After having returned to Dayton and caught up on work, the brothers sent out letters to the leading internal combustion manufacturers around the world, soliciting information on obtaining an engine producing at least 8 horsepower and weighing no more than 180 pounds. Most companies ignored the inquiry or sent at best dismissive or overly optimistic replies. At worst the brothers found this an annoyance, for they had, after all, already designed and built the engine that powered the bicycle "factory."
[from Richard P. Hallion, Taking Flight, Oxford, 2003, page 200]
As a result of [of the War Department's interest in an airplane because of the Spanish American War in 1898], Congress granted Langley $50,000 and asked him to go ahead and build such a machine.
Langley was now convinced that a gasoline engine offered more promise of powered flight than steam. He went to one manufacturer after another, asking for an engine that would deliver 12 horsepower and weigh only 100 pounds. When these requirements proved too formidable, he turned the problem over to his gifted assistant, Charles M. Manly.
[from the American Heritage History of Flight, page 84]
Langley was a great pioneer, but --like Maxim and Ader-- he was too concerned with power plants and wing surfaces. It was not enough. The line of endeavor that finally resulted in victory did not go through these ground-based engineers; rather it went through those men who had not only mechanical ingenuity but also the skill, imagination, and daring to seek, first of all, control in the air through gliding experiments: through Lilienthal, Pilcher, and Chanute to the Wright brothers.
[from the American Heritage History of Flight, page 85]
In contrast, Heppenheimer, "First Flight" wrote of Langley:
"He wanted 12 horsepower--with a total weight of less than 60 pounds, a demanding specification indeed for that day. It was to run for three hours without overheating, with the cost for the research and development being under $2,100.
No one responded." [p.175]
Heppenheimer described the efforts of the Wright Brothers:
"To provide a suitable reserve of power, leaving 5.5 horsepower for useful thrust, the motor was to put out 8 to 9 horsepower.
Even in 1902, such performance did nto seem difficult to attain. Accordingly, the Wrights sent letters to a number of engine manufacturers, presenting their request. They wanted considerably less power than Langley's specification of 12 horses, four years earlier, with the Wrights being willing to accept twice the weight. Even so, no one has a stock engine that was ready for sale." [pages 181-2]
There is a discussion of Charlie Taylor's work for the Wrights:
The body of the first engine was of cast aluminum, and was bored out on the lathe for independent cylinders. The pistons wer cast iron, and these were turned down and grooved for piston rings. The rings were cast iron, too...
Dry batteries were used for starting the engine and then we switched onto a magneto bought from the Dayton Electric Company. There was no battery on the plane...
[pp. 182-3. T.A. Heppenheimer, First Flight, Wiley 2003]