A Mechanical Horse Oiler
Page 63
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Scammell 6-10-ton M.H. Model with Compression-ignition Engine. Perkins Wolf the Power Unit at Present Adopted OR 1938 the range of chassis Faith /by Scarnme11 Lorries, Ltd., Watford, will include an oil-engined mechanical horse. It war be rated as a 6-10-tonner, and in general design will closely resemble the well-known 6-ton M.H. type petrol-engined machines.
Already a few of these latest products have been built. One has been ordered by the Great Western Railway as a result of trials this company has carried out. Two have been supplied to United Molasses, Ltd., and are now in use in the Liverpool district with four 1,200-gallon molasses tanker semitrailers, and regularly operate through the Mersey Tunnel, where speed must not be less than 6 m.p.h. A fourth is going to Australia, where the demand for oil engines is big because of the difficulty of obtaining petrol.
It is stated that the new oil-enginecl model with a 10-ton load has approximately the same performance as its petrol confrere with 6 tons.
In these first chassis, one of which is shown in the accompanying illustrations, a Perkins Wolf engine is installed. This has four cylinders of 3.35-in, bore and 4.75-in, stroke and develops, in the form used by the Scammell company, 45 b.h.p. at 2,500 r.p.m. The unit is so well known that a description of it here is unnecessary.
Engine Easily Installed.
No structural alterations to the standard frame were required for its accommodation. Briefly the main modifications made were in connection with the bell-housing, front mounting, hand-starting arrangements, fuel system and intake and exhaust pipes. In addition, a higher final-drive ratio is used.
. To consider these in order, the attachment of the Perkins engine to the standard mechanical-horse gearbox necessitated the employment of an intermediate housing, which serves to unite the rear of the engine body with the clutch housing bolted to the gearbox itself.
. At the rear, the list-named component is hung from a tubular crossmember, as on the petrol machine, whilst at the forward end of the power unit, the central engine bracket on the chassis carries a suspension member bolted to the engine.
This attachment is incorporated in the casting that encloses a bevel drive to the crankshaft, which can be engaged by a side starting handle. On petrol M.H. models a forward starting handle is used, this being dogged to the camshaft. With the new unit, this scheme was impracticable; a 2-to-1 gearing up is, obviously, undesirable for starting an oil engine, whilst the relation of the front wheel to the power unit prevented a forward extension of the crankshaft. A bevel drive to the near side was, therefore, devised, the handle being insertable from outside the frame.
Because of the proximity of the engine to the near-side frame longitu.dinal, the oil and petrol filters had to be moved/ The former is moved into a lower position, so that it is below the frame, whilst, outside the member, are mounted two fuel filters. In both cases Tecalemit units are employed.
With regard to the intake and exhaust systems, a special pipe has been designed for the former. This connects with an elbow on the ',back of the bonnet end, which in turn carries an air cleaner. As for the latter, the only modification is an increase in the size of the pipe.
The standard axle ratio of the mechanical horse oiler is 10 to 1, as against 18.23 to 1 on the petrol model. However, the lower ratio may be specified for use on the new machine where specially heavy loads have to be carried or exceptionally hilly roads traversed.
From our description of the handstarting arrangements readers must not be misled into thinking that there is no electric starting equipment. This system is standardized, but, obviously, an alternative is desirable. In this connection, the Ki-gass apparatus for facilitating starting is also installed. This comprises a device by which the air intake -can be primed with oil-fuel or paraffin, a hand-pump injecting a finely atomized spray into the two branches of the manifold.
Scammell Lorries, Ltd., informs us that on a three-day test in the Liverpool district, one of the machines, operated with a 640-ton tanker trailing unit, consumed fuel at a rate equivalent. to 14.5 m.p.g. It could cruise 'at 20-25 m.p.h., behaved. satisfactorily in thick traffic, and could negotiate the Mersey Tunnel in top and third gears, the minimum speed being approximately 13 m.p.h.
At the Liverpool Dock exit, up n gradient of 1 in 22, 9 m.p.h. could be maintained in second gear, 1,1 baulked, it could slow down on the ascent and recover its former speed.
The view is expressed that under easier conditions the machine could improve on the consumption figure quoted above.