CHAPTER IV.
PRINCIPALLY RELATING TO SCREWS.
In 1887 I was approached by several wealthy gentlemen who asked me if I thought it was possible to make a flying machine. I said, “certainly; the domestic goose is able to fly and why should not man be able to do as well as a goose?” They then asked me what it would cost and how long it would take, and, without a moment’s hesitation, I said it would require my undivided attention for five years and might cost £100,000. A great deal of experimenting would be necessary; the first three years would be devoted to developing an internal combustion engine of the Brayton or Otto type, and the next two years to experimenting with aeroplanes and screws and building a machine. Even at that time I had a clear idea of the system that would be the best. However, nothing was then done, but in 1889 I employed for the purpose two very skilful American mechanics, and put them to work at Baldwyn’s Park, Kent. At that time the petroleum motor had not been reduced to its present degree of efficiency and lightness; it was not suitable for a flying machine, and I saw that it would require a lot of experimental work in order to develop it. After taking into consideration all the facts of the case, I decided to use a steam engine. Had I been able to obtain the light and efficient motors which have been recently developed, thanks to the builders of racing cars, I should not have had to experiment at all with engines and boilers, as I could have obtained the necessary motors at once. As it was, I was obliged to content myself with the steam engine.
Fig. 9.—Group of screws and other objects used in my experiments.
Fig. 10.—Some of the principal screws experimented with—h, a screw with very thick blades, and g, a screw made after a French model.
I found that there was a great deal of misunderstanding regarding the action of aeroplanes, and also of screws working in the air. I procured all the literature available on the subject, both English and French, and attempted to make a thorough study of the question; but I was not satisfied, on account of the wide difference in the views of the writers and the conflicting formulæ that were employed. I therefore decided to make experiments myself, and to ascertain what could be done without the use of anybody’s formula. Although this was nearly twenty years ago, I find that there is still a great deal of discussion regarding the action of aeroplanes and screws, in which the majority taking part in the discussion are in the wrong. However, several good works on the subject have recently been published.
Fig. 11.—The three best screws. The screw on the right has a uniform pitch throughout, the middle screw has increasing pitch, and the left screw compound increasing pitch.