splashing of oil by the connecting-rod head. In order that this splashed oil may be collected in the base of the engine a suitably curved sheet-metal guard is mounted over the crank. A more serious difficulty is presented when the oil from a crank-bearing finds its way to the hub of the fly-wheel, whence it is driven by the centrifugal force to the rim. The oil is not only splashed against the walls of the engine-room, but it also destroys the adhesion of the belt if the fly-wheel be employed as a pulley. In order to overcome this objection the oil is prevented from spreading along the shaft by means of a circular guard (Fig. 73) mounted on that portion of the shaft toward the interior of the bearing.
Fig. 73.—Shaft with oil-guard.
The problem of lubrication is of particular importance if the engine is driven for several days at a time without a stop. This happens in the case of mill and shop engines. Lubricators of large volume or lubricators which can be readily filled without stopping the engine should be employed.
CHAPTER VII
THE CONDITIONS OF PERFECT OPERATION
General Care.—Gas-engines, as well as most machines in general, should be kept in perfect condition. Cleanliness, even in the case of parts of secondary importance, is indispensable. Unpainted and polished surfaces such as the shaft of the engine, the distributing cam-shafts, the levers, the connecting-rod and the like, should be kept in a condition equal to that when they were new. The absence of all traces of rust or corrosion in these parts affords sufficient evidence of the care taken of the invisible members such as the piston, the valves, ignition devices, and the like.
Lubrication.—The rubbing surfaces of a gas-engine should be regularly and perfectly lubricated. The absence of lost motion and backlash in the bearings, guides, and joints is of particular importance not only because of its influence on steady and silent running, but also on the power developed and on the consumption. As we have already seen in the chapter on lubrication, a special quality of oil should be employed for the lubrication of the cylinder. The feed of the lubricator supplying this most vital part of the engine is so regulated that it meets the actual requirements with the utmost nicety possible. In a subsequent chapter,