With the improvements in machinery and in the art of the application of the lubricants, marked improvements in the methods of refining the lubricants have naturally followed. New laboratory methods for determining and standardizing the features of the lubricant that modern requirements demand have been established.
As a result of the intensive study given to the subject of application two further general improvements since Tower's work have been made in the methods of applying the lubricants.
(5) Gravity-feed Circulating System.—In this method, the oil is carried in a tank higher than the bearing. to which it flows in a slightly restricted stream, and is then splashed around the parts in the crankcase. Bearings are continuously flooded with cool oil. Better results are obtained than with bath lubrication.
(6) Force-feed Lubrication System.—In this system, pro fuse quantities of lubricant are fed under pressures that can be made as high as may be desired to assure the complete flooding of the surfaces. Coolers, heaters, filters and various other refine ments have been added to this system of lubrication that have brought it to the highest engineering level.
These successive steps in the development of oiling equipment and in lubricants, from the primitive to the present highly de veloped stages, have shown progressively increased general econ omy one over the other. It follows that here is a method of classi fying the status of the lubrication of various groups of transporta tion, farm and industrial machinery.
The great fields of lubrication are as follows:— Farming Machinery.—Aside from general automotive ma chinery, this field includes practically all general equipment in the primitive or first (I) class for lubrication.
Steam Railroads.—Comprising locomotives using solid lubri cants (I) ; packed or pad lubrication (2) ; siphon or drop-oilers (3) ; with some modern roller-bearings.
Electric Railways.—Including power-house machinery, modern equipment in (5) or (6) classifications; motors and axles on cars using pad or packed lubrication (2) ; ring-oiling bearings (4); some roller and ball-bearings.
Marine Machinery.—Steam engines, in the primitive or (I) for all hand-oiling; wick or drop-oilers (3) ; Diesel engines (6).
Heavy Machinery.—Steel and iron mills. A combination of (I) primitive and bath or ring-oilers in the (4 ). Circulating and force feed systems for production machines in rolling and paper mills (6) ; with some power equipment in (5).
Medium-weight Machinery.—General manufacturing plants. Ring and bath lubrication (4). Very little (I) and (2) lubrication, and that difficult to displace.
Light Machinery.—Textile mills constituting the best-lubri cated industrial machinery. Bath and ring lubrication (4); power plants (5).
Automotive.—All types. Bath systems (4); gravity-feed (5); force-feed (6) ; and various combinations except that provisions are not always made for removing dirt and fuel contaminations from the lubricant.