An entirely Re-designed 4 h.p. Model for 1915. Improvements to Two-stroke.
WE have already announced the fact that the 1915 Triumphs would be a considerable departure from usual Triumph practice. Our announcement occasioned a good deal of interest, as is shown by the communications we have received on the subject. It can be said that for ten years the Triumph machine has undergone but detail improvement Year after year the little weaknesses have been eliminated and improvements embodied, all of which have helped to build up the proud position which the trusty Triumph holds. Last year a 4 h.p. machine and the introduction of a two-stroke lightweight mount were the most notable departures in the Triumph programme; but 1915 marks the appearance of an entirely new design of engine, a three-speed countershaft gear in the bottom bracket, and the increasingly popular chain-cum belt transmission.
We will deal with the 4 h.p. model first, as more alterations are notable in the design of this machine.
The bore and stroke are 85 x 97 mm. (550 c.c.). The timing gear is of the simplest possible description. There are but two wheels, the main driving wheel and the half-time wheel, with which latter three cams are formed from the solid, viz., the decompressor cam together with the exhaust cam and the inlet cam. The horizontal rockers lap over the cams so that a direct lift is obtained.
The cylinder casting is quite new, having ample air spaces between the cylinder and the valve pockets, which is bound to result in much improved cooling. The valves on the 1915 model are of l 5/8in. diameter (compared with 1 7/16in. in 1914), and have flat tops. Next year's timing gear case is circular in shape, and the cover is fixed with a spigot joint and internal lugs, resulting in a smooth exterior, rendering the cleaning process much easier.
The piston is of the flat top variety and fitted with three rings, two of small depth with diagonal slots at the top, and a deeper step cut ring at the bottom.
The silencing arrangement, too, has been entirely re-designed. Instead of the bracket which has usually formed the end plates for the silencer and a platform for the magneto, it will be noticed that the silencer is arranged immediately under the timing gear case, and thereafter a flat pipe conveys the gases to the rear.
To adjust the magneto driving chain a feather is formed on the platform and a corresponding keyway in the base of the instrument. Thus, it is impossible to fix in position out of alignment. The magneto, too, is l 5/8in. higher than on the current year's model.
The carburetter is of a new design, having the jet between the air and throttle barrels. It is practically automatic in action. One starts the engine with the air lever wide open, and it is only on very severe hills that it requires closing off.
Gear and Transmission
The countershaft gear of the Sturmey-Archer three-speed, which is highly spoken of on all hands. It is of the sliding dog clutch type, the changes being effected by a round lever, and we feel sure that the operation of changing up or down will possess not the slightest difficulty even to a person experiencing his first run.
For the first time on record, the standard Triumph has a hand-operated cork insert clutch controlled by a lever situated immediately in front of the valve lifter. This departure will, we feel sure, be commended by all practical motor cyclists.
A neat kick starter is embodied with the gear, the mechanism of which is entirely enclosed. The adoption of a countershaft gear and a kick starter, of course, leaves the back wheel simple and plain, and therefore readily removable. To simplify the removal process, a new type of brake has been adopted, the fibre block operating inside the groove of the belt pulley. It is just as powerful in this position as ever, which is saying much, as it will be agreed that the braking power of Triumphs has always been well studied.
The frame is similar to that in use in 1914, with a dropped top tube, but, of course, the bottom bracket has necessarily been re-designed to accommodate the countershaft type of gear. The front mudguard, too, it will be noticed, is practically the same as that used in 1913, as it has been found after extensive trial to be the most effective design.
The tank now holds one and a half gallons of petrol, an ordinary enclosed lubricating pump is resorted to, and another refinement We noticed were wings fitted to the rear guard below the carrier.
We enjoyed a short spin on the new Triumph, and found it extremely controllable. It started at the first kick with the decompressor in action, and would throttle down to very low speeds even on full compression. It accelerated in remarkable fashion, and, thanks to the handle-bar controlled clutch and an easy changing gear, we at once felt quite at home on the machine.
The latest Triumph has undergone exhaustive tests for 5,000 to 7,000 miles, and has proved superior to any production of the Triumph Works. In particular, it will stand hard driving for prolonged periods without a tendency to "dry up".
The Two-stroke Model.
To turn to the two-stroke, this mount for 1915 has undergone very little change, and it is interesting to observe that the main alteration is in connection with equipment, which formed the subject of criticism in a recent issue of The Motor Cycle. 2¼ in. tyres have been standardised on this little machine, and a Brooks saddle of large size.
Except for a new type carburetter with top feed and separate chambers for the air and throttle slides, the 1915 two-stroke Triumph is unaltered. The bore and stroke of this mount are 64 x 70 mm. (250 c.c.)
The Motor Cycle, December 17th, 1914. p585.
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