The Martini 75-cwt. Chassis.
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A New Arrival from Switzerland. Double-reduction Gear Axle.
Amongst several examples of round design and construction of commercial vehicles emanating from the little neutral country of Switzerland, there have been several which have proved, by actual service, their claim to a high place in the good opinion of the user. The latest example, just arrived, is the Martini 75-cwt. chassis, for nominal net loads of three tons.
Many of our readers will no doubt be familiar with the Martini tour
ing-car chassis, the same that have been sold in this country for many years ; this is, however, the first appearance of the maker's commercial types in this country. The first delivery of these machines from Switzerland amounts to 25 units. It would appear, therefore, either that the Central Powers and our Allies are able to obtain all their necessary supplies for transport without absorbing most of the output of this chassis, or that the industrial production with touringcar business so slack is sufficient to cater for civilian requirements also. It is a sign of the times, however, that they all arrive in this country minus magnetos and tires, which have to be provided here.
We are indebted to Mr. Brainshy Woollard, of 21, Panton Street, S.W., who is the concessionnaire, for the opportunity to examine the earliest arrivals. These are on view at present at the works of F.I.A.T. Motors, Ltd., at Wembley.
Strongly-built Frame. Large Brakes.
First impressions incline one to the view that the chassis is full of contradictions. The frame, which is built up of rolled-steel channels, is of considerable strength, the enormous rear brake drums and the very substantial foot-brake arrangement, as well as the strength and capacity for load carrying afforded by the spring attachments, render the remainder of the chassis by comparison somewhat light in appearance.
Engine and Radiator.
The engine is a four-cylinder, with a bore and stroke of 90mm. and 150 ram. respectively. It is, of course, water-cooled. All the four cylinders are cast in one block, with internal gas and water passages. The inlet and exhaust valves, which are interchangeable, are ranged down one side. Adjustable tappets are provided, and the whole of the valve gear for the four cylinders is enclosed by one large but readilydetachable cover. The cooling water is circulated by a pump of the centrifugal type, driven through skew gears to a cross-shaft in front of the engine. The other end of the same shaft is keyed to a special coupling which drives the Simms high-tension magneto. A feature of the coupling is that it is readily adjustable by small gradations, so that the ignition setting may be varied without disturbing the timing gear.
The engine lubrication is a combination of forced feed and splash. The pressure in the force system is indicated by a Bourdon type pressure gauge on the dash. The depth of the oil in the sump can be ascertained by means of a plunger rod which protrudes through an orifice at the top of the crankcase. The radiator centre is formed of crinkled tubes, the container being a pressed-metal one. We had thought that this method of manufactitring radiators had been entirely eliminated, at any rate, for commercial vehicles. The component is mounted on springs so as to mini mize so far as possible the liability to damage due to vibration. Cooling is assisted by means of the usual type of four-bladed, beltdriven fan.
Multi-disc Clutch. Four-speed Box.
The transmission from the engine is by means of a multiple-disc clutch, thence through a doublejointed clutch shaft to a four-speedand-reverse gearbox with gate change. This component is held to the frame by means of four special hook bolts. It would seem that its accessibility would he increased considerably by this method of suspension. It should only be necessary to loosen the 'lilts on the bolts and give them a half-turn, thus rendering it possible to drop the gearbox out underneath the chassis. Thence to the rear axle a propeller
shaft runs. This is fitted with exceptionally large universal joints 'at both ends. The one at the rear end is of the ring, type, it is very simply constructed, and vo'-ould seem Lobe suitable for ready dismantling, if needful:
Double-reduction Rear Axle.
The rear axle is a double-reduetion, full-floating type. The drive is taken first by a pair of bevel gears, to the crown wheel of which is bolted the differential case. From the differential two small pinions take the drive, gearing into large spur wheels keyed to the live-axle shafts. The advantage of this arrangement is that the differential .
is revolving at a much higher speed than it would be if it were coupled Up to the live axles provided, and consequently may be made much lighter, whilst at the same time being sufficiently strong for its purpose. The matter of reduction of dead weight on this rear axle has evidently received careful attention; the casing for the gears follows their outline very closely. No unnecessary metal has been put in. It is of cast-steel, and in halves along the vertical centre line. From here to the spring brackets the weight-carrying, portion of the axle is also of cast-steel, the final drive to the rear wheels being through dog clutches, The lessening of the unsprung weight is, without doubt, a commendable feature, and one which might usefully be kept in mind by some heavy-vehicle designers to a greater extent than at pi esent. This applies, of -course to a, greater extent, to constructions embodying live axles, and, in particular, those incorporating the doubleDeduction gear. This, with an ac
)352 cessibly designed casing, very easily adds up the avoirdupois.
A Trial Run. Ingenious Governing Arrangement.
We treated the machine to our customary trial in "the hill country." Although we were not fortunate enough to be able to take a loaded -vehicle nevertheless, by comparison with the behaviour of other chassis under similar conditions, we were able to satisfy ourselves that ample power was available. The steering is very free, the gearing being the usual worm-andsector type. A very large lock is available, this being due, in part, to the fact that the frame is.inswept in front of the seat. The side brake, which is of the push-on type, is very effective, as also is the foot brake. A little difficulty was experienced when changing gear, especially when attempting to get through -to the reverse. We have no doubt that this was due to the fact that the chassis was quite new
and untried and a little stiff in some of the moving parts.
An interesting fitment couples the change-speed lever up with the
governor on the engine. This is illustrated in one of our sketches. It comprises an ingenious arrangement wh.ereby, although the governor will permit a fairly-high engine speed on first and second gears where this is needful for hill,climbing and where it does not involve excessive road speed, on third and fourth speeds the throttle is closed a little by this mechanism. So that although this device effectually prevents excessive speeds on the level, it does not deprive the engine of a full supply of gas for a low speed, heavy pulling. The petrol tank is supplied, but its position is left to the discretion of the bodymaker. An air pump is fitted for maintaining the pressure in the tank if needful. Complete with tires, which are 120 mm. for 720 mm. rims (old size 000 ram. by 120 mm.), the price is £775.