M.Goodall, A.Tagg British Aircraft before the Great War (Schiffer)
Deleted by request of (c)Schiffer Publishing
P.Lewis British Aircraft 1809-1914 (Putnam)
Maxim 1910 Biplane
After a lapse of some fifteen years Sir Hiram Maxim produced his second aeroplane design. In the intervening period since his huge biplane of 1894 was built, powered flight had become a reality in several countries and, in the light of the experiences of others, his new machine displayed a rather more realistic approach to the problem.
Construction of the three-seater pusher biplane was undertaken by Wolseley at Crayford, (Cent, and was completed in 1910. Steel tubing was employed for the fuselage framework, and the three seats were arranged abreast at the leading edge of the lower wings, the pilot sitting in a central nacelle. Power was provided by a four-cylinder Maxim engine of 80 h.p., which was coupled to three pusher propellers, the central one of 5 ft. diameter being driven direct by the crankshaft, while the pair of 11 ft. 4 ins. diameter revolved around the steel-tubing upper tail booms and were connected to the engine through a rope drive tensioned by jockey pulleys.
The wings were of wood, covered with rubber-proofed Jap silk, and were of rectangular plan-form with straight centre-section and gull dihedral on the outer panels. Warping, operated by foot pedals, was employed for lateral control and the twin tail-wheels were coupled to the rudders for control on the ground.
Pre-flight testing by tethering with wires to a steel mast in the centre of a circular track was proposed, and this was prepared early in 1910. The track consisted of tar and sand, and was 25 ft. wide, with a circumference of 2,200 ft. A gyroscopic control mechanism was under development for the machine, but was not required, as the biplane never took to the air in free-flight. Span, 44 ft. Length, 35 ft. 6 ins. Wing area, 572 sq. ft. Endurance, 2 hrs.
Flight, January 8, 1910
THE NEW MAXIM AEROPLANE.
By SIR HIRAM S. MAXIM.
Six years ago I commenced making drawings with a view to building a flying machine with a petrol motor, but I did not finish it at that time, as I had a lot of other work on hand.
All the flying machines which have been built in recent years do not differ much from my original Baldwyn's Park machine, except as regards size and the kind of motive power employed.
About eighteen months ago, in making a careful study of the whole subject, it appeared to me that the Baldwyn's Park type of machine, with slight modifications, was still the best that could be devised. I therefore decided to make another machine, on practically the same lines, but very much smaller, and to drive it with a petrol engine.
I made the drawings, and about twelve months ago started to make a new light engine and a reliable carburettor, in fact, everything relating to my present flying machine.
The engine which I designed has four cylinders, each 5 ins. in diameter, with a common stroke of 5 5/8 ins. The cylinders, pistons, connecting-rods, and the crank-shaft, are made of a special brand of "Vickers" steel, which perhaps is the strongest and toughest steel that has ever been produced, in fact, I have never seen anything to compare with it. It has a tensile strength of 57 tons, with an elongation of 14 per cent. This is remarkable, and it enabled me to make all the parts of extreme lightness and still have a reasonable factor of safety, moreover, the great lightness of the moving parts enables the engine to run faster if required than it would if the parts were heavy.
I n order to get a high speed if required, I made all the passage ways and valves of the engine very large and free. I had noticed at the various places on the Continent where I had seen flying machine engines in action that they worked very badly and unsteadily, the exhaust being very irregular. A study of this question demonstrated only too clearly that the great trouble was with the carburettor; the explosive charge was not thoroughly mixed, or perhaps not mixed at all, and never of a uniform density.
I therefore experimented on a carburettor and made one that would produce gas of a uniform density, and it was found that when the air and the gas were thoroughly mixed before they entered the cylinder at all, the petrol engine behaved exactly as a gas engine does. The exhaust was perfectly regular, and, as a well-known steam engineer said on witnessing the running of my engine, "It runs as steady as any steam engine I have ever seen, and altogether different from any other petrol engine."
This engine has a forced water circulation, and everything about the engine, including the spindles of the exhaust valves, is cooled, so there is never any overheating.
A new system of oiling is also used. A small pump, having a bore of 1 1/4 in., and a stroke of 1 1/2 in., is so arranged and driven by a train of gears and "clockwork," that the piston is raised against the resistance of a spring, and liberated four times in a minute, and the spring is of sufficient strength to produce a pressure of 120 lbs. per sq. in. on the oil, the result being that every part of the engine, including the gudgeon-pins, is thoroughly lubricated four times a minute, and it has been found that no excess of oil gets past the piston into the explosion-chamber.
The screw propellers are three in number. One is placed directly on the screw shaft, and runs, of course, the same speed as the engine, and takes the place of a fly-wheel; the others are very much larger, and revolve at a much slower rate.
Two of the screws, the small one, and one of the large ones, rotate in a right-hand direction, and the other one in a left-hand direction, but the left-hand screw has a finer pitch than its mate, and revolves at a higher velocity, just high enough so that its gyroscopic action is equal to the gyroscopic action of the other two screws, and the rotating parts of the engine; therefore there is no gyroscopic action at all when the screws are considered "ensemble" as the left-hand screw exactly neutralises the gyroscopic action of all the other rotating parts.
The framework of the machine has been made of American yellow pine of a very fine quality. Although it is not quite so strong as spruce per square inch, it is really stronger than spruce when considered in terms of its own weight. Moreover, spruce was difficult to obtain.
The machine has fore and aft rudders (balanced) and one horizontal rudder also balanced.
The main part of the machine is made up of six aeroplanes; the central section carries the machinery and the driver, and the two side sections are simply superposed wings, but they are not level. The outside ends are raised very much above the central section, and their surfaces are curved in such a manner that when the machine is in the air whichever side is the lower will lift the most. This ensures lateral stability, without the necessity of any machinery.
I know that some mathematicians might dispute this, as they believe, or think they believe, that the pressure on the aeroplane is always perpendicular to its surface, but if they would give the matter one moment's careful consideration they would know that such is not the case.
It would be a case, I will admit, if the whole machine was mounted on a shaft, and could rotate in the air after the manner of a windmill, but the machine is not mounted on a shaft, it is suspended in the air and resting on the air, and falling through the air at the rate of 6 or 7 miles an hour. True, it is going ahead at the same time, but nevertheless it is falling as relates to the air, therefore its downward motion through the air, while travelling, has the same effect as it would if the machine was not travelling at all, but simply falling through the air. Therefore, the side that is lowest and presents the best angle to the wind, and also presents a lifting effect farthest from the centre of gravity, must lift the most, and have a strong tendency to keep the machine on an even keel. The centre of gravity, however, is very low, and very much below the centre of lifting effect. This, of course, also tends to keep the machine right side up.
I have also applied a device which I invented and patented many years ago, which enables the pilot to vary the pitch of the wings while the machine is still in flight; but instead of doing it after the manner of the Wright Brothers, I strictly adhere to my original patent, the wings being moved in one direction by hand, and in the reverse direction by a spring. But this device I do not think will be absolutely necessary on account of the shape of the wings and the arrangement of the weights.
In making this machine I have sought to group all the parts together, as near as I can, in line (tandem) in order to reduce the atmospheric resistance as much as possible, and to have what there is of it in the path of the screw, that is, the motor, the driver, the densest part of the framework, the magneto, steering-gear, and the petrol tank are all placed in line very low down, and all in the path of the small screw, so that if it should take, we will say, 10-h.p. to overcome the resistance of these parts, the 10-h.p., having been expended on the air itself, would draw the air forward in the direction of flight, so that the screw would be running in air which was already advancing, and fully 80 per cent, of the energy would be recovered by the screw.
It is the same also with the two large screws. All the parts that offer considerable resistance are forward of the screw, so that as much as possible of the energy lost in atmospheric resistance will be recovered.
The width of the aeroplanes fore and aft is 6 ft. 6 ins., and they are 6 ft. 6 ins. apart.
I have not given so much curvature to the aeroplanes as one would find on most of the machines of the present day, because in my early experiments I found that, when we consider the lifting effect of an aeroplane in terms of the drift, the thin aeroplanes, which are only slightly curved, do the best. Quite true, they do not lift so much per square foot, but they lift more per h.p., and I have preserved the shape which was found best at Baldwyn's Park.
Both the top and the bottom sides of the aeroplanes are covered with very thin and extremely strong waterproof silk. It is altogether the strongest and lightest I have ever seen, weighing only about 2 ozs. to the square yard.
This silk is laced on to the aeroplanes with a great deal of care, and the whole of it as tight as a drumhead.
The aeroplanes are thin and sharp. The stays are of two kinds - oval steel and fiat steel, and the struts partly of oval steel tubing and partly of American pine.
The total width of the machine is 44 ft.
One of the novel features of the machine which makes it look so much neater and simpler than other forms is the manner of constructing the frame and mounting the screws. Instead of having a lattice-work frame running round the screws to support the aft rudders, the screws are not mounted on a rotating shaft, but rotate themselves on a part of the framework of the machine.
In fact the real foundation of the machine consists of two steel tubes, to which everything else is suspended or attached, and it is these steel tubes on which the screw-propellers rotate.
This enables the principal member of the framework of the machine to pass directly through the centre of the screws, as an extension of these steel tubes carries all the rudders - fore, aft and vertical.
The screws being of very large size - over 11 ft. in diameter - of necessity have to be made very thin, in order to be light, and also in order to cut the air with little resistance. They are of pine, of the Baldwyn's Park type, which is common to nearly all machines at present, but a new feature has been introduced.
As the screws are not strong enough by themselves to stand the thrust without being distorted and broken, they are held back by strong steel strips 1/32 in. thick, and about 1 1/4 in. wide.
These strips, having the same pitch as the blades themselves, also act as a screw propeller, cutting the air keenly, and being very efficient. The screws are therefore held in position, their blades can neither be twisted nor deformed, and there is nothing to prevent their cutting through the air with the least possible resistance. By this means a very large amount of air can be engaged - a great deal more than has ever been engaged before per h.p. - therefore there would be less slip than with any other system so far invented.
Moreover, the resistance required for driving the machine through the air would be less, because everything is much sharper and smoother than in any other machine I have ever seen, but unfortunately a large and level field is not obtainable near the Crayford Gun Works at the present moment. True, land can be obtained, but it costs a lot to get it and to level it off and protect it, so I have devised a new system of testing - one that I think is quite different from anything suggested before.
I have constructed a tarred sand circular track, having a circumference of 2,200 ft. This track is 25 ft. wide, and in the centre I have erected a steel mast, to which I propose to attach a steel wire rope about 35 ft. from the ground, and to hold this rope up by very fine wires from another support over 100 ft. high. The steel wire will have attached to it three branches, which will take hold of the machine in three places, and in this way the machine will be held on an even keel, as far as relates to "port" and "starboard," but will be free to move forward, to ascend and descend ; and will also be free to depress or elevate the forward end, that is, every movement which is necessary to make when testing a machine is obtained, while the machine is prevented from flying off at a tangent.
It will therefore be possible not only to try the working of the engine, the cooling effect of the air, the propulsion of the screws, the lifting effect of the aeroplanes, the balancing of the weights, and, in fact, everything connected with' the working of the machine, without any danger whatsoever of injury to the pilot or breakage, while it affords a unique opportunity for the pilot to learn to manipulate all the necessary steering-gear, and so forth, and it is very evident that after this has been done for a certain length of time, the machine may be connected with a single wire, so as to find out if all the other movements are completely under control, and after this free flight ought to be quite simple and safe.
At any rate, a circular track will always afford a very simple manner of teaching men to fly, because they can do it without danger to themselves or to the machine.
Flight, April 30, 1910
THE MAXIM BIPLANE.
IT is given to few pioneers as early in the field as Sir Hiram Maxim was with his original experiments in Baldwyns Park to have an opportunity of again devoting themselves to practical work of the same description at a time when success is already a foregone conclusion along recognised lines. Yet Sir Hiram Maxim, who built his first machine at a time when it was impossible to achieve success owing to the absence of the modern petrol engine, has lived to see the conquest of the air by others and to again take an active part in the development of flight by the construction of another large machine. An account of the leading features of this machine, written by Sir Hiram Maxim himself, has already appeared in this volume of FLIGHT, p. 136, and we are now able to supplement that description with a very complete set of photographs and sketches, which give a very clear idea of the leading features of this interesting machine.
Some Leading Features.
The machine is a large biplane and is characterised by the unusual form of dihedral angle exhibited in the disposition of the main planes, and also by the use of a fore and aft control, which is obtained by the interconnection of a biplane tail with a biplane elevator. The main planes are constructed in three sections. The central section has a straight edge, but the outer sections are arched and form dihedral angles with the central section. This disposition of the planes is made for the purpose of introducing a factor of natural stability. The central section carries the engine and the pilot's seat, both being located on the lower deck, so that the centre of gravity is considerably below the centre of lifting effect.
The elevator and the tail are both pivoted to the extremities of two tubular spars that run fore and aft the whole length of the machine. These spars constitute the main members of the framework and are a very important feature of the design. They also carry the propellers and thus save the weight of independent brackets for this purpose. They are built up in three lengths, the central portion being steel and the two outer members being aluminium. The latter are stayed by diagonal struts to the lower deck of the main planes, and are not, therefore, subjected to any appreciably direct bending strain.
Materials of Construction.
The greater part of the framework of the machine has been made of a fine quality American yellow pine, but there is a limited amount of tubular metal work, and a little hard wood is also used in places. A pair of tubular steel struts are situated in the centre of the main-planes on either side of the engine, and these members have been employed as water pipes to communicate with the radiator, which lies below the upper deck. The machine is mounted upon a pair of pneumatic-shod wheels, which are independently attached to the frame, and together afford a very wide track. Each wheel is mounted on a short axle held by a massive wooden fork, which is hinged to the frame, and attached to a pneumatic spring. Jutting out from the fork is a bow-shaped member of ash forming a fender, which is intended as a protection to the more important parts of the machine in the event of accident. The tail is supported upon a pair of light wheels mounted on castors that are interconnected with the rudder mechanism, so that the machine can be steered upon terra firma at low speeds, when the rudder itself would have but a feeble effect. Immediately beneath the lower deck of the main-planes is an inclined board serving as the support to the petrol-tank, and a protection to the central propeller. It has been so arranged as to afford some lifting effort.
Strip Steel Ties.
An important and interesting feature of the framework is the bracing of the various lattice-girder members by diagonal ties of strip steel instead of wire. These ties are set edge on to the direction of flight. The main planes have been surfaced with a rubber - proofed Japanese silk, which Sir Hiram Maxim had specially woven for the purpose. It is exceedingly light and very strong for its weight. It is stretched very tightly over the framework of the main planes, and in order to maintain uniform curvature of surface under varying conditions of pressure, the lower surface of each deck is provided with a vent hole so located as to maintain equilibrium of the static pressures inside and outside the deck. The exact position of this air vent has an important bearing on its utility; for the particular camber employed on this machine the vents are situated about a quarter of the chord from the trailing edge. The vent holes are about 2 ins. in diameter, and have been covered with fine gauze in order to prevent flies being blown into the cavity.
(To be concluded,.)
Flight, May 7, 1910
THE MAXIM BIPLANE,
(Concluded from page 325.)
ONE of the most important features of the machine is the system of using three propellers. Two of the propellers are mounted on the main spars of the frame, while the third, which is much smaller in diameter, is direct driven by the engine. The larger screws revolve in opposite directions, and are driven by ropes. The right-hand screw, viewed from behind, rotates in the same direction as the central screw; the other propeller, which has a reverse direction of rotation, has therefore, a finer pitch and a higher velocity than its mate in order to compensate for the gyroscopic effect of the central screw. The propellers are two-bladed, and exceedingly thin and light for their size; in fact, the blades are so thin that they would bend if unsupported, and they have, therefore, been trussed by strip steel ties, which anchor their extremities to a tubular extension of the boss. These strips of steel are so arranged that their surfaces have approximately the same pitch as the screw itself, it being intended thereby to minimize as far as possible the loss caused by their rotation through the air. It will be observed, on reference to one of our photographs, which shows a propeller separately, that the tubular extension at the boss affords a remarkably long bearing surface for the support of the propeller upon its shaft.
The pulley for driving the propeller is fastened direct to the blades by steel brackets and also similarly to a pair of wooden stumps that project from the boss at right angles to the blades. It is thus supported at four points. The groove in which the rope runs is cogged to give an effective grip.
The Rope Drive.
The rope drive of the propellers is an interesting and original feature of the Maxim system, and much care has been taken in the construction of the ropes, which are woven on a special machine designed and erected at the Crayford works. The ropes are endless and are made of a very fine tough thread, such as is used by bootmakers for certain purposes in connection with their trade. The adjustment of the rope is effected by jockey pulleys, and the surface of the rope is prepared with the best quality beeswax.
A very important consideration to be borne in mind regarding the arrangement of the three propellers on the Maxim biplane is their disposition in respect to the principal masses represented by the various members of the machine itself. It will be observed, for instance, that the pilot, the engine, and the central screw are arranged in tandem; in fact, the central screw has been provided solely in order to recover some of the energy from the wake of this mass. This is a particularly interesting point, because the value of the wake is by no means accepted as an appreciable quantity by the majority of flight engineers, and this very definite verdict on the part of Sir Hiram Maxim should at least bring the matter into prominence.
No marine engineer would ever think of putting a screw in front of a ship; indeed it can be theoretically proved that with any wake whatsoever a boat can be propelled for less power than it can be towed. Deductions from water experiments do not apply to air in the same degree, but they undoubtedly afford useful information that should not be neglected. At the present time constructional considerations have more to do with locating the position of a propeller on a flying machine than anything else, but engineering fails to accomplish its purpose if constructional difficulties are allowed to limit design in such matters of fundamental importance.
Whether others will think it worth while to follow Sir Hiram Maxim's example of providing an additional propeller to work in the wake of the principal mass, naturally very much depends on the success of this particular machine.
The engine on the Maxim biplane, like the machine itself, has been designed by Sir Hiram Maxim. It has four separate steel cylinders with detachable heads and water-jackets; the former being made of steel, and the latter of German silver. Long steel bolts passing into the crank-chamber hold the cylinder-heads in place. The valves are all overhead, and are operated by an overhead cam-shaft, which is skew-gear driven from the crank-shaft.
A belt from the rear end of the cam-shaft drives a clockwork mechanism employed for operating the lubricating system. The oil reservoir contains a spring-loaded plunger-pump, which is raised and liberated four times a minute. The force of the pump exerts a pressure of about 120 lbs. per sq. in. on the oil, and delivers a momentary stream under this high pressure to all the principal bearings.
A transverse skew-gear driven shaft in front of the engine drives the magneto and the water-pump. The cylinder-heads are water cooled as well as the walls, and the cooling water passes through a radiator mounted on the upper deck of the main-planes. One of the hollow steel struts that support the upper deck is employed to convey the water to the radiator.
The carburettor on the Maxim engine is very noticeable on account of its large size, and it is also of somewhat peculiar construction, being mainly remarkable for the very large capacity of the mixing-chamber that contains the throttle-valve. The object of this chamber is to thoroughly mix the gas in large quantities before it is admitted to the cylinders. Part of the mixing-chamber is warmed by an arrangement of water pipes.
The control of the Maxim biplane involves the manipulation of the elevator, tail, and rudder, and also the warping of the wings. These operations are effected by a steering wheel riding upon a pivoted lever, and by a pivoted cross-bar under foot control. The interconnections are shown diagrammatically in an accompanying sketch. The elevator and the tail are interconnected by cross wires so that they work in unison, and the elevator is directly connected to the pivoted lever by a system of links, so as to be operated by a to-and-fro movement of the lever. The rudder, which is carried by the tail, is operated by a rotary motion of the steering wheel upon the pivoted lever as an axis. The warping of the planes is accomplished by means of the pedal. A feature of the warping system is that the planes are warped in one direction by the wires, and in the other direction by springs.
A minor detail in the control mechanism to which it is necessary to draw attention is the method of mounting the steering wheel upon the pivoted lever. The steering wheel is mounted on a sleeve fitted with a jaw-clutch that engages with a corresponding member on the rod. The rudder is thus locked in any desired position by this device, and it is necessary to force the steering wheel downwards against the action of a spring in order to rotate it. There is also a split collar on the steering wheel sleeve into which a handle bar can be screwed if the pilot prefers such a device to a steering wheel. Some of our photographs show the machine with the handle bar in place. It is made in halves and the split collar is automatically clipped in place by screwing the halves of the handle bar together.
It is Sir Hiram Maxim's intention, when the preliminary experiments have been brought to a satisfactory conclusion, to fit gyroscopic control. The gyroscopic mechanism has already been constructed for this purpose. The gyroscope, which consists of a spinning fly-wheel, is contained in a cylindrical casing, and it is designed to operate, through a relay mechanism, a cylinder containing a piston to which an operating rod is attached. Some very ingenious mechanical details have been introduced in the construction of this piece of apparatus.
Flight, November 30, 1916.
THE DEATH OF SIR HIRAM MAXIM.
BY the death of Sir Hiram Maxim aviation has lost one of its notable pioneers, although the world-fame brought to Sir Hiram by his invention of the Maxim gun overshadowed his work in connection with aeronautics. Being of a very mechanical turn of mind, it was, perhaps, not unnatural that he should attack the problem of making a machine to navigate the air, and in 1894 he experimented at Baldwyn's Park, Bexley, with a giant biplane fitted with a steam engine of 400 h.p. So sure was the inventor that the machine would lift, that he had special guards fitted to the track to prevent the aeroplane rising more than a few inches. And they proved its undoing, for the lift led to the breaking of one of the axles, while one of the guards was torn-up and catching the propeller smashed it, besides seriously damaging other parts of the machine. Those who are interested in these experiments will find a brief resume of them, written by Sir Hiram Maxim, in "FLIGHT" of March, 1910. Although Sir Hiram was convinced of the practicability of his machine, he saw that he would have to abandon the steam plant en account of the amount of water required for a long flight. He therefore set to work to design an internal combustion engine, but a severe illness, followed by great pressure of work in connection with his many other inventions, led to the scheme being abandoned. In 1909 Sir Hiram Maxim built a new biplane, this time at Erith, and full details, with photographs and scale drawings of the completed machine, were given in "FLIGHT" of April 30th, 1910.
In 1909 Sir Hiram Maxim published a little book, "Artificial and Natural Flight," which set forth the results of Sir Hiram's experiments to ascertain the relative effects produced by winds of known velocity upon objects of different shape, and also the resistance offered by similar shaped bodies passing through the air. Coming as it did at a time when there was not a great deal of literature available of a practical nature, this book, although the experiments were unfinished and the results unchecked, proved of great use to designers in the early days.
Sir Hiram Stevens Maxim had a frank, breezy nature, which won for him friends wherever he happened to be. Born at Sangerville, Maine, U.S.A., on February 5th, 1840, he started life as a coachbuilder, and tried his hand at various trades before coming to Europe in 1881. For the latter part of his life he made England his home, and, having been naturalised, he was knighted in 1901.
The funeral took place at Norwood Cemetery on November 28th, and among the mourners were Lady Maxim (widow), Master Maxim Joubert (grandson), the Hon. H. Fletcher Moulton (representing the Controller and the Munitions Inventions Department), Sir Trevor Dawson and Mr. V. C. Vickers (representing Messrs. Vickers, Ltd., of which firm Sir Hiram Maxim was for many years a director, its title then being Vickers, Sons and Maxim)