THE NEW ROBEY 6-TON STEAM WAGON
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Larger Boiler and Engine and Three-speed Gear, Modified Nickel-steel Frame and Ball-bearing Crankshaft, some of the New Features.
VOUNDED in the year 1852, Robey I: and Co., Ltd., have devoted much of their attention to the manufacture of steam vehicles, examples of which were placed on the road so lung ago as 1870. Witir such experience at their back, any new models which they produce nnist be treated with the greatest• respect,, and their .latest product, the new 6-ton wagon, embodies this accumulated knowledge, which displays itself-in the many practical points shown throughout the design.
In its general appearance the wagon closely resembles its prototype, but there are many important differences when the details are examined. For instance, the boiler, although of the same stay/ess type as that used on the 5-tott vehicle, has a larger beating surface, this being 91.5 sq. ft., with a grate area of 3.14 sq. ft., a working pressure of 250 lb. per sq. in. and a test pressure of 500 lb. per sq. in.
,Another very important alteration is the provision of a third speed, the gearing now giving 3 m.p.h., 8 m.p.h. and 12 m.p:h. at normal. engine speed.
The engine itself has been increased in size, the cylinders now having diameters of 4-1. ins, and 7. ins. a.nd a stroke of 7 ins. The design of the steam ports has also been modified to give in creased efficiency.A new and unusual feature is the provision of ball bearings for the crankshaft, whichconsiderably reduce friction and ConSequent consumption of fuel, and also give a very long wearing life. Much attention has also
been paid to the enclosing of the engine by steel shields, both to prevent the entry of dirt and the throwing of oil into the cab.
It will be noted from the illustration that a special type of tubular-spoked cast-steel wheel is employed. These take the place of the pressed-steel builtup wheels which were formerly employed on some models. This change was effected during last year, and some of the 5-ton models were fitted with the new type of wheel.
The frame of a steam wagon is submitted in the course of its work to all kinds of bending and twisting stresses, .and in the new models the frames are constructed of nickel steel, which:is giv big excellent results in everyday service.
In connection with the side-members, therehas been a certain amount of modification, for they are no longer in— swept and bolted direct to the boiler, as was previously the case. They are now brought out straight to the front, and are there joined to the smokebox by Means of brackets riveted in position through the medium of angle-pieces shaped to the curve 4)f the smokehox. This also allows riore room for the Spur wheel for the new third speed. Iii eonneCtion with this gear it is interesting to note that a horizontal type of gatechange is employed, a somewhat unusual feature to find in a steam wagon.
The rear axle is of particularly strong design. It is reduced at the centre and swept up at. the ends in a very long radius, so that there are no abrupt differences in strength. There is no
doubt that in past years much .trouble has been experienced with this important part of a steam wagon, but experience has shown how such trouble can be obviated.
The braking on the Robey wagon is particularly efficient. The shoes are of the internal-expanding type, one shoe acting oneach wheel. Each brake drum—or ring, as it should perhaps be called—is bolted to the inside of its wheel, an air space being provided between the outer rim and the wheel, thus preventing heat from being conducted to. the tyres. . The diameter afforded is the maximum possible, and the brakes are enormously powerful, whilst the braking surface is an large that the shoes have a very long life.
For those of our readers who are not fully accivainted with the general design of the Robey wagon, we will now give a brief description of its salient features.
It is of the overtype pattern, in which a compound--engine is fixed to the top of a km-type boiler. This boiler has a round firebox and no stays, the diameter at the bottom being somewhat larger than elsewhere, thus giving the maximum grate area and so enabling_ coke to be employed as fuel. The complete boiler Consists of only seven plates and a foundation ring, these including the pressed-steel seating for mounting the cylinders arid the forecarriage saddle, whilst the domed top of the firebox obviates the necessity for roof stays, and thus greatly reduces any risk of failure, and the tube plate can breathe with any unequal expansion of the tubes. As regards the tubes, the principle followed has beery to use a comparatively small number of large diameter. The amount of riveting is thus reduced to a minimum, and there is less risk of seepage. The feed pump is driven by an eccentric, and so arranged that it. -Can be operated while the wagon is standing. The drive to the eccentric is through spur gears. The boiler fittings also include a reliable injector.
The rear mounting of the boiler is somewhat novel, as it is carried on is shaft which runs right through the boiler in a steel tube, the ends of the shaft being fixed by bearings to the main frame.
Engine efficiency is promoted by steamjacketing the cylinders, aad the valve gear, which is of the piston type, may be adjusted while the engine is being erected. The pistons themselves are mild-steel stampings in one with the rods and hollowed out for lightness. They are provided with the ordinary form of Ramsbottom ring. The crossheads are cylindrical, and fit bored guides formed in the front cylinder cover and provided with large lubricators. Mild-steel stampings are employed for the connecting rods. The crankShaft is a one-piece steel !urging, which is cat to form the cranks and balance weights. Six aplines -are cut at one end of the shaft for carrying the change,speed gear pinians, and the shaft itself is supported in gun-metal bearings fitted to brackets mounted on a special shaft which runs through the boiler, and to which we have already referred. These brackets are stayed to the cylinder by means of tubes and bolts, so that the distance between the crankshaft and the secondmotion shaft is always constant.
Gun-metal is employed for the regulator valve, which is provided with a steel spindle working through gun-metal glands. The • valve is, of course, operated from the driver's seat. The reverse gear is of the usual Stephenson type, all wearing parts being made of case-hardened steel, and the engine may be run as a double highpressure if required. Transmission is by spur pinions on the crankshaft, meshing with large spur gears on the countershaft, which carries the sprocket for the final-drive chain. Cast-steel is employed for the chain wheel on the rear axle, and the differ ential gears within this are all machine cut and enclosed by covers. The bearings of the rear axle are of gun-metal and uf generous proportions. The bottom of each is provided with a large oil reservoir, which affords ample lubrication, and is designed to be com pletely clu.stproof. The forecarriage is of cast-steel, whilst the front axle is of special steel of great strength, the front wheels being carried on lung phosphorbronze bushes, which reducethe wear to a minimum.
The steering gear and the arrangement of the front pivot are similar to
those employed on the previous model. The gear is of the worm and quadrant type, with rubber buffers fitted between the quadrant and the axle to take road shocks. The quadrant itself is fitted with large ball bearings, and the whole
gear is bothefficient and light to use.
The water-tank capacity is 140 gal. Ionsand the bunker capacity 4 cwt., whilst the overall length of the wagon is 22 ft. 6 ins., as a standard tipper. A semicircular shape is employed i"or the water tank, which is constructed of. mild-attei plates, strongly riveted together and with • pressed-steel ends. There are no flat surfaces under pros-. sure, and baffle plates are provided to prevent surging Of the water. By sup
porting this tank well forward the weight. on tire rear wheels has been .reduced very considerably. It is supported in the chassis frame by steel
straps and does not interfere in any way with the fitting of any type of body.
A large manhole is provided at the back in order to give free access to its interior, and underneathit is a very simple and efficient combination of tank cleaner, strainer and emptier, so arranged that by operating one cock
these three functions are performed simultaneously.
The back of the tank serves as a base for the fuel bunker, and extra accommodation for fuel. is arranged. by bunkers under the driver's seat. The -meal steam-water lifter and armoured hose for filling the tank form part of the equipmeat.
In addition to this model the company have also produced a new six-wheeled steam tractor-lorry, of which the motive unit closely ,resembles that described in connection -withthe steam wagon_ The tractor-lorry is, however, capable of carrying loads of ten tons. The company do not believe in the Ordinary type of turntable with a central king-pin, and in their tractor-lorry there are two points of connection between the trailer and tractor portions.
In the case of the tractor-lorry, there are two independent foot brake, one acting °Otte driving wheels of the tractor and the other on the wheels f the trailer portion. The trailer brake shoes are duplicates a those employed for the driving wheels and exert avery powerful braking effort, whilst being so arranged as to give constant pressure on the brake. rings, whatever he the position of the trailer in relation to the hauling unit.
• Figures obtained in a. recent test of the tractor-lorry may be of interest. The distance traversed was 32 miles; the average road speed was 15 m.p.h. with a net load of ten tons. The fuel consumed was 1 cwt. per 16.96 miles—
equal to 6.6 lb. per mile. The water consumption proved to be 63 lb per mile.
It may be pointed out that when running light speeds up to 25 m.p.h. have been achieved.