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.
[Illustration: "SANTOS-DUMONT No. 4"]
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
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.
[Illustration: Fig. 7]
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.
[Illustration: MOTOR OF "No. 4"]
A distinguished member of the Congress, Professor Langley, desired to be
present a few days 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 (59-1/2 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.
[Illustration: VISIT OF PROFESSOR LANGLEY]
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, 8/10ths 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.
[Illustration: "No. 4." FLIGHT BEFORE PROFESSOR LANGLEY]
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.
[Illustration: Fig. 8]
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,
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.
[Illustration: Fig. 9]
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.
[Illustration: "SANTOS-DUMONT No. 5"]