PL. 82. DYNAMOMETER TESTS OF LARGE ENGINE◊
PL. 82. DYNAMOMETER TESTS OF LARGE ENGINE◊
PL. 83. DYNAMOMETER TESTS OF LARGE ENGINE◊
PL. 83. DYNAMOMETER TESTS OF LARGE ENGINE◊
PL. 84. DYNAMOMETER TESTS OF LARGE ENGINE◊
PL. 84. DYNAMOMETER TESTS OF LARGE ENGINE◊
The water for cooling the cylinders is led from the bottom of the tankEto the circulating pumpF, supported in a discarded lower pyramid of the aerodrome frame, the pump being driven by the small vertical shaft, as already described. The water, after passing through the pump and the engine cylinders, is led back to the upper part of the tank. By suitable connections to the water mains and sewer, the water in the tank is kept at any desired temperature. The gasoline supply tank is seen on the left-hand side of the testing frame, as viewed in Plate82, the carburetor being placed below it and the gas supply pipe from the carburetor passing through the gasoline tank. Instead of jacketing the carburetor, a grid formed of thin copper tubes is supported just above the multitude of small air pipes leading into the carburetor, and some of[p249]the hot water from the engine is by-passed through this grid and thus warms the air as it passes into the carburetor. The small pipe that by-passes this water through the grid is seen connected to the outlet water pipe just above the cylinders, a small butterfly valve in the outlet pipe enabling the amount of heated water passing through the grid to be controlled. The return from the grid is by means of the small pipe leading to the top of the large water tank. The tachometer, which gives instantaneous readings of the speed of the engine, is seen atG, where it is at all times in full view of the operator.
These dynamometers proved to be excellently suited for the testing work, and far ahead of anything else the writer has ever found for engine testing. Since the power required to rotate the rotor plates, with a uniform amount of water in the drums, varies as the cube of the speed, it is readily seen that it is impossible for the engine to race or injure itself by running away, as frequently happens where there is no engine governor and Prony brakes are used to measure the power.
In the early tests the engine was never allowed to develop more than 40 horse-power, as it was feared that by letting it develop more, which it was clearly seen to be capable of, it might be injured and cause a delay in the tests of the aerodrome. In the second series of tests it was allowed to develop 51 horse-power at 935 R. P. M., but it was not thought to be advisable to let it run at maximum power for more than an hour, for the same reason as before. In the summer of 1904, after it was seen that there was no immediate possibility of securing funds for continuing the tests of the aerodrome, it was planned to enter the engine in the competitive tests at the St. Louis Exposition, where a prize of $2500 was offered for the lightest engine for its power. As the conditions specified in this competition required that the engine run at its maximum power for one hour, and that this be followed by a durability test of ten hours’ continuous running, it was decided to make some durability tests of the engine before taking it to St. Louis. In these tests, the engine was run on three separate trials for a period of ten hours45with a constant load of 52.4 horse-power at 950 R. P. M. Even in these long durability tests the engine and the dynamometers both worked so smoothly and evenly that the engine did not vary its speed more than ten revolutions per minute, and the pull on the spring scales varied less than ten pounds in the entire ten hours. Considerable correspondence was had with the officials of the St. Louis Exposition regarding the entrance of the engine in the competition, in order to make sure that suitable facilities for conducting the tests had been provided. After receiving assurance that everything necessary had been provided, the engine and its testing dynamometers were boxed for shipment to St. Louis and arrangements were just being completed for their transportation when the following telegram was[p250]received from the director in charge of the aeronautical department of the Exposition: “On account of lack of competition engine tests abandoned.” As the main object of entering the engine in the competition was to insure for it an unquestioned record of its performance it was decided to reassemble it in the testing frame in Washington and invite some engineers of prominence to witness and certify to its performance, but on account of the lack of funds for meeting the expenses incident to such a series of tests as it was planned to make this was never done.
In the tests which were witnessed on April 26, 1902, by Captain I. N. Lewis, Recorder of the Board of Ordnance and Fortification, the engine was held down to a pull of 200 pounds on a 13-inch lever, when running at 1000 revolutions per minute. In the later tests in May, 1903, which were witnessed by Captain Gibson, who was then Recorder of the Board of Ordnance and Fortification, and Mr. G. H. Powell, the Secretary of the Board, the engine was allowed to work at a pull of 265 pounds on the 13-inch lever arm at a speed of 950 revolutions per minute. In the tests made in August, 1904, the engine was run for ten consecutive hours46at a pull which varied from 263 to 271 pounds, or an average of 267 pounds, on a 13-inch lever, with the speed varying from 945 to 955 revolutions per minute, thus showing 52.4 horse-power at the average speed of 950 R. P. M.
DETAILEDWEIGHTOFNEWLARGEENGINE.Name of part.Weight in grammes.Crank shaft5,225Connecting rods (total)5,005Pistons—No. 11,652No. 21,647No. 31,655No. 41,660No. 51,646Cylinders—No. 1 (including exhaust and inlet valves, oil cups, etc.)4,768No. 2 (including exhaust and inlet valves, oil cups, etc.)4,685No. 3 (including exhaust and inlet valves, oil cups, etc.)4,638No. 4 (including exhaust and inlet valves, oil cups, etc.)4,637No. 5 (including exhaust and inlet valves, oil cups, etc.)4,796Port crank chamber drum, including cam, cam gears, punch rods, etc.5,225Starboard crank chamber drum3,440Spark plugs (5)450Outlet water pipe450Inlet water pipe360Inlet gas manifold1,700Primary and secondary sparkers and wires512Balance arm with braces for same—starboard1,040Balance arm with braces for same—port1,067Total56,323 gm.=124.17 lbs.Starboard fly wheel3,946Port fly wheel3,234Total weight of engine and fly wheels63,503 gm.=140.00 lbs.Spark coil and batteries6,800Carburetor3,751Inlet gas pipe from carburetor to manifold756Gasoline tank1,004Water tank717Water circulating pump and shaft807Radiator7,700Total weight of power plant85,038 gm.=187.47 lbs.