F. W. D. Chassis.
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An American Four-wheel-drive Chassis which is Made in Three Sizes for Nominal Net Loads of 11, 5, and 5 Tons.
The Great War has been responsible for the loss of many reputations and the making of others. It has proved and disproved many theories relating to offence and defence, to transport arid supply, and in particular, of course, to the employment of mechanical transport. One type of machine which has made good during the "great reliability trials" is the fonr-wheel or ' all-drive" chassis. The American Government long ago adolited this construction as the basis fur its.,subsidy.. specification. The French ArMy ha A been, experimenting for some years, and has many tractars embodying this-principle.
On a recerit:occasion we -deScribed the Jeery, a typical example 'of Americ,an.."
construction, and llave PileastlVe placing before Mir readers the following dcizcription of, the. F.W.D. -(Four-Wheel
Drive) chassis It is made" in three. si-zes, to carry .net loads of onefirid-a-h'alf, three and five tons, and We' belieye the British War Office is buying a considerable number of the three-tonners similar in outline to one Previously described. In general the lay-out is very similar to that of the Jeffery. The power unit is situated under the driver's seat, with a radiator of the tubular type in front. The transmission is by means of a Hale Shaw multiple-disc clutch to a short clutch shaft, incorporating a special type of flexible coupling, to a three-speed and ieverse gearbox, thence by silent chains to a secondary or layshaft running parallel to the engine shaft, contained in the same casing as the gears, and close to
the near side of the chassis, . The shaft -itself is divided, and the ends which protrude from the case are fitted with universal joints of the jaw and star-piece type: From these joints cardan shafts run fore and aft to the front and rear Elie axles. These are of the full-floating type, the final drive being by bevel gear with spur-pinion differential enclosed in the axle case. The front wheels only are used as steering wheels, the rear wheels taking the drive only, as in an ordinary chassis which has drive to rear wheels only.
Axles Call for Criticism.
There is nothing out of the common aboutthe design of the rear axle. We may say that it is not the type we antselves. would have chosen for a vehicle destined to carry loads such as the one we examined (a three-tinnier), and which, furthermore, is liable to be called :upon to tow a trailer carrying anything up to a-similar load, The final drive to the rear wheels i,s by means. of clogs, on the square ends of the axle shafts, pro.Vided With claws which engage with car: esponding recesses in the road wheels. I •Wciuld 'appear that, after taking off the hnb caps; it should be -possible to re--move these shafts but in order to get atthe main bevel and cliffetentiai gear, . ing, either. for ,inspection or iePait;it leould Probably be necessary_ to dis-: itiMitie the rear portion ...of the -chaSsici Salt'ogether.
•• ---The -Front Axle.
. .; The front .axle is similar to the rear as regards the drive and the. casing for the bevels and differentia); fact, the two axle § are 'identical up to a point just outside the spring seats. On the front axle at this point flanges are formed on the outer tubular portion, and to these are bolted hollow, ball-end forgings, with projections above and below. Another forging in halves is bored so as to fit this spherical portion, and this has bolted to it the stub axles proper, carrying the self aligning ball bearings on which the road wheels are mounted, The live axle is articulated within the spherical forging referred to, and the actual final drive to the road wheels is similar to that already described as pplying to the rear wheels. The Engine.
It should be here noted that the power unit employed on this chassis is the Wisconsin, being made by the same firm as those which are used on the Amen can Stutz rac,m, which attained such Phenotrienal succeSS biIndianapolis. It is a four-cyliiider engine with cylinders of the T=heed"type,' 'amply water jacketed, cast in_ pairs:: The valve tap. pets-are.„ of. eourtie,adjustable, and the valve sterns, springs and tappet gear are inditidnally;encloSed. by cast covers in halves held in Position by spring clips. The bore and. stroke are 41 ins. and
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54MS. respectively. It is interesting to note that the cylinders are offset to the extent of a in. Fairly long pistons are fitted, each of whieh has. four rings. The crankshaft is a substantial one, with good bearing surfaces. The valves also are ample, the inlet and exhaust being interchangeable and 4 ins, in diameter. The carburetter fitted is a Stromberg, but any other standard make can be substituted on request; the vital spark is supplied by a high-tension magneto. As is customary with American-made power units, a governor is fitted, of the centrifugal type, and. contained in the timing case; it operates on the throttle valve, and the mechanism is totally enclosed and sealed, thus obviating the possibility of its being . tampered with by any unauthorized person. The standard setting is 1100 revolutions per minute. With an engine placed under the seat, as is this one, it is, of course, fairly obvious that thermo-syphon circulation of the ,7.4-,oling water would he difficult, if not impossible. Consequently, a centrifugal pump is provided, driven in the usual manner from the timing gear. The lubrication of the engine is by combined folio and splash, the main hearings receiving oil under pressure from a pump driven off the camshaft ; the surplus oil is caught in troughZ and scooped therefrom by the
connecting rods. .
The gearbOk is Made by the F.W.D. Co., and provides three speeds forwaid as well as a reverse. It is of the constant. mesh type, each gear being engaged through the medium of stepped dog clutches, features contributing to foolproofness and ease of gear changing.
Front Drive, Rear Drive, or All Drive Possible.
Provision is made so that the vehicle may be used either as a normal reardrive lorry ; it may be used independently as a front-wheel-driven machine, or both front and rear wheels may be driven together. This is effected
Brakes.
External-contracting band brakes are fitted to the rear wheels only. Braking on all four 'wheels, however, is effected by means of the footbrake, which takes effect on a drum on the rear of the gearbox, and operates, of course, through the transmission..
The brakes on the rear wheels are operated by a hand lever through compensating gear, and are provided with ready means of adjustment. The footbrake, which is also of the band type, and external contracting, is of good diameter and width; it shows evidence of careful design and is simply constructed. There can be no doubt that on a chassis such as the present one, which may be liable to use as a tractor in addition to Carrying its ordinary load, the question of brakingis a very important one; it appears to have received all necessary consideration on the part of the designers Of the F.W.D. chassis.
No Radius Rods. Springing.
The power is transmitted from the axles to. the chassis through the portions.
the road springs; spring suspended torque rods, built up of steel tubing, are provided and attached to the 'casings. The front springs are semi-elliptic, and the-rear • endsof these -are 'arranged' to slide on specially-prepared brackets bolted to the frame. The rear springs at their rear ends are shackled to a transverse spring. With the exception of the axle construction, which we have criticised, the chassis appears to be in every sense soundly constructed, and should be reliable. We did not have the , • ...
pleasure of a demonstration, but may possibly be afforded an opportunity for a run on a loaded vehicle in the near future, when we shall, of course, have the pleasure of describing our experiences to our readers.
Steering and Control. Unusual Accelerator Pedal.
The control of the machine is similar in all respects to what we are accustomed to on the ordinary commercial-motor vehicle. The steering column, topped by a particularly large wheel, is placed near the off side of the chassis. It operates
through the medium of a worm and wheel, by means of the'customary ballend 'rod, to a lever keyedto the front axle steering arm. The change-speed and brake levers are also situated at the• right-hand side of the chaisis, and the engine control is by means of. two throttle and ignition levers below the steering wheel and a special type of accelerator, pedal. The latter is" not, aS is usual, operated by pressure of the sole of the foot, but slides horizontally in a groove in the foot plate.
The particular advantage of this arrangement, of course, is that there is no fear of the •driver accidentally mistaking the accelerator pedal for the brake pedal with disastrous results, as occasionally happens. On the other hand, experience has shown that, contrary to what might be expected, the operation of this pecu liar type of pedal, in the course of any considerable amount of traffic driving is very tiring. It seems as though the peculiar twisting action necessary on the ankle, brings into play muscles which are normally not much in use, and the effict is the reverse of comfortable.
Strongly-built Frame, Prepared for Towing.
The frame is a particularly strong one, and at the rear end, in order to accommodate the unusual stresses resulting from the use of the "machine as a tractor, it is reinforced arid stiffened by the addition of a couple of substantial cross members. The petrol tank is a cylindrical' one carried behind the driver's seat. The manufacturers draw attention to the fact that this is prO.vided with a lead at each end, so that, no matter how little fuel may remain, and no matter how much the chassis may be tilted to one side or the other, it will always be possible for the petrol to flow to the carburetter.
It is interesting to note that all four wheels are interchangeable, as well as the ball bearings on which they run ; each Wheel is supported by -two, of the self. aligning type, which also provide for some proportion of end thrust. The wheels themselves are prepared for American-size tires, as might be expected. Single solid band tires 36 ins. by 6 ins., to the S.A.E. standard, are fitted on all four.
Light Chassis. Dimensions. .
For a chassis of this peculiar construction, involving no fewer than three differential gars and two complete sets of final-drive bevels, propeller shafts, and So on, the weight is not excessive, being only 6000 lb. The following overall dimensions of the chassis may he useful to anyone who is considering the possibility of adapting it to his .own particular purpose. The wheelbase is 10 ft. 4 ins., and the tread 4 ft. 8 ins. With the standard lock, the machine is capable of turning in a circle of.radius 46 ft. The overall length of-the-chassis is. 16 -ft..8ins., and the distance available for bodywork, that is tii..Say from the back of .the drivers seat to the end of the ebassis, is 11 ft. 4 ins. The overall width is 6 ft : 104 iind the chassis frarnOis 3ft. wide.
Equipment.
The equipment includes a complete set of tools, toolbox, oilcan, horn, and a set of spanners, two oil side lamps and one oil tail lamp. We are indebted to Gaston, Williains and Wigmore, of Alexandra House, Knigsway, for the opportunity to examine this machine. They are the agents, and any inquiries as regards price and delivery of machines of this type should be addressed to them.