FIG. 92.-Sectional View of Motor Showing Complete Constant Level Splash Lubricating System.

Constant Level Splash System. The constant level splash system has become very popular on motor cars and is also widely used on gas-tractor power plants that are based on automobile engineering practice. The application of a typical system of this kind is shown at

Fig. 92, and in view of the clear manner in which the various parts are outlined, very little explanation is necessary. The lubricant is carried in a sump or oil container at the bottom of the crank case which may be filled through the breather pipe conveniently arranged at the top of the crank case and having a removable cap to permit the introduction of lubricant to the crank case interior. The oil level in the sump is shown by means of an oil gauge carried by a small float which falls when the oil level decreases to the point where the supply in the crank case must be renewed.

FIG. 93.-Method of Lubricating Main Bearings From Oil Reservoirs Integral With Crankcase.

The oil is taken from the sump by means of a geared oil pump and is discharged into the crank case. It fills the crank case to the level determined by the overflow pipe, the position of which may be varied as desired by rocking it in its bearings. The oil level is usually of such height that will permit the splasher or oil scoop on the bottom cap of the connecting rod to dip into it. With this system all of the interior mechanism is lubricated.

by means of the oil mist produced by the rapidly-revolving crank shaft. All excess oil supplied flows back into the sump through the overflow pipe and is filtered through the screen at the oil outlet before it is again supplied to the crank-case interior. In this manner only clean oil is supplied and one filling of lubricant will last for a run of three or four hundred miles. At the end of this period all the old oil is cleared out of the crank case and oil sump through a suitable drain cock and the supply is replenished with new, unused oil.

In the systems previously outlined the main bearings are lubricated either by oil supplied by individual leads or by a mist which is present in the crank case all times that the engine is in operation. Another method of lubricating main bearings, which has been applied to stationary engines with some degree of success and which is also suitable for tractor power plants where the cylinder is oiled from a sight-feed oiler, is shown at Fig. 93. The main-bearing pedestal is cored out, as shown at C, this forming an oil chamber which can be filled through the plug D. As the oil level at C is higher than the bottom of the bearing oil will be supplied continuously through the passageway S which provides communication between the shaft and the oil container. The brasses B are thus covered with a film of oil which is maintained automatically as long as the oil level in chamber C is higher than the bottom of the bearing B.

CHAPTER VII.

FUNCTIONS AND CONSTRUCTION OF CLUTCH, GEARSET AND DIFFERENTIAL.

Why Clutch is Needed-Action of Simple Clutch DescribedSome Typical Tractor Clutches-Friction Disc and Roll Clutches-Why Reversing Mechanism is Needed-Typical Reversing Mechanism-Why Speed Changing is Necessary -Action of Simple Change Speed Gears Outlined-The Differential Gear and Its Use.

Why Clutch Is Needed. One of the important members of the power-transmission system of the gas tractor is the friction clutch employed to connect the power plant to the rear wheels or to break the driving connection between the power generating and traction members when desired. A clutch is absolutely necessary on a gas tractor, though on a steam tractor it is not customary to provide a clutch between the engine and the driving wheels, though in some cases this device is furnished on the steam-power plant as well. Steam engines are capable of delivering power considerably in excess of their rating, and as the steam which furnishes the power is stored under pressure in the boiler it is possible to start the steam engine under load. The amount of power delivered from a steam engine may be varied by regulating the quantity and pressure of the steam going to the cylinders and a simple throttle-valve lever is all that is needed to control the speed of the steam tractor and to start or interrupt the drive when desired.