A NEW DIESEL
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Made by a Concern of Engine Specialists.
A Two-cylindered Dorman Power Unit Embodying the Acro Principle
FOR many years W. H. Dorman and Co., Ltd., Stafford, has been making internal-combustion engines, and the present range of these includes 19 petrol engines having b.h.p. outputs from 8.5 to 100, at 1,000 r.p.m. The twentieth type of engine is now introduced; it is known as type RB and is a two-cylindered model working on the four-stroke cycle, with compression ignition and solid injection. It also embodies the great advantage of cold starting. The various outputs at specified speeds are as follow :-12 b.h.p. at 600 r.p.m., 17 b.h.p. at 800 r.p.m., 21.5 .b.h.p. at 1,000 r.p.m., 26 b.h.p. at 1,200 r.p.m., 30 b.h.p. at 1,400 r.p.m., 34 b.h.p. at 1,600 r.p.m. and 35 b.h.p. at 1,800 r.p.m. It is recommended that the engine should not exceed 1,250 r.p.m. for continuous heavy duty.
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Paraffin, gas oil, Solar oil or fuel oil having a viscosity of about 50 secs. Redwood at 100 degrees F,, can be employed. It is stated that at full load the fuel consumption is .45 lb. per b.h.p.-hour on average Diesel oil. Provided it be feasible to employ a sufficiently heavy flywheel, starting
can be effected by hand.. If preferred, however, two electric startermotors can be The engine, it should be noted, is sold by the Dorman concern for use in rail locomotives, inspection ears, industrial plants and it might be utilized in tractors, but it is not marketed—in the form to which we refer—for road-vehicle employment. When equipped with a flywheel sufficiently heavy for hand-starting the weight of the unit is 16 cwt.
Turning to details of the construction of the Dorman Diesel, we find that the crankcase is 1 ft. 61 ins. deep and is in cast iron. The bearer brackets are bolted in position, the two rear ones being made to house starter-motors if specified. Rigidity is obtained by the use of " through " bolts, extending from the bearing caps to the top of the cylinder head. Four of the cylinder-head studs are actually hollow to allow for the passage through them of the valveoperating push rods, whilst the head is, of course, further retained by plain studs and the " through " bolts, of which we have made mention. The lower portion of the crankcase holds three gallons of oil and serves as a reservoir. The crankcase -casting is open at the forward end and is formed to house the timing gears which operate the camshaft, Bosch fuel pump and dynamo. The cams are integral with their shaft.
A high-tensile steel forging forms the crankshaft, which rotates in three 3k-in. bearings; integral balance weights ate used. Steel connecting rods carry white-metallined steel shells for the big-ends, whilst the floating gudgeon pins turn in the piston bosses and in phosphorbronze bearings in the small ends of the connecting rods. Aluminium alloy is used for the four-ringed pistons, which have depressions on the off side in line with the fuel nozzles ; the last-named are mounted -in the cylinder block and inclined upwards, discharging the fuel oil from the Bosch nozzles into the Acro air cells and venturis.
Vertically mounted overhead valves are carried in the detachable cylinder head; they are operated through rockers which work under • the influence of cup-ended push rods.
A gear-type oil pnmp is driven from the front end of the crankshaft ; the filter can be removed without loss of oil. If required, a positively driven centrifugal water pump can be installed. Likewise a six-volt or 12-volt dynamo can be provided.
One of the well-known Bosch fuel pumps is used, and the fuel-injector valves are of the same make, likewise the fuel-oil . filter. The output of the pump is regulated by a centrifugaltype governor.
As can be gathered from the illustrations, the proportions of the working parts of the new Dorman Diesel are exceptionally robust. The bore and stroke are 110 mm. and' 180 mm. respectively, giving a swept volume of 3,420 c.c.