In imitating as nearly as possible the conditions to which the carburetor of the engine would be subjected during the period of launching, numerous tests were made in which the engine was brought to its maximum speed and, without changing the adjustment of the mixture-controlling devices of the carburetor, sudden blasts of air were turned on it from various directions, and these were continued until the mixture-control devices were perfected to such a point that gusts of thirty miles an hour suddenly directed from any point against any portion of the apparatus would in no way effect the speed and power of the engine. These tests were considered necessary in view of the very sudden changes in conditions to which the aerodrome would be subjected during its brief run down the launching track, the conditions changing in approximately three seconds from absolute quiescence of the aerodrome to a plunge through space at thirty-five feet per second. An aviator would be more than occupied with maintaining control of himself and of the aerodrome, which at the moment of leaving the track might require considerable change in the adjustment of the Pénaud tail, and he would, therefore, not be able to make any adjustments of the engine-control devices. This supposition was entirely confirmed in the actual tests of the aerodrome which are to be later described, the rush down the track being [p254] so very brief that the engine could not have been given any attention by the aviator had it needed it, which fortunately it did not.

It is hardly necessary to recount at any length the great difficulties which was experienced in these tests of the engine in the aerodrome frame before the shafts, bearings, propellers, and, in fact, the frame itself were all properly co-ordinated so that confidence could be felt that all of the parts would stand the strains which were likely to come on them when the aerodrome was in flight. These tests were really not tests of the engine itself, but of the frame, shafts, and bearings. Suffice it to say that nearly a year was consumed by the various breakages of the shafts, bearings, and propellers before it was felt that all of these parts could be depended on, and even then the weakness of the bearings above referred to was fully recognized. Had some of the better-grade balls and steels for the bearings, which have since that time come on the market, been obtainable then, there would have been no difficulty with these bearings. However, this same remark might be made with reference to nearly all of the details of the aerodrome, for it was the accessories, such as bearings for the transmission and propeller shafts, spark plugs, coils, batteries, and a suitable carburetor for the engine, that caused the chief delay after the main difficulty of getting a suitable engine had been overcome.

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[p255]

CHAPTER XII
FIELD-TRIALS IN 1903

The extended series of shop tests which had occupied a considerable portion of the late winter and early spring of 1903 had demonstrated the following facts: First, with the aerodrome mounted on the launching car, a propeller thrust of from 450 to 475 pounds could be maintained indefinitely by the engine, and even when the engine was delivering its full power to the propellers, the vibration was so small as to cause no apprehension that the wings and rudder would be made to vibrate sufficiently to produce undue strains in them. Second, with the aerodrome suspended from the ceiling by springs at the points at which the wings would be attached, the vibration produced by the engine developing it’s full power was even less than when the machine was mounted on the launching car and there was, consequently, even less cause for concern that the wings and rudder might be set in vibration when the machine was free in the air. Third, the engine could be depended upon to deliver something over 52 horse-power when the five cylinders were working properly, and even with one cylinder not working, but acting as a dead load against the others, approximately 35 horse-power could be developed, while with two cylinders not working at all, the three which were working would deliver about 25 horse-power. Therefore, even assuming that two of the five cylinders might become deranged during a flight, there should still be sufficient power to propel the machine. These tests, some of which had been witnessed by members of the Board of Ordnance and Fortification, clearly demonstrated that the time had arrived when it was safe to give the aerodrome a test in free flight. The machine itself together with all its appurtenances and much extra material for repairs in case of breakages, which previous experience had shown to be almost certain, was accordingly taken from the shop and placed on the house-boat preparatory to taking it down the river to the point opposite Widewater, Va., which had already been selected as the “experimental ground.”

Owing to the limited size of the shops it had been impossible to place the wings and rudder in their proper positions on the aerodrome and determine its balancing in a way similar to that practiced with the models. The approximate settings for the wings and rudder had, however, been determined by calculation from the data obtained in the test of the quarter-size model, so that it remained only to place the wings and a weight to represent the rudder actually on the machine in the large space of the house-boat (which, however, was not large enough to permit the rudder to be assembled along with the wings), and thus check the balancing previously determined by calculation. There were very [p256] few appurtenances which could be shifted in balancing the aerodrome, but the proper disposition of weight had been so accurately determined by calculation that the floats, which, as will be seen from the various photographs, were merely cylindrical tanks with pointed ends, and of a sufficient capacity to cause a displacement great enough to float the aerodrome when it came down into the water, proved sufficient ballast for shifting the center of gravity to its proper point. The flying weight of the aerodrome was 830 pounds,[47] including the weight of the writer, which was 125 pounds. The total area of the wings or supporting surfaces was 1040 square feet, or the ratio of supporting surface to weight was 1.25 square feet per pound, which is the same as .8 pound per square foot.

After the balancing of the large aerodrome had been completed on the house-boat, and everything else got in readiness as far as could be done before actually arriving at the point at which the test was to be made, the house-boat was towed down the river on July 14, 1903, and fastened to its mooring buoy, which had been placed in the middle of the river at a point practically opposite Widewater, Va., and approximately forty miles from Washington. See Coast-Survey Chart, Plate [85].

Sleeping quarters for the force of eight workmen and the regular soldier from the United States Army, who had been detailed as a special guard, had been provided on the boat, but owing to the lack of space it had been found impracticable to arrange proper cooking facilities on the boat, and it had been found necessary to arrange to transport the workmen to Chopawamsic Island, near Quantico, Va., for their meals. It had been planned to use the twenty-five-foot power launch for this purpose, but owing to the heavy storms which became quite frequent soon after the house-boat was taken down the river, it was found that the small launch was not sufficient, and it was necessary to employ a tug-boat and keep it stationed there at all times. This added very considerably to the expense of the experiments, as the hire of this one tug-boat very nearly equalled the pay-roll of the workmen, and while it was not expected that the stay down the river would be so greatly prolonged as afterwards proved the case it was felt certain that minor delays were sure to occur and the experiments would at the very least require several weeks.