M.Goodall, A.Tagg British Aircraft before the Great War (Schiffer)
Deleted by request of (c)Schiffer Publishing
W.Green, G.Swanborough The Complete Book of Fighters
MANN & GRIMMER M.1 UK
Designed by R F Mann and R P Grimmer, the M.1 two-seat fighter represented an attempt to combine the superior performance offered by a tractor configuration with the clear forward field of fire provided by a pusher arrangement. The conventionally-mounted Anzani 10-cylinder air-cooled radial engine drove two pusher propellers by means of an extended shaft via a gearbox and chains. The gunner was seated immediately aft of the engine, the pilot's cockpit being just behind the plane of the propellers. The M.1 was first flown on 19 February 1915, but difficulties were experienced with the chain transmission and with handling. Various modifications were made and the 100 hp Anzani engine was replaced by one rated at 125 hp, but after some 18 hours of flight testing, the M.1 was wrecked on 16 November 1915 before it could be evaluated by the RFC, and although work on the prototype of an improved version, the M.2, was begun, no further aircraft was completed.
Max speed, 85 mph (137 km/h).
Time to 3,000 ft (915 m), 8 min.
Endurance, 4.5 his.
Approx empty weight, 2,100 lb (953 kg).
Approx loaded weight, 2,800 lb (1270 kg).
Span, 34 ft 9 in (10,59 m).
Length, 26 ft 5 in (8.05 m).
Wing area, 322 sq ft (29,91 m2).
J.Bruce British Aeroplanes 1914-1918 (Putnam)
Mann & Grimmer M.i
IN the years before the outbreak of the 1914-18 war, Reginald Frank Mann made something of a name for himself while still a schoolboy as the designer of some successful model aeroplanes. In 1913, at the age of 16, he went into partnership with his schoolmaster, Robert P. Grimmer, for the manufacture of model aeroplanes on a commercial basis. Both had shared an interest in aviation since 1908.
Even before the outbreak of war, Mann had realised that there would be a need for aeroplanes from which a machine-gun could be fired effectively. One of the more remarkable facts in our aeronautical history is that in 1914 the Edward brothers had patented a synchronising gear to enable guns to be fired through the revolving airscrew of a tractor aeroplane: their patent was No. 23790 A.D. 1914. For some reason best known to the War Office, whence a working model of the gear was sent, no more was heard of the device; our designers were obliged to produce pusher machines such as the D.H.2, F.E.2b, F.E.8 and Vickers F.B.5 in order to provide forward-firing armament; and our pilots were confronted in 1915 by enemy aeroplanes with synchronised machine-guns.
R. F. Mann was aware that, in general, the tractor aeroplanes of the day had a better performance than contemporary pushers, but it was obvious that the frontal airscrew made it impossible, in the absence of any form of synchronising gear, to fit a machine-gun having a forward field of fire. Before the war, Mann and Grimmer had had a desire to produce an aeroplane with twin outboard pusher airscrews, and had secured the interest of W. H. Bonham-Carter in their project.
The outbreak of war made the need for Service aircraft one of urgency. Convinced of the practicability of his ideas, Mann got out his first design drawings in August, 1914. Mr Bonham-Carter provided most of the cash required, and construction of the Mann & Grimmer M.1 began in September, 1914.
Design and construction work were pushed forward at great pressure, in the hope that the M.1 might be used against the enemy early in 1915. Work began in the disused church, which was the workshop, at 7 a.m. each morning and continued until midnight on many nights. The completed components were taken to Hendon at the end of January, 1915, and were assembled early in February.
The basic configuration of the M.1 was that of a two-bay fuselage-type biplane with conventional tail surfaces. The engine installation was quite unlike anything which had been attempted up to that time.
Power was provided by a 100 h.p. Anzani radial engine, which was installed at the forward end of the fuselage. The engine was mounted backwards, and drove a long shaft which passed under the observer’s seat and terminated in a gear-box amidships. From the gear-box, chains drove two outboard pusher airscrews which, with their shafts and sprockets, were mounted on a diamond-shaped system of wires and struts about the inner rear interplane strut on each side. The gear-box was installed to obviate the need for crossing one of the chains to obtain oppositely-rotating airscrews, but imposed a severe weight penalty, for it weighed 100 lb.
The pilot sat well behind the wings, and the observer occupied a seat immediately behind the engine. He therefore had an excellent view forwards and a good field of fire for his Lewis gun.
The undercarriage was originally of the twin-skid type, and the mainplanes had a pronounced taper: the leading edges were swept back.
The first flight of the Mann & Grimmer M.1 was made by Rowland Ding on February 19th, 1915. This was only a short straight hop, but next day he took the machine clear of the aerodrome. He then found that the rudder was not very effective, no doubt because of the absence of slipstream over it, and the throttle jammed at two-thirds open. However, he succeeded in getting back to the aerodrome safely.
The chain transmission behaved in a rather alarming fashion, so a month was spent in attempting to improve its functioning; at the same time a larger rudder and improved airscrews were designed. On March 20th the M.1 reached a speed of 70 m.p.h., a figure which was not bettered on two subsequent flights. The performance fell so far short of Mann’s expectations that he decided to replace the 100 h.p. engine by a 125 h.p. Anzani, and the machine was taken back to Surbiton for modification on April 1st, 1915, after less than one hour’s total flying time.
The new engine required new shafts, sprockets, chains and gear-box. Other modifications included the fitting of a plain vee undercarriage with larger wheels and an even larger rudder, whilst the wires which braced the forward ends of the airscrew shafts were replaced by struts of steel tubes. The stagger was increased, stronger interplane struts were fitted, and new airscrews were installed.
When flown again on June 29th the machine still did not perform well, and other airscrews were fitted in an attempt to improve performance. On July 4th a stay tube broke and shattered the port airscrew, but Ding brought the M.1 down safely. Ding made a number of later flights on the machine, but Sidney Pickles took over the test flying on August 4th.
By August 21st the M.1 was flying quite well: the speed was now 75-80 m.p.h., and the initial rate of climb 500 feet per minute. Unfortunately, the terms of Pickles’ contract with an American firm forbade him to fly machines other than those of his firm’s manufacture, and he had to relinquish the flying of the M.1.
It was not until October 2nd that another pilot was found to fly the Mann & Grimmer machine. He was A. E. Barrs, one of the pre-war Hendon pilots, who had been invalided out of the R.F.C. Barrs made thirty flights on the M.1, some with war load, and reached a height of about 9,000 feet on one occasion. The maximum speed was 85 m.p.h., and its builders claimed that the M.1 was the fastest pusher biplane in existence.
Various refinements were made to improve performance. The stay tubes supporting the airscrew shafts were carefully faired, and at one time the machine was flown with the inner rear interplane strut removed and a fairing fitted over each outboard sprocket and airscrew shaft. A large spinner-like cowling was fitted over what was normally the rear of the engine. By this time the empty weight was some 800 lb greater than it originally was.
On November 16th, 1915, Barrs took off with J. G. Woodley in the passenger’s seat in an attempt to break the British altitude record. About 45 minutes after take-off the M.1 was at a height of between 8,000 and 9,000 feet, and was still climbing well when the gear-box seized. The starboard chain broke and vanished into space, and Barrs switched off and began to glide down. The glide lasted 21 minutes, but near the ground bumpy conditions brought the machine down short of the aerodrome. It ran into some trees and was completely wrecked, though neither occupant was injured in any way.
In its nine months of existence, the M.1 flew for no more than 18 hours, but its builders felt that it had ultimately fulfilled their expectations. After its demise they at once set about the construction of a much improved successor, which was known as the M.2. When half finished the new machine had to be abandoned owing to lack of official support.
R. F. Mann joined the Army, but within a month contracted a severe cold which ultimately developed into tuberculosis. He was invalided out, and died in Rhodesia some years later.
Manufacturers: Messrs Marin & Grimmer, Surbiton, Surrey.
Power: 100 h.p. Anzani; 125 h.p. Anzani.
Dimensions: Span: 34 ft 9 in. Length: 26 ft 5 in. Gap: 5 ft 9 in.
Areas: Wings: 322 sq ft.
Weights: Empty: originally approximately 1,300 lb; in final form about 2,100 lb. Useful load: 700 lb. Weight loaded: approximately 2,800 lb.
Performance: Maximum speed: 85 m.p.h. Initial rate of climb: 500 ft per minute. Climb to 3,000 ft: 8 min. Endurance: 4 1/2 hours.
Armament: One free Lewis machine-gun fired by the observer.
H.King Armament of British Aircraft (Putnam)
Mann & Grimmer
M.1. The two men responsible for this imaginative single-engined twin-airscrew biplane of 1914/15 will be named in the second volume of this work because of Mr Grimmer's particular interest in military aeronautics as expressed in Flight. It was intended to arm the M.1 with a Lewis gun, installed in the cockpit behind the nose-mounted engine, under the wing leading edge.
Flight, February 5, 1915.
Another new machine arrived at the aerodrome on Saturday. The newcomer has been designed and built by Messsr. Mann and Grimmer, the well-known model constructors, and is of unusual appearance. From an inspection of the various parts, as they lay in the L. and P. sheds, it is evident that, when erected, she will be a fuselage biplane with two "pushers." The body is very deep and covered with aluminium in front, whilst the rear portion is covered with fabric. The two seats are arranged in tandem, the pilot sitting far back and the observer being placed immediately behind the engine plate in the nose of the body. I learn that a 100 h.p. Anzani engine will be fitted, and as the new machine is of such original form, her performances will be watched with interest.
Flight, March 26, 1915.
THE NEW "MANN" BIPLANE.
AMONG the new machines that have made their appearance lately, one of the most original is the Mann "pusher" biplane, built by Messrs, Mann and Grimmer, and erected at Hendon a short while ago. As reported in FLIGHT some time back, it flew successfully for the first time of asking, and last week further flights were made, a few modifications having been made. On both occasions Mr. Rowland Ding was the pilot.
Briefly speaking, the Mann biplane is a fuselage machine with the engine in front and the two chain-driven propellers at the rear of the main planes. In the extreme nose of the very deep body is placed the seat for the observer or gunner, and from here an unrestricted view is obtained owing to the absence of a tractor screw to obscure the view. A 100 h.p. Anzani drives the two propellers through a shaft and chain transmission - designed by Mr. Leper, who has had many years experience with chain transmission - the shaft terminating at the rear in a spur gearing driving the sprockets, so that crossing of one chain is avoided although the propellers run in opposite directions.
A short distance behind the main planes is the pilot's cockpit, from whence the pilot is able to look straight down behind the lower main plain and to obtain a good view in a forward direction over the leading edge of the lower plane. The tail planes are of large size, and consist of the usual members, a fixed stabilising plane, a divided elevator, and the rudder. The under-carriage is of the wheel and skid type, the two disc wheels being carried on short stub axles sprung from the skids by rubber shock-absorbers.
The main planes, of which both upper and lower are fitted with inter-connected ailerons, have a slight backward sweep similar to that found in a number of German machines. This, however, only applies to the leading edge, as the trailing edge is straight, as seen in plan.
Owing to the unusual design of this machine, a considerable amount of interest attaches to its forthcoming trial flights. If the new "Mann" biplane proves a success from the aerodynamical point of view, it should be of value for military purposes, owing to the facility with which a gun can be mounted in the nose of the body.
After a short rest in dock, during which a few alterations have been made, the Mann and Grimmer biplane was out again for a flight at Hendon on the morning of Friday last. Those who saw the flights agreed that an enormous improvement was noticeable, and that the machine must have been doing close on up to the 70 miles mark, the Anzani engine pulling like a demon. It appears that the propellers with which the "Mann" was originally fitted were too big for the engine, and that the improvements were chiefly due to the fitting of different propellers. The pilot was, as in its first flight sometime ago, Mr. Rowland Ding, who was highly pleased with the behaviour of the "Mann."
By the way, this week a few more details of the Mann and Grimmer creation appear on another page in FLIGHT, the Censor having now "released" these for publication. It will be remembered I hinted a few weeks ago, at official embargo having been temporarily enforced upon the issue of any particulars. The ways of officialdom are truly obscure.
Flight, April 9, 1915.
Mr. Ding, of the Northern Aircraft Co., indulged in a couple of flights on the "Mann" biplane on Sunday, March 28th. He had hoped to try the machine in the strong wind that was asserting itself during the early part of the afternoon, but greatly to his disappointment it eased off directly the 'bus was brought out, thus preventing the wind test from being carried out. Instead, Mr. Ding made a couple of flights, each of about 15 minutes' duration, the first one solo, and in the second accompanied by the designer, Mr. Mann. On both occasions she got up to about 1,000 ft. and was flown "hands off." The designer has now come to the conclusion that a little extra power is required to make the machine fly as he wants her to, and a 125 h.p. Anzani is being fitted instead of the original 100 h.p. This should give the desired climb and speed, especially as the machine itself will be considerably lightened.
Flight, July 9, 1915.
FLYING AT HENDON.
THIS last week-end at Hendon saw some very good flying that was, however, not without an exciting incident or two. Of special interest was the re-appearance of the Mann twin-pusher biplane, now fitted with a 125 h.p. Anzani engine. The first flight in its altered condition was made on Tuesday of last week, when W. Rowland Ding took it up for a short trial. It was soon found that the propellers were unsuitable, several minor adjustments also being required, as it did not prove so fast as with the 100 h.p. engine. The necessary adjustments were completed by Saturday afternoon, and in the evening Ding took it up once more just as rain commenced to fall. Improvement was at once discernible by the way it got off and climbed, and after several circuits an altitude of 1,500 ft. was reached. At this height Ding executed some banked turns, and descending a few hundred feet indulged in some switchbacks to show the machine was under perfect control. This time the speed had been increased to 70 m.p.h. As the rain was getting somewhat unpleasant, Ding decided to descend, and proceeded to come down, in over the hangars. Needless to say, both Mr. Mann and Mr. Grimmer were "all smiles," but at the last moment these smiles faded, for just as Ding was entering the aerodrome a fledgeling, on one of the numerous machines of a type that has become very popular, was taxying right across in front of the descending machine. It was one of those moments when it was hard to tell whether or not the machine in front would pass by before the other landed. However, it was soon evident that a collision was there in the making, unless Ding could hop over the machine on the ground, for it was then too late to turn. Would the engine, which was well throttled down, pick up quickly enough? Being an Anzani, it naturally did the right thing, and all concerned were relieved to see the Mann 'bus shoot upwards, missing the other machine by a few feet only. Ding continued on his way, and eventually effected a safe landing.
On Sunday afternoon most of the previous day's pilots and machines put in considerable air work, Manton, Osipenko and Winter were very busy with passengers on the 50 h.p. G.-W. school 'bus, the first-named pilot on one occasion making a very long flight with a passenger. W. Roche-Kelly and C. B. Prodger were out on the 50 h.p. and 60 h.p. Beatty-Wright biplanes respectively. E. Baumann flew the 50 h.p. Ruffy-Baumann biplane, whilst J. L. Hall made a high trip on his 45 h.p. Caudron. The event of the day, however, was the flying of the Mann biplane. Since its trial the evening before different propellers had been fitted, and shortly before 4 o'clock Ding took it up for a test, reaching an altitude of 1,500 ft. Although the machine flew as well as ever, the propellers were found to be not so good as those previously used, and so the latter were re-installed. At 5.30 p.m., Ding was away again, this time a speed of 73 m.p.h. being obtained. Unfortunately the trial was brought to an abrupt conclusion in a somewhat exciting fashion. Ding, to show the comparative speed, flew alongside and overhauled a G.-W. 'bus opposite the paddock enclosure. He had no sooner passed the other machine, and was making a sharply banked turn by No. 2 pylon, when those who were watching him closely were alarmed to see some dark objects fall from his machine, hearing immediately after a metallic "tearing" report. For a moment the machine banked over still more, and it was seen that the right hand propeller was revolving at a very much increased speed, so that it was evident that the other propeller had broken. Then the machine began to get back to an even keel, the engine being simultaneously switched off, and a descent commenced. In coming down it was still necessary to steer to the left a little in order to clear the railway, and so on landing - on ground none too smooth - the machine still continued to turn until by the time it came to rest it faced in the opposite direction. It was a wonderful landing and "save" which drew forth well-merited and appreciative cheers from the spectators. An inspection of the biplane showed that one of the stay tubes supporting the left hand propeller had sheared close to the latter, so that it swing back into the propeller and smashed it. However, no other damage - except for torn fabric here and there - had resulted, and as soon as certain modifications suggested by the trials have been made the Mann biplane will be out again. Messrs. Mann and Grimmer, as well as Mr. Rowland Ding, are to be congratulated both on the good performance of the machine and the fortunate issue to this little episode.
The Mann biplane was responsible for another little incident on the Saturday evening, which demonstrated its controllability. Ding, whilst making a fairly steep descent into the aerodrome with the engine throttle down, found he was flying straight into another machine taxying on the ground. The only possible way of avoiding a nasty collision was by opening out the engine and jumping the machine, but as the distance separating the machines was only a matter of fifty yards or so when the descending biplane had almost touched the ground things looked pretty mixed up. The manoeuvre proved entirely successful, however, for the Mann literally sprang into the air over the other biplane in a manner that dispelled, once and for all, the belief held by some that this 'bus is nose heavy, etc.
One important factor governing both these incidents which stands out pre-eminent is the magnificent pilotage of W. Rowland Ding. The manner of his flying the B.E.2C at Hendon, to which I referred recently, confirmed my opinion of him as a first-class pilot. His presence of mind in what looked like providing the nucleus of a nasty accident proves him also one of prompt and decisive action in an emergency.
Flight, August 13, 1915.
FLYING AT HENDON.
ON Wednesday and Thursday of last week the 125 h.p. Mann twin pusher biplane was introduced to a new pilot, when Sydney Pickles - who, once more attired in civilian raiment, has lost no time in getting to work at the all-important matter of testing new machines - brought out further good points in this interesting craft. After a preliminary straight on the Wednesday evening, he climbed up to about 3,000 ft., taking ten minutes for that elevation. The next evening, with Mr. R. F. Mann in the passenger's seat, he made a flight lasting 1 hour 5 mins., getting up to an altitude of 5,000 ft. in the first 20 mins. The 'bus climbed with great steadiness and seemed capable of double the height, but darkness and rain said "No." The speed, with passenger, was 75 m.p.h., and the climbing speed was only a little below 70 m.p.h. This, it must be admitted, is rather exceptional, and a very important factor where "Zeppstraffing" is considered. Pickles said he was very satisfied with the manner in which the machine behaved, and that it was certainly quite a nice 'bus to handle in the air. On each of these occasions "Mann" propellers were fitted, and considerable improvement had been accomplished in the petrol system. At present an examination is being made of the gear-box, but in all probability further trials will be made this week-end.
Flight, October 29, 1915.
It has not taken long for Mr. A. E. Barrs to get a feeling of quite-at-homeness on board the "Mann" biplane. The two accompanying photos, will bear witness to the fact, if proof were needed. These were taken by Barrs at a height of 4,000 ft. Mr. Mann, the designer of the machine, who was in the passenger's seat, not knowing of Barrs' intention of taking the snaps, his attention had to be called by some means or other. As shouting was of no avail in the roar of the 125 h.p. Anzani engine, Barrs tried to roll the 'bus from side to side. The first time Mann took no notice, thinking that Barrs was only testing the ailerons, but a renewed attempt had the desired effect. Mann looked over his shoulder and Barrs in a moment had camera in position and pressed the button. The result is shown in one of the photographs. Taking both hands off the controls Barrs then calmly changed his plate and took a snap of the transmission gear. All the while the 'bus was flying by herself. As the photograph shows, there is no vibration noticeable, although the speed at which the chain was travelling is stated by the Mann and Grimmer firm to have been something like 20 m.p.h. These chains, by the way, have recently been examined at the works of the makers, Messrs. Hans Renold of Manchester, and it was found that the stretch of each, if indeed there had been any, was not noticeable. This after having transmitted the 125 h.p. of the Anzani engine for a run that is stated by the makers of the machine to have been over 600 miles. But of course they are Renold's chains. Enough said.
Flight, November 26, 1915.
FROM the small photograph on this page, a very good idea may be formed of the extent of the damage done to the "Mann" biplane recently, when it collided with some trees after a flight to a height of a little over 8,000 ft., piloted by Mr. A. E. Barrs, with Mr. J. G. Woodley as passenger. This incident has been given quite an appreciable amount of publicity in the daily press; unfortunately the various accounts were, almost without exception, so worded as to give a totally erroneous impression of what really did happen. From a letter received from Mr. Grimmer, it appears that the facts of the case were, briefly, as follows. Mr. Barrs accompanied by Mr. Woodley ascended in the "Mann" to try if possible to establish a new altitude record for pilot and passenger. At a height of between 8,000 and 9,000 ft. one of the chains went out of business and the engine stopped. The succeeding vol plane would have presented nothing out of the ordinary had not the machine when nearing the ground managed to get into one of the remous that are so fond of playing tricks with aviators, with the result that it was found impossible to make the aerodrome, and by way of a compromise a landing had to be made outside. The final run ended in a collision with some trees. Comparatively little damage was done, however, even at that, the fuselage being intact and both occupants uninjured. In mere justness to the Hans Renolds chains employed, Mr. Grimmer wishes it stated that the fracture came about through no defect in the chain, but was due to the gearbox seizing up, the momentum of the propeller snapping the chain.
Flight, March 9, 1916.
DESIGNING AND BUILDING A BIPLANE.
THE STORY OF A SUCCESSFUL EXPERIMENT.
By ROBERT P. GRIMMER.
[In the following story Mr. Grimmer has given a detailed summary of the ups and downs to which an experimenter in aviation has to be prepared to submit. He has adopted a very light style in handling his subject, and treats his firm's misfortunes in an almost Mark Tapley spirit, worthy of admiration. The mistakes made and the difficulties encountered should be helpful to new workers in the same direction, a suggesting what to avoid. Mr. Grimmer's views as to the comparative merits of twin-propeller and chain pusher machines as opposed to direct driven tractor machines are worth careful consideration., although it must not be taken that we necessarily are in agreement with all the author sets forth. Altogether the story is both amusing and instructive, and we heartily wish the Mann firm the success which Mr. Grimmer foretells in his concluding paragraph in connection with M.2 now under construction. - ED.]
THE Mann Gun-Carrying Biplane is probably familiar enough to the average reader of "FLIGHT," but very few people seem to know the raison d'etre of its existence. The general opinion would appear to be that the transmission was put in for a joke, or else was a misguided attempt to make the 'bus dissimilar to the ordinary type of fuselage machine. Nothing could possibly be more erroneous than these views, and I am now attempting to explain the exact reason why M.1 came into being.
The great majority of aeroplanes belong to the tractor type - that is, with the airscrew in front drawing the machine forward. The other type with the propeller behind are known as "pushers." Previous to the war, the "pusher" type had been greatly neglected, owing to the fact that its design and construction from a "performance" point of view presented great difficulties. The tail booms caused a certain amount of resistance, and there was always the possibility of their being broken by fragments of a damaged propeller. Further, there was the objection against the placing of the engine and tanks behind the crew, which, any way in theory, were liable to break loose and crush the pilot and passenger in the event of a bad landing. Whether this objection has always been substantiated by facts I am not prepared to say, but on paper the "engine-behind" machine certainly does look unhealthy.
Until the war broke out, all the best aeroplanes, without except ion, were of the tractor biplane type, and the most successful of these were single-seaters or "scouts.'' Both the British and French Governments possessed a few "pushers," but it is very doubtful if the best of these had a speed much in excess of 65-70 miles per hour, with a climb of some 300 ft. per minute. The Service value of the "pusher" consists in the excellent view obtained by the crew and the ideal gun emplacement afforded by the projecting body or nacelle. But the "tractor" scored at that time (1914) by virtue of its superior speed and climb. If by a stroke of a magic wand the Allied Governments could have transformed their "tractors" into "pushers," retaining at the same time the superior performance of the former type, there is very little reason to doubt that this would have been done at the beginning of the war. It was not until some time afterwards that the device of firing through the tractor screw was introduced by Garros. This device has the great disadvantage that the gun cannot be properly aimed, as it is on a fixed mounting. The Huns were even worse off as regards "pushers" than ouselves, as they had pinned their faith entirely to the "performance tractor."
I have explained the virtues and vices of the "tractor" and "pusher" types; the one gave good performance, medium view and a bad gun platform, and the other bad performance, good view and a super excellent gun platform. Mr. Mann and I had been connected with aviation in various capacities since its inception in 1908, and we had for some time previously recognised what we considered the disabilities of the contemporary types for Service work. The first really successful flying machine was the Wright, which in its time (1908-09) put up some quite astonishing performances, including a double crossing of the Channel with an engine giving only approximately the same horse-power (20) as the Ford tin-can car! The great characteristic of the Wright was its twin geared-down propellers driven by chains. It is an undeniable fact that propellers of large pitch rotating slowly are more efficient than propellers of small pitch rotating at very high speeds. Propeller speeds of anything up to 1,000 r.p.m. are regarded as being slow, anything approaching 2,000 r.p.m. is very fast. High speed propellers have a very large percentage of "slip," and they lack the grip on the air of the slow speed variety. There are other objections as well, the chief being the tendency to disintegrate, owing to the terrific velocity of the tips, but this latter is worse in theory than in practice, though cases are reported from time to time. At one time the Wright machine was supreme, but as the designers made no real attempt to keep pace with the times by installing really high-power engines, their "twin-pusher" was in course of time completely eclipsed by single-propeller types, chiefly of the "tractor" variety. Mr. Mann and I always recognised the possibilities of the "twin-pusher," properly developed, and we had always wished to construct such a machine on modern lines. But in those days we never secured the weighty financial backing necessary for so great a project.
Just before the outbreak of the great war Mr. Mann and I were fortunate enough to secure the interest of Mr. W, H. Bonham-Carter in our project, with the result that we were able to commence construction in September, 1914, Mr. Mann having got out the rough designs in August. I must here pay a tribute to the magnanimity and the disinterested patriotism of Mr. Bonham-Carter, who at the time of writing has tome the greater part of the burden of financing our experimental work for a period of over eighteen months, and who at the outset had no guarantee whatever that he was backing the right horse.
M.1 was designed and built at great pressure in the hope that she might be used against the Huns early in 1915. Mature reflection inclines me to the view that we should have done better if we had advanced at a more leisurely pace. The design and construction of such an experimental machine was a very big contract, so big indeed that no established constructor would have risked his reputation by taking it on. Having no reputation as constructors to lose, we took the risk - there was a distinct risk, although we were unaware of it at the time - and boldly grasped the bull by the horns. The only building we had available for the purpose was a disused tin church 20 ft. by 40 ft., with a vestry that we converted into two offices. This building had the reputation of being haunted, and it certainly had been standing empty for many years before we got possession of it. A particularly gruesome story is told about this epoch, but the episode occurred so many years ago that it is impossible to verify it. Such was the reputation of the building where M.1 was built.
M.1 was a fuselage biplane with twin chain-driven propellers. Mr, Mann, who was solely responsible for the design, was actuated by the desire to combine in one machine the virtues of the tractor and pusher without any of their vices. The wings were heavily cambered with the front edges sloped back partly for stability and partly to enable the Lewis automatic gun to be fired sideways. A 100 h. p. Anzani engine, hereafter sometimes known as the "Starfish," was mounted at the extreme prow, and the power was transmitted by means of a shaft and universal couplings to a gearbox behind the observer's seat. The gearbox was installed for the purpose of reversing one of the driving chains that emerged from it, and it weighed over 100 lbs. By the way, the reversing of one chain by any method otherwise than the Wright system of crossing it is a task sufficient to daunt the boldest designer, and is by far the biggest problem to be tackled in a chain driven aeroplane. The two chains emerging from the gearbox ran on two sprockets attached to the propeller-shafts, which were supported by means of diamond-shaped brackets and tubes and wires at the sides of the inner pair of struts. The propellers, of course, revolved in opposite directions for the sake of stability.
On September 7th, 1914, we possessed a works indifferently equipped with tools, but with neither staff nor materials, and the designs of the machine itself only roughly worked out. Yet we only allowed ourselves three months in theory to get the "steamroller" - as she was afterwards called - completed. In practice, and for the best of reasons, the construction represented five months of hard work, for it was not till the end of January, 1915, that the "steamroller" appeared at Hendon. I have never worked so hard in my life as during that five months, and the toil was so arduous, and the difficulties so numerous and complex, that the end of the period brought me a severe nervous breakdown, from which I did not finally recover until I took a month's holiday in the spring. The first difficulty we encountered was the problem of getting together an adequate staff. The next difficulty was the question of materials. The unprecedented demand for wood, fabric, sheet-steel, aluminium, tubing, nuts and bolts, wire strainers, &c., had created a veritable famine in these articles, and in some cases one had to wait months for delivery. Such material as we did get had mainly to be obtained by making personal visits to the various manufacturers and cadging - that is the only appropriate word - a sheet of steel here, a few lengths of tubing there, a dozen wire strainers, and so forth. Then there was the problem of drawings. It was well into October before we were able to get even one "stress merchant," and the middle of November before we could lay our hands on two more. In the meantime the foreman had to extemporise drawings of a kind on the back of sheets of emery paper, that being the time-honoured method employed in the early days of aviation in practically all shops.
The overtime worked during this period was something cruel; it was no uncommon thing to start work at 7 a.m. and to go on, with intervals for meals, till midnight. We frequently worked right through Friday night till noon on Saturday, and on these occasions it was not an uncommon thing for fillers to fall asleep at their vices until aroused by the fireman. On all our night shifts a pint of light ale was served out to each man at the firm's expense every two hours, and we found it very efficacious in keeping the men up to the mark. I should like here to pay a tribute to the energy and zeal of the average British workman, who has been so much decried by those who do not know him. We have never known the meaning of labour troubles, and it is my experience that in the aeroplane trade at least the average workman will deal with you as you deal by him. My far the most arduous task that fell to my personal lot was that of keeping a drawing office staff awake on the night shifts. I have sat up many a night doping the "stress merchants" with strong coffee at intervals, but in spite of this and other drastic methods more than once they were compelled to surrender to Morpheus. I recollect that on one occasion a "stress merchant" collapsed from his stool on to the floor at 3 a.m.
This particular man was a Sunday school teacher and a prominent church member, and had never been known to utter even the mildest "cuss word" on any other occasion, but when the wall was banged close to his head to arouse him, he responded with such a torrent of bad language in his sleep as shocked our most hardened fitters. We let him sleep on till breakfast, as he was obviously too muddled to distinguish "pi" from "cos," or "sine" from "tan."
With much labour the "steam-roller," was completed at the end of January, 1915, and duly transported to Hendon, permission having finally been obtained from the somewhat reluctant authorities.
It was erected early in February, and no sooner was she ready for her maiden flight when the pilot we had engaged to fly her discovered that he had more pressing business elsewhere. After same delay we made arrangements with Mr. W. R. Ding, and on Friday, (Friday is regarded by pilots, both aviation and marine, as a very unlucky day) February 19th, the machine was pushed out and the engine run preliminary to a flight. Strong as was my faith in the old "'bus," I shivered with terror when the engine was started and the chains began to run round the sprockets and scream through their guides.
The chains, instead of running smoothly round the sprockets as all self-respecting chains should, progressed in a series of leaps and bounds and appeared to be animated with the desire of moving sideways as well as forward. A tinny clanging noise emanated from the transmission gear, and the wires in the propeller brackets vibrated until they resembled bird cages. The propellers gave one the impression that they wanted to come forward through the inter-plane struts. However, Ding said he would make a flight, and we all let go. The "steam-roller" ran along the ground, duly lifted amid a cloud of smoke from the engine, made a short straight flight and landed somewhat abruptly. It transpired that the pilot's seat had collapsed owing to the "wood butcher" responsible for its fixing having been called away to a prayer meeting and thus forgetting to finish his job. The following day, Saturday, Ding made another flight, partially across country, but this latter quite against his wish and inclination. On attempting to turn, he discovered that the steadying effect of the twin propellers was so great that the rudder had very little effect, and he was compelled to edge the "'bus" round very gradually in order to get back. As the propellers did not suit the engine, and the throttle had jambed at two-thirds open, he had the unexpected pleasure of flying low over Collindale Avenue and only just clearing trees and houses. However, he got back all right, and had sufficient presence of mind left to fly hands off before he landed. A speed of 60 m.p.h. was attained, which was not so bad under the circumstances.
After a month spent in sundry alterations, chiefly to the transmission gear, with a view to steadying the jumping chains, a further flight of ten minutes was made on March 20th. A larger rudder and improved propellers had been designed, and this time the throttle was induced to go wide open. The improvement was quite marked, and a speed of 70 m.p.h. attained. An altitude of 1,000 ft. was reached without difficulty in a 30 m.p.h. wind. Unfortunately, however, one of the wires in the diamond supporting a propeller bracket came adrift, and the great weight of the "'bus" caused her to burst a tyre on landing. Jumping chain trouble was still prevalent, and the tail skid was not satisfactory. A week was spent in further slight modifications.
( To be concluded.)
Flight, March 16, 1916.
DESIGNING AND BUILDING A BIPLANE.
THE STORY OF A SUCCESSFUL EXPERIMENT.
By ROBERT P. GRIMMER.
(Concluded from page 206.)
ON March 38th, Ding made two further flights of 15 minutes each, taking Mr. Mann as passenger in the second one. The chains jumped worse than ever, and two of Hans Renold's experts were absolutely horrified at their extraordinary behaviour. The speed was about 70 m.p.h., but the general performance was so short of Mr. Mann's expectation that it was decided to make very drastic alterations and to install a 125 h.p. Anzani in place of the original 100 h.p. In the light of subsequent knowledge I regard the substitution of engines as a very great mistake, as it materially increased the loading and head resistance, and thus nullified the extra power. Later, I shall give a short list of the alterations, and point out the defects in the original machine, and the reasons that led to these defects. It is worthy of note that in this first Hendon period we only got in less than an hour's flying. On April 1st (of all days) we moved back to Surbiton with the "'bus" and all our impedimenta.
Now, our troubles were two in number: (1) lack of rigidity in the transmission, chiefly in the diamond-shaped stays supporting the propeller shafts, of which stays the front pair were wires and the rear pair steel tubes, and (2) the excessive weight of the machine necessary to secure a high factor of safety in so experimental a "'bus." The original machine with crew and fuel on board weighed over a ton, and the loading approximated to 9 lbs. to the square foot, but in spite of the manifest defects, its early performance of 70 m.p.h. speed and its 400-500 ft. per min. climb, put it in the very front ranks of "pushers." Had the transmission gear been as reliable as it afterwards became, there is very little doubt but that the machine would have been at once purchased by the Government, but the alterations occupied so long a period that by the time they were completed we had to face a rival in the shape of the twin-engined gun 'bus, of which more anon. When the "steamroller" was dissembled after the flight of March 28th, it was discovered that the gearbox and its plate had been moving about and bashing the petrol tank, which would assuredly have burst had the flight, in which Mr. Mann went up as passenger, been prolonged a few more minutes. Furthermore, each radius rod had sheared through its bolt at the gearbox end, with the result that the chains had each been pulling to the extent of a thousand pounds or so against the wing spars. Owing to the jambing of the safety valve in one of the petrol tanks, not the one "strafed" by the gearbox, it was on the point of bursting with the volume of air pumped into it by our automatic pump and was distorted completely out of shape. By way of climax the chains had only kept on their sprockets by a miracle. A period of drastic alterations now commenced, including a new chassis, larger wheels, new propellers to absorb the increased power, a still larger rudder, more forward stagger, and the complete elimination of wires from the transmission. The new engine necessitated heavier shafts, sprockets, chains, radius rods, bridge pieces and gearbox. The difficulty in obtaining material was so great that it was not until the end of June that we saw Hendon again.
During part of our first visit to Hendon we had been housed in one of the L. and P. sheds, but we were soon moved from this to the large Navy shed. When we returned at the end of June, we were unable to get a shed of any kind either from the Navy or the Grahame-White Co., so we were compelled to import a tent, which was pitched near the Hall School. Ding made his sixth flight on Tuesday, June 29th, and the general show the "'bus'' put up was inferior to her March form, and necessitated further experiment with propellers to recover the lost speed and climb. The ill-luck that had haunted us in the spring was still in evidence, for a serious accident was only narrowly averted during Ding's seventh flight on July 3rd, The "steamroller" had been up several minutes at a height of 1,500 feet, and was on the point of landing on vol plane, when a pupil on a Caudron taxied right in front of him. With great presence of mind Ding switched the engine on again, and had it not picked up immediately the Caudion would have been smashed to matchwood by over a ton of "steamroller'' moving through the air at 70 m.p.h. However, he was just able to jump over the "louse," the embryo pilot of which was in great need of a substantial dose of phospherine. On Sunday, July 4th, Ding made his eighth and ninth flights, in the latter of which a very interesting episode occurred. The old '"bus" was in great form and travelling at 73 m.p.h. Ding had just passed a "box-kite" to confute a rumour that the Mann was slower than machines of that type, and was banking to turn, when suddenly a shower of objects flew out behind the left rear of the machine and simultaneously everybody on the aerodrome heard a crashing report. At the same time the right-hand propeller was observed to increase its revolutions, but the "bank" grew no worse and Ding switched off, got the machine at a level keel, and landed without accident. Investigations showed that one of the steel stay tubes supporting the left hand propeller shaft had broken, and falling back into the propeller, had caused it to disintegrate. This incident was really a blessing in disguise, for it demonstrated the utter fallacy of the theory that any accident to one of the propellers of a twin-propeller machine must inevitably "crash" the '"bus."
A fortnight was spent in making a new propeller and strengthening up the propeller brackets, and on Sunday, July 18th, the "steamroller'' was again pushed out. Jupiter Pluvius had been busy during that fortnight, and the whole machine had been saturated with water which had percolated through the roof of the tent. The result of all this soaking was a shocking attack of "nonstarteris" on the part of the "starfish," which was not improved by the confusion of high tension wires 6 and 9 by a careless mechanic. The figures on the Anzani crank case, it transpired, were to be read upside down, which is somewhat embarrassing. M. Hagons, the Anzani expert, seemed greatly amused at our contusion of 6 and 9. During the following week short flights were made on July 19th, 20th and 21st, but trouble developed with both the petrol system and the air speed indicator, which restricted us to 10 minute flights at an alleged speed of 50 m.p.h. On the last day of July and August 1st some more or less "dud" flights were put up, and then Ding returned to Windermere in disgust, having flown the "'bus" altogether about three hours.
Having in the meantime secured that rara avis, a petrol pump that pumps petrol, we induced Mr. Sydney Pickles to try the machine on August 4th. For once in a way the "steamroller" was on her best behaviour, and climbed without any forcing to 3,000 ft. in ten minutes, remaining in the air the record time for her of half an hour. On the following night, Thursday, August 5th, Pickles took up Mr. Mann as passenger for an hour's flight, climbing the first 5,000 feet in less than 20 minutes. After the transmission gear had been overhauled and found quite satisfactory, Pickles took up the writer on August 21st, and Mr. Jones, of "FLIGHT," on the same day. The climb had by this time been increased to 500 ft. per minute and the speed to 75-80 m.p.h. All our troubles seemed to be over, and the machine, now highly successful, was about to be re-offered to the Government when the thunderbolt fell. Pickles was forbidden by an American firm, with which he had just completed a contract, to fly any machine but their own particular make. The fatal day was August 22nd. Pickles had flown the "'bus" almost as long as Ding, i.e., 3 hours.
A weary, discouraging wait ensued, for it was not until October 2nd that we were able to secure another pilot in the person of Mr. A. E. Bans, invalided from the Royal Flying Corps. All the intervening six weeks the poor old "steamroller" was steadily deteriorating in our damp tent, the fabric getting slacker and slacker daily, and rust collecting on all the metal parts despite paint and grease After two excellent preliminary flights of 18 minutes and 9 minutes respectively, during the second of which he carried a passenger, on the following day, October 3rd, he ascended with another passenger to the height of 5,000 ft., but as the weather was misty he decided to go no higher, and remained at that altitude for 40 minutes. After tea he took up a third passenger for 15 minutes and performed some astonishing evolutions, including heavily banked right and left-hand turns with hands off the controls, a feat that the exceptional stability of the Mann biplane renders quite easy. During all these flights the "steamroller" attained a speed of 80m.p.h., which at that time was a record pace for a two-seated "pusher" machine, and surpassed by very few two-seater "tractors". Unfortunately, after landing and taxiing some distance, the wheels became embedded in a filled-in trench, with the result that the chassis and one propeller were broken. This, however, was in no way the fault of the machine. We had a lovely job getting the "'bus" to our tent in the dark. To lift a dead weight of over a ton on to a trolley at night with only six pairs of hands and no mechanical appliances is "some" feat. Still, it was done with much pinching of ringers and uttering of strange oaths, and we "teedled" the trolley for home with one mechanic leading the way as guide and steering by the stars, a task for which his former experience in the Navy would seem to render him specially suitable. After we had been pushing and shoving for half an hour or so without any sign of the home fires in the tent, the ground seemed so very familiar that we stopped to investigate. Enquiries showed that our guide, who had that day been treated to a special "joy" ride in the "steamroller," had been celebrating the occasion to such an extent that he had been travelling in a circle. On being remonstrated with by the foreman, he immediately took that worthy's left eye between his finger and thumb with the apparent intention of plucking it out. He may have been a Bible student anxious to add practice to theory. Anyway, he and the foreman rolled about in the mud under the trolley, the old "'bus" trying to fall off on top of them in the meantime, using most horrible language, the foreman continually repeating "Leave go of my - eye, you - Hun!" Eventually the Bible student let go and staggered away into the darkness. It transpired later that he found a nice comfortable bed in the damp grass from which he only emerged to frighten Langridge with his dishevelled appearance at dawn. He had forgotten about the whole episode, which indeed would afford a fine text for a temperance lecturer. We freely forgave him, and he is one of our very best men at the present time. By the way, we had to serve out frequent rations of rum in the leaky tent to keep the staff from catching pneumonia, but this is the only time I have ever seen one of our men the worse for drink.
The damage to the "'bus" was soon repaired, and the critics of the Mann biplane were treated to six weeks of consistent flying without a mishap of any kind. During this period Bans flew the machine over 10 hours at an average speed of 80 m.p.h. and a maximum of 85, he ascended on 30 occasions and carried no fewer than 18 different passengers without any untoward incident. He secured with ease a low speed of 40 m.p.h. in spite of the exceptional heavy loading. The only direction in which the "'bus" might be held defective was the "climb." The falling off in this respect since August was simply due to the slackening off of the wing fabric caused by exposure in the damp and dripping tent. But in spite of her "soggy" wings the machine repeatedly climbed with five hours' fuel, gun and ammunition and two up to 3,000 ft. in 8 minutes, and that with a dead weight of over a ton and the wings loaded to 10 pounds per square foot. She frequently ascended to 5,000 ft., once to 7,000 ft., and once to nearly 9,000 ft. All the old faults had long since been eradicated, and the transmission gear gave no trouble at all. The Mann was undoubtedly the fastest two-seater "pusher" in existence, and the improvement since February was generally commented upon in aviation circles. It is my opinion that single-seater "scouts" cannot be regarded as serious "gun 'buses" from which proper aim can be taken, as the pilot is too occupied with his controls to give adequate attention to his gun. Such makeshift gun-carriers are only effective at pointblank range, and fall easy victims to a two-seater of distinctly less "performance."
How this improvement had been effected is a long story, but I will give my readers a few details. Contrary to general expectation, the chains by themselves gave very little trouble, the stretch was negligible, and we never had a single broken roller. Their vibration, however, was the cause of the acutest anxiety to us in the early days. This vibration proceeded from a variety of causes - wires in the original propeller brackets, too long chain guides which compelled the chain to take its slack on the sprockets themselves, insufficiently rigid radius rods, and last, but by no means least, a critical period of vibration in the engine. By sheer process of elimination we eventually succeeded in inducing the chains not to jump, and a photograph in "FLIGHT" of October 29th last illustrates their smooth running. In this photograph the chains are as rigid as bars of steel. This photograph, by the way, was taken by Karrs himself from the pilot's seat, he having left go of the controls for that purpose. The bias against chains that one is constantly meeting with is surprising. There is an altogether fallacious and erroneous impression that they break! Our shafts and couplings gave no trouble at all, and we only had trouble with a propeller bracket on one occasion. Some pseudo-experts have expressed the opinion that the resistance of chains, guides and sprockets prevent high speeds from being obtained, but the fact that we were able to attain a speed of 85 m.p.h. with a crude experimental "'bus," weighing over a ton, would seem to show that there is some fallacy here. The design of the propellers involved a great deal of experiment, and we must have tried nearly a dozen pairs. The best results were obtained from the 125 h.p. engine by a pair of propellers that had proved utterly hopeless on a 100 h.p. engine. They were extremely crude in appearance, having been designed by a "wood butcher" more in joke than anything else. But with the 125 h.p. engine they pushed like elephants, giving a combined thrust of one-third the weight of the machine and licking into the proverbial cocked hat the best productions of professional propeller designers. The various propellers to Mr. Mann's own design gave excellent results, but invariably slowed the "'bus" from 5 to 10 miles per hour, while the propellers designed by the professionals pave much poorer performance.
The speed and climb of the '"bus" were worked up principally in three ways - (1) propeller experiment, (2) diminishing chain vibration, which absorbed quite a lot of power, and (3) streamlining transmission tubes and stays. Experiments with struts, both chassis and interplane, produced good results, as also did lessening the weight, but the initial ponderosity of the "steamroller" was so great that any attempt to diminish it was like sandpapering an elephant. It is the opinion of both Mr. Mann and myself that the admittedly good performance of the "'bus" was entirely due to its twin propellers, for how else could a machine weighing nearly a ton and a quarter and loaded 10 lbs. to the square foot, be induced to climb at the rate of 500 ft. per minute as actually happened when she was in good form? It is very much to be doubted if any single propeller or tractor screw would have got her off the ground at all.
Our long and protracted experimental period, which really ended in August, for Barrs had merely picked up the broken thread that Pickles had dropped, had given the mysterious "technical advisers" to the Admiralty and War Office a distinct bias against the Mann. Why, I am not prepared to say, for the practical experiments that are necessary before one can standardise a new type of aeroplane had been amply justified by the results obtained. Rehearsals are always needed before a successful public performance, and aviation is no exception to the rule. It is only on paper and in drawing offices that one designs a new type that requires neither alteration nor experiment.
However, finally, we were on the point of obtaining permission to fly the "'bus" for official trials, when she was "crashed" in an altogether unexpected manner. On November 16th Burrs had ascended with a passenger in an attempt to break the British altitude record. In about three-quarters of an hour he had ascended to a height of between 8,000 and 9,000 feet, and was still climbing strongly. Suddenly the gearbox seized up dead and the momentum of the whirling propeller broke the chain on the right-hand side. Please note that the propeller broke the chain and not the chain the propeller. The chain flew out between the two end interplane struts and vanished, as I had always prophesied it would do in the very unlikely event of a breakage, and Barrs switched off his engine and commenced a glide which lasted 21 minutes. Mr. J. G. Woodley, the passenger, was so little concerned that he calmly went on making entries in his diary, which was reproduced at the time in the pages of "FLIGHT." On nearing the ground, the poor old "'bus" was caught by a strong downward current which brought her down just outside the aerodrome in a small field. She taxied into some trees, felling three of them, but although the chassis and wings were smashed to atoms, such was the strength of the fuselage that neither Barrs nor Woodley sustained the slightest injury. The passenger's escape in particular was due to the main shaft connecting the engine and gearbox making his compartment extremely rigid and unyielding. Such a smash on an engine-behind machine would have probably left no survivors to tell the tale. The initial cause of the "crash'' was the negligence of a mechanic to put grease in the gearbox, though but for that wretched remou at the last moment the '"bus" would have landed in the aerodrome without breaking a wire. Extremely lurid and misleading accounts of the accident appeared in the pages of the contemporary daily press. Such was the end of the "steamroller" after some nine months of strenuous life.
The "crash," however, got us out of one difficulty. Our canvas hangar had become almost uninhabitable owing to the heavy rains, and a miniature river was flowing through the tent from side to side. Any further flying of the "steamroller" at Hendon had become well-nigh impossible, but the remou that brought the "'bus" down just on the wrong side of the fence effectually cut the Gordian Knot. It is worthy of note that the "steamroller" was flown three hours by Ding, three by Pickles, and 12 by Barrs, 18 hours in all, and she must have covered in that time a distance of nearly 1,500 miles.
At the time of writing, some ten weeks afterwards, we have half finished the "steamroller's" successor, M.2, who, I will venture to say without any risk of boasting, will regain for Mr. Mann the "pusher" supremacy he lost in November. M.1 all but completely vindicated the principle of chain-drive and geared down propellers; M.2, with her loading reduced to half, hundreds of pounds less in weight, will completely do so. M.1 was built in the typical "Middle Ages" manner with great clumsy fitting and full of unnecessary weight and head resistance. M.2 will be in every way an up to-date 1916 machine with transmission added. Her performance will astonish the few remaining critics of the type.
Invidious comparisons have recently been made between twin-engine and transmission machines, to the detriment of the latter. To my mind, the twin-engine machine weighs much more than a transmission machine, its head resistance is much greater, and it has more vulnerable points, e.g., two engines afford a better target for hostile fire than one, also they obviously require more attention. The twin-engine machine can fly after a fashion with one propeller, so can the transmission machine. On a transmission machine you can put your propellers where you like and run them at any desired speed. On a twin-engine machine you mutt place your engines in two particular spots, or the efficiency will suffer, and your propeller revolutions are arbitrarily fixed. Twin-engines usually indicate twin-chassis, which are not necessary on a transmission machine. The only point where the twin-engine machine scores is in simplicity, but an aeroplane transmission, once the experimental stage is passed, requires no more attention than that of a car.
My tale is told. I have made it clear to my readers why we have persevered with the Mann biplane so long, and also that the path of the experimenter is by no means easy and pleasant, though it may easily lead him to destruction. Ridicule and calumny are poured on him at every step, and all men wish him ill. He has to tight rigid conservatism and wrestle with invincible ignorance. His sole assets are the courage of his convictions and a saving sense of humour. But we forget the toil and danger of the past as we daily watch the Mann biplane rise like the Phoenix from the ashes of its predecessor. And perhaps this true story of how we wrested success from apparent failure may encourage others among the readers of "FLIGHT" to follow in our footsteps. Per Ardua ad Astra !