Section of the Liberty two-stroke unit, manufactured by A. W. Wall, Ltd. The cylinder dimensions are 70x 70 mm. (269 c.c.)
The Liberty crankshaft is built up of two forgings. A roller bearing big end is used. R. Piston of Liberty two-stroke, showing the lower ring groove. The ring acts as a gudgeon keep.
ASSOCIATED with the motor cycle industry from the earliest days, A. W. Wall, Ltd., of Hay Mills, Birmingham, may justly claim to be one of the oldest purely motor cycle firms, for they did not migrate from the cycle trade. Moreover, they have been responsible for many striking innovations since 1904.
Latterly, two-speed gear boxes, frames, hubs, and other components have been the firm's specialities, but a departure is now being made in the form of a thoroughly up-to-date 2½ h.p. two-stroke engine unit to be known as the Liberty.
Equal Bore and Stroke.
Having a bore and stroke of 70x70 mm. (259 c.c), the engine is based on the three-port system, and has a particularly cleanly cast cylinder. The piston has a streamlined deflector, and is extremely light. Roller-bearings are used in the big end, which works on a built-up crank pin carried between small crank discs or small internal flywheels. Plain bearings of ample size are used for the mainshaft, and the large outside flywheel has provision on the boss for either a pulley or sprocket.
Amongst details to be noted are the concealed passage from the release valve to the exhaust port, and the special bracket which carries the magneto on the side of the crank case. The drive is taken directly off the crankshaft.
The unit is to be sold complete with engine plates, silencer with tail pipe, and Runbaken magneto. A carburetter is not supplied, but the makers recommend the Cox-Atmos as being most suitable. We had a short run on a machine fitted with the Liberty engine, and found it to be smooth in operation and lively. At very slow speeds some little amount of four-stroking was noticeable, but with the least load on the engine the firing was as regular as cpuld be desired. The firm of A. W. Wall, Ltd., should well uphold its prestige with the Liberty unit.
A direct driven magneto is one of the features of the 2½ h.p. Liberty two-stroke unit.
On the Liberty two-stroke engine fitted to the Jupp and the Reynolds runabout, the magneto is driven by an extension of the crankshaft.
STEADY progress is being made in the design of Liberty two-stroke engine manufactured by A. W. Wall, Ltd., of Tyseley, Birmingham, and several modifications are included in the design for 1922. The engine is of the normal three-port design, and is beautifully made, the crankshaft being a particularly fine piece of work. Each shaft and crank cheek is formed from a special steel forging, and is machined and ground until it takes the form of a miniature internal flywheel, complete with balance weight. Plain bearings are used on the main shaft, but the crank pin, which is utilised to bolt together the two sides of the shaft, is fitted with a roller bearing big end. The hollow gudgeon pin is carried rather high up in the piston, and is located endwise by the lower of two piston rings, the lower edge of the groove being bevelled off so as to trap the oil. The cylinder is well finned, and in practice has been found to cool very satisfactorily. Every engine is given a thorough bench test before it leaves the works. An Amac carburetter has been found to give excellent results.
Naturally, an outside flywheel is also fitted. Besides the increased rigidity of the built-up form of crank construction, another advantage is that, by reducing the crank case volume, crank case pressure is increased.
The Reynolds runabout, which is manufactured by the same firm, and is, of course, fitted with the Liberty engine, will in future be fitted with 24 in. wheels and all-chain drive. It is probable that further developments on interesting lines will take place in the near future, but for the moment our tongue is tied.
The Motor Cycle, November 3rd, 1921
