached to the exhaust valve camshaft. A sleeve mechanism attached to a lever allowed the operator to advance and retard the spark as necessary for starting and different power settings. While the spark was supplied during flight by a magneto mounted next to the operator, dry cell batteries were used for start-up purposes, then removed before flight. Parts could be fashioned from materials available in the bicycle shop or easily procured nearby.
Carburetors available at the time were too heavy and too complex for the Wrights’ weight limits and timetable. So, once again, they made their own. The intake manifold was a sheet steel “box” mounted across the tops of the valve chambers. There was a flat induction chamber at each cylinder opening on the side toward the engine. A sheet steel “can” (some say Taylor used a soup can from his lunch) was attached to the manifold and a fuel line was attached to it, creating a crude carburetor that would introduce the fuel from the wing-mounted, 47-ounce tank, gravity fed through the line to the engine. Incoming fuel actually contacted the wall of the crankcase which also helped in vaporizing the incoming mixture. The system had two valves — one a simple on/off valve and the other providing a more gradual rate of supply in order to maintain a constant air/fuel ratio as fuel in the tank was used up.
Historians and engineers have marveled at the fact that the 1903, and subsequent Wright Flyer engines, not only had no real exhaust piping nor muffling system, but also that the engine was mounted in such a way that the noise and exhaust heat came out practically in the face of the operator lying on the lower wing. The reason for this was that the spark control mechanism and fuel valves were located on that side of the engine within reach of the operator. Changing the position would required more parts (and weight). The Wrights recognized the problem and Wilbur wrote of some work he was doing on a “muffling system” for later designs.
Completion and testing
The little engine was completed by late February 1903, in large part to Taylor’s master machining skills and input in the design features. Unlike the later engines, the 1903 engine was never tested on a prony brake, test-fan system to ascertain brake horsepower. Calculations were made related to engine speed and displacement. Horsepower ratings ranged from 8.25 hp at 670 rpm to 16 hp at 1,200 rpm. There were a few setbacks such as in April when the engine seized as a result of fuel leaking onto the exhaust valve camshaft from the manifold, requiring Taylor to do a complete engine rebuild. Testing went on until June when they determined the final engine design generated 13 hp and weighed 150 pounds. But their work was far from over.
Transferring the engine’s rotary power to the propellers required additional design challenges. Contrary to some speculation, they did not select a chain drive system from the engine to the propellers simply because they were in the bicycle business and had a lot of chain and sprockets available (though that certainly didn’t hurt). At the time many final drive mechanisms, including automobiles, used chain drives, so it wasn’t a stretch to decide on that design. It was a simple design, easy to maintain and service, even though the chain “whip” could create some instability, especially with engine misfires.
On to Kitty Hawk
As with any new design, there were many “bugs” that had to be worked out once the Wright brothers got to North Carolina. Taylor stayed behind in Dayton, as he was manager of the Wrights’ ongoing bicycle business. Thus, he was also available in the shop to rebuild or repair parts for the aircraft. They sent him plenty of work. For example, there was a 10-day delay after the propeller shafts were damaged when the sprockets sheered off. He eventually had to remanufacture the propeller shafts after one of the heavy gauge tubes cracked during testing. He replaced it with smaller solid tool steel material so the replacement shafts could better absorb the engine’s occasional misfiring or pre-ignition explosive forces. Taylor also had to repair the engine’s magneto when it failed to produce a spark, plus advise the brothers about a fuel feed problem.
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