A 2¼ h.p. Four-stroke - Detail Alterations only to Present Machines - Caged Roller Bearings Adopted for Big End.
As the result of experience gained, the B.S.A. Co. have found it unnecessary to make any radical alterations to their present machines.
The 3½ h.p. engine is now only fitted to the T.T. model; the engine has undergone practically no changes, with the exception of the fitting of a roller bearing big end. This bearing is unusual, in that the rollers are mounted in a cage, and consequently are not allowed to touch each other, but bear only on the crank pin and the inner end of the hardened connecting rod. An interesting alteration has been carried out in the frame, for the head lug is curved slightly upwards. This construction, when properly carried out, is extremely strong and yet light. The addition of a long tail pipe for the exhaust completes the innovations in this type, which is, of course, still fitted with a B.S.A. carburetter and spring forks.
Improvements to Existing Models.
The three-speed countershaft geared models, fitted with big 4¼ h.p. engines, are particularly suitable for all types of sidecar work. The construction throughout is extremely solid, while the engine develops its full power at speeds which can be conveniently used on the road. The engine in practice is very flexible, and has a good turn of speed. In this engine, also, a roller, bearing has been introduced in the big end.
The tank has been enlarged to take 1 ¾ gallons of petrol. The front forks are made somewhat wider to accommodate a specially wide front guard. A refinement which will be fully appreciated by practical riders is that an internal V type brake has been fitted to the front wheel, operating on a dummy belt rim; this gives the necessary power, and yet permits the front wheel to be dropped out in case of tyre repair without disturbing any brake gear. The front forks have been altered slightly in detail, and the spring links are somewhat longer, but the general design remains the same.
The foregoing remarks apply to both the chain and belt-driven machines, and also to the all-chain model. This model is, of course, fitted with a B.S.A. spring shock absorber, which has proved eminently satisfactory, and absorbs all the harshness of the drive
The B.S.A. Sidecar and Trade Carrier.
For use with these machines a neat sidecar is marketed. The chassis and fixings are, particularly strong, and the springing is very comfortable. It may be recalled that the rear portion of the B.S.A. sidecar is suspended on enclosed coil springs, which are connected to a rail carried high up behind the back of the sidecar. The only alterations to the sidecar chassis are a somewhat strengthened mudguard stay and the addition of a simple pivoted stand for the sidecar wheel.
A special tradesman's carrier will be put on the market for the first time. The sidecar chassis has been somewhat lengthened, and the box, which is very commodious, is carried on four short C springs. The machine we inspected was fitted with a neat electric lighting set, which can be supplied if specially ordered.
By far the most interesting B.S.A. innovation is the new 2¼ h.p. machine. The company are thorough believers in the future of the small machine, but favour a four-stroke engine. They have made no attempt to turn out an extremely light and cheap machine, but have rather designed and constructed a sound go-anywhere mount, which is to sell at a moderate price, and which will be fitted as completely as the larger models. It may be mentioned that at the present time there is no idea of putting the new machine on the market before the spring, and though the machine has successfully passed the experimental stage, the company are so busy on other work that there is little likelihood of the next model making a public appearance before that time.
The engine is a well-designed single-cylinder of 68 mm. x 68 mm. which gives a cubic capacity of 247 c.c The designer has, obviously had in view the important point of making an engine which shall be both cleanly in running and easy to clean, for there is an absolute minimum of external excrescences to act as mud traps.
The valves are placed side by side, and besides being of good diameter the ports are well designed and allow a very easy passage for the gases. Both valves are operated by separate cams, which are mounted on a single camshaft, the rocker gear being extremely simple. The same shaft is used to drive the magneto, which is placed behind the engine in an accessible position and out of the way of mud.
Both gudgeon pin and big end are extremely large; in fact, they are of the same dimensions as those used on the 3½ h.p. model. This is a point very often overlooked by designers of light machines, and small bearings are frequently fitted, with the result that wear soon becomes apparent, and the machine rattles and becomes noisy. The B.S.A. have guarded against this in every possible way. A ball bearing is fitted on the pulley side, and a very long, plain bearing on the timing gear side. Lubrication is by ordinary hand pump, oil being splashed in the usual way, but a special groove is formed in the timing gear side flywheel, and is so arranged that it traps any excess of oil from the timing gear bush and, by centrifugal force, throws it to the inside of the big end bearing through specially formed leads. As a proof of its efficiency, we may state that the experimental engine was running with no other oil hole to the big end, and the results have been excellent.
A chain drive connects the engine to. a three-speed gear box designed much on the lines of the standard and well-known B.S.A. gear. It is, of course, smaller, and has neither clutch nor kick-starter. A large diameter belt pulley is fitted, and the final drive is by means of a 7/8in. belt. The ratios supplied as standard are 5.7 to 1 on top, 8.5 to 1 middle, and 15.9 to 1 low. The driving chain is carefully enclosed.
Little Things that Matter.
Passing on to the frame and fittings, we find that every detail has been carefully thought out, and, besides, a very stout and sensible frame, which is sprung in front by a modification of the B.S.A. fork, having round instead of oval section blades, large footboards, a pan seat, and 26in. wheels, all help to increase the rider's comfort. As on all other B.S.A. models, the mudguarding is particularly well carried out. The rear brake is heel-operated and acts internally oh the belt rim, so that the wheel can be removed without interfering with the brake gear.
The tank fittings are excellent, including as they do a screw-down petrol tap and a priming device for the cylinder. A large armoured tool bag is fitted at the back of the carrier.
The whole machine is turned out in a most excellent manner. It does not look unduly small, and is in no way flimsy. For a high grade machine of medium power, it will be difficult to find a more inviting proposition at the price of forty guineas than the new 2¼ h.p. B.S.A.
The Motor Cycle, November 19th, 1914. pp555-556.