operation. Oil, benzine, and other so-called carbureted-air engines are particularly difficult to control because of many phenomena which cannot be recorded. In order to test the operation of high-speed engines, two different types of instruments are at present employed: the manograph and the continuous explosion recorder.
The Manograph.—The manograph, which is the invention of Hospitalier, is an optical instrument in which a series of closed diagrams are superimposed upon a polished mirror similar in form to Watt diagrams. Because the images persist in affecting the retina of the eye an absolutely continuous, but temporary, gleam is seen. Still, it is possible to obtain a photograph or a tracing of these diagrams.
The Continuous Explosion Recorder for High-speed Engines.—The author has devised an explosion and pressure recorder, which is mounted upon the explosion chamber to be tested and which communicates with the chamber through the medium of a cock r (Fig. 136). The instrument is somewhat similar in form to the ordinary indicator. Its record, however, is made on a paper tape which is continuously unwound. The cylinder c is provided with a piston p, about the stem of which a spring s is coiled. A clock train contained in the chamber b unwinds the strip of paper from the roll p′ and draws it over the drum p′′, where the pencil t leaves its mark. The tape is then rewound on the spindle p′′′. A small stylus or pencil f traces "the atmospheric line" on the paper as it passes
over the drum p′′. In order to obviate the binding of the piston p when subjected to the high temperature of the explosions, the cylinder c is provided with a casing e in which water is circulated by means of a small rubber tube which fits over the nipple e′. This recorder
analyzes with absolute precision the work of all engines, whatever may be their speed. It gives a continuous graphic record from which the number of explosions, together with the initial pressure of each, can be determined, and the order of their succession. Consequently the regularity or irregularity of the variations can be observed and traced to the secondary influences producing them, such as the section of the inlet and outlet valves and the sensitiveness of the governor. It renders it possible to estimate the resistance to suction and the back pressure due to expelling the burnt gases, the chief causes of loss in efficiency in high-speed engines. Furthermore, the influence of compression is markedly shown from the diagram obtained.
Fig. 136.—R. Mathot's continuous explosion recorder.
Fig. 137.—12 H.P. Oil-engine.
