More about the New Sheppee Steamer.
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Great Britain's Latest Evidence of a Steam Revival.
The thoroughness with which several steam-veilicle manufacturers are overhauling their designs, in respect equally of large and small output, is one of the outstanding features of current happenings in the commercial-motor world.
The new Sheppee design is in the nature or developments of that maker's earlier superheated-steam system, rather than in the nature of a radical departure, in which Latter category we must class other new manufacturing programmes of which we have advance information. Steam-wagon makers appear to have awakened to the fart that they will have to take many lessons from petrol-vehicle practice, in respect or the more-general employment of high-grade. materials, in order that they may be in a position to hold their own in certain branches of their trade in the near future. We refer, more particularly, to competition with internal-combustion-engined lorries of load capacities varying between two tons and four tons, because it is here that the steam-vehicle maker has wonderful new opportunities for fresh sales in front of him, if he but elect to take advantage of them. It goes without saying that the new types will he tired throughout with rubber, that they will employ high degrees of superheat, and that they will give a better ratio of useful platform area to total area occupied than has hitherto been. commonly accepted as satisfactory.
The new Sbeppee three-ton lorry, the completion of which we forecasted in the course of an article which was published in this. journal on the alst January last, has now been on the road for some little time. We reproduced a photograph of the chassis last week, and we now have pleasure in giving supplementary particulars, and further illustrations front the road.
The frame is of channel steel, and is strongly braced by cross members of suitable section ; the springs are of the half-elliptic type, working on slides. The road wheels are of steel, with rubber tires. The boiler and burner, we regret to say, are at the moment the subject of uncompleted patents, and we are not, therefore, in a position to publish definite particulars of them. We may state that the Sheppee boiler is the outcome of very long experience in the adaptation of superheated steam to road work, and that it is neatly accommodated under a bonnet ; the burner uses paraffin only, both for the main burner and the pilot light. Neither petrol nor any other kind of motor spirit. is required. The two-cylinder ' simple " engine is of the doubleacting type, fitted with mushroom valves, and this has proved itself suitable for use with very highly superheated steam ; all the valves are on the top, and are easily accessible. The normal engine speed is WO ap.m., at a road speed of 17 m.p.h., and the company makes a special feature of this comparatively-low speed in the claims which it advances on behalf of its engine, qua long life of all parts.
The lubrication system, which has been &signed and adapted for use with superheated steam on light steam wagons, is dependent upon a patented lubricator, which is worked from the engine. There are no valves or springs in the interior of this lubricator, which attends to : the main throttle valve ; the mainengine cylinders, pistons and valves ; the donkeypump throttle, cylinder, piston and valves. A telltale glass is arranged on the dashboard. Positive force-feed lubrication serves the main bearings of the engine, and the big ends and small ends of the connecting rods ; the crankshaft is drilled centrally, and the connecting rods are provided with small lubricating pipes to convey the oil to the small ends. This part of the lubrication system is supplied with oil from an oil pump that is driven off the engine ; the pump draws oil from an ample sump at the bottom of the crank chamber, and effective straining is arranged. There is also an oil-pressure indicatOr on the dashboard.
A single silent chain connects the crankshaft to the countershaft, and the differential gear is mounted on this second motion shaft ; the final drive from the
c:.:untershaft is by side chains to the back wheels. The drive between the crankshaft and the countershaft is encased, and the silent chain runs in oil ; the gear ratio, from engine to back wheels, is six to one. Two sets of brakes are provided : one is a powerful locomotive-type brake, applied to a drum on the countershaft ; the other is an internal-expansion type bsake, applied to drums on the back wheels.
The paraffin is taken, by means of a pump that is driven from the engine, to one of two small pressure receivers which are located at the sides of the chassis under the footboards ; the other pressure receiver, which is in connection with the first-mentioned one, contains air. The paraffin pump is provided with an adjustable relief valve, to permit the setting of the
pressure to any pre-determined point ; on relief through this valve, any excess of paraffin, passes back to the main tank. The object of this arrangement is to ensure that there shall be no large body of fuel under pressure at any time, whilst the main tank can always be refilled without the necessity to extinguish the burner. Further, when the vehicle is in service, there is always sufficient pressure in the airpressure receiver to restart the burner each morning, without use of the hand pump. In point of fact, the air receiver does not require to be replenished more often than once a week.
The standard Sheppee arrangements of thermostatic and pressure controls are applied to the oil system, which are rendered independent of the driver. They are the outcome of long experience, having proved not to deteriorate or to become inefficient after use ; they remain usefully sensitive and effective under traffic conditions, when the vehicle has to be slowed up and speeded up frequently. None the less, as a safeguard, to provide against delay in the event of physical damage to any of the parts, an alternative hand control is introduced, so that. the driver may work the burner in that manner should necessity arise. At such times, however, the temperature and pressure of the steam in the boiler are clearly indicated by dials on the dashboard, and excuse for overheating the boiler is thus removed.
Another pump, also worked by the engine, and also having an adjustable relief valve, is used to feud the boiler with water ; there is a steam-driven donkey pump as a stand-by. When running on the level, or on any average gradient, it is not necessary to use the donkey pump, which is available for starting-up purposes, or to give auxiliary feed to the boiler for climbmg stiff gradients with heavy loads. At such times, the donkey pump is used to raise the steam pressure to a point above that to which the relief valve on the svater pump is set. The vehicle which we illustrate was built at the York works.