A REVOLUTIONARY BICYCLE AND A CHEAP CYCLE CAR.
FIRST TECHNICAL DESCRIPTION.
The A.B.C. motor bicycle was rapidly acquiring a unique reputation when war broke out. During the past four and a half years its designer, Mr. Granville E. Bradshaw, has become famous as a member of that select band of brilliant young engineers who achieved miracles' by extending the application of air-cooling from engines of 8h.p. or so up to aero engines of 200 or 300 h. p. Motor cyclists have been anxiously waiting to hear what the firm's post-war programme might embrace, and there was a widespread apprehension that its energies might be wholly diverted into the aircraft industry. We are glad to announce that this fear has no foundation in fact. A.B.C. Motors, Ltd., and its allied concerns take the view that for the next few years aviation may- be regarded as a very stormy sea. The possibilities of commercial aviation have yet to be demonstrated. Europe is full of all types of aircraft engines, many of which are brand new, will be sold cheaply, and are available for flight experiments. On the other hand, the world is clamouring for up-to-date cars and cycles, the road motor industry having been either stagnant or suspended for nearly five years. Here is a huge and profitable market in which firms with ideas may find a surer outlet for their productions.
A.B.C. Works, a Laboratory.
When the armistice was signed, the A.B.C. Co. found itself in an enviable position. The war had brought it into close association with several of the largest aircraft constructing factories in the kingdom, most of which will shortly be seeking employment for their expensive plant and large staffs of skilled employees. These firms include at least two whose names are household words in the R. A.F. Details of some sensational amalgamations may be announced shortly. The original A.B.C. works have been transformed into a laboratory for technical experiment and research. Three or four ideas are various stages of progress, and fortunately the two notions which are most advanced and are earmarked for priority are those of interest to motor cyclists, who are assured both a lightweight cycle and a cheap cycle car of A.B.C. origin. As each design is perfected, it will pass to one of the associated factories for mass production.
To summarise the firm's policy, aero engine experience, has rendered it possible to extract so much power from a given c.c. that it regards 500 c.c. as too much for a solo mount, and its motor bicycle will be appreciably smaller than this figure indicates. On the other hand, the firm does not believe in sidecar outfits, granting that it is possible to design a technically sound cycle car and to market it at a figure which competes with the high-powered sidecar outfit. Consequently, the 500 c.c. pattern disappears from its motor cycle catalogue.
It will be remembered that as long ago as September 30th, 1915, The Motor Cycle described and illustrated an A.B.C. flat twin of 250 c.c. which developed over 4b.h.p. This engine was originally evolved for motor cycling purposes, and during the war it has been steadily manufactured for driving blowers and dynamos, for starting seaplane engines, and for a variety of auxiliary Service uses. Needless to say, Mr. Bradshaw has perfected it during the last 4½ years, and the armistice finds him ready with a somewhat similar engine thoroughly adapted for solo touring work. At the present moment the first sample engine has completed sixty-one hours' running under full load on the stand, and is expected to pass into production as soon as the destruction bench tests are completed, and the outdoor staff have had time to test its manners under actual road conditions.
The "Firefly" Lightweight.
The public will expect to find strong reminiscences of aero engine practice in all the post-war A.B.C. engines. The “Firefly,” as the little fellow is christened, is no exception. It has one-piece steel cylinders with wafer fins, machined to the closest dimensions inside and out, and is absolutely symmetrical from every point of view, so that no distortion — the modern name for the ancient bugbear of overheating — can occur. The pistons are of aluminium, deeply recessed at the waist to avoid gumming, and bantam weights on the scales. Both inlet and exhaust valves are of the overhead type, machined from unbreakable aero steels. The connecting rod big ends thread over the cranks of the one-piece crankshaft; the crank pins and the “eyes” of the big ends are hardened, and the annular spaces between crank pins and biff ends are filled with rollers, located and secured by split distance collars. This type of big end requires oil only as a protection against rust, and permits the lubrication to be cut down to the minimum.
Mechanical oiling and an automatic single-lever carburetter are provided. The induction pipe is heated from the exhaust box, and a good mixture is obtained with an extraordinarily small jet with consequent economy of fuel.
The final c.c. will be determined when the road testers report on the top gear climbing of the experimental batch of machines. It is intended to combine a maximum speed of 60m.p.h. on the level with good top gear climbing capacity. In any case the engine will be well below the 500 c.c. mark, and its exact size will be determined irrespective of pre-war conventions; if necessary a special size of engine will be turned out for the heavy competition programme which is contemplated.
Now comes a surprise for our readers. In 1914 everybody liked the flat twin engine, but everybody noticed how awkward it was to house in a normal cycle frame, and how inevitably the front cylinder was better cooled than the rear, Mr. Bradshaw has cut these Gordian knots by boldly mounting the Firefly athwart the frame. The crank case is mounted low down at the front of what an Irishman might term a “square-loop” frame, with the tiny cylinders projecting to the right and left, and the crankshaft axis in line with the track. The overall width of the engine has been reduced to such a figure that if the machine should fall damage cannot occur, nor do the cylinder heads appear to project or seem in any way obtrusive. This, of course, is accounted for by the fact that war experience has rendered a “tabloid” power unit practicable.
Heterodox Features.
The gear is enclosed in the flywheel, and embodies three forward gears on the epicyclic principle. The whole revolves solid on top gear, and furnishes the maximum flywheel effect for high gear work, whilst the lower gears have the effect of temporarily lightening the flywheel, which is desirable for revving on a low gear. From the rear of the gear box a propeller-shaft drives a ball bearing countershaft, through bevel gearing, and the final drive to the rear wheel is by enclosed chain. Provision is made on the countershaft for driving a speedometer and an electric lighting dynamo. A sleeve mounting for the latter is provided in an alternative form of top casing for the bevel gears, and this mounting can be substituted at any time after purchase. The entire power unit, including the gear box, can be taken out of the frame after withdrawing three bolts.
The frame is also by no means devoid of originality. Mr. Bradshaw frankly runs counter to ancient prejudices when he denounces the fetish of a straight tube frame. He holds that a rigid frame conveys the maximum amount of vibration to the rider, holds the road badly, and is apt to fracture when the tubes butt into the lugs unless these parts are built absurdly heavy. The Firefly frame is built up of two tubes. The upper tube is sharply slanted backwards, and has a downward turn towards the rear, giving extra clearance for a long coat or a skirt. Lugs are brazed to each end of it, and into these lugs the lower or “loop” tube is butted. The loop is given rather a squarish contour fore and aft of its bottom run. As the engine weights under 30lb. the designer can afford to mass strength in the vital parts of his frame, and simultaneously to allow a little natural spring between these points. The frame appears to serve these twin ideals well.
It is efficiently sprung fore and aft, flat laminated springs being used at both ends. The fork more or less resembles the well-tried 1914 A.B.C. type. The rear springing is quite new. The hinged joint between main and rear frame is equipped with roller bearings, and the hinge at the base of the carrier strut with encased ball bearings. It has no “thick end,” but is “stepped” both above and below.
The machine adds a new point to the brake controversy, for both brakes are of the cone type, now coming into favour on cars in America, but as yet practically unknown in this country. We are unable to illustrate them at the moment, but they resemble an ordinary friction cone clutch, one cone being mounted on the spindle, and the other on the wheel. The advantages claimed by the American originators are that they give a maximum frictional area in a minimum space, and are practically self-adjusting for wear, as the male cone slides deeper and deeper into the female cone, as wear occurs.
No kick-starter is fitted, the machine being designed to start in a yard or two by the “paddle-off” method, a hand clutch being provided in case it is desired to take a rider on the carrier or to pull a sidecar. Owing to the absence of internal flywheels, the restricted lubrication required when the crank case is almost devoid of plain bearings, and the piston clearance described above, “gumming up” does not occur on this engine, and even an elderly man can easily start it.
The machine should prove economical to run; 2½in. tyres are fitted, as the best insurance against those aggravating tyre stops which befall the most reliable machine. A special induction system, which we have no space to describe in this issue, permits power to be obtained from an abnormally small jet, and judging by bench tests-the fuel economy should be phenomenal. The bearing and piston design renders floods of oil in the crank case as unnecessary as they are always undesirable. In the sixty-one hours' bench testing above-mentioned, the average oil consumption has been just under 4 oz. per hour, equivalent to something like 2,000 m.p.g. on the road at high speed.
In view of the demand from old clients and agents, numerous firms would already have passed this machine into production; but, as the output is to be on a very large scale, it has been thought prudent to test the main components to destruction as a preliminary. The engine is to complete 100 hours on the bench, after which a score of machines are to be given a heavy gruelling on the road. Meanwhile the gear boxes are to do fifty hours on the stand on each separate ratio, concluding with another fifty hours, during which a special trip mechanism will make brutal gear changes every minute. The machine will then be marketable with the same confidence which its sponsor firms hope to inspire from their new customers.
It is hoped that the bench tests will be concluded early in December, and production will not be delayed a moment longer than is inevitable, as several thousands of aircraft workers are waiting to pass into peacetime employment.
A Welcome Innovation.
Writing before we have enjoyed personal road experience of the new design, we are bound to welcome its appearance, even on paper, as a fact of some importance in motor cycling history. Our veteran readers will remember that on previous occasions a machine which outraged all motor cycling conventions has proved a very healthy stimulus to the sport, hobby, and industry. The Douglas and the Scott are notable examples. We hope the experience of the next few months will endorse the view that the new A.B.C. will mark a somewhat similar epoch. For the moment we can only say that it is the bantling of a brain which has achieved real distinction in war engineering, and, having discussed the machine in detail with its designer, we know that he has a sound engineering principle for each departure from orthodox practice.
It is perhaps needless to add that the machine is a lightweight de luxe, and that at the present rate of wages and cost of material it will not be cheap as compared with pre-war standards. There is, nevertheless, every reason to hope that prices will drop sharply when industry settles down to its new occupations; and in the meantime the price will compare quite satisfactorily with market standards.
THE A.B.C. CYCLE CAR. First Announcement.
This cycle ear is frankly a profession of unfaith. It proclaims a disbelief in the sidecar. No 500c.c. A.B.C. will be made, and the firm is not anxious to see sidecars attached to the new Firefly model (which is described in this issue), though it can unquestionably pull them. In the A. B.C. programme there is a considerable gap between the Firefly and' the 1,200c.c. cycle car, which will be listed at 100 guineas, if the wages of labour and cost of materials do not disappoint its sponsors. A perusal of the simple specification suggests that in any case a low price should be practicable. The engine, of course, is a flat twin of approximately 1,200c.c. , built and designed on aero principles, and developing some 12b.h.p. This will be mounted horizontally across the front of a 4½ cwt. chassis, with the valve chests protruding on each side from a cowling resembling the nose of a fuselage.
In technical details this engine is a bigger edition of the Fireflv. It is rather in the transmission that the cyclecar chassis is revolutionary. The usual gear box, differential gear, and clutch are all compressed into a novel form of friction drive, which we shall describe in our next issue. This cycle car will not go into production until the motor bicycle is passed as absolutely perfect; but, unless unexpected difficulties are encountered during reconstruction, we may hope to see it on the road next spring, when it bids fair to prove a formidable competitor of the sidecar de luxe. The most superficial glance at its design indicates to us that it is a true cycle car, and can be built far more cheaply than any car type of vehicle. There is not a of any kind in the entire transmission, and on paper the fraction drive promises to be satisfactory.
From “The Motor Cycle”, November 28th, 1918