The Model DH De La Vergne gas engine brought out about 1915 by the De La Vergne Machine Co., New York City, was one of the last steps in the evolution of the solid injection Diesel. It compresses to about half the pressure of a full Diesel, and fires with the aid of an uncooled plate in the bottom of the head. It starts cold with the aid of a smouldering fuse made from impregnated cloth rolled up to form a bar about the size and shape of a cigarette. This fuse is lighted and introduced to the combustion chamber in a special T-handled plug, and the engine is then quickly rolled over with compressed air. The fuse burns long enough to provide ignition until the engine is warmed up, and eventually is completely consumed. If, through some accident, the cylinder pressure becomes excessive, the dead-weighted relief valve under the head opens and allows pressure to blow off.
Figure 2 shows a cross section through the governor head and fuel pump. The by-pass valve beside the governor thrust collar controls both the beginning and the end of injection by allowing pumped oil to return to the tank. It gives the good sharp action necessary to avoid dribble from the nozzle, and meters the injected charge according to the length of time the governor allows it to be closed. This governor is driven through a spring, its heavy head acting as a flywheel to keep it from responding to short-term speed variations as the engine compresses and fires.
The DH was also one of the first large engines to lubricate the wrist pin from the crankshaft through a drilled con rod. The passage in the rod holds about a quart of oil, and a necessary part of the starting procedure is to remove a plug from the top of the rod and fill it up!
Bore and stroke are 14-inch by 24-inch, flywheels are 76 inches diameter with an 8-inch face, and total weight is 20,600 lb. A similar De La Vergne is in the collection of A.D. Mast, 1316 Clayton Rd., Lancaster, Pa. and may be seen on the Rough and Tumble show grounds at Kinzers, Pa.. A. D. was the previous owner of the little Domestic gas engine, and did a fine job of cleaning it up and putting it in running order for me.