At this time, October, 1893, the aerodrome (Old No. 4) was practically complete, and the most anxious thought was given to lightening it in every way consistent with the ever-present demand for more power, which necessitated an increase in the weight of both burners and boilers to supply the requisite steam.
On November 14, when the aerodrome was prepared to be shipped to Quantico for trial, its condition was about as follows. The steam-generating apparatus—the parts of which were of substantially the forms last described, although some slight improvements had been introduced—had been developed to [p063] such a point that a pressure of from 70 to 80 pounds of steam could be maintained for 70 seconds, when it was tested in the shop. What it would do under the unfavorable conditions imposed by flight was to be learned only by trial.
At this pressure, the engines, the efficiency of which had been increased by an improvement in packing, would develop approximately 0.4 indicated H. P., while at 105 pounds pressure they at times developed as much as 0.8 H. P. When the aerodrome was tested on the pendulum, these engines, when making less than 700 revolutions per minute, lifted over 40 per cent of the total flying weight.
The propellers used at this time were accurate helices, having a diameter of 60 cm., a width of blade of approximately 36 degrees, and a pitch-ratio of 1.25. They were formed of wood, and were bushed with brass where they were attached to the shafts.
AERODROME OLD NO. 4 AS PREPARED FOR FLIGHT BEFORE BEING SHIPPED FOR TRIAL ON NOVEMBER 14, 1893 | ||||
| Part. | Copper. | Steel. | Brass. | Iron. |
|---|---|---|---|---|
| gms. | gms. | gms. | gms. | |
| Aeolipile | 200 | .. | 92 | .. |
| Boiler | 350 | .. | 37 | .. |
| Separator and pumps | 300 | 30 | 100 | 20 |
| Engine and frame | .. | 350 | 570 | .. |
| Midrod (200 cm. long) | .. | 220 | .. | .. |
| Two smoke-stacks | 70 | .. | .. | .. |
| Asbestos jacketing | .. | .. | .. | .. |
| Air chamber | .. | .. | .. | 82 |
| Spider between boiler and burner | 32 | .. | .. | .. |
| Intake valve | .. | .. | 15 | .. |
| Total | 952 | 600 | 814 | 102 |
| Hull | 50 | .. | 50 | .. |
| Pins for starter | .. | 15 | .. | .. |
| Two large wings and tail | .. | .. | .. | .. |
| Buffer and steerer | .. | .. | .. | .. |
| Propellers | .. | .. | .. | .. |
| Total | 50 | 15 | 50 | .. |
| Grand total | 1002 | 615 | 864 | 102 |
| Density | 8.9 | 7.8 | 8.5 | 7.5 |
| Volume (cu. cms.) | 113 | 79 | 102 | 136 |
| Alcohol | .. | .. | .. | .. |
| Water | .. | .. | .. | .. |
| Total | .. | .. | .. | .. |
| Density | .. | .. | .. | .. |
| Volume (cu. cm.) | .. | .. | .. | .. |
| AERODROME OLD NO. 4 DATA, CONTINUED | ||||||
| Part. | Wood and silk. | Mica and asbestos. | Fluid. | Total and mean weights. | ||
|---|---|---|---|---|---|---|
| gms. | gms. | gms. | gms. | |||
| Aeolipile | .. | .. | .. | 292 | ||
| Boiler | .. | .. | .. | 387 | ||
| Separator and pumps | .. | .. | .. | 450 | ||
| Engine and frame | .. | .. | .. | 920 | ||
| Midrod (200 cm. long) | .. | .. | .. | 220 | ||
| Two smoke-stacks | .. | .. | .. | 70 | ||
| Asbestos jacketing | .. | 50 | .. | 50 | ||
| Air chamber | .. | .. | .. | 82 | ||
| Spider between boiler and burner | .. | .. | .. | 32 | ||
| Intake valve | .. | .. | .. | 15 | ||
| Total | .. | 50 | .. | 2518 | =5.54lbs. | |
| Hull | .. | 25 | .. | 125 | ||
| Pins for starter | .. | .. | .. | 15 | ||
| Two large wings and tail | 571 | .. | .. | 571 | ||
| Buffer and steerer | 53 | .. | .. | 53 | ||
| Propellers | 250 | .. | .. | 250 | ||
| Total | 874 | 25 | .. | 1014 | =2.33lbs. | |
| Grandtotal | 874 | 75 | .. |  | ||
| Density | 0.8 | 3.0 | .. | |||
| Volume (cu. cms.) | 1092 | 25 | .. | |||
| Alcohol | .. | .. | 100 | 100 | ||
| Water | .. | .. | 500 | 500 | ||
| Total | .. | .. | .. |  | ||
| Density | .. | .. |  | |||
| Volume (cu. cm.) | .. | .. | .. | |||
Permanent air spaces: in midrod, vol. = 355 cc. in engine frame, vol. = 100 cc. volume as per II. 2050 cc. 2505 cc. Density = 41322505 = 1.65
| ||||||
[p064]
The total flying weight of Old No. 4, including fuel and water, was 4132 grammes (9.1 lbs.), a much larger weight than had been contemplated when the original designs were made. A detailed statement of the weights of the various parts of the aerodrome, together with some data as to its density, is given on the preceding page. There were provided in the wings and tail approximately 2 sq. ft. of supporting surface to the pound of weight, which would have been barely sufficient to sustain the aerodrome, even if it had been successfully launched and the wings had been built much stronger than the flimsy construction in use at this time.
An air chamber, which served the double purpose of floating the aerodrome and of providing a moveable weight by which the center of gravity could be shifted to the proper position relatively to the center of pressure, was constructed of the thinnest sheet-iron and attached to the midrod.
This aerodrome, the fifth in actual construction, and the first, after years of experiment, to be carried into the field, was transported to Quantico, where the first trial with it was made on November 20, under the conditions described in Chapter IX [◊].