My Airships/Chapter 11

by Alberto Santos-Dumont

THE EXPOSITION SUMMER

THE Exposition of 1900, with its learned congresses, was now approaching. Its International Congress of Aeronautics being set for the month of September I resolved that the new air-ship should be ready to be shown to it.

This was my "No. 4," finished 1st August 1900, and by far the most familiar to the world at large of all my air-ships. This is due to the fact that when I won the Deutsch prize, nearly eighteen months later and in quite a different construction, the newspapers of the world came out with old cuts of this "No. 4," which they had kept on file.

It was the air-ship with the bicycle saddle. In it the 10-metre (33-foot) bamboo pole of my "No. 3" came nearer to being a real keel in that it no longer hung above my head, but, amplified by vertical and horizontal cross pieces and a system of tightly-stretched cords, sustained within itself motor, propeller, and connecting machinery, petroleum reservoir, ballast, and navigator in a kind of spider web without a basket (see photograph, page 135).

I was obliged to sit in the midst of the spider web below the balloon on the saddle of a bicycle frame which I had incorporated into it. Thus the absence of the traditional balloon basket appeared to leave me astride a pole in the midst of a confusion of ropes, tubes, and machinery. Nevertheless, the device was very handy, because round this bicycle frame I had united cords for controlling the shifting weights, for striking the motor's electric spark, for opening and shutting the balloon's valves, for turning on and off the water-ballast spigots and certain other functions of the air-ship. Under my feet I had the starting pedals of a new 7 horse-power petroleum motor, driving a propeller with two wings 4 metres (13 feet) across each. They were of silk, stretched over steel plates, and very strong. For steering, my hands reposed on the bicycle handle-bars connected with my rudder.

Above all this there stretched the balloon, 39 metres (129 feet) long, with a middle diameter of 5*10 metres (17 feet) and a gas capacity of

"SANTOS-DUMONT No. 4"

420 cubic metres (nearly 15,000 cubic feet). In form it was a compromise between the slender cylinders of my first constructions and the clumsy compactness of the "No. 3." (See Fig. 7.) For this reason I thought it prudent to give it an interior compensating air balloon fed by a rotary ventilator like that of the "No. 2," and

as the balloon was smaller than its predecessor I was obliged to return again to hydrogen to get sufficient lifting power. For that matter, there was no longer any reason why I should not employ hydrogen. I now had my own hydrogen gas generator, and my "No. 4," safely housed in the aerodrome, might be kept inflated during weeks.

In the "Santos-Dumont, No. 4," I also tried the experiment of placing the propeller at the stem instead of the stern of the air-ship. So, attached to the pole keel in front, the screw pulled, instead of pushing it through the air. The new 7 horse-power motor with two cylinders turned it with a velocity of 100 revolutions per minute, and produced, from a fixed point, a traction effort of some 30 kilogrammes (66 lbs.).

The pole keel with its cross pieces, bicycle frame, and mechanism weighed heavy. Therefore, although the balloon was filled with hydrogen, I could not take up more than 50 kilogrammes (110 lbs.) of ballast.

I made almost daily experiments with this new air-ship during August and September 1900 at the Aéro Club's grounds at St Cloud, but my most memorable trial with it took place on 19th September in presence of the members of the International Congress of Aeronautics. Although an accident to my rudder at the last moment prevented me from making a free ascent before these men of science I, nevertheless, held my own against a very strong wind that was blowing at the time, and gave what they were good enough to proclaim a satisfying demonstration of the effectiveness of an aerial propeller driven by a petroleum motor.

A distinguished member of the Congress, Professor Langley, desired to be present a few days

MOTOR OF "No. 4"

later at one of my usual trials, and from him I received the heartiest kind of encouragement.

The result of these trials was, nevertheless, to decide me to double the propeller's power by the adoption of the four-cylinder type of petroleum motor without water jacket—that is to say, the system of cooling à ailettes. The new motor was delivered to me very promptly, and I immediately set about adapting the air-ship to it. Its extra weight demanded either that I should construct a new balloon or else enlarge the old one. I tried the latter course. Cutting the balloon in half I had a piece put in it, as one puts a leaf in an extension table. This brought the balloon's length to 33 metres (109 feet). Then I found that the aerodrome was too short by 3 metres (10 feet) to receive it. In prevision of future needs I added 4 metres (13 feet) to its length.

Motor, balloon, and shed were all transformed in fifteen days. The Exposition was still open, but the autumn rains had set in. After waiting, with the balloon filled with hydrogen, through two weeks of the worst possible weather I let out the gas and began experimenting with the motor and propeller. It was not lost time, for, bringing the speed of the propeller up to 140 revolutions per minute, I realised, from a fixed point, a traction effort of 55 kilogrammes (120 lbs.). Indeed, the propeller turned with such force that I took pneumonia in its current of cold air.

I betook myself to Nice for the pneumonia, and there, while convalescing, an idea came to me.

This new idea took the form of my first true air-ship keel.

In a small carpenter shop at Nice I worked it out with my own hands—a long, triangular-sectioned pine framework of great lightness and rigidity. Though 18 metres (59${\tfrac {1}{2}}$ feet) in length it weighed only 41 kilogrammes (90 lbs.). Its joints were in aluminium, and, to secure its lightness and rigidity, to cause it to offer less resistance to the air and make it less subject to hygrometric variations, it occurred to me to reinforce it with tightly-drawn piano wires instead of cords.

Then what turned out to be an utterly new idea in aeronautics followed. I asked myself why I should not use this same piano wire for all my dirigible balloon suspensions in place of the cords and ropes used in all kinds of balloons up to this time. I did it, and the innovation turned out to be peculiarly valuable. These piano wires, ${\tfrac {8}{10}}$ths

VISIT OF PROFESSOR LANGLEY

of a millimetre (0*032 inch) in diameter, possess a high coefficient of rupture and a surface so slight that their substitution for the ordinary cord suspensions constitutes a greater progress than many

a more showy device. Indeed, it has been calculated that the cord suspensions offered almost as much resistance to the air as did the balloon itself.

At the stern of this air-ship keel I again established my propeller. I had found no advantage result from placing it in front of the "No. 4," where it was an actual hindrance to the free working of the guide rope. The propeller was now driven by a new 12 horse-power four-cylinder motor without water jacket, through the intermediary of a long, hollow steel shaft. Placing this motor in the centre of the keel I balanced its weight by taking my position in my basket well to the front, while the guide rope hung suspended from a point still farther forward (Fig. 8). To it, some distance down its length, I fastened the end of a lighter cord run up to a pulley fixed in the after part of the keel, and thence to my basket, where I fastened it convenient to my hand. Thus I made the guide rope do the work of shifting weights. Imagine, for example, that going on a straight horizontal course (as in Fig. 8) I should desire to rise. I would have but to pull in the guide rope shifter. It would pull the guide rope itself back (Fig. 9), and thus shift back the centre of gravity of the whole system that much. The stem of the air-ship would rise (as in Fig. 9), and,

consequently, my propeller force would push me up along the new diagonal line.

The rudder was fixed at the stern as usual, and water-ballast cylinders, accessory shifting weights, petroleum reservoir, and the other parts of the machinery, were disposed in the new keel, well balanced. For the first time in these experiments, as well as the first time in aeronautics, I used liquid ballast. Two brass reservoirs, very thin,

"No. 4." FLIGHT BEFORE PROFESSOR LANGLEY

and holding altogether 54 litres (12 gallons), were filled with water and fixed in the keel, as above stated, between motor and propeller, and their two spigots were so arranged that they could be

opened and shut from my basket by means of two steel wires.

Before this new keel was fitted to the enlarged balloon of my "No. 5," and in acknowledgment of the work I had done in 1900, the Scientific Commission of the Paris Aéro Club had awarded me its Encouragement prize, founded by M. Deutsch (de la Meurthe), and consisting of the yearly interest on 100,000 francs. To induce others to follow up the difficult and expensive problem of dirigible ballooning I left this 4000 francs at the disposition of the Aéro Club to found a new prize. I made the conditions of winning it very simple:

"The Santos-Dumont prize shall be awarded to the aeronaut, a member of the Paris Aéro Club, and not the founder of this prize, who between 1st May and 1st October 1901, starting from the Parc d'Aerostation of St Cloud, shall turn round the Eiffel Tower and come back to the starting-point, at the end of whatever time, without having touched ground, and by his self-contained means on board alone.

"If the Santos-Dumont prize is not won in 1901 it shall remain open the following year, always from 1st May to 1st October, and so on, until it be won."

The Aéro Club signified the importance of such a trial by deciding to give its highest reward, a gold medal, to the winner of the Santos-Dumont prize, as may be seen by its minutes of the time. Since then the 4000 francs have remained in the treasury of the Club.

"SANTOS-DUMONT No. 5"