Fig. 31.—The grouping of condenser tubes, made in the form of Philipps’ sustainers. This arrangement is very effective, condenses the steam or cools the water, and gives a lifting effect at the same time. The shape and arrangement of tubes shown at b, b, although effective as a condenser, produce no lifting effect, but a rather heavy drift.

Having ascertained the lifting effect of wooden aeroplanes of various forms and at varying velocities of the wind, and, also, the resistance offered by various bodies driven through the air, I next turned my attention to the question of condensation. I wished to recover as much water as possible from my exhaust steam. I had already experimented with Mr. Horatio Philipps’ sustainers, and I found that their lifting effect was remarkable. A curious thing about these aeroplanes was that they gave an appreciable lift when the front edge was rather lower than the rear. I therefore determined to take advantage of this peculiar phenomenon, and to make my condenser tubes as far as possible in the shape of Mr. Philipps’ sustainers. [Fig. 30] shows a section of one of these tubes, in which a, a is the top surface, b a soldered joint, and c the steam space. These were mounted on a frame as shown at a ([Fig. 31]). I had already found that bodies placed near to each other offered an increased resistance to the air, but by placing these sustainers in the manner shown this was avoided, as the air had sufficient space to pass through without being either driven forward or compressed. It was found by experiment that the arrangement of tubes or sustainers, shown at d, d ([Fig. 31]), was very efficient as a condenser, but it gave a very heavy drift and no lifting effect at all; whereas, on the other hand, the arrangement shown at a was equally efficient, and, at the same time, gave a decided lifting effect. When twelve of these tubes or sustainers were placed at an angle of 1 in 12, the lifting effect was 12·63 lbs. and the drift 2·06 lbs. It was found, however, that a good deal of the drift was due to the wind getting at the framework that was used for holding the sustainers in position. With a wind velocity of 40 miles an hour and a temperature of 62° F., 2·25 lbs. of water were condensed in five minutes, and, while running, the back edge of the sustainers was quite cool. At another trial of the same arrangement under the same conditions, the lift was 11 lbs. and the drift 2·63 lbs. It is quite possible on this occasion that the metal was so extremely thin that the angles were not always maintained; consequently, that no two readings would be alike. It was found at this point that the belt was slipping, and a larger pulley was put on the driving shaft of the screws; and under these conditions, with a wind of 49 miles per hour and an angle of 1 in 8, the lifting effect ran up to 14·87 lbs. with a drift of 2·44 lbs., and the condenser delivered 2·87 lbs. of water from dry steam in five minutes. The weight of metal in this condenser was extremely small, the thickness being only about 1⁄500 of an inch. This condenser delivered the weight of the sustainers in water every five minutes. They should, however, have been twice as heavy. Cylinder oil was now introduced with the steam in order to ascertain what effect this would have. After seven minutes’ steaming, 2·25 lbs. of water were condensed in five minutes. It will be seen from these experiments that an atmospheric condenser, if properly constructed, is fairly efficient. Roughly speaking, it requires 2,400 times as much air in volume as of water to use as a cooling agent. With the steam engine condenser only a relatively small amount of water is admitted, and this is found to be sufficient; but in an atmospheric condenser working in the atmosphere, it must be as open as possible, so that no air which has struck one heated surface can ever come in contact with another.

CHAPTER V.
EXPERIMENTS WITH APPARATUS ATTACHED TO A ROTATING ARM.

From what information I have at hand, it appears that Prof. Langley made his first experiments with a small apparatus, using aeroplanes only a few inches in dimensions which travelled round a circle perhaps 12 feet in diameter. With this little apparatus, he was able to show that the lifting effect of aeroplanes was a great deal more than had previously been supposed. After having made these first experiments, he seems to have come to the conclusion that Newton’s law was erroneous. Shortly after Langley had made these experiments on what he called a whirling table, which, however, was not a very appropriate name, I made an apparatus myself, but very much larger than that employed by Prof. Langley. I reckoned the size of my aeroplanes in feet, where he had reckoned his in inches. The circumference of the circle around which my aeroplanes were driven was exactly 200 feet, and shortly after this Langley constructed another apparatus, the same dimensions as my own. From an engraving which I have before me, it appears that he constructed an extremely large wooden scale beam supported by numerous braces, but free to be tilted in a vertical direction after the manner of all other scale beams. As this apparatus was of great weight and offered enormous resistance to the air, I do not understand how it was possible to obtain any very correct readings, especially as it was in the open and subject to every varying current of air.

Fig. 32.—Machine with a rotating arm, 31·8 feet long, to which is attached the object to be experimented with. Professor Langley had a similar machine and called it a “whirling table.”

[Fig. 32 enlarged] (70 kB)