WRIGHT BROTHERS — BAKER 219 



Throughout all their writings, the Wrights seemed to depreciate 

 the design of their early engines, and yet, as we look over their work 

 now, we see innumerable instances of outstanding ingenuity. 



The Kitty Hawk had a horizontal four-cylinder engine of 4-inch 

 bore (chosen for high displacement) and 4-inch stroke (chosen 

 in the interest of light weight) . The cylinders were individual cast- 

 iron units fitted into a single-piece cast-aluminum crankcase that 

 extended far enough to form a water jacket around the cylinder bar- 

 rels. A camshaft driven from the crankshaft by a chain operated 

 the exhaust valves and the individual breaker arms for cylinder fir- 

 ing. The intake valves were spring closed and opened by natural 

 aspiration. 



The crankshaft was machined from a solid l^Q-i^'^^^^^-thick sheet of 

 armor plate and had five babbitted main bearings. The rear end of the 

 crankshaft was fitted with a 15-inch-diameter flywheel weighing 26 

 pounds and a double sprocket for driving the propeller chains. The 

 crankshaft was lubricated by splash and strategically placed troughs. 

 The connecting rods were tubular with bronze fittings — pinned and 

 soft soldered — and the crank ends were babbitted. The pistons were 

 lubricated by small engirie oil cups near the end of the stroke. 



The ignition for running was supplied by a low-tension horseshoe 

 generator with induced electromotive field, driven by a contact wheel 

 against the flywheel. A starter box, not carried in the airplane, con- 

 taining four dry-cell batteries and a homemade inductance coil made 

 by wrapping bell wire around a core of cut lengths of broom wire, 

 furnished a hot spark for starting only. The spark timing was re- 

 tarded for starting by a cam movement to advance the normal position 

 of the camshaft sprocket, thus changing the exhaust-valve timing 

 at the same time. Most of the "old-timers" recall that the Wrights' 

 early engines started easily. Cooling water for the engine was sup- 

 plied by thermosiphon flow from a long narrow radiator mounted on 

 one of the center-section struts. 



The fuel system involved simply gravity flow from the gasoline tank 

 mounted near the top of one center-section strut, through a copper line 

 leading to a shallow enclosed and baffled pan covering the four cylin- 

 ders above their water jacket. There were two valves in the fuel line, 

 the first for metering adjustment and the second for full throw between 

 open and closed positions. The only way to stop this engine was to 

 close this second valve. The dimensions of the fuel tank indicate an 

 actual capacity of three-eighths gallon. 



It has often been stated that the power dropped from 16 to 12 horse- 

 power after warm-up and we can only surmise that this was due to the 

 type of carburetion used, the inherently late intake timing, and the 

 15-cent kerosene-byproduct fuel that was available. 



