British-built /Viotorcabs.
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The Napier Two-cylinder and Four-cylinder Cab Chassis, of which Large Numbers are now under Construction at Acton Vale.
The names: of Mr. S. F. Edge and Mr. M. Napier are so intimately associated with the production of vehicles in which the propelling engine has six cylinders that it came as a surprise to many vehicle users when, a few months ago, an announcement was made that a two-cylinder model was being prepared for the market. A very large number of these machines, which are specially designed for " taxicab " service in London and the Provinces, are now being mannfactored and erected at the Napier works at Acton Vale. At the invitation of S. F. Edge, Limited, of 14, New Burlington Street, XV., a representative of " THE COMMERCIAL MOTOR " recently paid a visit to the works and was there afforded the opportunity to examine the many interesting details of the new two-cylinder model, and also of the fourcylinder model, the introduction of which latter machine is intended to meet the requirements of those towns where the local conditions demand something more powerful than the simpler vehicle, or where it is highly desirable, as far as possible, to avoid frequent changing of gears. In general design the two machines are practically identical in au i respects except the number of cylinders; the two photographs, which we reproduce, of a complete four-cylinder-engine chassis, may, therefore, be taken as illustrating also the two-cylinder model. The cylinders of both the engines on these machines are three-and-a-quarter inches in diameter, and are cast in pairs, with all the valves on one side. The valve stems, guides, and springs are housed within a casing which is cast integral with the cylinder casting, and are enclosed by a large inspection door. This feature in the engine's design is a very good one, as it affords to the tappet gear full protection from dust and grit, and renders the working of the valves almost inaudible. The designer, we note, has selected for the high-tension magneto a position immediately in front of the valve-tappet cover, and the magneto thus almost completely prevents access to the valves for the purpose of fitting a new spring or cottar. The magneto, however, is secured to its base in such a simple manner that it requires only the work of a few minutes for its removal, but the necessity for this operation is an undesirable feature of design.
XVith a piston-stroke of five inches, and when running at 1,ocio revolutions per minute, the two-cylinder engine will develop toh.p., whilst the four-cylinder model is rated at 15h.p., but will give considerably over that power. The crankshaft is mounted on roller bearings of very large size and the rollers themselves are three-quarters of an inch in diameter and one inch long. In the case of the four-cylinder engine, the crankshaft is made in two pieces which are joined together in the centre. The two joined ends of the crankshaft terminate in flanges, which are ground on their faces and rims and " spigoted " into an intermediate piece which is hardened and ground; the parts are then securely bolted together by means of turned bolts that are fitted into reamered holes. This form of construction has been adopted in order to permit of the fitting of a roller bearing between the centre pair of cylinders, and not with any idea of cutting down the cost of production. The intermediate piece forms the roller race for the centre bearing. The main bearings are lubricated under pressure, from a gear type of rotary pump, and the big-ends receive their oil through channels in the crankshaft, but not under pressure. The oil pump is situated in the bottom of the crankcase sump, from which it draws the oil, and is driven from the camshaft, through skew gearing. As already mentioned, the high-tension
magneto is situated on the valve side of the engine, and, immediately below it, the water-circulating pump is mounted; this is of the centrifugal type and is driven from the czanshaft. The exact arrangement of the dining gears upun the engine is as follow :—A spur pinion, with extra wide teeth, is secured to the crankshaft, and this meshes with a half-speed wheel on the camshaft ‘vhIch, in turn, 1114''MVS with the wheels on the pump shaft, and zhe tnagneto shaft, both of which shafts rotate at the sante speed as the crankshaft.
The carburetter is fitted low down on the olf-side of the O]) ate, and is of the annular-float type, with a fixed jet opening, and the main air pressure is restricted so as to maintain a practically constant velocity for the air; trt auxiliary-air valve is mounted over the mixing chamber, in the latter of which the throttle valve is fitted. The throttle valve is operated by means of a pedal, and the minimum-enginespeed position of this pedal may be adjusted by means of a screw-operated regulator which is secured to the dashboard.
The metal-to-metal cone clutch is of very small diameter, and is completely enclosed by an extension of die gearbox casing, whilst the casing is provided with a large irregularlyshaped flange which is bolted to a flange of similar shape on the crankcase; the engine, clutch, gearbox and foot brake are thus combined in one unit which certainly simplifies the erection of the chassis, but, for public-service work, this form of construction imparts both advantages and objections—these were discussed in our issue of the 23rd of April last. In order to keep the she of the casing within reasonable limits, the flywheel on the Napier cab is fitted on the forward end of the crankshaft, The spur pon on the after end of the crankshaft, in addition to driving the camshaft wheel, is wide enough to mesh with in internallytoothed ring that is fixed to the outer member of the cone eluteh, and thus it forms it positive connection bemeen the friction-clutch member and the crankshaft, The gearbox provides for three speeds in a forward direction, with it direct through drive on the top speed, and one reverse speed ; all the changes of gear ratio are effected by .a lover with a gatechange quadrant, which is carried by a tubular extension from the side of the gearbox, as is shown in the illustrations. The foot brake is of the locomotive type, as /my be seen in one of our illustrations, and this is operated by means of the same pedal which actuates the clutch. The hand-lever brake blocks act within two drums which are titled on the driving wheels.
A tubular propeller shaft transmits the drive from the gearbox to the bevel-driven back axle, the casing of which is of cast steel, and is made in two halves. All the transmission shafts are mounted on either ball or roller hearings, and ball-thrust bearings are fitted wherever necessary.
The steering gear is of very simple, yet very practical, desig-n. and is %veil alb: to guide the vehicle about the
regulation radius, whilst the front axle is made from a straight piece of hammered steel bar, which is milled to an " I " section, The complete chassis presents a most pleasing appearance, and we shall watch-, with great interest, its per
formance in London service. Our representative was driven through many of the busy streets in the West End, and his report on the running of the cab was very satisfactory. About
no of the two-cylinder machines, and some 200 of the more powerful model, are being laid down.
The cab, subject to the detail named in our first paragraph, is admirably designed and constructed. After the visit to the works, we had an opportunity to test it, in town service, on Saturday evening last, for a number of hours. The smoothness of running is remarkable; the engine's ability to pick up and to pull on rising grades is fully is good as any two-cylinder model we know, and may be recorded, having regard to the substantial coachwork, as superior to anything yet on the London streets; the absence of noise, whether from engine or gears, is a feature in respect of which this vehicle stands unrivalled : in short, the cab has all the merits of a high-class private car.