Keeping the wheels turning
What do the Fiesta, the new Rover 3500, works rally TR7s and Escorts, most Formula One cars and Concorde have in mechanical accord? The answer lies in some of the bearings they use, either in wheel hubs, differentials or gearboxes: tapered roller bearings made by Timken, whose European headquarters, British Timken at Duston, Northampton, I visited recently.
British Timken is part of the Timken Co. of Canton, Ohio, the world’s largest manufacturer of tapered roller hearings, a crown which is fitting since it was Henry Timken who designed and patented this type of bearing in the USA in the late nineteenth century, Apparently he demonstrated its almost friction-free capabilities in St. Louis to cries of “Cruelty!” by loading a large cart up to enormous weight and attaching one horse to it. The unperturbed horse pulled it relatively easily; Timken had proved his point. Today Timken is a public company, with 20 manufacturing plants and 20,000 employees throughout the world, but the Timken family retains the major shareholding through a Foundation. Timken Europe’s Managing Director, based at Duston, is Mr. E. R. Knapp.
British Timken’s history goes back to 1909 when Vickers Ltd. through its subsidiary company, the Electric and Ordnance Accessories Ltd., Birmingham, made an agreement to manufacture Timken bearings in England. This led to the first organised manufacture of tapered roller hearings in Europe, at Cheston Road, Aston. The greatest demand came from the expanding motor industry: vehicles known to have fitted Timken hub bearings in those days included Daimler, Darracq, Sentinel Steam Waggon, Mann Steam Cart and Ransomes Sims and Jefferies Electric Vehicles. Demand escalated in the First World War, particularly when tanks reached the battlefields in 1917, the year that reorganisation within Vickers made the Timken Co. section a department of another Vickers company, Wolseley Motors Ltd., at Common Lane, Birmingham. British Timken Ltd. was formed in 1920 as a subsidiary of Wolseley Motors Ltd. The Vickers and Wolseley connection was severed in 1927 when Mr. Michael Dewar reached agreement with the Timken Co. to take over British Timken as a joint enterprise, based at the original Cheston Road works, acquired from Vickers. Wartime factory dispersal led to the Duston factory foundation in 1941, In 1959 British Timken and its subsidiary company in South Africa became a division of the Timken Co.
Bearings tend to be accepted but forgotten by most of us, who wouldn’t really care whether our cars used ball, straight roller, needle roller, plain or tapered roller hearings, so long as they worked. To the design engineer the differences are much more important: the vital superiority of the tapered roller bearing is that it is the only anti-friction bearing capable of taking both radial and thrust loads.
It has a greater radial capacity than a ballbearing of the same size, equal capacity to a straight-roller-bearing and will take all combinations of radial and thrust loads. Another big advantage is that it allows wear to be compensated for. The principle is a simple one, based upon four parts: the cone, or inner race; the tapered rollers, which roll freely between the cup and cone; the cage, which maintains the proper spacing between the rollers; and the cup, or outer race, which fits around the cone and roller assembly. The cone, rollers and cage are assembled as one and cannot be separated; their assembly fits loosely into the cup. Whatever the size, and Timken make a range from 0.3125 in. bore through the centre of the cone to 67 in. bore (their biggest ever was 111 in. bore for machinery involved in Saturn rocket construction) and from a few ounces in weight to 8 tons, the basic tapered principle remains the same. Different loading applications may require changes in angles to the cup, cone or rollers or the inclusion of two-row or four-row assemblies. If there is a high proportion of radial load the angle will be flat, if the crossload is proportionately high, the angle will be steep.
Ford and Leyland have both helped to give the public more awareness of Timken tapered rollers in recent times by promoting their own new developments, both big breakthroughs for Timken, Alan Wright, the Chief Engineer, Automotive Applications, told me. Leyland’s project is the 77 mm. gearbox, already fitted to the Rover 3500, some US market (plus a handful of British market) TR7s and the works rally TR7s, with more applications on the way. This five-speed manual ‘box use’s Timken tapered roller bearings on the rnainshaft and layshaft, the first time such bearings have been fitted on both shafts of a production gearbox. Amongst the benefits is compactness and rigidity of the gearbox, which leads to a smoother, more positive gearchange, the ability to take greater torque throughputs, longer life and ease of assembly. The ‘box carries five Timken bearings, in three sizes, all high-volume wheelhub hearings, including one used in Fiesta hubs and was designed by Leyland (initially Triumph) engineers in conjunction with Timken. Talks began ten years before production! “The first tapered roller gearbox we did was a conversion on a four-speed Jaguar gearbox to convince a sceptical Harry Mundy at Jaguar that it would work.” said Wright. “We then helped to produce a five-speed gearbox for Jaguar [See Motor Sport, page 855, August, 1975—C.R.) which unfortunately proved too expensive to tool up for projected low demand. The 77 mm. gearbox followed on from the Jaguar box.” Jaguar, by the way, have always used Timken bearings 100%, including standard components in the Le Mans winning C and D-types.
Timken’s innovatory contribution to Fiesta fortunes is the design of a new front hub bearing called Set Right. Close-width tolerance control in the manufacture of the bearings and associated parts, and extension of the inner races of the inner and outer bearings to butt together, precludes the need for adjustment. In Fiesta’s production there is no need for selective assembly of these lubricated-for-life bearings and no need for adjustment— the hub nut is simply set to the advised clamping torque. In service terms this means that a do-it-yourself Fiesta owner can buy a hub-bearing off the shelf and fit it without the complications of adjustments. Timken are proud too that these Fiesta bearings have proved their international interchangeability system: the bearings use a combination of British and French Timken inner and outer races assembled on Ford hubs at Ford plants in Britain, Germany and Spain. Such interchangeability of parts from different plants is made possible by Timken’s master gauging system controlled from the American HQ to ensure universal consistency of dimensions, materials and quality. Work gauges for all plants are made from master gauges held in Canton.
If Ford reach their full production potential for Fiesta, Timken will be called upon to supply no less than 5 million tapered roller bearings annually for that model alone, at 10 bearings per car. “That means one heck of an investment for us and illustrates the importance of component suppliers in the motor industry,” Mike Ctements, British Timken’s Sales Manager, Automotive Division, remarked.
A Ford application with considerably less volume potential, but of which Paul Slade, British Timken’s Automotive Sales Engineer, is equally proud, is the recent adoption of Timken bearings for the rear hubs of works rally Escorts, which were suffering from ballraces breaking up. For the first time the rally cars now have adjustable rear hubs (Timken bearings are standard wear in Escort and Cortina front hubs), though with a weight penalty, admits Slade. “Now we are considering the use of unit bearings in a semi-floating axle for the rally cars.” Unit tapered roller hub bearings are an innovation in Britain, used for the first time on the new Rover 3500, though most American cars, the big Volvos and the VW LT van have them. The cup, cone, cage and rollers of this bearing are one inseparable unit capable of taking side thrusts in two directions. Thus only one bearing is required per hub, giving increased capacity without an increase in cross-sectional area or weight.
Modern Formula One tyres impose terrific loads and deflections upon wheel bearings and John Hunt, Area Manager, Automotive Sales, will tell you that tapered roller bearings are much superior for the job. So far he has persuaded Timken on to Brabham, Surtees, Shadow and BRM, “although practically all F1 cars use Timken bearings in some way, because we have them in the Hewland differential and the latest Hewland F1 box has a Timken pinion bearing.” Ball bearings in F1 hubs need changing every race to be on the safe side; tapered roller bearings could possibly last a season, though Timken wouldn’t expect them to be allowed to do so. Whether the Timken application is for F1 or Mini 1275 GT hubs, all the bearings are standard, high-volume production bearings, as are those used by Lola, who have never used anything else except Timken bearings and are Timken’s biggest racing car manufacturing customer.
The Duston factory, the first fully automated tapered roller bearings plant in Europe, concentrates on small bearings, such as those for the automotive industry. Another Plant at Daventry produces large bearings. Races for the small bearings at Duston are machined from rotary-forged, seamless, high-alloy steel tubing, produced by Tube Investments from BSC steel. The tube is cut and then machined into cups and cones on Conomatic single spindle automatic machines, the importInt bearing number stamped upon these races while they are still in the “soft” stage and the chamber machined on the outside. Transference between machines is by magnetic conveyor belt. Next comes the vital case carburising process, the hardening process in which the races and rollers have carbon introduced into their surfaces to a depth adequate to sustain bearing loads. Timken maintain that case carburising gives the metal much superior “fracture toughness”, fatigue resistance, to the alternative through-hardening process used by most other manufacturers in which the entire metal is given a high carbon content. They claim that through-hardened high carbon steel creates the potential of catastrophic failure in tapered roller bearings.
After hardening the races are fed automatically to Cincinnati Micro-Centric fully-automatic race grinders for grinding to close limits. The final finish is achieved on cone tape boners. The rollers undergo a similar process after being banged into a die (“cold headed”) from a roll of wire in the same steel as the races. The cages are pressed out of mild steel plate. Quality control is vital in bearing manufacture : statistical checks are carried out on the races on all the machines, they are given an air-gauge check at the end of the line, then every single one is checked by eye. Once races, rollers and cage have been brought together into a complete bearing, every bearing goes through a noise check, either on a three-channel or 12-channel analyser. Finally each bearing is checked visually.
The final stage is greasing in a hot slushing machine using a grease suitable for maintaining shelf life and compatible with lubricating grease, so that degreasing is not required before assembly and dry-start lubrication is assured. All Timken small bearings are then packed into tubes and boxed in “standard packing modules” used in Timken plants world-wide to ensure the compatability of handling equipment. The entire production at Duston is computer controlled as is the automatic distribution centre at Daventry.
Timken’s considerable experience and accumulation of test data for test comparison purposes enables them to offer a unique test facility for customers. In the case of axles, for example, they have the results of tests with some 1,000 axles to go by. Their test rig enables low speed deflection tests to be made, readings being taken from numerous dial indicators, some from c.w.p. tooth contacts, to measure whether the bearings are mounted sufficiently rigidly and not deflecting to upset bearing performance. Records of previous results show just how much deflection is permissible.
Having seen and heard of the technical skill and effort involved in development and production of bearings, in future I’ll be taking more notice of what keeps my wheels turning. C.R.
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