SHORT NOTES AND PHOTOGRAPHS OF MACHINES COMPETING IN THE TOURIST TROPHY RACES.
For 1926 this firm have made no startling alterations in the design of their T.T. machines. The bicycles are to all intents and purposes standard G.R.7 (350 c.c.) and G.io (500 c.c.) models as supplied to the public. The only deviations from standard concern the very large petrol tanks holding 3/ gallons of petrol and, in certain cases, non-standard brake controls are fitted to suit individual riders. The machines differ from those used last year in having the valve clearance adjustment on the tappet tube end of the overhead rockers, the tappets themselves do not protrude from the timing cover. Rocker return springs are again fitted. A larger exhaust port, with a finned pipe union, is also a new feature so far as the T.T. is concerned. A simple handlebar or pedal operated oil only is used for engine lubrication.
The riders include most of those who performed last year, supplemented by J. H. Stevens, who won the French Grand Prix last year and C. E. Wise.
For the Junior event Howard Davies is relying on standard 350 c.c. machines except for small details of equipment. The 500 c.c. machines, however, have a very fine duplex frame, extending from the head, beneath the engine and gear-box, to the back wheel, which results in wonderful strength, road holding, and a very low centre of gravity. It is probable that the twoport J.A.P. engine will have the new system of valve springing, consisting of one central coil and seven small coils disposed at intervals round the centre one, all bearing on to a flower-shaped collar. A large saddle tank is fitted, and the footrests and brake pedals have a very wide range of independent adjustment. Burman gear-boxes, foot-operated 8 in, brakes, and wired-on tyres are fitted.
The senior riders include the Twemlows, C. P. Wood, and H. R. Davies himself, and are bound to start hot favourites.
The Norton T.T. machines look very formidable with their enormous saddle tanks, 8 in. brakes, and prominent steering dampers. The oil tank, too, is of very large
capacity, and a small auxiliary tank feeds oil on to the chains. A special form of dry sump lubrication is used, their being no adjustment of the mechanical pump itself, though the ” dryness ” of the sump can be varied. Apart from these modifications the machines are practically standard, the equipment including Terry saddle, Webb forks and B. & B. carburetter.
The Norton team is very strong, as it includes A. Bennett, S. Woods (two previous winners), and J. Craig, one of the premier Irish road racers.
Roughly speaking, the standard T.T. Panther will be used in the races, though several small but important alterations have been made. The inlet port is now at right angles to the cylinder bore, and the gudgeon pin is now clamped into the small end of the connecting rod. The makers have decided that lubrication is the most important item in a T.T. machine, and a special system has been devised. A standard mechanical pump delivers oil under pressure (adjustable) through the crankshaft and flywheels to the crank-pin, which is provided with four holes. These holes allow the oil to penetrate to the big-end rollers, thence to the sprayer into the cylinder bore, and the inside of the piston. Separate feeds are provided for the timing gear and inlet valve guide, the overhead rocker gear being lubricated
by oil from the timing case via, the tappet enclosing tube. The saddle pillar tank is carried as a stand.-by should the other system fail and serves to lubricate the chains. A four-speed close ratio box is fitted, the petrol tank holds 3 gallons, and the sump 3 pints of oil. The engine develops 22 h.p., and is capable of 90 m.p.h.
C. T. Ashby, H. M. ‘Walters, and T. F. Bullus, all good men, are the riders.
The T.T. Triumphs are extremely interesting machines and depart considerably from anything previously emanating from the Coventry works. The two-valve engine is modelled on the machines used so successfully at Brooklands by Victor Horsman, but now boasts two exhaust ports. The push rods and tappets are totally enclosed, and the magneto is placed behind the engine, thus allowing the latter to be brought well forward.
A large two-piece tank is strapped securely to the top tubes, and a separate oil tank behind the saddle tube. These are not shown in the photograph. A Triumph three-speed gear is fitted, with a new form of gear lever, having a concealed gate and a positive stop for middle gear. The forks are a new type, with a single tension spring and friction dampers. Eight-inch brakes are fitted front and rear.
The riders include H. Willis, who has performed well on a Montgomery, W. Evans, a scramble specialist, and C. H. Young, the South African.
As will be seen from the photograph, the T.T. Levis is on similar lines to previous Levis racers. The most noticeable change being in the tank and top tube design.
The riders are Phil Pike and A. R. Edwards.
Great innovations have been made by the Scott Company in designing their T.T. machines. For the first time, three-speed gears will be used, having a gate control on the side of the tank. At first glance the machine looks similar to previous models, but in reality an entirely new frame is used with two pairs of tubes running from the head to the top and bottom of the crankcase respectively ; torque tubes and chain stays in an unbroken line from crankcase to back wheel complete the lower portions of the frame. The most startling feature, however, is a top tube, pin-jointed at either end, joining saddle tube and head, and running through the tank, which, being of the usual Scott shape conceals this feature. The front forks have extra girders and an imenclosed spring, but otherwise operate on the usual Scott system.
These machines do not appear to have undergone any radical change from last year, and resemble standard O.C. T.T. models. The star riders are F. W. Dixon:and J. Whalley, both of whom have been well up in previous races. Douglases are usually among the fastest machines in the island, and their entry is always keenly watched by rival firms.
Once again it can only be said of the T.T. Sunbeams that they are standard two-port models fitted with 3jgallon tanks and 8-in. brakes, the rear brake now being on the neat side. A new form of hairpin valve spring is used, having coils on both sides of the valves, well away from the stem, really only a double form of the well-known single hairpin type used before. Double pedals are provided for the back brake as usual. The Sunbeam dry sump lubrication system is employed, supplemented by a handlebar controlled pump. Except for engine size and gear ratios, the 350 c.c. and 5oo c.c. machines are identical.
The Enfield company are the latest recruits to the standard machine policy ; it being possible to purchase a machine almost identical with the actual racer. The only modifications being an 8 in. back brake and a 21 gallon petrol tank. The engine is a two-port J.A.P., modified to include the Enfield lubrication system. Enfield forks and brakes are fitted, and it is interesting to note that about half a dozen prominent trade entries in the races are also using Enfield brakes. A Sturmey Archer close ratio gear-box is used with a gate change. Dunlop wired-on tyres are fitted, and a small tank drips oil on to the rear chain. The machines have quite racy lines, and in the hands of C. H. Young and J. G. Burney should perform well. The 250 c.c. machines are similar, except for tyre sizes and gear ratios.
The O.K. Bradshaw machines for the Junior Race are practically standard sports models as sold for £56, but have larger tanks and brakes and detail modifications to suit individual riders’ requirements. The
Supreme-J.A.P. machines were designed specially as T.T. super sports models, so that, although not yet in production, they can be described as standard models.
This firm has taken the bold step of forsaking a proved proprietary engine for one of its own design. Both 350 c.c. and 250 c.c. engines are on the lines of the standard 250 c.c. unit. The 250 c.c. machine has the standard loop frame as used last year. Both have large tanks, standard gear-boxes and special servo brakes.
0. S. Davison is now one of tl’e New Imperial team.
The Sunbeam concern usually contrive to do something a little different from anyone else. In 1923 they used 350 c.c. machines in the Senior race, although they had 500 c.c. machines ready. Another year some of their riders did only one week’s practising for fear of getting stale. This year’s little stunt is that no rider is performing in more than one race, the most surprising point being that G. Dance will not be riding in the Senior. On paper the Sunbeam team does not look any too strong, but doubtless the team manager has something up his sleeve. We wonder what has become of T. C. de la Hay.
The Sunbeam machines for this year are practically standard o.h.v. two-port machines, fitted, however, with larger tanks and larger brakes, two features which are only called for by the special conditions imposed by the race.