A _mechanical lubricator_, or _oiler_, consists of several small oil pumps placed in an oil tank, each pump feeding one special bearing, and all driven by the engine. Figure 82 is a top view of a 2-cylinder horizontal engine oiled by a six-feed oiler. The bearings that it oils are the two ends of the crank shaft, the two ends of the cam shaft, and the two cylinders; the gears and other bearings are oiled by splash. An oiler is adjustable, so that it will feed any desired quantity of oil. [Illustration: FIG. 83.—“I.H.C.” METHOD OF OILING CRANK PINS] Figure 83 shows a side view and an end view of the crank shaft of a 2-cylinder horizontal engine. To each end of the crank is attached a ring, B, formed into a channel; oil splashing into this ring is thrown into the channel by centrifugal force, and flows by holes, A, to the crank pin bearings. The oil forced to the cylinders from the oiler, Figure 82, reaches the wrist pin by grooves and holes, A, Figure 83. A 6-feed oiler is also shown in Figure 84. [Illustration: FIG. 84.—“HART-PARR” OILING SYSTEM] [Illustration: FIG. 85.—OIL CUP] [Illustration] [Illustration] [Illustration: FIG. 86.—PROPER USE OF A GREASE CUP] Figure 85 is an _oil cup_, which is used to feed an individual bearing. It is a glass cup holding oil with an opening at the bottom into which fits a needle valve. When the engine is at rest, the needle valve handle at the top is turned down, which allows a spring to close the needle valve; on starting the engine the needle valve is raised, and the oil flows out by gravity. The dripping oil may be seen through a sight glass at the bottom. In the force feed and oiler systems the oil feeds only when the engine is running, but with an oil cup the oil feeds all of the time that the needle valve is raised. Care must therefore be taken to turn on the oil cup when starting the engine, and to turn it off when the engine is stopped. Change speed gears and differentials are usually enclosed in oil-tight housings that contain a supply of oil or grease. The only attention that is required is to see that they have the necessary amount, and that the lubricant is of the right kind. [Illustration: FIG. 87.—“TITAN” 10-20 OILING DIAGRAM] [Illustration: FIG. 88.—“INTERNATIONAL” OILING DIAGRAM] The bearings of wheels and of many other parts of a tractor are lubricated with grease fed by _grease cups_; a grease cup has a cover that, when screwed down, forces the grease out of a hole in the bottom of the cup. In using a grease cup it is not sufficient simply to give the cover a turn or two; the cover should be screwed down enough to force an ample supply of grease to the bearing. This is illustrated in Figure 86. Figures 87 and 88 are oiling diagrams. They show the many points at which a tractor must be lubricated, and it should be remembered that the failure to maintain a plentiful supply of lubricant at any one of these points will mean the wear and breakdown of that particular part.