HINTS AS TO THE BUILDING OF FLYING MACHINES.
[Illustration: Fig. 40.--Front elevation of proposed aeroplane
machine--_a_, _a_, the aeroplanes; _g_, _g_, condenser; _f_, the engine;
_q_, guard for screw; _k_, _k_, support for wheels.]
[Illustration: Fig. 41.--Side elevation of proposed superposed aeroplane
machine--_a_, _a_, main aeroplanes; _b_, _b_, rear aeroplanes; _c_,
vertical rudder; _d_, horizontal front rudder; _e_, screw; _f_, motor;
_g_, condenser; _h_, steering gear; _i_ and _j_, pneumatic buffers; _k_
and _l_, wheels; _m_, point at which _k_ is pivoted to the main frame;
_n_, handle of the steering gear.]
[Illustration: Fig. 42.--Plan of proposed aeroplane machine, in which
_a_, _a_ are the proposed superposed main aeroplanes; _b_, _b_, the
after superposed aeroplanes; _c_, _c_, the forward horizontal rudder;
_d_, platform; _e_, screw; _h_, _h_, and _i_, _i_, pulleys used in
communicating motion from the steering gear, _f_, to the rudder, _j_;
_g_, lever attached to the aeroplane or rudder, _c_, _c_, and connected
to the steering gear, _f_.]
For those who really wish to build a flying machine that will actually
fly with very little experimental work, I have given an outline sketch
sufficiently explicit to enable a skilful draughtsman to make a working
drawing in which Fig. 40 is a front elevation, Fig. 41 a side elevation,
and Fig. 42 a plan. Fig. 41, _a_, _a_, shows the two forward or main
aeroplanes; _b_, _b_, the two after aeroplanes, which are smaller and
shorter; _c_, the rudder; _d_, the forward horizontal rudder; _e_, the
screw; _f_, the motor; _g_, the condenser or cooler; _h_, the steering
gear; _i_, and _j_, atmospheric buffers; _k_ and _l_, wheels attached to
a lever pivoted to the body of the machine; _q_, a shield for protecting
the screw. It will be observed that the framework is extremely long,
and, consequently, the distance between the aeroplanes is very great;
but it should be borne in mind that the longer the machine, the less any
change of center of lifting effect, as relates to the center of gravity,
will be felt. Moreover, it is much easier to manœuvre a machine of
great length than one which is very short, because it gives one more
time to think and act. If the length was infinitely great the tendency
to pitch would be infinitely small. I have shown a steering gear
consisting of a lever with a handle _n_, arranged in such a manner that
it moves both the vertical rudder _c_, and the horizontal rudder _d_, so
that the man who steers the machine has nothing to think of except to
point the lever _n_, _p_, in the direction that he wishes the machine to
go. This lever is mounted on a universal joint at _h_, and is connected
with suitable wires to the two rudders. In order to prevent shock when
the machine alights, it is necessary to provide something that is strong
and, at the same time, yielding, and able to travel through a
considerable distance before the machine comes to a state of rest. In
the machines which I have seen on the Continent, a very elaborate
apparatus is employed, which is not only very heavy, but also offers a
considerable resistance to the forward motion of the machine through the
air. It consists of many tubes, very long levers and heavy spiral
springs, etc. In the device which I am recommending, all this is
dispensed with, and something very much simpler, cheaper, and lighter is
substituted. Moreover, with my proposed apparatus a certain amount of
lifting effect is produced. The levers _k_, _k_, to which the wheels are
attached, should be of thin wood, light and strong, and say about a foot
wide, strongly pivoted to the frame and held in position by an
atmospheric buffer made of strong and thin steel tubing, shown in
section (Fig. 51). These pneumatic cylinders may be pumped up to any
degree, so as to support the weight of the machine, and then, as it
comes down, the compression and escape of air arrest its motion. The
condenser _g_, is placed in such a position that it will act even while
the machine is on the ground and the propellers working. In Continental
machines, very small screw propellers are used. These screws have
probably been made small because the experimenters have found that they
encounter a good deal of friction in the atmosphere, but this is caused
by imperfect shape and the rib of steel at the back of the blades. In
order to use a small screw, experimenters have been forced to use a very
quick-running engine which makes it necessary to have the cylinders very
short, so, in order to get the necessary power, they are obliged to use
no less than eight cylinders. However, by increasing the diameter of the
screw and making it of such a form that very little or no atmospheric
skin friction is encountered, a much better and cheaper engine of a
totally different type may be employed. There is no reason why more than
four cylinders should be used, but the stroke of the piston and diameter
of the cylinder should be increased. Doubtless Continental experimenters
have an idea that, as the engine cannot be provided with a flywheel, it
must have a very large number of cylinders in order to give a steady
pull completely around the circle, and thus avoid so-called “dead
centers”; but, when we consider the enormously high velocity of the
periphery of the screw, and also take into consideration that the
momentum is in proportion to the square of the velocity, it is quite
obvious that there can be no slowing up between strokes even if only
one cylinder should be employed working on the four-cycle principle, in
which work is only done one stroke in four. Then, again, I find that the
weight of these Continental engines can be greatly reduced, providing
that they are made with the same degree of refinement that I employed in
building my steam engines.
Recently there has been a great deal of discussion in _Engineering_ and
other journals regarding the comparative merits of the aeroplane system
and the hélicoptère. Some condemn both systems and pin their faith to
flapping wings. It has been contended that the screw propeller is
extremely wasteful in energy, and that in all Nature neither fish nor
bird propels itself by means of a screw. As we do not find a screw in
Nature, why then should we employ it in a machine for performing
artificial flight?
Why not stick to Nature? In reply to this, I would say that even Nature
has her limits, beyond which she cannot go. When a boy was told that
everything was possible with God, he asked; “Could God make a two-year
old calf in five minutes?” He was told that God certainly could. “But,”
said the boy, “would the calf be two years old?” It appears to me that
there is nothing in Nature which is more efficient, or gets a better
grip on the water than a well-made screw propeller, and no doubt there
would have been fish with screw propellers, providing that Dame Nature
could have made an animal in two pieces. It is very evident that no
living creature could be made in two pieces, and two pieces are
necessary if one part is stationary and the other revolves; however, the
tails and fins very often approximate to the action of the propeller
blades; they turn first to the right and then to the left, producing a
sculling effect which is practically the same. This argument might also
be used against locomotives. In all Nature, we do not find an animal
travelling on wheels, but it is quite possible that a locomotive might
be made that would walk on legs at the rate of two or three miles an
hour. But locomotives with wheels are able to travel at least three
times as fast as the fleetest animal with legs, and to continue doing so
for many hours at a time, even when attached to a very heavy load. In
order to build a flying machine with flapping wings, to exactly imitate
birds, a very complicated system of levers, cams, cranks, etc., would
have to be employed, and these of themselves would weigh more than the
wings would be able to lift. However, it is quite possible to approach
very closely to the motion of a bird’s wings with no reciprocating or
vibrating parts, and without flapping at all.
[Illustration: Fig. 43.--Plan of a hélicoptère machine showing position
of the screws. Owing to the tilting of the shaft forward, the blades
present no angle when at _d_, _d_, but 10° at _c_, _c_, while at _f_,
_f_ their angle above the horizontal is 5°. The horizontal arrows show
the direction of the wind against the machine.]
[Illustration: Fig. 44.--Shows the position of the blades of a
hélicoptère as they pass around a circle, when the angle of the shaft
and the angle of the blades are the same.]
In Fig. 43, I have shown a plan of a hélicoptère machine in which two
screws are employed rotating in opposite directions, _a_, _a_, being the
port screw; _b_, _b_, the starboard screw; and _d_, _d_, the platform
for the machinery and operator. The screws should be 20 feet in diameter
and made of wood. Suppose now that the pitch of these screws is such
that the extremities of the blades have an angle of 5°; if now we tilt
the shaft forward in the direction of flight to the extent of 5°, we
shall completely wipe out the angle of inclination of the blades when at
_b_ (Fig. 44), whereas it will be observed that the pitch as regards the
horizontal will be increased to 10° at _a_, on the outer side, and
remain unchanged at _c_, and _d_. If the peripheral velocity of the
blades is, say, four times the velocity at which the machine is expected
to travel, the blades will get a good grip on the air at _c_, _d_, but
when they travel forward and encounter air which is travelling at a high
velocity in the opposite direction, they assume the position shown at
_b_. If the pitch of the screw blades was a little more than the angle
of the shaft, the blades at _b_ would also produce a lifting effect, and
as the velocity with which they pass through the air is extremely high,
a very strong lifting effect would be produced even if the angle was not
more than 1 in 40. By tracing the path and noting the position of the
ends of the blades as they pass completely around the circle as shown
(Fig. 44), it will be observed that they very closely resemble the
motion of a bird’s wing. I have no doubt that a properly made machine on
this plan would be highly satisfactory, but one should not lose sight of
the fact that even with a machine of this type, well designed and
sufficiently light to sustain itself in the air while flying, it would
still be necessary for it to move along rapidly when starting in order
to get the necessary grip on the air. Upon starting the engine, in a
machine of this kind, a very strong downward draught of air would be
produced, and the whole power of the engines would be used in
maintaining this downward blast, but if the machine should at the same
time be given a rapid forward motion sufficiently great to bring the
blades into contact with new air, the inertia of which had not been
disturbed, and which was not moving downwards, the lifting effect would
be increased sufficiently to lift the machine off the ground. It would,
therefore, work very much like an aeroplane machine. It would also be
possible to provide a third screw of less dimensions and running at a
less velocity, to push the machine forward, so as not to render it
necessary to give such a decided tilt to the shafts.
As before stated, great care should be taken in designing and making the
framework of flying machines, and no stone should be left unturned in
order to arrive at the greatest degree of lightness without diminishing
the strength too much; then, again, elasticity should be considered. If
we use a thin tube all the material is at the surface, far from the
neutral centre, and great stiffness is obtained, but such a tube will
not stand so much deflection as a piece of wood; then, again, wood is
cheaper than steel, and in case of an accident, repairs are very quickly
and easily made. Wood, however, cannot be obtained in long lengths
absolutely free from blemishes. It therefore becomes necessary to find
some way of making these long members of flying machines of such wood as
may be found suitable in the following table.
+---------------------+-------------+-------------+----------+
| | Strength | Weight of a | |
| | per Sq. In. | Cube Foot | Relative |
| | in Lbs. | in Lbs. | Value. |
+---------------------+-------------+-------------+----------+
| Alder, | ... | 50 | ... |
| Apple, | ... | 49·562 | ... |
| Ash, English, | 16,000 | 52·812 | 302·9 |
| Ash, White, | 14,000 | 43·125 | 324·6 |
| Bamboo, | 6,300 | 25 | 252 |
| Beech, English, | 11,500 | 53·25 | 215·9 |
| Birch, | 15,000 | 45 | 333·3 |
| Box, African, | 23,000 | ... | ... |
| „ France, | ... | 83 | ... |
| Cedar, American, | 11,600 | 35·062 | 330·8 |
| Deal, Christiania, | 12,400 | ... | ... |
| Ebony, | 27,000 | 83·187 | 324·6 |
| Elm, | 6,000 | 35·625 | 168·4 |
| „ Rock, | 13,000 | 50 | 260 |
| Fir, Norway Spruce, | ... | 32 | ... |
| „ Dantzic, | ... | 36·375 | ... |
| Hackmatack, | 12,000 | 37 | 324·3 |
| Hickory, | 11,000 | 49·5 | 222·2 |
| Ironwood, | ... | 61·875 | ... |
| Juniper, | ... | 36·375 | ... |
| Lance, | 23,000 | 45 | 511·1 |
| Lignum-Vitæ, | 11,800 | 83·312 | 141·6 |
| Lime, | ... | 50·25 | ... |
| Locust, | 20,500 | 45·5 | 450·5 |
| Mahogany, Honduras, | 21,000 | 35 | 600 |
| „ Spanish, | 12,000 | 53·25 | 225·3 |
| Maple, | ... | 46·875 | ... |
| Oak, African, | 9,500 | 51·437 | 184·7 |
| „ Canadian, | ... | 54·5 | ... |
| „ Dantzic, | 4,200 | 47·437 | 88·5 |
| „ English, | 7,571 | 53·625 | 141·2 |
| „ Live, | 16,380 | 66·75 | 245·4 |
| „ Pa, seasoned, | 20,333 | ... | ... |
| „ White, | 16,500 | 53·75 | 306·9 |
| „ Va, | 25,222 | ... | ... |
| Pine, Norway, | 14,000 | 46·25 | 302·7 |
| „ Pitch, | ... | 41·25 | ... |
| „ Red, | 13,000 | 36·875 | 352·5 |
| „ White, | 11,800 | 34·625 | 340·8 |
| „ Yellow, | 13,000 | 28·812 | 451·2 |
| „ Va, | 19,200 | ... | ... |
| Poplar, | 7,000 | 23·937 | 292·4 |
| „ White, | ... | 33·062 | ... |
| Redwood, Cal, | 10,833 | ... | ... |
| Spruce, | 12,400 | 31·25 | 396·8 |
| Sycamore, | 13,000 | 38·937 | 333·8 |
| Tamarack, | ... | 23·937 | ... |
| Teak, African, | 21,000 | 61·25 | 342·8 |
| „ Indian, | 15,000 | 41·062 | 365·3 |
| Walnut, | ... | 41·937 | ... |
| „ Black, | 16,633 | 31·25 | 532·2 |
| „ Michigan, | 17,500 | ... | ... |
| Willow, | 13,000 | 36·562 | 355·5 |
+---------------------+-------------+-------------+----------+
The relative value of different kinds of wood is shown in this table,
and it will be observed that some are much more suitable for the purpose
than others. The true value of a wood to be used in flying machines is
only ascertained by considering its strength in comparison with its own
weight--that is, the wood which is strongest in proportion to its weight
is the best. It will be seen that Honduras mahogany stands at the head
of the list, but American white pine is very good for certain purposes,
as it is light, strong, easily obtained, and takes the glue very well
indeed. In Fig. 45, I have shown a good system of producing the long
members necessary in flying machines. I will admit that it costs
something to fit up and produce the kind of joints which I have shown,
but when the members are once made, they are exceedingly strong and
stiff. Fig. 46 shows sections of the struts, and these may be made of
either straight-grained Honduras mahogany or of lance wood; either
answers the purpose very well, because being very strong and
straight-grained, permits the struts to be made of such a shape and size
as to offer very little resistance in cutting their way through the air.
The framework of the aeroplane unless carefully designed will offer
great resistance to being driven through the air. Suppose that the
bottom member of the truss (Fig. 47) is straight, and the top one curved
in the direction shown; no matter how taut the cloth may be drawn, the
pressure of the air will cause it to bag upwards between the different
trusses, so as to present very nearly the correct curve which is
necessary to produce the maximum lifting effect, and without offering
too much resistance to the air; however, one must not forget for a
single moment that the air flows over both sides of the aeroplane. When
the aeroplane is made very thick in the middle and sharp at the edges
(Fig. 48), with the bottom side dead level, it produces a decided
lifting effect no matter which way it is being propelled through the
air. This is not because the bottom side produces any lifting effect of
itself, but because the air running over the top follows the surface.
The aeroplane encounters air which is not moving at all. The air is
first moved upwards slightly, but it also has to run down the incline to
the rear edge of the aeroplane, so that, when it is discharged, it has a
decided downward trend; therefore, the air passing over the top side
instead of under the bottom side, produces the lifting effect, showing
that the top side of an aeroplane as well as the lower side should be
considered. The top side should, therefore, be free from all
obstructions.
[Illustration: Fig. 45.--System of splicing and building up wooden
members. When they have to be curved and to keep their shape, they
should be bent at the curve at the time of being glued together, and
joined in the middle as at _d_.]
[Illustration: Fig. 46.--Cross-section of struts.]
[Illustration: Fig. 47.--Truss suitable for use with flying machines,
having aeroplanes about 6 feet to 8 feet wide.]
The top of the aeroplane as well as the bottom should be covered with
some light material, if the very best results are to be obtained. In
another chapter I have shown a form of fabric-covered aeroplane, made by
myself, that was not distorted in the least by the air pressure, and
produced just as good effects as it would have done if it had been
carefully carved out of a piece of wood. On more than one occasion Lord
Kelvin came to my place; he said that my workshop was a perfect museum
of invention. At the Oxford Meeting of the British Association for the
Advancement of Science, Lord Salisbury in the chair, I was much
gratified when Lord Kelvin said that he had examined my work, and found
that it was beautifully designed and splendidly executed. He
complimented me very highly indeed. While at my place, he said that the
most ingenious thing that he had seen was the way I had prevented my
aeroplanes from being distorted by the air. He spoke of this several
times with great admiration, and, I think, if the fabric-covered
aeroplane is to be used at all, that my particular system will be found
altogether the best.
[Illustration: Fig. 48.--The paradox aeroplane that lifts no matter in
which direction it is being driven.]
[Illustration: Fig. 49.--The Antoinette motor.]
Regarding the motors now being employed, I think that there is still
room for a great deal of improvement in the direction of greater
lightness, higher efficiency and reliability. At the present time,
flying machine motors have such small cylinders, the rotation is so
rapid, and the cooling appliances so imperfect, that the engine soon
becomes intensely heated, and then its efficiency is said to fall off
about 40 or 50 per cent., some say even 60 per cent. This is probably on
account of the high temperature of the cylinder, piston, and air inlet.
The heat expands the air as it enters, so that the actual weight of air
in the cylinder is greatly reduced, and the engine power reduced in a
corresponding degree. There is no trouble about cooling the motor, and a
condenser of high efficiency may be made that will cool the water
perfectly, and, at the same time, lift a good deal more than its own
weight. All the conditions are favourable for using a very effective
atmospheric condenser (see Figs. 30 and 31).
Water may be considered as 2400 times as efficient as air, volume for
volume, in condensing steam. When a condenser is made for the purpose of
using water as a cooling agent, a large number of small tubes may be
closely grouped together in a box, and the water pumped in at one end of
the box and discharged at the other end through relatively small
openings; but when air is employed, the tubes or condensing surfaces
must be widely distributed, so that a very large amount of air is
encountered, and air which has struck one tube and become heated must
never touch a second tube (see Figs. 30 and 31, also Appendix).
[Illustration: Fig. 50.--Section showing the Antoinette motor, such as
used in the Farman and De la Grange machines.]
Fig. 51 shows a pneumatic buffer which I have designed, in which _a_,
_a_, is a steel tube highly polished on the inside; _b_, a nozzle for
connecting the air-pump, which is of the bicycle variety; _c_, a nipple
to which is attached a strong india-rubber bulb; _d_, a piston which is
made air-tight by a leather cup; and _f_, the connection to the lever
carrying the wheels on which the machine runs. While the machine is at a
state of rest on the ground, the piston-rod _d_, is run out to its full
extent, and supports the weight of the machine--the pressure being about
150 lbs. to the square inch. When, however, the machine comes violently
down to the earth, the piston is pushed inward, compressing the air,
and by the time it has travelled, say, one-half the stroke, the air
pressure will have mounted to 300 lbs. to the square inch. At this
point, the rubber bulb _c_, ought to burst and allow the compressed air
to escape under a high pressure. Air escaping through a relatively small
hole absorbs the momentum of the descent and brings the machine to a
state of rest without a destructive shock. It is, of course, necessary
for the navigator to select a broad and level field for descent, and
then to approach it from the leeward and slow up his machine as near the
ground as possible, tilting the forward end upwards in order to arrest
its forward motion, and touching the ground while still moving against
the wind at a fairly high velocity. If all these points are studied, and
well carried out, very little danger will result; then, again, the
aeroplanes _b_, _b_, and the forward rudder _d_ (Fig. 41), should be so
arranged that, in case of an accident, their outward sides may be
instantly turned upwards, in such a manner as to prevent the machine
from plunging, and keep it on an even keel while the engines are not
running.
[Illustration: Fig. 51.--Pneumatic buffer--_a_, _a_, cylinder; _b_,
attachment for pumping up; _c_, air outlet, covered with a rubber
thimble made to burst under about 300 lbs. pressure; _d_, the piston.]
STEERING BY MEANS OF A GYROSCOPE.
A ship at sea has only to be steered in a horizontal direction; the
water in which it is floated assures its stability in a vertical
direction; but when a flying machine is once launched in the air, it has
to be steered in two directions--that is, the vertical and the
horizontal. Moreover, it is constantly encountering air currents that
are moving with a much higher velocity than any water currents that have
ever to be encountered. It is, therefore, evident that, as far as
vertical steering is concerned, it should be automatic. Some have
suggested shifting weights, flowing mercury, and swinging pendulums; but
none of these is of the least value, on account of the swaying action
which always has to be encountered. A pendulum could not be depended
upon for working machinery on board a ship, and the same laws apply to
an airship. We have but one means at our disposal, and that is the
gyroscope. When a gyroscope is spun at a very high velocity on a
vertical axis, with the point of support very much above the center of
gyration, it has a tendency to maintain a vertical axis; a horizontal or
swinging motion of its support will not cause it to swing like a
pendulum. It therefore becomes possible by its use to maintain an
airship on an even keel. In a steam steering apparatus, such as is used
on shipboard, it is not sufficient to apply steam-power to move the
rudders, unless some means are provided whereby the movement of the
rudder closes off the steam, otherwise the rudder might continue to
travel after the effect had been produced, and ultimately be broken; and
so it is with steering a flying machine in a vertical direction.
Whenever the fore and aft rudders respond to the action of the gyroscope
and are set in motion, they must at once commence to shut off the power
that works them, otherwise they would continue to travel. In the
photograph (Fig. 52) I have shown an apparatus which I constructed at
Baldwyn’s Park. It will be seen that the gyroscope is enclosed in a
metal case; a tangent screw, just above the case, rotates a pointer
around a small disc, which admits of the speed of the gyroscope being
observed. Steam is admitted through a universal joint, descends through
the shaft and escapes through a series of small openings placed at a
tangent, so as to give rotation to the wheel after the manner of a
Barker’s mill. The casing about the rotating wheel is extremely light as
relates to the wheel, so that, when the gyroscope is once spun on a
vertical axis, the rest of the apparatus may be tilted in any direction,
while the gyroscope and its attachments maintain a vertical axis. The
gyroscope and its attachments are suspended from a long steel tube,
which in reality is a steam cylinder. The sleeve which supports the
gyroscope moves freely in a longitudinal direction, and the whole is
held in position by a triple-threaded screw on the small tube above the
cylinder. The steam is admitted through a piston value operated by a
species of link motion, as shown. The piston-rod extends to each end of
the cylinder, and regulates the rudders by pulling a small wire rope,
the travel of the piston being about 8 feet. At the end of the cylinder
(not shown) the piston-rod is provided with an arm and a nut which
engages the small top tube--this tube being provided with a long
spiral--so that, as the piston moves, the top tube is rotated, and
thereby slides the gyroscope’s support, and changes its position as
relates to the piston valve. It will, therefore, be seen that the action
is the same as with the common steam steering gear used on shipboard. A
little adjusting screw at the right hand of the print is shown. The
upward projecting arm of the bell crank lever is for the purpose of
attaching the wooden handle, making it possible to move the
connecting-rod instantly into a position where the steam piston will
move the rudders into the position shown (Fig. 56).
I copy the following from a description which I wrote of this apparatus
at the time:--
“GYROSCOPE APPARATUS FOR AUTOMATICALLY STEERING MACHINE IN A VERTICAL
DIRECTION.
“This apparatus consists of a long steam cylinder which is provided with
a piston, the piston-rod extending beyond the cylinder at each end; the
ropes working the fore and aft rudders are attached to the ends of this
piston-rod, and steam is supplied through an equilibrium valve. The
gyroscope is contained in a gunmetal case, and is driven by a jet of
steam entering through the trunnions. When the gyroscope is spinning at
a high velocity, the casing holding it becomes very rigid and is not
easily moved from its vertical position. If the machine rears or
pitches, the cylinder and valve are moved with the machine while the
gyroscope remains in a vertical position. This causes the steam valve to
be moved so as to admit steam into the cylinder and move the piston in
the proper direction to instantly bring the machine back into its normal
position. As the fore and aft rudders are moved, the long tubular shaft
immediately over the steam cylinder is rotated in such a manner as to
move the whole gyroscope in the proper direction to close off the steam.
The apparatus may be made to regulate at any angle by adjusting the
screw which regulates the position of the tubular shaft. The link that
suspends the end of the steam valve connecting-rod is supported by a
bell crank lever, and while the machine is moving ahead, the lever
occupies the position shown in the photograph (Fig. 52); but if the
machinery and engine stop, the bell crank lever may be moved so as to
throw the connecting-rod below the centre, when the steam will move the
piston in the proper direction to throw both the rudders into the
falling position, as shown in Fig. 56.”
[Illustration: Fig. 52.--Gyroscope, used for the control of the fore and
aft horizontal rudders, thus keeping the machine on an even keel while
in the air.]
[Illustration: Fig. 53.--In order to adjust the lifting effect so that
it was directly over the centre of gravity, and to test the action of my
fore and aft horizontal rudders, I ran the machine along the steel rail
_i_, _i_, and adjusted my weights and aeroplanes in such a manner that,
when the machine was run at a speed of 30 miles an hour along the track,
with the rudders adjusted in the manner shown, the front wheel _j_, was
raised from the steel track and the small wheel _m_, brought into
contact with the upper track _h_. When the rudder _b_, _b_, is in this
position, it produces a strong lifting effect, while the rudder _c_,
_c_, does not lift at all.]
[Illustration: Fig. 54.--This shows the rudders placed in such a
position that _b_, _b_, does not lift at all, while _c_, is placed at
such an angle as to produce a strong lifting effect, especially so as it
is in the blast of the screws _d_, _d_. With the rudders in this
position, and at a speed of 30 miles an hour, I was able to lift the
rear wheels _k_, _k_, off the steel rails and to bring the small wheel
_l_, in contact with the upper track _h_. These experiments showed that
the machine could be tilted in either direction by changing the position
of the rudder.]
[Illustration: Fig. 55.--When the rudders were placed in the position
shown, and the machine was run over the track at a rate of 40 miles an
hour, all the weight was lifted off the wheels, _j_, and _k_, and both
the small wheels _m_, and _l_, engaged the upper track.]
[Illustration: Fig. 56.--In case of a breakdown or failure of the
engines when the machine is in flight, it is necessary to place the
rudders in the position shown, in order to prevent the machine from
diving to the earth. When the rudders are in this position, a rapid and
destructive descent is not possible, as the machine will preserve an
even keel while falling.]