702 
The Trials of Oil Engines at Cambridge. 
mencement of the suction stroke by an ordinary plunger pump 
having suction and delivery valves in duplicate for security 
against sticking. Neither ignition-tube nor lamp is required, 
as the explosion of the last stroke and heat of exhaust gases keep 
the vaporiser at the requisite temperature. At starting it is 
heated by an external duplicate cast-iron lamp, with hand blast, 
for about nine minutes. The governor acts upon the oil supply, 
intercepting some of it through a by-pass, when the speed is 
too high, and returning it to the tank. The oil-tank is in the 
bed-plate of the engine, but was replaced for the purposes of the 
trial by a temporary tank in which a measuring point gauge 
was inserted. The air and exhaust valves are driven by 
Fig. 2. — Section through cylinder and valves of the “Hornsby-Akroyd” Oil Engine. 
cams on a lay shaft, and a water-jacketed back-pressure valve is 
provided between the valve-chamber and the vaporiser to prevent 
the possibility of pre-ignition at explosion. The amount of 
compression can be altered for oils of different specific gravity by 
inserting packing pieces in the connecting-rod end. The mean 
pressure and initial pressure of this engine are comparatively 
low, from which the makers claim the advantage that it re- 
duces the leakage past the piston and diminishes the strain 
upon working parts. The size of engine for a given power 
is, however, proportionately large. For simplicity, neatness 
of design, workmanship, and general appearance this engine is 
admirable. 
