The French Kolb-Danvin engine of the hor_A History of Aeronautics（#874）

in 1905, was probably the first two-stroke cycle engine designed to

be applied to the propulsion of aircraft; it never got beyond the

experimental stage, although its trials gave very good results. Stepped

pistons were adopted, and the charging pump at one end was used to

scavenge the power cylinder at the other ends of the engine, the

transfer ports being formed in the main casting. The openings of these

ports were controlled at both ends by the pistons, and the location of

the ports appears to have made it necessary to take the exhaust from the

bottom of one cylinder and from the top of the other. The carburetted

mixture was drawn into the scavenging cylinders, and the usual

deflectors were cast on the piston heads to assist in the scavenging and

to prevent the fresh gas from passing out of the exhaust ports.

VI. THE TWO-STROKE CYCLE ENGINE

Although it has been little used for aircraft propulsion, the

possibilities of the two-stroke cycle engine render some study of

it desirable in this brief review of the various types of internal

combustion engine applicable both to aeroplanes and airships.

Theoretically the two-stroke cycle engine--or as it is more commonly

termed, the 'two-stroke,' is the ideal power producer; the doubling of

impulses per revolution of the crankshaft should render it of very much

more even torque than the four-stroke cycle types, while, theoretically,

there should be a considerable saving of fuel, owing to the doubling of

the number of power strokes per total of piston strokes. In practice,

however, the inefficient scavenging of virtually every two-stroke cycle

engine produced nullifies or more than nullifies its advantages over the

four-stroke cycle engine; in many types, too, there is a waste of fuel

gases through the exhaust ports, and much has yet to be done in the way

of experiment and resulting design before the two-stroke cycle engine

can be regarded as equally reliable, economical, and powerful with its

elder brother.

The first commercially successful engine operating on the two-stroke

cycle was invented by Mr Dugald Clerk, who in 1881 proved the design

feasible. As is more or less generally understood, the exhaust gases of

this engine are discharged from the cylinder during the time that

the piston is passing the inner dead centre, and the compression,

combustion, and expansion of the charge take place in similar manner

to that of the four-stroke cycle engine. The exhaust period is usually

controlled by the piston overrunning ports in the cylinder at the end

of its working stroke, these ports communicating direct with the outer

air--the complication of an exhaust valve is thus obviated; immediately

after the escape of the exhaust gases, charging of the cylinder occurs,

and the fresh gas may be introduced either through a valve in the

cylinder head or through ports situated diametrically opposite to the

exhaust ports. The continuation of the outward stroke of the piston,

after the exhaust ports have been closed, compresses the charge into

the combustion chamber of the cylinder, and the ignition of the mixture

produces a recurrence of the working stroke.

Thus, theoretically, is obtained the maximum of energy with the minimum

of expenditure; in practice, however, the scavenging of the power

cylinder, a matter of great importance in all internal combustion

engines, is often imperfect, owing to the opening of the exhaust ports

being of relatively short duration; clearing the exhaust gases out of

the cylinder is not fully accomplished, and these gases mix with the

fresh charge and detract from its efficiency. Similarly, owing to the

shorter space of time allowed, the charging of the cylinder with the

fresh mixture is not so efficient as in the four-stroke cycle type; the

fresh charge is usually compressed slightly in a separate chamber--crank

case, independent cylinder, or charging pump, and is delivered to

the working cylinder during the beginning of the return stroke of the

piston, while in engines working on the four-stroke cycle principle a

complete stroke is devoted to the expulsion of the waste gases of the

exhaust, and another full stroke to recharging the cylinder with fresh

explosive mixture.

Theoretically the two-stroke and the four-stroke cycle engines possess

exactly the same thermal efficiency, but actually this is modified by a

series of practical conditions which to some extent tend to neutralise

the very strong case in favour of the two-stroke cycle engine. The

specific capacity of the engine operating on the two-stroke principle is

theoretically twice that of one operating on the four-stroke cycle, and

consequently, for equal power, the former should require only about half

the cylinder volume of the latter; and, owing to the greater superficial

area of the smaller cylinder, relatively, the latter should be far more

easily cooled than the larger four-stroke cycle cylinder; thus it should

be possible to get higher compression pressures, which in turn should

result in great economy of working. Also the obtaining of a working

impulse in the cylinder for each revolution of the crankshaft should

give a great advantage in regularity of rotation--which it undoubtedly

does--and the elimination of the operating gear for the valves, inlet

and exhaust, should give greater simplicity of design.

In spite of all these theoretical--and some practical--advantages the

four-stroke cycle engine was universally adopted for aircraft work;

owing to the practical equality of the two principles of operation, so

far as thermal efficiency and friction losses are concerned, there is no

doubt that the simplicity of design (in theory) and high power output

to weight ratio (also in theory) ought to have given the 'two-stroke'

a place on the aeroplane. But this engine has to be developed so as to

overcome its inherent drawbacks; better scavenging methods have yet to

be devised--for this is the principal drawback--before the two-stroke

can come to its own as a prime mover for aircraft.

Mr Dugald Clerk's original two-stroke cycle engine is indicated roughly,

as regards principle, by the accompanying diagram, from which it will

be seen that the elimination of the ordinary inlet and exhaust valves

of the four-stroke type is more than compensated by a separate cylinder

which, having a piston worked from the connecting-rod of the power

cylinder, was used to charging, drawing the mixture from the carburettor

past the valve in the top of the charging cylinder, and then forcing it

through the connecting pipe into the power cylinder. The inlet valves

both on the charging and the power cylinders are automatic; when the

power piston is near the bottom of its stroke the piston in the charging

cylinder is compressing the carburetted air, so that as soon as the

pressure within the power cylinder is relieved by the exit of the burnt

gases through the exhaust ports the pressure in the charging cylinder

causes the valve in the head of the power cylinder to open, and fresh

mixture flows into the cylinder, replacing the exhaust gases. After

the piston has again covered the exhaust ports the mixture begins to be

compressed, thus automatically closing the inlet valve. Ignition

occurs near the end of the compression stroke, and the working stroke

immediately follows, thus giving an impulse to the crankshaft on every

down stroke of the piston. If the scavenging of the cylinder were

complete, and the cylinder were to receive a full charge of fresh

mixture for every stroke, the same mean effective pressure as is

obtained with four-stroke cycle engines ought to be realised, and at

an equal speed of rotation this engine should give twice the power

obtainable from a four-stroke cycle engine of equal dimensions. This

result was not achieved, and, with the improvements in construction

brought about by experiment up to 1912, the output was found to be only

about fifty per cent more than that of a four-stroke cycle engine of the

same size, so that, when the charging cylinder is included, this engine

has a greater weight per horse-power, while the lowest rate of fuel

consumption recorded was 0.68 lb. per horse-power per hour.

In 1891 Mr Day invented a two-stroke cycle engine which used the crank

case as a scavenging chamber, and a very large number of these engines

have been built for industrial purposes. The charge of carburetted air

is drawn through a non-return valve into the crank chamber during the

upstroke of the piston, and compressed to about 4 lbs. pressure per

square inch on the down stroke. When the piston approaches the bottom

end of its stroke the upper edge first overruns an exhaust port, and

almost immediately after uncovers an inlet port on the opposite side of

the cylinder and in communication with the crank chamber; the entering

charge, being under pressure, assists in expelling the exhaust gases

from the cylinder. On the next upstroke the charge is compressed into

the combustion space of the cylinder, a further charge simultaneously

entering the crank case to be compressed after the ignition for the

working stroke. To prevent the incoming charge escaping through the

exhaust ports of the cylinder a deflector is formed on the top of the

piston, causing the fresh gas to travel in an upward direction, thus

avoiding as far as possible escape of the mixture to the atmosphere.

From experiments conducted in 1910 by Professor Watson and Mr Fleming

it was found that the proportion of fresh gases which escaped unburnt

through the exhaust ports diminished with increase of speed; at 600

revolutions per minute about 36 per cent of the fresh charge was lost;

at 1,200 revolutions per minute this was reduced to 20 per cent, and at

1,500 revolutions it was still farther reduced to 6 per cent.

So much for the early designs. With regard to engines of this type

specially constructed for use with aircraft, three designs call for

special mention. Messrs A. Gobe and H. Diard, Parisian engineers,

produced an eight-cylindered two-stroke cycle engine of rotary design,

the cylinders being co-axial. Each pair of opposite pistons was secured

together by a rigid connecting rod, connected to a pin on a rotating

crankshaft which was mounted eccentrically to the axis of rotation

of the cylinders. The crankshaft carried a pinion gearing with an

internally toothed wheel on the transmission shaft which carried the

air-screw. The combustible mixture, emanating from a common supply pipe,

was led through conduits to the front ends of the cylinders, in which

the charges were compressed before being transferred to the working

spaces through ports in tubular extensions carried by the pistons.

These extensions had also exhaust ports, registering with ports in the

cylinder which communicated with the outer air, and the extensions slid

over depending cylinder heads attached to the crank case by long studs.

The pump charge was compressed in one end of each cylinder, and the

pump spaces each delivered into their corresponding adjacent combustion

spaces. The charges entered the pump spaces during the suction period

through passages which communicated with a central stationary supply

passage at one end of the crank case, communication being cut off when

the inlet orifice to the passage passed out of register with the port

in the stationary member. The exhaust ports at the outer end of the

combustion space opened just before and closed a little later than the

air ports, and the incoming charge assisted in expelling the exhaust

gases in a manner similar to that of the earlier types of two-stroke

cycle engine; The accompanying rough diagram assists in showing the

working of this engine.

Exhibited in the Paris Aero Exhibition of 1912, the Laviator two-stroke

cycle engine, six-cylindered, could be operated either as a radial or

as a rotary engine, all its pistons acting on a single crank. Cylinder

dimensions of this engine were 3.94 inches bore by 5.12 inches stroke,

and a power output of 50 horse-power was obtained when working at a rate

of 1,200 revolutions per minute. Used as a radial engine, it developed

65 horse-power at the same rate of revolution, and, as the total weight

was about 198 lbs., the weight of about 3 lbs. per horse-power was

attained in radial use. Stepped pistons were employed, the annular space

between the smaller or power piston and the walls of the larger cylinder

being used as a charging pump for the power cylinder situated 120

degrees in rear of it. The charging cylinders were connected by short

pipes to ports in the crank case which communicated with the hollow

crankshaft through which the fresh gas was supplied, and once in each

revolution each port in the case registered with the port in the

hollow shaft. The mixture which then entered the charging cylinder was

transferred to the corresponding working cylinder when the piston of

that cylinder had reached the end of its power stroke, and immediately

before this the exhaust ports diametrically opposite the inlet ports

were uncovered; scavenging was thus assisted in the usual way. The very

desirable feature of being entirely valveless was accomplished with this

engine, which is also noteworthy for exceedingly compact design.

The Lamplough six-cylinder two-stroke cycle rotary, shown at the Aero

Exhibition at Olympia in 1911, had several innovations, including a

charging pump of rotary blower type. With the six cylinders, six power

impulses at regular intervals were given on each rotation; otherwise,

the cycle of operations was carried out much as in other two-stroke

cycle engines. The pump supplied the mixture under slight pressure to

an inlet port in each cylinder, which was opened at the same time as the

exhaust port, the period of opening being controlled by the piston. The

rotary blower sucked the mixture from the carburettor and delivered it

to a passage communicating with the inlet ports in the cylinder walls.

A mechanically-operated exhaust valve was placed in the centre of each

cylinder head, and towards the end of the working stroke this valve

opened, allowing part of the burnt gases to escape to the atmosphere;

the remainder was pushed out by the fresh mixture going in through the

ports at the bottom end of the cylinder. In practice, one or other of

the cylinders was always taking fresh mixture while working, therefore

the delivery from the pump was continuous and the mixture had not to be

stored under pressure.

The piston of this engine was long enough to keep the ports covered

when it was at the top of the stroke, and a bottom ring was provided

to prevent the mixture from entering the crank case. In addition to

preventing leakage, this ring no doubt prevented an excess of oil

working up the piston into the cylinder. As the cylinder fired with

every revolution, the valve gear was of the simplest construction, a

fixed cam lifting each valve as the cylinder came into position. The

spring of the exhaust valve was not placed round the stem in the usual

way, but at the end of a short lever, away from the heat of the exhaust

gases. The cylinders were of cast steel, the crank case of aluminium,

and ball-bearings were fitted to the crankshaft, crank pins, and the

rotary blower pump. Ignition was by means of a high-tension magneto of

the two-spark pattern, and with a total weight of 300 lbs. the maximum

output was 102 brake horse-power, giving a weight of just under 3 lbs.

per horse-power.

One of the most successful of the two-stroke cycle engines was that

With four cylinders of 3.69 inches bore by 4.5 inches stroke, and

running at 1,250 revolutions per minute, this engine developed 50 brake

horse-power; the total weight of the engine was 155 lbs., thus giving a

weight of 3.1 lbs. per horse-power. A scavenging pump of the rotary type

was employed, driven by means of gearing from the engine crankshaft, and

in order to reduce weight to a minimum the vanes were of aluminium. This

engine was tried on a biplane, and gave very satisfactory results.

American design yields two apparently successful two-stroke cycle aero

engines. A rotary called the Fredericson engine was said to give an

output of 70 brake horse-power with five cylinders 4.5 inches diameter

by 4.75 inches stroke, running at 1,000 revolutions per minute. Another,

the Roberts two-stroke cycle engine, yielded 100 brake horse-power

from six cylinders of the stepped piston design; two carburettors, each

supplying three cylinders, were fitted to this engine. Ignition was

by means of the usual high-tension magneto, gear-driven from the

crankshaft, and the engine, which was water-cooled, was of compact

design.

It may thus be seen that the two-stroke cycle type got as far as actual

experiment in air work, and that with considerable success. So far,

however, the greater reliability of the four-stroke cycle has rendered

it practically the only aircraft engine, and the two-stroke has yet some

way to travel before it becomes a formidable competitor, in spite of its

admitted theoretical and questioned practical advantages.

VII. ENGINES OF THE WAR PERIOD

The principal engines of British, French, and American design used in

the war period and since are briefly described under the four distinct

types of aero engine; such notable examples as the Rolls-Royce,

Sunbeam, and Napier engines have been given special mention, as they

embodied--and still embody--all that is best in aero engine practice. So

far, however, little has been said about the development of German aero

engine design, apart from the early Daimler and other pioneer makes.

At the outbreak of hostilities in 1914, thanks to subsidies to

contractors and prizes to aircraft pilots, the German aeroplane

industry was in a comparatively flourishing condition. There were about

twenty-two establishments making different types of heavier-than-air

machines, monoplane and biplane, engined for the most part with the

four-cylinder Argus or the six-cylinder Mercedes vertical type engines,

each of these being of 100 horse-power--it was not till war brought

increasing demands on aircraft that the limit of power began to rise.

Contemporary with the Argus and Mercedes were the Austro-Daimler,

Benz, and N.A.G., in vertical design, while as far as rotary types were

concerned there were two, the Oberursel and the Stahlhertz; of these the

former was by far the most promising, and it came to virtual monopoly

of the rotary-engined plane as soon as the war demand began. It was

practically a copy of the famous Gnome rotary, and thus deserves little

description.

Germany, from the outbreak of war, practically, concentrated on the

development of the Mercedes engine; and it is noteworthy that, with one

exception, increase of power corresponding with the increased demand

for power was attained without increasing the number of cylinders. The

various models ranged between 75 and 260 horse-power, the latter being

the most recent production of this type. The exception to the rule

was the eight-cylinder 240 horse-power, which was replaced by the 260

horse-power six-cylinder model, the latter being more reliable and but

very slightly heavier. Of the other engines, the 120 horsepower Argus

and the 160 and 225 horse-power Benz were the most used, the Oberursel

being very largely discarded after the Fokker monoplane had had its day,

and the N.A.G. and Austro-Daimler Daimler also falling to comparative

disuse. It may be said that the development of the Mercedes engine

contributed very largely to such success as was achieved in the war

period by German aircraft, and, in developing the engine, the builders

were careful to make alterations in such a way as to effect the least

possible change in the design of aeroplane to which they were to be

fitted. Thus the engine base of the 175 horse-power model coincided

precisely with that of the 150 horse-power model, and the 200 and 240

horse-power models retained the same base dimensions. It was estimated,

in 1918, that well over eighty per cent of German aircraft was engined

with the Mercedes type.

In design and construction, there was nothing abnormal about the

Mercedes engine, the keynote throughout being extreme reliability and

such simplification of design as would permit of mass production in

different factories. Even before the war, the long list of records set

up by this engine formed practical application of the wisdom of this

policy; Bohn's flight of 24 hours 10 minutes, accomplished on July 10th

and 11th, 1914, 9is an instance of this--the flight was accomplished on

an Albatross biplane with a 75 horsepower Mercedes engine. The radial

type, instanced in other countries by the Salmson and Anzani makes, was

not developed in Germany; two radial engines were made in that country

before the war, but the Germans seemed to lose faith in the type under

war conditions, or it may have been that insistence on standardisation

ruled out all but the proved examples of engine.

Details of one of the middle sizes of Mercedes motor, the 176

horse-power type, apply very generally to the whole range; this size was

in use up to and beyond the conclusion of hostilities, and it may still

be regarded as characteristic of modern (1920) German practice. The

engine is of the fixed vertical type, has six cylinders in line, not

off-set, and is water-cooled. The cam shaft is carried in a special

bronze casing, seated on the immediate top of the cylinders, and a

vertical shaft is interposed between crankshaft and camshaft, the latter

being driven by bevel gearing.

On this vertical connecting-shaft the water pump is located, serving to

steady the motion of the shaft. Extending immediately below the camshaft

is another vertical shaft, driven by bevel gears from the crank-shaft,

and terminating in a worm which drives the multiple piston oil pumps.

The cylinders are made from steel forgings, as are the valve chamber

elbows, which are machined all over and welded together. A jacket of

light steel is welded over the valve elbows and attached to a flange

on the cylinders, forming a water-cooling space with a section of about

7/16 of an inch. The cylinder bore is 5.5 inches, and the stroke 6.29

inches. The cylinders are attached to the crank case by means of dogs

and long through bolts, which have shoulders near their lower ends and

are bolted to the lower half of the crank chamber. A very light and

rigid structure is thus obtained, and the method of construction won the

flattery of imitation by makers of other nationality.

The cooling system for the cylinders is extremely efficient. After

leaving the water pump, the water enters the top of the front cylinders

and passes successively through each of the six cylinders of the row;

short tubes, welded to the tops of the cylinders, serve as connecting

links in the system. The Panhard car engines for years were fitted with

a similar cooling system, and the White and Poppe lorry engines were

also similarly fitted; the system gives excellent cooling effect where

it is most needed, round the valve chambers and the cylinder heads.

The pistons are built up from two pieces; a dropped forged steel piston

head, from which depend the piston pin bosses, is combined with a

cast-iron skirt, into which the steel head is screwed. Four rings are

fitted, three at the upper and one at the lower end of the piston skirt,

and two lubricating oil grooves are cut in the skirt, in addition to the

ring grooves. Two small rivets retain the steel head on the piston skirt

after it has been screwed into position, and it is also welded at two

points. The coefficient of friction between the cast-iron and steel is

considerably less than that which would exist between two steel parts,

and there is less tendency for the skirt to score the cylinder walls

than would be the case if all steel were used--so noticeable is this

that many makers, after giving steel pistons a trial, discarded them in

favour of cast-iron; the Gnome is an example of this, being originally

fitted with a steel piston carrying a brass ring, discarded in favour of

a cast-iron piston with a percentage of steel in the metal mixture. In

the Le Rhone engine the difficulty is overcome by a cast-iron liner to

the cylinders.

The piston pin of the Mercedes is of chrome nickel steel, and is

retained in the piston by means of a set screw and cotter pin. The

connecting rods, of I section, are very short and rigid, carrying

floating bronze bushes which fit the piston pins at the small end, and

carrying an oil tube on each for conveying oil from the crank pin to the

piston pin.

The crankshaft is of chrome nickel steel, carried on seven bearings.

Holes are drilled through each of the crank pins and main bearings, for

half the diameter of the shaft, and these are plugged with pressed brass

studs. Small holes, drilled through the crank cheeks, serve to convey

lubricant from the main bearings to the crank pins. The propeller thrust

is taken by a simple ball thrust bearing at the propeller end of the

crankshaft, this thrust bearing being seated in a steel retainer which

is clamped between the two halves of the crank case. At the forward end

of the crankshaft there is mounted a master bevel gear on six splines;

this bevel floats on the splines against a ball thrust bearing, and,

in turn, the thrust is taken by the crank case cover. A stuffing

box prevents the loss of lubricant out of the front end of the crank

chamber, and an oil thrower ring serves a similar purpose at the

propeller end of the crank chamber.

With a motor speed of 1,450 r.p.m., the vertical shaft at the forward

end of the motor turns at 2,175 r.p.m., this being the speed of the two

magnetos and the water pump. The lower vertical shaft bevel gear and the

magneto driving gear are made integral with the vertical driving shaft,

which is carried in plain bearings in an aluminium housing. This housing

is clamped to the upper half of the crank case by means of three studs.

The cam-shaft carries eighteen cams, these being the inlet and exhaust

cams, and a set of half compression cams which are formed with the

exhaust cams and are put into action when required by means of a lever

at the forward end of the cam-shaft. The cam-shaft is hollow, and

serves as a channel for the conveyance of lubricating oil to each of

the camshaft bearings. At the forward end of this shaft there is also

mounted an air pump for maintaining pressure on the fuel supply tank,

and a bevel gear tachometer drive.

Lubrication of the engine is carried out by a full pressure system.

The oil is pumped through a single manifold, with seven branches to the

crankshaft main bearings, and then in turn through the hollow crankshaft

to the connecting-rod big ends and thence through small tubes, already

noted, to the small end bearings. The oil pump has four pistons and two

double valves driven from a single eccentric shaft on which are mounted

four eccentrics. The pump is continuously submerged in oil; in order to

avoid great variations in pressure in the oil lines there is a piston

operated pressure regulator, cut in between the pump and the oil lines.

The two small pistons of the pump take fresh oil from a tank located in

the fuselage of the machine; one of these delivers oil to the cam shaft,

and one delivers to the crankshaft; this fresh oil mixes with the used

oil, returns to the base, and back to the main large oil pump cylinders.

By means of these small pump pistons a constant quantity of oil is kept

in the motor, and the oil is continually being freshened by means of the

new oil coming in. All the oil pipes are very securely fastened to the

lower half of the crank case, and some cooling of the oil is effected

by air passing through channels cast in the crank case on its way to the

carburettor.

A light steel manifold serves to connect the exhaust ports of the

cylinders to the main exhaust pipe, which is inclined about 25 degrees

from vertical and is arranged to give on to the atmosphere just over the

top of the upper wing of the aeroplane.

As regards carburation, an automatic air valve surrounds the throat of

the carburettor, maintaining normal composition of mixture. A small jet

is fitted for starting and running without load. The channels cast in

the crank chamber, already alluded to in connection with oil-cooling,

serve to warm the air before it reaches the carburettor, of which the

body is water-jacketed.

Ignition of the engine is by means of two Bosch ZH6 magnetos, driven at

a speed of 2,175 revolutions per minute when the engine is running at

its normal speed of 1,450 revolutions. The maximum advance of spark is

12 mm., or 32 degrees before the top dead centre, and the firing order

of the cylinders is 1,5,3,6,2,4.

The radiator fitted to this engine, together with the water-jackets,

has a capacity of 25 litres of water, it is rectangular in shape, and is

normally tilted at an angle of 30 degrees from vertical. Its weight is

26 kg., and it offers but slight head resistance in flight.

The radial type of engine, neglected altogether in Germany, was brought

to a very high state of perfection at the end of the War period by

British makers. Two makes, the Cosmos Engineering Company's 'Jupiter'

and 'Lucifer,' and the A.B.C. 'Wasp II' and 'Dragon Fly 1A' require

special mention for their light weight and reliability on trials.

The Cosmos 'Jupiter' was--for it is no longer being made--a 450

horse-power nine-cylinder radial engine, air-cooled, with the cylinders

set in one single row; it was made both geared to reduce the propeller

revolutions relatively to the crankshaft revolutions, and ungeared;

the normal power of the geared type was 450 horse-power, and the total

weight of the engine, including carburettors, magnetos, etc., was only

757 lbs.; the engine speed was 1,850 revolutions per minute, and the

propeller revolutions were reduced by the gearing to 1,200. Fitted to a

'Bristol Badger' aeroplane, the total weight was 2,800 lbs., including

pilot, passenger, two machine-guns, and full military load; at 7,000

feet the registered speed, with corrections for density, was 137 miles

per hour; in climbing, the first 2,000 feet was accomplished in 1 minute

4 seconds; 4,000 feet was reached in 2 minutes 10 seconds; 6,000 feet

was reached in 3 minutes 33 seconds, and 7,000 feet in 4 minutes 15

seconds. It was intended to modify the plane design and fit a new

propeller, in order to attain even better results, but, if trials were

made with these modifications, the results are not obtainable.

The Cosmos 'Lucifer' was a three-cylinder radial type engine of 100

horse-power, inverted Y design, made on the simplest possible principles

with a view to quantity production and extreme reliability. The rated

100 horse-power was attained at 1,600 revolutions per minute, and the

cylinder dimensions were 5.75 bore by 6.25 inches stroke. The cylinders

were of aluminium and steel mixture, with aluminium heads; overhead

valves, operated by push rods on the front side of the cylinders, were

fitted, and a simple reducing gear ran them at half engine speed. The

crank case was a circular aluminium casting, the engine being attached

to the fuselage of the aeroplane by a circular flange situated at the

back of the case; propeller shaft and crankshaft were integral. Dual

ignition was provided, the generator and distributors being driven off

the back end of the engine and the distributors being easily accessible.

Lubrication was by means of two pumps, one scavenging and one suction,

oil being fed under pressure from the crankshaft. A single carburettor

fed all three cylinders, the branch pipe from the carburettor to the

circular ring being provided with an exhaust heater. The total weight of

the engine, 'all on,' was 280 lbs.

The A.B.C. 'Wasp II,' made by Walton Motors, Limited, is a

seven-cylinder radial, air-cooled engine, the cylinders having a bore

of 4.75 inches and stroke 6.25 inches. The normal brake horse-power

at 1,650 revolutions is 160, and the maximum 200 at a speed of 1,850

revolutions per minute. Lubrication is by means of two rotary pumps,

one feeding through the hollow crankshaft to the crank pin, giving

centrifugal feed to big end and thence splash oiling, and one feeding to

the nose of the engine, dropping on to the cams and forming a permanent

sump for the gears on the bottom of the engine nose. Two carburettors

are fitted, and two two-spark magnetos, running at one and

three-quarters engine speed. The total weight of this engine is 350

lbs., or 1.75 lbs. per horse-power. Oil consumption at 1,850 revolutions

is.03 pints per horse-power per hour, and petrol consumption is.56 pints

per horsepower per hour. The engine thus shows as very economical in

consumption, as well as very light in weight.

The A.B.C. 'Dragon Fly 1A 'is a nine-cylinder radial engine having

one overhead inlet and two overhead exhaust valves per cylinder. The

cylinder dimensions are 5.5 inches bore by 6.5 inches stroke, and

the normal rate of speed, 1,650 revolutions per minute, gives 340

horse-power. The oiling is by means of two pumps, the system being

practically identical with that of the 'Wasp II.' Oil consumption

is.021 pints per brake horse-power per hour, and petrol consumption.56

pints--the same as that of the 'Wasp II.' The weight of the complete

engine, including propeller boss, is 600 lbs., or 1,765 lbs. per

horse-power.

These A.B.C. radials have proved highly satisfactory on tests, and their

extreme simplicity of design and reliability commend them as engineering

products and at the same time demonstrate the value, for aero work, of

the air-cooled radial design--when this latter is accompanied by sound

workmanship. These and the Cosmos engines represent the minimum of

weight per horse-power yet attained, together with a practicable degree

of reliability, in radial and probably any aero engine design.

APPENDIX A

GENERAL MENSIER'S REPORT ON THE TRIALS OF CLEMENT ADER'S AVION.

Paris, October 21, 1897.

Report on the trials of M. Clement Ader's aviation apparatus.

M. Ader having notified the Minister of War by letter, July 21, 1897,

that the Apparatus of Aviation which he had agreed to build under the

conditions set forth in the convention of July 24th, 1894, was ready,

and therefore requesting that trials be undertaken before a Committee

appointed for this purpose as per the decision of August 4th, the

Committee was appointed as follows:--

Division General Mensier, Chairman; Division General Delambre, Inspector

General of the Permanent Works of Coast Defence, Member of the Technical

Committee of the Engineering Corps; Colonel Laussedat, Director of the

Conservatoire des Arts et Metiers; Sarrau, Member of the Institute,

Professor of Mechanical Engineering at the Polytechnic School; Leaute,

Member of the Institute, Professor of Mechanical Engineering at the

Polytechnique School.

Colonel Laussedat gave notice at once that his health and work as

Director of the Conservatoire des Arts et Metiers did not permit him

to be a member of the Committee; the Minister therefore accepted his

resignation on September 24th, and decided not to replace him.

Later on, however, on the request of the Chairman of the Committee, the

Minister appointed a new member General Grillon, commanding the Engineer

Corps of the Military Government of Paris.

To carry on the trials which were to take place at the camp of Satory,

the Minister ordered the Governor of the Military Forces of Paris to

requisition from the Engineer Corps, on the request of the Chairman of

the Committee, the men necessary to prepare the grounds at Satory.

After an inspection made on the 16th an aerodrome was chosen. M. Ader's

idea was to have it of circular shape with a width of 40 metres and an

average diameter of 450 metres. The preliminary work, laying out the

grounds, interior and exterior circumference, etc., was finished at the

end of August; the work of smoothing off the grounds began September 1st

with forty-five men and two rollers, and was finished on the day of the

first tests, October 12th.

The first meeting of the Committee was held August 18th in M. Ader's

workshop; the object being to demonstrate the machine to the Committee

and give all the information possible on the tests that were to be held.

After a careful examination and after having heard all the explanations

by the inventor which were deemed useful and necessary, the Committee

decided that the apparatus seemed to be built with a perfect

understanding of the purpose to be fulfilled as far as one could judge

from a study of the apparatus at rest; they therefore authorised M. Ader

to take the machine apart and carry it to the camp at Satory so as to

proceed with the trials.

By letter of August 19th the Chairman made report to the Minister of the

findings of the Committee.

The work on the grounds having taken longer than was anticipated, the

Chairman took advantage of this delay to call the Committee together

for a second meeting, during which M. Ader was to run the two propulsive

screws situated at the forward end of the apparatus.

The meeting was held October 2nd. It gave the Committee an opportunity

to appreciate the motive power in all its details; firebox, boiler,

engine, under perfect control, absolute condensation, automatic fuel

and feed of the liquid to be vaporised, automatic lubrication and

scavenging; everything, in a word, seemed well designed and executed.

The weights in comparison with the power of the engine realised a

considerable advance over anything made to date, since the two engines

weighed together realised 42 kg., the firebox and boiler 60 kg., the

condenser 15 kg., or a total of 117 kg. for approximately 40 horse-power

or a little less than 3 kg. per horse-power.

One of the members summed up the general opinion by saying: 'Whatever

may be the result from an aviation point of view, a result which could

not be foreseen for the moment, it was nevertheless proven that from

a mechanical point of view M. Ader's apparatus was of the greatest

interest and real ingeniosity. He expressed a hope that in any case the

machine would not be lost to science.'

The second experiment in the workshop was made in the presence of the

Chairman, the purpose being to demonstrate that the wings, having a

spread of 17 metres, were sufficiently strong to support the weight of

the apparatus. With this object in view, 14 sliding supports were placed

under each one of these, representing imperfectly the manner in which

the wings would support the machine in the air; by gradually raising the

supports with the slides, the wheels on which the machine rested were

lifted from the ground. It was evident at that time that the members

composing the skeleton of the wings supported the apparatus, and it was

quite evident that when the wings were supported by the air on every

point of their surface, the stress would be better equalised than when

resting on a few supports, and therefore the resistance to breakage

would be considerably greater.

After this last test, the work on the ground being practically finished,

the machine was transported to Satory, assembled and again made ready

for trial.

At first M. Ader was to manoeuvre the machine on the ground at a

moderate speed, then increase this until it was possible to judge

whether there was a tendency for the machine to rise; and it was only

after M. Ader had acquired sufficient practice that a meeting of the

Committee was to be called to be present at the first part of the

trials; namely, volutions of the apparatus on the ground.

The first test took place on Tuesday, October 12th, in the presence

of the Chairman of the Committee. It had rained a good deal during the

night and the clay track would have offered considerable resistance to

the rolling of the machine; furthermore, a moderate wind was blowing

from the south-west, too strong during the early part of the afternoon

to allow of any trials.

Toward sunset, however, the wind having weakened, M. Ader decided to

make his first trial; the machine was taken out of its hangar, the wings

were mounted and steam raised. M. Ader in his seat had, on each side of

him, one man to the right and one to the left, whose duty was to rectify

the direction of the apparatus in the event that the action of the

rear wheel as a rudder would not be sufficient to hold the machine in a

straight course.

At 5.25 p.m. the machine was started, at first slowly and then at an

increased speed; after 250 or 300 metres, the two men who were being

dragged by the apparatus were exhausted and forced to fall flat on

the ground in order to allow the wings to pass over them, and the

trip around the track was completed, a total of 1,400 metres, without

incident, at a fair speed, which could be estimated to be from 300 to

400 metres per minute. Notwithstanding M. Ader's inexperience, this

being the first time that he had run his apparatus, he followed

approximately the chalk line which marked the centre of the track and he

stopped at the exact point from which he started.

The marks of the wheels on the ground, which was rather soft, did not

show up very much, and it was clear that a part of the weight of the

apparatus had been supported by the wings, though the speed was only

about one-third of what the machine could do had M. Ader used all its

motive power; he was running at a pressure of from 3 to 4 atmospheres,

when he could have used 10 to 12.

This first trial, so fortunately accomplished, was of great importance;

it was the first time that a comparatively heavy vehicle (nearly 400

kg., including the weight of the operator, fuel, and water) had been set

in motion by a tractive apparatus, using the air solely as a propelling

medium. The favourable report turned in by the Committee after the

meeting of October 2nd was found justified by the results demonstrated

on the grounds, and the first problem of aviation, namely, the creation

of efficient motive power, could be considered as solved, since the

propulsion of the apparatus in the air would be a great deal easier

than the traction on the ground, provided that the second part of the

problem, the sustaining of the machine in the air, would be realised.

The next day, Wednesday the 13th, no further trials were made on account

of the rain and wind.

On Thursday the 14th the Chairman requested that General Grillon, who

had just been appointed a member of the Committee, accompany him so as

to have a second witness.

The weather was fine, but a fairly strong, gusty wind was blowing from

the south. M. Ader explained to the two members of the Committee the

danger of these gusts, since at two points of the circumference the wind

would strike him sideways. The wind was blowing in the direction A B,

the apparatus starting from C, and running in the direction shown by the

arrow. The first dangerous spot would be at B. The apparatus had been

kept in readiness in the event of the wind dying down. Toward sunset the

wind seemed to die down, as it had done on the evening of the 12th. M.

Ader hesitated, which, unfortunately, further events only justified, but

decided to make a new trial.

At the start, which took place at 5.15 p.m., the apparatus, having

the wind in the rear, seemed to run at a fairly regular speed; it was,

nevertheless, easy to note from the marks of the wheels on the ground

that the rear part of the apparatus had been lifted and that the rear

wheel, being the rudder, had not been in constant contact with the

ground. When the machine came to the neighbourhood of B, the two members

of the Committee saw the machine swerve suddenly out of the track in a

semicircle, lean over to the right and finally stop. They immediately

proceeded to the point where the accident had taken place and

endeavoured to find an explanation for the same. The Chairman finally

decided as follows:

M. Ader was the victim of a gust of wind which he had feared as he

explained before starting out; feeling himself thrown out of his course,

he tried to use the rudder energetically, but at that time the rear

wheel was not in contact with the ground, and therefore did not

perform its function; the canvas rudder, which had as its purpose the

manoeuvring of the machine in the air, did not have sufficient action

on the ground. It would have been possible without any doubt to react

by using the propellers at unequal speed, but M. Ader, being still

inexperienced, had not thought of this. Furthermore, he was thrown

out of his course so quickly that he decided, in order to avoid a more

serious accident, to stop both engines. This sudden stop produced the

half-circle already described and the fall of the machine on its side.

The damage to the machine was serious; consisting at first sight of the

rupture of both propellers, the rear left wheel and the bending of the

left wing tip. It will only be possible to determine after the machine

is taken apart whether the engine, and more particularly the organs of

transmission, have been put out of line.

Whatever the damage may be, though comparatively easy to repair, it will

take a certain amount of time, and taking into consideration the time

of year it is evident that the tests will have to be adjourned for the

present.

As has been said in the above report, the tests, though prematurely

interrupted, have shown results of great importance, and though the

final results are hard to foresee, it would seem advisable to continue

the trials. By waiting for the return of spring there will be plenty of

time to finish the tests and it will not be necessary to rush matters,

which was a partial cause of the accident. The Chairman of the Committee

personally has but one hope, and that is that a decision be reached

accordingly.

Division General,

Chairman of the Committee,

Mensier.

Boulogne-sur-Seine, October 21st, 1897.

Annex to the Report of October 21st.

General Grillon, who was present at the trials of the 14th, and who saw

the report relative to what happened during that day, made the following

observations in writing, which are reproduced herewith in quotation

marks. The Chairman of the Committee does not agree with General Grillon

and he answers these observations paragraph by paragraph.

1. 'If the rear wheel (there is only one of these) left but intermittent

tracks on the ground, does that prove that the machine has a tendency to

rise when running at a certain speed?'

Answer.--This does not prove anything in any way, and I was very careful

not to mention this in my report, this point being exactly what was

needed and that was not demonstrated during the two tests made on the

grounds.

'Does not this unequal pressure of the two pair of wheels on the ground

show that the centre of gravity of the apparatus is placed too far

forward and that under the impulse of the propellers the machine has a

tendency to tilt forward, due to the resistance of the air?'

Answer.--The tendency of the apparatus to rise from the rear when it was

running with the wind seemed to be brought about by the effects of the

wind on the huge wings, having a spread of 17 metres, and I believe that

when the machine would have faced the wind the front wheels would have

been lifted.

During the trials of October 12th, when a complete circuit of the track

was accomplished without incidents, as I and Lieut. Binet witnessed,

there was practically no wind. I was therefore unable to verify whether

during this circuit the two front wheels or the rear wheel were in

constant contact with the ground, because when the trial was over it was

dark (it was 5.30) and the next day it was impossible to see anything

because it had rained during the night and during Wednesday morning. But

what would prove that the rear wheel was in contact with the ground at

all times is the fact that M. Ader, though inexperienced, did not swerve

from the circular track, which would prove that he steered pretty well

with his rear wheel--this he could not have done if he had been in the

air.

In the tests of the 12th, the speed was at least as great as on the

14th.

2. 'It would seem to me that if M. Ader thought that his rear wheels

were off the ground he should have used his canvas rudder in order to

regain his proper course; this was the best way of causing the machine

to rotate, since it would have given an angular motion to the front

axle.'

Answer.--I state in my report that the canvas rudder whose object was

the manoeuvre of the apparatus in the air could have no effect on the

apparatus on the ground, and to convince oneself of this point it is

only necessary to consider the small surface of this canvas rudder

compared with the mass to be handled on the ground, a weight of

approximately 400 kg. According to my idea, and as I have stated in my

report, M. Ader should have steered by increasing the speed on one of

his propellers and slowing down the other. He admitted afterward that

this remark was well founded, but that he did not have time to think of

it owing to the suddenness of the accident.

3. 'When the apparatus fell on its side it was under the sole influence

of the wind, since M. Ader had stopped the machine. Have we not a result

here which will always be the same when the machine comes to the ground,

since the engines will always have to be stopped or slowed down when

coming to the ground? Here seems to be a bad defect of the apparatus

under trial.'

Answer.--I believe that the apparatus fell on its side after coming to

a stop, not on account of the wind, but because the semicircle described

was on rough ground and one of the wheels had collapsed.

Mensier.

October 27th, 1897.

APPENDIX B

Specification and Claims of Wright Patent, No. 821393. Filed March 23rd,

1903. Issued May 22nd, 1906. Expires May 22nd, 1923.

To all whom it may concern.

Be it known that we, Orville Wright and Wilbur Wright, citizens of the

United States, residing in the city of Dayton, county of Montgomery,

and State of Ohio, have invented certain new and useful Improvements in

Flying Machines, of which the following is a specification.

Our invention relates to that class of flying-machines in which

the weight is sustained by the reactions resulting when one or more

aeroplanes are moved through the air edgewise at a small angle of

incidence, either by the application of mechanical power or by the

utilisation of the force of gravity.

The objects of our invention are to provide means for maintaining

or restoring the equilibrium or lateral balance of the apparatus, to

provide means for guiding the machine both vertically and horizontally,

and to provide a structure combining lightness, strength, convenience of

construction and certain other advantages which will hereinafter appear.

To these ends our invention consists in certain novel features, which we

will now proceed to describe and will then particularly point out in the

claims. In the accompanying drawings, Figure I 1 is a perspective view

of an apparatus embodying our invention in one form. Fig. 2 is a plan

view of the same, partly in horizontal section and partly broken away.

Fig. 3 is a side elevation, and Figs. 4 and 5 are detail views, of one

form of flexible joint for connecting the upright standards with the

aeroplanes.

In flying machines of the character to which this invention relates the

apparatus is supported in the air by reason of the contact between the

air and the under surface of one or more aeroplanes, the contact surface

being presented at a small angle of incidence to the air. The relative

movements of the air and aeroplane may be derived from the motion of

the air in the form of wind blowing in the direction opposite to that in

which the apparatus is travelling or by a combined downward and forward

movement of the machine, as in starting from an elevated position or

by combination of these two things, and in either case the operation is

that of a soaring-machine, while power applied to the machine to propel

it positively forward will cause the air to support the machine in a

similar manner. In either case owing to the varying conditions to be

met there are numerous disturbing forces which tend to shift the machine

from the position which it should occupy to obtain the desired results.

It is the chief object of our invention to provide means for remedying

this difficulty, and we will now proceed to describe the construction by

means of which these results are accomplished.

In the accompanying drawing we have shown an apparatus embodying our

invention in one form. In this illustrative embodiment the machine is

shown as comprising two parallel superposed aeroplanes, 1 and 2, may be

embodied in a structure having a single aeroplane. Each aeroplane is of

considerably greater width from side to side than from front to rear.

The four corners of the upper aeroplane are indicated by the reference

letters a, b, c, and d, while the corresponding corners of the lower

aeroplane 2 are indicated by the reference letters e, f, g, and h. The

marginal lines ab and ef indicate the front edges of the aeroplanes, the

lateral margins of the upper aeroplane are indicated, respectively,

by the lines ad and bc, the lateral margins of the lower aeroplane are

indicated, respectively, by the lines eh and fg, while the rear margins

of the upper and lower aeroplanes are indicated, respectively, by the

lines cd and gh.

Before proceeding to a description of the fundamental theory of

operation of the structure we will first describe the preferred mode of

constructing the aeroplanes and those portions of the structure which

serve to connect the two aeroplanes.

Each aeroplane is formed by stretching cloth or other suitable fabric

over a frame composed of two parallel transverse spars 3, extending

from side to side of the machine, their ends being connected by bows 4

extending from front to rear of the machine. The front and rear spars

3 of each aeroplane are connected by a series of parallel ribs 5, which

preferably extend somewhat beyond the rear spar, as shown. These spars,

bows, and ribs are preferably constructed of wood having the necessary

strength, combined with lightness and flexibility. Upon this framework

the cloth which forms the supporting surface of the aeroplane is

secured, the frame being enclosed in the cloth. The cloth for each

aeroplane previous to its attachment to its frame is cut on the bias

and made up into a single piece approximately the size and shape of the

aeroplane, having the threads of the fabric arranged diagonally to the

transverse spars and longitudinal ribs, as indicated at 6 in Fig. 2.

Thus the diagonal threads of the cloth form truss systems with the spars

and ribs, the threads constituting the diagonal members. A hem is formed

at the rear edge of the cloth to receive a wire 7, which is connected to

the ends of the rear spar and supported by the rearwardly-extending ends

of the longitudinal ribs 5, thus forming a rearwardly-extending flap

or portion of the aeroplane. This construction of the aeroplane gives

a surface which has very great strength to withstand lateral and

longitudinal strains, at the same time being capable of being bent or

twisted in the manner hereinafter described.

When two aeroplanes are employed, as in the construction illustrated,

they are connected together by upright standards 8. These standards are

substantially rigid, being preferably constructed of wood and of equal

length, equally spaced along the front and rear edges of the aeroplane,

to which they are connected at their top and bottom ends by hinged

joints or universal joints of any suitable description. We have shown

one form of connection which may be used for this purpose in Figs. 4 and

5 of the drawings. In this construction each end of the standard 8

has secured to it an eye 9 which engages with a hook 10, secured to a

bracket plate 11, which latter plate is in turn fastened to the spar 3.

Diagonal braces or stay-wires 12 extend from each end of each standard

to the opposite ends of the adjacent standards, and as a convenient mode

of attaching these parts I have shown a hook 13 made integral with the

hook 10 to receive the end of one of the stay-wires, the other stay-wire

being mounted on the hook 10. The hook 13 is shown as bent down to

retain the stay-wire in connection to it, while the hook 10 is shown

as provided with a pin 14 to hold the staywire 12 and eye 9 in position

thereon. It will be seen that this construction forms a truss system

which gives the whole machine great transverse rigidity and strength,

while at the same time the jointed connections of the parts permit the

aeroplanes to be bent or twisted in the manner which we will now proceed

to describe.

15 indicates a rope or other flexible connection extending lengthwise

of the front of the machine above the lower aeroplane, passing under

pulleys or other suitable guides 16 at the front corners e and f of the

lower aeroplane, and extending thence upward and rearward to the upper

rear corners c and d, of the upper aeroplane, where they are attached,

as indicated at 17. To the central portion of the rope there is

connected a laterally-movable cradle 18, which forms a means for moving

the rope lengthwise in one direction or the other, the cradle being

movable toward either side of the machine. We have devised this cradle

as a convenient means for operating the rope 15, and the machine is

intended to be generally used with the operator lying face downward on

the lower aeroplane, with his head to the front, so that the operator's

body rests on the cradle, and the cradle can be moved laterally by the

movements of the operator's body. It will be understood, however, that

the rope 15 may be manipulated in any suitable manner.

19 indicates a second rope extending transversely of the machine along

the rear edge of the body portion of the lower aeroplane, passing under

suitable pulleys or guides 20 at the rear corners g and h of the lower

aeroplane and extending thence diagonally upward to the front corners a

and b of the upper aeroplane, where its ends are secured in any suitable

manner, as indicated at 21.

Considering the structure so far as we have now described it, and

assuming that the cradle 18 be moved to the right in Figs. 1 and 2,

as indicated by the arrows applied to the cradle in Fig. 1 and by the

dotted lines in Fig. 2, it will be seen that that portion of the rope 15

passing under the guide pulley at the corner e and secured to the corner

d will be under tension, while slack is paid out throughout the other

side or half of the rope 15. The part of the rope 15 under tension

exercises a downward pull upon the rear upper corner d of the structure

and an upward pull upon the front lower corner e, as indicated by the

arrows. This causes the corner d to move downward and the corner e to

move upward. As the corner e moves upward it carries the corner a upward

with it, since the intermediate standard 8 is substantially rigid and

maintains an equal distance between the corners a and e at all times.

Similarly, the standard 8, connecting the corners d and h, causes the

corner h to move downward in unison with the corner d. Since the corner

a thus moves upward and the corner h moves downward, that portion of

the rope 19 connected to the corner a will be pulled upward through the

pulley 20 at the corner h, and the pull thus exerted on the rope 19 will

pull the corner b on the other wise of the machine downward and at the

same time pull the corner g at said other side of the machine upward.

This results in a downward movement of the corner b and an upward

movement of the corner c. Thus it results from a lateral movement of the

cradle 18 to the right in Fig. 1 that the lateral margins ad and eh at

one side of the machine are moved from their normal positions in which

they lie in the normal planes of their respective aeroplanes, into

angular relations with said normal planes, each lateral margin on this

side of the machine being raised above said normal plane at its forward

end and depressed below said normal plane at its rear end, said lateral

margins being thus inclined upward and forward. At the same time a

reverse inclination is imparted to the lateral margins bc end fg at the

other side of the machine, their inclination being downward and forward.

These positions are indicated in dotted lines in Fig. 1 of the drawings.

A movement of the cradle 18 in the opposite direction from its normal

position will reverse the angular inclination of the lateral margins of

the aeroplanes in an obvious manner. By reason of this construction it

will be seen that with the particular mode of construction now under

consideration it is possible to move the forward corner of the lateral

edges of the aeroplane on one side of the machine either above or below

the normal planes of the aeroplanes, a reverse movement of the forward

corners of the lateral margins on the other side of the machine

occurring simultaneously. During this operation each aeroplane is

twisted or distorted around a line extending centrally across the same

from the middle of one lateral margin to the middle of the other lateral

margin, the twist due to the moving of the lateral margins to different

angles extending across each aeroplane from side to side, so that each

aeroplane surface is given a helicoidal warp or twist. We prefer this

construction and mode of operation for the reason that it gives a

gradually increasing angle to the body of each aeroplane from the

centre longitudinal line thereof outward to the margin, thus giving a

continuous surface on each side of the machine, which has a gradually

increasing or decreasing angle of incidence from the centre of the

machine to either side. We wish it to be understood, however, that our

invention is not limited to this particular construction, since any

construction whereby the angular relations of the lateral margins of

the aeroplanes may be varied in opposite directions with respect to

the normal planes of said aeroplanes comes within the scope of our

invention. Furthermore, it should be understood that while the lateral

margins of the aeroplanes move to different angular positions with

respect to or above and below the normal planes of said aeroplanes,

it does not necessarily follow that these movements bring the opposite

lateral edges to different angles respectively above and below a

horizontal plane since the normal planes of the bodies of the aeroplanes

are inclined to the horizontal when the machine is in flight, said

inclination being downward from front to rear, and while the forward

corners on one side of the machine may be depressed below the

normal planes of the bodies of the aeroplanes said depression is not

necessarily sufficient to carry them below the horizontal planes passing

through the rear corners on that side. Moreover, although we prefer to

so construct the apparatus that the movements of the lateral margins

on the opposite sides of the machine are equal in extent and opposite m

direction, yet our invention is not limited to a construction producing

this result, since it may be desirable under certain circumstances

to move the lateral margins on one side of the machine just described

without moving the lateral margins on the other side of the machine to

an equal extent in the opposite direction. Turning now to the purpose of

this provision for moving the lateral margins of the aeroplanes in the

manner described, it should be premised that owing to various conditions

of wind pressure and other causes the body of the machine is apt to

become unbalanced laterally, one side tending to sink and the other side

tending to rise, the machine turning around its central longitudinal

axis. The provision which we have just described enables the operator

to meet this difficulty and preserve the lateral balance of the machine.

Assuming that for some cause that side of the machine which lies to

the left of the observer in Figs. 1 and 2 has shown a tendency to drop

downward, a movement of the cradle 18 to the right of said figures, as

herein before assumed, will move the lateral margins of the aeroplanes

in the manner already described, so that the margins ad and eh will be

inclined downward and rearward, and the lateral margins bc and fg will

be inclined upward and rearward with respect to the normal planes of the

bodies of the aeroplanes. With the parts of the machine in this position

it will be seen that the lateral margins ad and eh present a larger

angle of incidence to the resisting air, while the lateral margins on

the other side of the machine present a smaller angle of incidence.

Owing to this fact, the side of the machine presenting the larger angle

of incidence will tend to lift or move upward, and this upward movement

will restore the lateral balance of the machine. When the other side of

the machine tends to drop, a movement of the cradle 18 in the reverse

direction will restore the machine to its normal lateral equilibrium. Of

course, the same effect will be produced in the same way in the case of

a machine employing only a single aeroplane.

In connection with the body of the machine as thus operated we employ

a vertical rudder or tail 22, so supported as to turn around a vertical

axis. This rudder is supported at the rear ends on supports or arms 23,

pivoted at their forward ends to the rear margins of the upper and lower

aeroplanes, respectively. These supports are preferably V-shaped, as

shown, so that their forward ends are comparatively widely separated,

their pivots being indicated at 24. Said supports are free to swing

upward at their free rear ends, as indicated in dotted lines in Fig.

3, their downward movement being limited in any suitable manner. The

vertical pivots of the rudder 22 are indicated at 25, and one of these

pivots has mounted thereon a sheave or pulley 26, around which passes a

tiller-rope 27, the ends of which are extended out laterally and secured

to the rope 19 on opposite sides of the central point of said rope. By

reason of this construction the lateral shifting of the cradle 18 serves

to turn the rudder to one side or the other of the line of flight. It

will be observed in this connection that the construction is such that

the rudder will always be so turned as to present its resisting

surface on that side of the machine on which the lateral margins of the

aeroplanes present the least angle of resistance. The reason of this

construction is that when the lateral margins of the aeroplanes are

so turned in the manner hereinbefore described as to present different

angles of incidence to the atmosphere, that side presenting the largest

angle of incidence, although being lifted or moved upward in the manner

already described, at the same time meets with an increased resistance

to its forward motion, while at the same time the other side of the

machine, presenting a smaller angle of incidence, meets with less

resistance to its forward motion and tends to move forward more rapidly

than the retarded side. This gives the machine a tendency to turn around

its vertical axis, and this tendency if not properly met will not only

change the direction of the front of the machine, but will ultimately

permit one side thereof to drop into a position vertically below the

other side with the aero planes in vertical position, thus causing the

machine to fall. The movement of the rudder, hereinbefore described,

prevents this action, since it exerts a retarding influence on that side

of the machine which tends to move forward too rapidly and keeps the

machine with its front properly presented to the direction of flight and

with its body properly balanced around its central longitudinal axis.

The pivoting of the supports 23 so as to permit them to swing upward

prevents injury to the rudder and its supports in case the machine

alights at such an angle as to cause the rudder to strike the ground

first, the parts yielding upward, as indicated in dotted lines in Fig.

3, and thus preventing injury or breakage. We wish it to be understood,

however, that we do not limit ourselves to the particular description of

rudder set forth, the essential being that the rudder shall be vertical

and shall be so moved as to present its resisting surface on that side

of the machine which offers the least resistance to the atmosphere, so

as to counteract the tendency of the machine to turn around a vertical

axis when the two sides thereof offer different resistances to the air.

From the central portion of the front of the machine struts 28 extend

horizontally forward from the lower aeroplane, and struts 29 extend

downward and forward from the central portion of the upper aeroplane,

their front ends being united to the struts 28, the forward extremities

of which are turned up, as indicated at 30. These struts 28 and 29 form

truss-skids projecting in front of the whole frame of the machine

and serving to prevent the machine from rolling over forward when it

alights. The struts 29 serve to brace the upper portion of the main

frame and resist its tendency to move forward after the lower aeroplane

has been stopped by its contact with the earth, thereby relieving the

rope 19 from undue strain, for it will be understood that when the

machine comes into contact with the earth, further forward movement of

the lower portion thereof being suddenly arrested, the inertia of the

upper portion would tend to cause it to continue to move forward if

not prevented by the struts 29, and this forward movement of the upper

portion would bring a very violent strain upon the rope 19, since it

is fastened to the upper portion at both of its ends, while its lower

portion is connected by the guides 20 to the lower portion. The struts

28 and 29 also serve to support the front or horizontal rudder, the

construction of which we will now proceed to describe.

The front rudder 31 is a horizontal rudder having a flexible body, the

same consisting of three stiff crosspieces or sticks 32, 33, and 34, and

the flexible ribs 35, connecting said cross-pieces and extending from

front to rear. The frame thus provided is covered by a suitable fabric

stretched over the same to form the body of the rudder. The rudder is

supported from the struts 29 by means of the intermediate cross-piece

32, which is located near the centre of pressure slightly in front of

a line equidistant between the front and rear edges of the rudder,

the cross-piece 32 forming the pivotal axis of the rudder, so as to

constitute a balanced rudder. To the front edge of the rudder there are

connected springs 36 which springs are connected to the upturned ends 30

of the struts 28, the construction being such that said springs tend to

resist any movement either upward or downward of the front edge of the

horizontal rudder. The rear edge of the rudder lies immediately in front

of the operator and may be operated by him in any suitable manner. We

have shown a mechanism for this purpose comprising a roller or shaft 37,

which may be grasped by the operator so as to turn the same in either

direction. Bands 38 extend from the roller 37 forward to and around a

similar roller or shaft 39, both rollers or shafts being supported in

suitable bearings on the struts 28. The forward roller or shaft has

rearwardly-extending arms 40, which are connected by links 41 with the

rear edge of the rudder 31. The normal position of the rudder 31 is

neutral or substantially parallel with the aeroplanes 1 and 2; but its

rear edge may be moved upward or downward, so as to be above or below

the normal plane of said rudder through the mechanism provided for that

purpose. It will be seen that the springs 36 will resist any tendency of

the forward edge of the rudder to move in either direction, so that when

force is applied to the rear edge of said rudder the longitudinal ribs

35 bend, and the rudder thus presents a concave surface to the action of

the wind either above or below its normal plane, said surface presenting

a small angle of incidence at its forward portion and said angle of

incidence rapidly increasing toward the rear. This greatly increases the

efficiency of the rudder as compared with a plane surface of equal area.

By regulating the pressure on the upper and lower sides of the rudder

through changes of angle and curvature in the manner described a

turning movement of the main structure around its transverse axis may be

effected, and the course of the machine may thus be directed upward

or downward at the will of the operator and the longitudinal balance

thereof maintained.

Contrary to the usual custom, we place the horizontal rudder in front of

the aeroplanes at a negative angle and employ no horizontal tail at all.

By this arrangement we obtain a forward surface which is almost entirely

free from pressure under ordinary conditions of flight, but which even

if not moved at all from its original position becomes an efficient

lifting-surface whenever the speed of the machine is accidentally

reduced very much below the normal, and thus largely counteracts that

backward travel of the centre of pressure on the aeroplanes which has

frequently been productive of serious injuries by causing the machine

to turn downward and forward and strike the ground head-on. We are aware

that a forward horizontal rudder of different construction has been used

in combination with a supporting surface and a rear horizontal-rudder;

but this combination was not intended to effect and does not effect the

object which we obtain by the arrangement hereinbefore described.

We have used the term 'aeroplane' in this specification and the appended

claims to indicate the supporting surface or supporting surfaces by

means of which the machine is sustained in the air, and by this term we

wish to be understood as including any suitable supporting surface which

normally is substantially flat, although. Of course, when constructed

of cloth or other flexible fabric, as we prefer to construct them, these

surfaces may receive more or less curvature from the resistance of the

air, as indicated in Fig. 3.

We do not wish to be understood as limiting ourselves strictly to the

precise details of construction hereinbefore described and shown in

the accompanying drawings, as it is obvious that these details may be

modified without departing from the principles of our invention. For

instance, while we prefer the construction illustrated in which each

aeroplane is given a twist along its entire length in order to set its

opposite lateral margins at different angles, we have already pointed

out that our invention is not limited to this form of construction,

since it is only necessary to move the lateral marginal portions, and

where these portions alone are moved only those upright standards which

support the movable portion require flexible connections at their ends.

Having thus fully described our invention, what we claim as new, and

desire to secure by Letters Patent, is:--

1. In a flying machine, a normally flat aeroplane having lateral

marginal portions capable of movement to different positions above or

below the normal plane of the body of the aeroplane, such movement being

about an axis transverse to the line of flight, whereby said lateral

marginal portions may be moved to different angles relatively to the

normal plane of the body of the aeroplane, so as to present to the

atmosphere different angles of incidence, and means for so moving said

lateral marginal portions, substantially as described.

2. In a flying machine, the combination, with two normally parallel

aeroplanes, superposed the one above the other, of upright standards

connecting said planes at their margins, the connections between the

standards and aeroplanes at the lateral portions of the aeroplanes being

by means of flexible joints, each of said aeroplanes having lateral

marginal portions capable of movement to different positions above or

below the normal plane of the body of the aeroplane, such movement being

about an axis transverse to the line of flight, whereby said lateral

marginal portions may be moved to different angles relatively to the

normal plane of the body of the aeroplane, so as to present to the

atmosphere different angles of incidence, the standards maintaining

a fixed distance between the portions of the aeroplanes which they

connect, and means for imparting such movement to the lateral marginal

portions of the aeroplanes, substantially as described.

3. In a flying machine, a normally flat aeroplane having lateral

marginal portions capable of movement to different positions above or

below the normal plane of the body of the aeroplane, such movement being

about an axis transverse to the line of flight, whereby said lateral

marginal portions may be moved to different angles relatively to the

normal plane of the body of the aeroplane, and also to different angles

relatively to each other, so as to present to the atmosphere different

angles of incidence, and means for simultaneously imparting such

movement to said lateral marginal portions, substantially as described.

4. In a flying machine, the combination, with parallel superposed

aeroplanes, each having lateral marginal portions capable of movement to

different positions above or below the normal plane of the body of the

aeroplane, such movement being about an axis transverse to the line of

flight, whereby said lateral marginal portions may be moved to different

angles relatively to the normal plane of the body of the aeroplane, and

to different angles relatively to each other, so as to present to the

atmosphere different angles of incidence, of uprights connecting said

aeroplanes at their edges, the uprights connecting the lateral portions

of the aeroplanes being connected with said aeroplanes by flexible

joints, and means for simultaneously imparting such movement to said

lateral marginal portions, the standards maintaining a fixed distance

between the parts which they connect, whereby the lateral portions on

the same side of the machine are moved to the same angle, substantially

as described.

5. In a flying machine, an aeroplane having substantially the form of a

normally flat rectangle elongated transversely to the line of flight,

in combination which means for imparting to the lateral margins of said

aeroplane a movement about an axis lying in the body of the aeroplane

perpendicular to said lateral margins, and thereby moving said lateral

margins into different angular relations to the normal plane of the body

of the aeroplane, substantially as described.

6. In a flying machine, the combination, with two superposed and

normally parallel aeroplanes, each having substantially the form of a

normally flat rectangle elongated transversely to the line of flight,

of upright standards connecting the edges of said aeroplanes to maintain

their equidistance, those standards at the lateral portions of said

aeroplanes being connected therewith by flexible joints, and means for

simultaneously imparting to both lateral margins of both aeroplanes a

movement about axes which are perpendicular to said margins and in the

planes of the bodies of the respective aeroplanes, and thereby moving

the lateral margins on the opposite sides of the machine into different

angular relations to the normal planes of the respective aeroplanes, the

margins on the same side of the machine moving to the same angle, and

the margins on one side of the machine moving to an angle different from

the angle to which the margins on the other side of the machine move,

substantially as described.

7. In a flying machine, the combination, with an aeroplane, and means

for simultaneously moving the lateral portions thereof into different

angular relations to the normal plane of the body of the aeroplane and

to each other, so as to present to the atmosphere different angles of

incidence, of a vertical rudder, and means whereby said rudder is

caused to present to the wind that side thereof nearest the side of the

aeroplane having the smaller angle of incidence and offering the least

resistance to the atmosphere, substantially as described.

8. In a flying machine, the combination, with two superposed and

normally parallel aeroplanes, upright standards connecting the edges of

said aeroplanes to maintain their equidistance, those standards at

the lateral portions of said aeroplanes being connected therewith

by flexible joints, and means for simultaneously moving both lateral

portions of both aeroplanes into different angular relations to the

normal planes of the bodies of the respective aeroplanes, the lateral

portions on one side of the machine being moved to an angle different

from that to which the lateral portions on the other side of the machine

are moved, so as to present different angles of incidence at the two

sides of the machine, of a vertical rudder, and means whereby said

rudder is caused to present to the wind that side thereof nearest

the side of the aeroplanes having the smaller angle of incidence and

offering the least resistance to the atmosphere, substantially as

described.

9. In a flying machine, an aeroplane normally flat and elongated

transversely to the line of flight, in combination with means for

imparting to said aeroplane a helicoidal warp around an axis transverse

to the line of flight and extending centrally along the body aeroplane

in the direction of the elongation aeroplane, substantially as

described.

10. In a flying machine, two aeroplanes, each normally flat and

elongated transversely to the line of flight, and upright standards

connecting the edges of said aeroplanes to maintain their equidistance,

the connections between said standards and aeroplanes being by means of

flexible joints, in combination with means for simultaneously imparting

to each of said aeroplanes a helicoidal warp around an axis transverse

to the line of flight and extending centrally along the body of the

aeroplane in the direction of the aeroplane, substantially as described.

11. In a flying machine, two aeroplanes, each normally flat and

elongated transversely to the line of flight, and upright standards

connecting the edges of said aeroplanes to maintain their equidistance,

the connections between such standards and aeroplanes being by means of

flexible joints, in combination with means for simultaneously imparting

to each of said aeroplanes a helicoidal warp around an axis transverse

to the line of flight and extending centrally along the body of the

aeroplane in the direction of the elongation of the aeroplane, a

vertical rudder, and means whereby said rudder is caused to present to

the wind that side thereof nearest the side of the aeroplanes having

the smaller angle of incidence and offering the least resistance to the

atmosphere, substantially as described.

12. In a flying machine, the combination, with an aeroplane, of a

normally flat and substantially horizontal flexible rudder, and means

for curving said rudder rearwardly and upwardly or rearwardly and

downwardly with respect to its normal plane, substantially as described.

13. In a flying machine, the combination, with an aeroplane, of a

normally flat and substantially horizontal flexible rudder pivotally

mounted on an axis transverse to the line of flight near its centre,

springs resisting vertical movement of the front edge of said rudder,

and means for moving the rear edge of said rudder, above or below the

normal plane thereof, substantially as described.

14. A flying machine comprising superposed connected aeroplanes means

for moving the opposite lateral portions of said aeroplanes to different

angles to the normal planes thereof, a vertical rudder, means for moving

said vertical rudder toward that side of the machine presenting the

smaller angle of incidence and the least resistance to the atmosphere,

and a horizontal rudder provided with means for presenting its upper

or under surface to the resistance of the atmosphere, substantially as

described.

15. A flying machine comprising superposed connected aeroplanes, means

for moving the opposite lateral portions of said aeroplanes to different

angles to the normal planes thereof, a vertical rudder, means for moving

said vertical rudder toward that side of the machine presenting the

smaller angle of incidence and the least resistance to the atmosphere,

and a horizontal rudder provided with means for presenting its upper or

under surface to the resistance of the atmosphere, said vertical rudder

being located at the rear of the machine and said horizontal rudder at

the front of the machine, substantially as described.

16. In a flying machine, the combination, with two superposed and

connected aeroplanes, of an arm extending rearward from each aeroplane,

said arms being parallel and free to swing upward at their rear ends,

and a vertical rudder pivotally mounted in the rear ends of said arms,

substantially as described.

17. A flying machine comprising two superposed aeroplanes, normally

flat but flexible, upright standards connecting the margins of said

aeroplanes, said standards being connected to said aeroplanes by

universal joints, diagonal stay-wires connecting the opposite ends of

the adjacent standards, a rope extending along the front edge of the

lower aeroplane, passing through guides at the front corners thereof,

and having its ends secured to the rear corners of the upper aeroplane,

and a rope extending along the rear edge of the lower aeroplane, passing

through guides at the rear corners thereof, and having its ends secured

to the front corners of the upper aeroplane, substantially as described.

18. A flying machine comprising two superposed aeroplanes, normally