ric

or resistance met with, is determined by the nature of these two rubbing surfaces. The oil, or grease, or whatever suave, slippery substance is to be used as a lubricant, interposes itself in a thin film between the two rubbing surfaces and smooths matters over, as i

t there is no room for the interposition of an oil film, the shaft and journal will at once heat. The greater the pressure of the shaft in its box, the thicke

ount of friction, or heat, will be generated. A metal rubbing over oil, however-as is the case with a well-lubricated bearing-will arouse but little resentment and its pathway will be made smooth and easy, fo

uent power development. Thus, a lubricant that will prevent wear between the moving parts may be supplied to the bearings and pistons of a motor, and under this condition the engine might "last" indefinitely; bu

ubricated portion of a motor either moves in a bath of oil or is connected with an oil reservoir so that a certain amount will be fed regularly to the rubbing surfaces. There is always some heat generated in

r the ignition system is out of order, the motor will not run, but no actual harm to the mechanism will result from this fact. On the other hand, a motor may be run indefinitely w

cam shafts, each with five bearings and half a dozen cams; these will require, together with the magneto and pump shafts, five or six gears in the forward train; and the six pistons will demand their share of attention from the lubricating system. Here is a grand total of over fifty rubbing surfaces on a large motor, and

revolving at higher speed and carrying heavier loads. But it is the hardest-worked bearings that form the majority of the friction surfaces of a motor, as will be realized when it is remembered

vels is rather a high rate of speed when it is considered that it is entirely a rubbing or a sliding motion, and that the direction is reversed more than two thousand times during each sixty-second period. This means that each piston slides or rubs within the cylinder walls for a distance of between two and three thousand miles during an ordinary season. And remember that this is not a rolling motion, but

e cylinder walls. Whatever oil reaches the upper portion of the cylinder walls will be burned and will contribute to the formation of the carbon that is the mortal enemy of efficient running. Large quantities of oil burned in the cyli

the touch of a match to burn almost with the rapidity of an explosion. But notwithstanding the excitable family to which the mineral oils belong, the modern motor car lubricants are removed a sufficient distance from their more inflammable relatives to enable them to withstand a temperature of between 400 and 500 degrees, Fahrenheit. This is sufficient heat-resisting ability to enable the oil to stay on the cylinder walls near the bottom of the stro

ture does not exist throughout the stroke, for as the piston descends and the gas expands, heat is given off until the oil on the lower portions of the cylinder uncovered by the piston is sometimes able to remain in comparative peace. And even though this oil remaining on the cylinder walls at the bottom of the stroke

ut down his lubricant to the point where there will be no smoke. As there are no ordinances that absolutely prohibit the slightest appearance of smoke at the exhaust, and as a faint blue trail

ts exhaust should not necessarily be taken as an indication that the motor is not well lubricated. If the owner would satisfy himself that the cylinders are receiving a sufficient amount of oil, he may open the indiv

cups whenever the motor is started, the modern driver merely twirls the starting crank or presses the button of the self-starter, secure in the knowledge that whenever the motor runs, the lubricating system operates-provided, of course, the reservoir is filled and there is no

some systems, there is a separate pump for each oil lead. This is known as a mechanical oiler, and generally consists of an oil tank located on the dashboard of the car-either in front of the driver, or under the motor hood-and connected by means of a belt or gear with some shaft of the motor. The belt or gear drives a shaft to which is connected the plungers of

l is fed directly to the piston, but that the lubricant is first distributed to the oil wells in the crank case. Here, the splash of the cranks as they revolve in the oil is depended

ere be burned-with the attendant formation of clouds of objectionable smoke. This trouble is overcome to a certain extent in some motors by the use of a type of ring set in the piston that prevents the lubricant from

ove-described system is used they may be regulated independently of the splash feed lubricating pipes. Excess oil at the bearings will c

some manufacturers. This consists in placing a channel, or trough, directly under the lower sweep of each connecting rod bearing. Each channel is kept filled to overflowing by a separate pipe connected with the main lead from the pump, and a constant level is consequently maintained at all speeds of

ous bearings and troughs through the different pipes leading from the pump. As a further precaution against a smoking exhaust, some designers have added a baffle plate above each crank case compartme

a level in the crank cases will cause the motor to smoke; while the supply should not be allowed to become so low that when the angle of the crank case is changed-as in ascending a hill-the lubricant will run t

tinuously until it becomes "worn" or filled with sediment and particles of dirt and other foreign matter. The pump used for maintaining this circulation may be either of the plunger, centrifugal, or gear type, and is generally housed in a portion of the crank case. A strainer is usually placed in the suc

ding its "arms" and connecting rod bearings. At each bearing, one or two small oil holes connect with this main artery and extend radially to the surface. Oil is forced into the longitudinal oil hole by means of a small pum

the old gravity systems, the flow of oil depended largely upon its viscosity, or thickness. Therefore, in winter, a thinner oil was required than in summer, for the more a lubricant is warmed, the thinner does it become-and vice versa. With the mechanical force systems now in use, however, practically the same kind of oil may be used th

ouble can be remedied. If a sufficient supply of oil is not fed to the rubbing surfaces between the piston and the cylinder walls, a high degree of heat is generated which will tend to expand the piston until it grips the cylinder so closely that the former cannot be moved. In this event the motor will stop "dead," and cannot be started again until the piston has cooled and contracted to its normal size. Even t

k and forth by the flywheel to give the kerosene an opportunity to reach all parts of the piston and rings. The kerosene will serve to cut and remove much of the carbon and gummed oil and to make the way free for the fresh lubricant, which should be po