The frame of the safety bicycle, used by the million, is made of seamless steel tubing of the finest grade. Hundreds of components are used in the making of every machine. Many of these items are supplied by specialist firms
COMPLETED MACHINES undergoing a final inspection before they are packed for dispatch. The bicycles are assembled along the route of an overhead conveyer. The tandem in the foreground is fitted with a special type of change-speed gear.
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SPECIALLY light materials, ball bearings, accurate machining and careful finish — all have contributed to the perfection of the bicycle. The most striking development, however, in the evolution of the cycle has been the introduction of the pneumatic tyre. Bicycles can now be counted in millions and their use is general throughout the world.
The bicycle first appeared in the form of the hobby-horse of 1818. This consisted of two wheels carrying a wooden framework and saddle. The front wheel was pivoted as in the modern bicycle, and steering was effected by the use of handlebars. There were no pedals or chain and progress was dependent on the feet, used paddle-fashion. Despite its weight (about 50 lb.) and somewhat clumsy construction, the hobby-horse was capable of being ridden at ten miles an hour on a level road.
The machine was patented in France by Baron von Drais and was introduced into England by Denis Johnson, a London coachmaker. Johnson introduced also a ladies’ hobby-horse in 1819, with a drop-frame that bore a striking resemblance to those used for ladies’ machines a hundred years later. The machine was built of wood, plated with iron, and the wooden wheels were provided with iron tyres. Examples of these hobby-horses may be seen in the Science Museum, South Kensington.
The connecting link between the hobby-horse and the bicycle was provided by a Scottish blacksmith, Kirkpatrick Macmillan. Wood and iron again formed the materials for the machine and the weight was 57 lb. — an interesting comparison with a modern bicycle weighing less than 25 lb. The Macmillan machine was provided with cranks at the ends of the rear axle, and these were driven by treadles and connecting rods in exactly the same way as a modern toy motor car for children. The saddle was sprung and a tyre brake was fitted to the back wheel. This brake was worked by a cord that could be tightened by rotating the handlebar in the manner of the twist-grip control of the modern motor cycle.
It was not until the 1860s that the bicycle began to develop on the lines of the present-day machine. The next step forward was the famous “boneshaker” introduced from France in 1868. The frame of the machine was of wrought iron, but wood was used for the wheels, which were fitted with iron tyres. The handlebar twist-grip idea was used for operating a brake on the rear wheel and the drive was by pedals attached to cranks on the front axle.
The following year the bicycle had improved to the extent of wheels with wire spokes, and in 1870 James Starley produced the first all-metal bicycle with wire wheels shod with solid rubber tyres.
Next followed a period of bicycle development devoted to the quest for speed. The sprocket-and-chain drive had not yet been introduced and the pedals were attached direct to the front axle. The front or driving wheel thus grew in size until it attained, in some instances, a diameter of seven feet. The rear wheel, carrying the long curved saddle pillar (generally known as the “backbone”), remained comparatively small: hence the nickname of “penny farthing” that was bestowed on these early types of bicycle.
By 1879 the safety bicycle had made its appearance on the market. This machine, introduced under the name of “Bicyclette” by Henry Lawson, was driven by a pair of pedals and a sprocket mounted on a crank bracket. The drive was transmitted to the rear wheel by a chain.
By the beginning of the 1880s the use of steel tubular frames, ball bearings and other refinements had been applied to the bicycle and the “ordinary” machine had been reduced in weight to less than 50 lb. The safety bicycle was destined, however, to take first place, and during the 1890s the chain-driven machine with equal-sized wheels came into general use. Further improvements at the end of the nineteenth century were the introduction of the free wheel and of the change-speed gear.
First Pneumatic Tyre
Among all the improvements, however, that were introduced for the benefit of the bicycle, none had such far-reaching results as the pneumatic tyre. An Irish veterinary surgeon, John B. Dunlop, was a keen cyclist, and he was anxious that his son should enjoy the pastime also. Bad roads, solid tyres and the delicate state of his son’s health militated against the elder Dunlop’s wishes, and he began to devise means to eliminate the chief source of trouble — vibration. Saddles were at that time sprung, but Dunlop held that the place to combat vibration was where the bicycle wheel touched the ground, at the tyre. He decided that the best means of turning the tyre into a cushioning device was to make it hollow and fill it with air under pressure. A rubber tube was therefore made and fitted with a valve through which air could be pumped. The tube was secured to the wheel rim by a canvas casing that was provided with a rubber tread.
From that one improvement to an individual bicycle there has sprung up one of the largest and most remarkable industries in the world. On it depend not only the bicycle but also the motor-car industry.
The basis of the modern bicycle is the frame, made of the finest-grade steel tubing to ensure the maximum of strength with the minimum of weight. It is largely due to the perfection of modern steel tubing that the weight of the bicycle is now so much less than it was some fifty years ago. Only the best seamless or welded steel tubing is used in bicycle making, and two main processes are available for its manufacture.
ROTARY PLATING VAT in which various component parts of the bicycle are plated with nickel or chromium. The components are cleaned and plated with copper before the final coating is applied. The plating process is described in the chapter “Electro-Plating Plant”.
In one method a cylindrical billet or bloom of steel is pierced with a central hole by a hydraulic press or on a special boring mill. The hollow steel billet, of, say, 4 in. diameter and 24 in. long, is then heated to a temperature of about 1,200 degrees centigrade and fed between steel rollers with curved outline. The curved rollers are placed at an angle to one another so that as they revolve they rotate the billet and force it forward. Under tremendous pressure the billet is forced against a pointed mandrel held on a long rod. The resulting heavy tube, between 4 and 5 feet long, is then passed through a rolling mill, in which the rolls are provided with semicircular grooves of various sizes. By the use of the rolls and mandrels of the required diameters, the tube is finally reduced to its correct size and thickness.
A second method of making cycle tubes is known as cold drawing, as distinct from the rolling process. In this instance the rough rolled tube (the methods are similar up to this point) is reduced under a power hammer to form a “tag”. The tube is next annealed or heated and allowed to cool slowly. It is then washed in acid, to remove scale, and is finally rinsed in water. The tube is now lubricated and placed on a bar of the same size as the required inside diameter.
The tube, with the bar inside, is then drawn by the tag through a steel die that reduces the gauge (wall thickness) to the required dimension. The tube is then passed through rolls that close it down in the exact internal diameter, determined by the bar that is still inside it. Finally the tube is withdrawn from the bar, the tag is cut off and, after further annealing, the finished product is polished bright. A variation of the cold drawing process is to force a special mandrel through the tube as it is drawn through the die.
The Brazing Process
Bicycle tubing is not all of circular section, and the familiar D and similar sections are made from round tube by rolling or pressing. The interior of a bicycle frame tube is not necessarily parallel. In the best machines the tube ends are specially thickened to withstand the stresses which are imposed during the brazing process and which the frame will bear in service on the road. With the tubes cut to correct lengths or pressed to special shapes, the next process is frame building. In the best types of modern bicycle the lugs into which the frame tubes fit are steel forgings and are machined all over. Lugs made from malleable castings are used for cycles of moderate price, and in some makes the lugs are pressed from high-grade sheet steel.
Frames and front forks are built on “jigs”, or special holding devices that keep lugs and tubes in their relative positions during assembly. When the framework has been alined and all the lugs are in their proper places, the whole fixture is tightened up and small holes are drilled through tubes and lugs at every joint. Taper pins or pegs are driven into the holes and the frame, now rigid in itself, is removed from the jig for the brazing process, by which all the joints are united with molten brass.
There are two methods of brazing in general use, the “hearth” process and the more modern “liquid” method. Hearth brazing involves the use of powerful gas blow-torches that are directed on to an open fire of small coke. The joints where the tubes enter the lugs are coated with a paste, consisting mainly of borax. This serves as a flux to dissolve the layer of oxide that forms during the heating process, and so preserves a clean metallic surface for adhesion of the molten brass. The remaining portions of the lugs and the tubes, to within a short distance of the joints, are coated with blacklead or paint which prevents the brass from adhering where it is unwanted.
The joints are placed in turn on the glowing hearth and brought to a bright red heat. The flux melts and a special quality brass, either as a stick or in the form of powder, is applied to the joint. The brazing metal flows right into the joint, searching out every tiny crevice so that, on cooling, the lug and tubes are as firmly united as though they had been machined from a solid piece of steel. In the “liquid” brazing process the work is dipped into a gas-heated bath of molten brazing metal and, as the lugs and tube ends attain the temperature of the metal, it flows into the joints.
The cleaning of joints may be done by sandblasting. In this interesting operation, sand or shot is blown through flexible pipes by a powerful blast of compressed air. The operators wear helmets and special protective clothing, as they direct the artificial sandstorm against the joints and scour away the unwanted material.
INGENIOUS APPARATUS FOR TESTING WHEELS in the works of the Birmingham Small Arms Co., Ltd. A beam of light is reflected from the rim of the wheel on to a “ target ” screen at the back of the machine. Any inaccuracy on the rim will cause the white spot of light to deviate from the centre of the “target.”
After the cleaning of the joints, the frames and forks are polished by special machinery using belts of emery cloth. Finally, the work passes to the enamelling shop. Here the various operations have undergone many alterations since the early days of the bicycle. The older methods of preliminary cleaning with turpentine have given place to the use of a special chemical bath which instantly frees the work from all traces of oil or grease, ready for enamelling. A process of enamelling by dipping was formerly in general use, but this has now been superseded in some works by spray painting with compressed air.
After enamelling, the frames are “stoved” or heated for some hours in high-temperature gas ovens. Finally, ornamental lines and makers’ name transfers are applied to the enamelled frames. Cellulose, although expensive, is sometimes used for giving special colours that cannot be obtained readily by the use of stove enamel.
“Mopping” Plated Parts
Tube work is not confined to frames and forks. Seat pillars and handlebars are bent from the finest steel tubing by experts. Handlebars are made in a number of special shapes that are given distinguishing names in the cycle trade. Their manufacture requires considerable skill to ensure smooth and symmetrical bends. The modern handlebar is made with a thickening piece in the centre that is gripped by a separate stem fitting into the steering head. All of the above fittings, with chains, sprockets, pedals, hubs, spokes, rims and other components, are finished by the familiar plating process with nickel or chromium. A preliminary to either method is the chemical cleansing of the components as for enamelling, generally followed by plating with copper, to form a foundation for the final coating of nickel or chromium. The plating process is described in the chapter “Electro-Plating Plant”.
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When the handlebars and other components have been plated they are polished by a process known as “mopping”. A “mop” comprises a number of calico disks attached to a spindle and revolved at high speed. The disks are impregnated with grease and fine-grade abrasive powder. They revolve at so high a speed that they become rigid and permit the work to be pushed hard against them during the polishing operation.
During the manufacture of the tubular portions of the bicycle, such as frames, forks and handlebars, other departments in the factory are busily engaged in manufacturing the hundreds of components that go to the making of every machine. In the best cycles such items as saddles, lightweight mudguards and pumps are nearly always supplied by specialist firms. The manufacture of
cycle tyres is a highly specialized trade also. British cycle manufacturers, through their own Standardization Committee and in conjunction with the British Standards Institution, have agreed that certain cycle fittings shall be of uniform size. For example, handlebars and their stems, seat pillars and saddles, are interchangeable on all British makes of bicycle. Wheel diameters and rims are also standardized to take any of the standard makes of inner tube and outer cover. The same standardization applies to cycle screw threads and other items in manufacture.
Wheel rims are pressed from strips of high-grade steel and the ends are joined by brazing or welding. For the spoke nipples the rims are punched or drilled in special machines that automatically space out the holes to accommodate the required number of spokes. After drilling, the rims are polished and plated and are then built up with spokes and hubs held in special wheel jigs. The hubs are produced, with their ball races and the flanges drilled for spokes, on automatic machines.
Wheel building is an art in itself and is generally done by girls, who exhibit a wonderful degree of skill in assembling the different parts to produce a wheel that runs dead true.
DRILLING MACHINES are used extensively in the machine shop of a bicycle factory. Components such as cranks are generally machined in batches on special milling machines.
A hub is taken in one hand and the operator drops a number of spokes through alternate holes in one of the flanges. The hub now resembles a “spoked spider” and is held suspended by one “leg”. This spoke is quickly inserted in one of the upper holes of a wheel rim standing on the bench. A nipple is slipped on the spoke-end protruding outside the rim, and is given a flick with the finger to screw it up a few turns. Similar treatment with one or two other spokes roughly centralizes the hub and the remaining spokes are then inserted and provided with nipples. The wheel, with all spokes loose, is then placed in a special jig for the tightening process. The jig consists of a horizontal disk, from the edge of which rise a number of pointed steel cones. The rim of the wheel rests against the cones, and another fixture automatically centres the hub. A girl with a ratchet screwdriver then tightens up the nipples, and the wheel is ready for the final truing process that ensures perfect running of the rim.
At the works of the Birmingham Small Arms Co., Ltd., a battery of highly ingenious devices is used for the truing of bicycle wheels. The device resembles a miniature rifle range with the “butts” covered in by a canopy. The “target” consists of a circle drawn on a white background. Cutting this ring are a horizontal line and a number of equally spaced vertical lines, of which the middle one passes through the centre of the circle. Below the canopy is a stand for holding the wheel, and behind this is a seat for the operator.
On the front of the canopy, just above the stand, is an electric lamp with a lens focusing a beam of light down on to the rim of the wheel. Within the rim of the wheel there “floats” a small roller held at either end by small chains. The roller carries a tiny
mirror which reflects the small beam of light on to the target. As the wheel is turned, any radial inaccuracies are shown up on the target by a movement of the light spot above or below the horizontal line, and nipples are adjusted accordingly with a special key.
Lateral movement or “wobble” is similarly indicated by the light spot as it moves to right or left across the vertical lines. Finally, with the wheel spinning and the spot of light scoring a “bull”, the job can be passed.
Variable Gears
The machine shop, with its batteries of automatic lathes turning out thousands of spindles, nuts, bolts and washers, is one of the most important departments in the modern bicycle factory. Here, also, are made the various components of brakes and pedals, with cones, cotter-pins, free wheels and similar parts. Cranks are generally machined in batches on special milling machines; other machinery produces the sprocket wheels for driving chains. The making of bicycle chains is another highly specialized process in which the various components are produced by automatic machines. The rollers of the chain are ground to size in special machines, and are assembled on pins riveted into the pressed steel side links.
The making of change-speed gears is again a specialist’s job, for in the small space provided within a cycle hub a complete set of gear wheels is accommodated. The parts for hub gears that give two or three changes of gear ratio on the touch of a small lever are remarkable mechanisms. Despite their small size, the gears transmit the whole thrust of the pedals to the rear wheel, even the double thrust on a tandem machine. A comparatively recent development in change-speed gears involves the use of two or three sprockets of different sizes on the rear hub. The chain is provided with a special tensioning device, and it can, by touching a small lever on frame or handlebars, be momentarily slackened and moved from one sprocket to another, thus altering the gear ratio.
The final assembly of a modern bicycle is generally done on what is known as the belt system, with groups of expert assemblers stationed at various positions along a moving conveyer. The finished components are brought to the conveyer, and each part is fitted by one man until, when the end of the conveyer track is reached the bicycle is complete and ready for the road.
THE BENDING OF HANDLEBARS is done by experts at this particular task, and requires considerable skill to ensure smooth and symmetrical bends. The modern handlebar is made with a thickening piece in the centre. This is gripped by a separate stem fitting into the steering head.
