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The Napier 45-cwt. Chassis.

6th May 1915, Page 4
6th May 1915
Page 4
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Page 4, 6th May 1915 — The Napier 45-cwt. Chassis.
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20 h.p. Engine—Leather Universal Couplings—Solid-Forged Back Axle.

The latest Napier production is unique in at least one respect, that it is an entirely new production and has been brought into being since the beginning of the war. Its de sign, of course, was all cut and. dried quite a long time ago, but D. Napier and Son, Ltd.. was only prepared to proceed with its manufacture some few months since.

The Unit System Discarded.

Many of our readers will remember a description of the Napier 30-cwt. van chassis which a,_ppeared in our columns on the 30th January, 1913. This new model supersedes the one to which we now refer, As a matter of fact, much experience gained with the older model has been embodied in the new chassis. The outstanding feature of the 30cwt. van, it may be remembered, was the adoption of unit construction for the engine and gearbox. Although perfectly satisfactory up to a certain point, it has been concluded that this arrangement did not allow of sufficient accessibility, particularly in regard to the clutch. One or two other minor disabilities also have been remedied, and it was further decided to increase the capacity somewhat. The present model, as we say, is the result, and is rated at 45 cwt. gross ; the net load, of course, is equal to this amount less the actual weight of the body fitted.

A22 The Load-Rating Includes the Body.

Buyers will always do well when considering the body question to keep in view as much as possible the question of the reduction of weight, bearing in mind'the necessity for an adequate reserve of strength under the often rough-andready service to which a commercial vehicle in committed.

Before indulging in any detailed. description of this chassis, we may record our opinion that this latest Napier model is in many other ways than those we have mentioned a considerable improvement on the type which it supersedes, although that has given and still continues to give service of a quality to which users of both Napier " Business and Pleasure" vehicles of all kinds are accustomed. Many of them also are doing duty at the Front, both on behalf of our own and the Allied Governments.

A 20 h.p. Engine.

The engine of the new 45-cwt. chassis, although differing considerably in detail from its predecessor, is, nevertheless, of the same size, being of 3,?2,7 ins, by 5 ins, bore and stroke respectively. The exterior appearance is neat, and so far as possible awkward casting excrescences and recesses have been avoided, so that it is a comparatively easy matter to keep the surfaces free from any accumulation of dirty oil and road grit, by no means so unimportant a feature as the inexperienced might be led to imagine. The cylinders are cast in

pairs, and to judge by the exterior of the castings ample water-jacketing space is provided. The crankcase is of aluminium, and is suspended from four separate cast brackets bolted to the main frame members.

The valves are all ranged upon the near side' being operated by one camshaft through adjustable tappets. The whole of the valve gear is enclosed by quickly-detachable covers a feature of each of which is the bayonet-type fastening; of this we are able to give an illustration. In the course of our examination we were able to point out to the designer that there was some little difficulty in removing one of these covers, and, with characteristic readiness to profit by experience, the responsible department took immediate means to eradicate this small blemish from an otherwise most desirable engine design.

Silent Chains for Tinting Gear. Splitdorf Magneto.

The timing gears are driven by neans of silent chains, and adepate provision is made for their ;ension adjustment. The magneto mad centrifugal water puinp are 'riven off the same spindle ; the [atter is situated in .front of the ;iming-case cover, and the magneto aehind. The magneto adopted as tandard is the American 8plitdorf. Ft is driven through a flexible, xmpling, and carried off the aluaiinium crankcase in a rather neat 3ast-steel cradle bolted thereto. f he method of fastening the magjet° is by means of the usual horsehoe-shaped clip. Incorporated With the timing gear, and entirely 3fielosed by the timing-case cover, [S. a centrifugal governor. This operates on a special throttle placed in the induction pipe, and can be set so as to come into operation at a pre-determined engine speed.

SI.U. Carburetter. Pressed-Steel ran. Cast Headers for Radiator.

The carburetter used is the Napier 8.U. It is situated on the near side of the engine and is controlled independently by hand or foot. The fan fitted with this engine is a particularly neat and light one, it is stamped flat in one piece, the blades afterwards being set to the correct angle in a speciallyprepared jig. The adjustment for the tension of the fan driving belt is particularly neat. Another notable departure from the practice adopted in the older chassis is noted in the design of the radiator. As May be remembered, in the• other one the sheet-brass type was standardized. In the present instance, a more modern and Much better form of cooler, incorporating east top and bottom headers with vertical gilled tubes, is used.

The engine lubrication system has evidently been the subject of much careful thought, and is best described by the word "thorough." Oil is poured in at the large funnelshaped orifice which may be seen in thephotograph of the off side of the engine. The cover of this opening is removed by being swung

flow tap in the crank-case. Oil should be poured in until it commences to overflow. By replacing the cover, the overflow tap is auto matically closed. From the reservoir the lubricant is taken by a gear pump driven from the camshaft and is forced therefrom to the main bearings, through the holloW crankshaft to the big-ends ; the eXL cess oil is splashed into the interior of the cylinders and on to the gudgeon-pin bearings. The whore of the oil pump, together with it's filter, may be entirely removed on the removal of three nuts, and the undoing of one union. If on the other hand, it be only 'desired to examine and clean the filter, this may be removed without disturbing the remainder.

Dry-plate Clutch. Leather.Diic Universal Joints.

The multi-disc clutch used on the 30-cwt. model has been replaced by one in which a central steel disc is gripped between two Ohers of Ferodo. Its inechanisins simplicity itself, and the necessary pressure for engagement is provided by ten small springs, of which the tension is readily adjustable. Behind the clutch comes the inevitable pair of universal joints. These are both of the leather-disc type. The arrangement, as will be seen from our illustration, is rather unusual, as instead of these being coupled by a short shaft they are joined by a kind of double-ended snider.

Four . speed Box, Incorporating Hoffmgum Roller Bearings and Self-contained Operating Gear. The gearbox provides four speeds and a reverse. The shafts and gears are obviously of such a size as to render them easily capable of transmitting the power. We noted in particular that the length of the shafts had been kept -to a minimum. Hoffrn.ann roller bearings are utilized throughoutThe selecting gear, which is on the customary gate principle, is carried by a casting bolted directly to the gearbox. As a consequence, the possibility of any binding of the operating shaft, owing to diste-rtion of the frame or other parts, is A25

entirely obviated. For this component, 'three-point suspension has been adopted.

Locomotive-type Foot Brake with Unlined Shoes.

Incorporated in the gearbox casting is a substantial housing which totally surrounds the foot-brake drum and gear. This is of the locomotive type, very strongly

made, with cast-iron shoes bearing on a cast-steel drum. The shoes are plain and simple castings, so that they may be easily and cheaply renewed. The operating gear for this brake struck us as being rather interesting. We reproduce on p. 185 a special sketch, from which it will be gathered that the brake is put on and taken off by means of a cam.

Tubular Propeller Shaft.

The universal joint behind the, gearbox is of the two-jaw type, special provision being made for its

lubrication. Thence to the rear axle is the propeller shaft, which is a hollow tube of large diameter, the object for so constructing this being to eliminate the possibility of any whip, as the shaft itself is rather longer than usual.

Full Floating Rear Axle. Worm Drive.

The rear axle is a full floating one, with overtype worm and spurgear differential. Both torque and thrust are borne by the rear

springs. These, as well as the front ones, are ample, both in width and length. Accessibility, we should say, is one of the strong points of the hind axle ; it is quite a simple matter to remove the whole of its mechanismi`without disturbing the load-bearing structure. The escape of grease‘from the worm spindle casing isR;prevented by a stuffing box, and it is

A26 possible readily to adjust this to take up any wear.

Solid-forged Rear Axle.

The load-bearing part of the axle is a fine piece of work. It is a solid forging of the double-banjo type, the centre portion being particularly deep and affording ample strength in the direction in which the load is applied. The worm and wheel are carried on Hoffmann roller hearings, and ample provision

for thrust is made by means of ballthrust washers. From the differential, the drive is taken by the live axles, which are vlined at both ends—at the inner end to fit the differential wheel at the outer end the hub caps. These hub caps are of large diameter, and have four

projecting pieces cast on their inner faces. These projecting pieces fit into four corresponding slots in the hubs •of the cast-steel wheels, and take the whole of the drive. .

Cast-steel Hollow-spoke Wheels. Well-designed Brake Gear.

Cast-steel hollow-spoke wheels are used for both front and rear. These are detachable after the removal of four or six nuts, as the case may be. Solid-rubber tires 810 mm. by 90mm. are fitted, single ones to the iront and twins to the rear. The hub bearings are roller of the Timken type. The 'braking is effected by means of the usual foot pedal and side lever. We have already described the mechanism of the footbrake. The side brake operates on internal-expanding shoes, Ferodo-lined, in drums bolted to the rear wheels. A special feature of this brake gear is in regard to the pins. These are particularly long and present, we should say, more than twice the bearing surface that is usually found in such circumstances; • they bear in all cases in bushed holes. A similar feature is notable in conneetion with the steering gear. The actual steering gear consists of a worm and a complete wheel, this latter being so arranged that when wear has taken place a new portion of the circumference can be offered to the worm.

The wheelbase of this capital example of an all-British chassis is 10 ft. 6 ins. It is capable of turning in a roadway of 44 ft. The length of frame available for the bodyis 9 ft. 6 ins. With a low loading line of 29 ins., the road clearance is nevectheless as much as sq ins. The track is 5 ft. Brown Bros., Ltd.' has been appointed sole British agent for the New Departure" ball bearing, a component which, it is estimated, is used on 84 per cent. of American. made chassis.

At a recent meeting of the St. Albans Chamber of Commerce, Councillor Watson advocated the establishment of a co-operative system of motor haulage by the local Tradesmen's Association, in order to obviate delays in delivery. Successful operation of this kind at Watford was quoted by the speaker.

The difficulties of provincial motorbus, owners at the present time were reflected in a communication from the East Surrey Traction Co. which was read to the Caterham Council at its last meeting. The service to Godstone, it appears, has had to be temporarily withdrawn, because the company could not obtain new buses or spare parts and is moreover faced with difficulties with regard to the staff to work the machines, even if it had them.

At the Parish Council of Amersham, Dr. Wynne suggested that the fire-engine might be hauled about by means of a motor trolley. He added that this was a matter requiring careful consideration, as there was much to be said against the proposal. It was not, however, neceF_eary to spend more than 2100. He thought they must have expert advice and a report. There is very little doubt that it would be helpful —at that price.

A handy little booklet, giv:ng the experience of car owners using Zenith carburetters, can be obtained by application to the Zenith Carburetter Co., Ltd., 42, Newman Street, Oxford Street, W.

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