Зображення сторінки
PDF
ePub

that the bearings will be burnt, cylinder and piston walls scored and other damage done.

Q. How can oil supply be regulated ?

A. One of the advantages of the constant level splash system of lubrication is that the amount of oil required is determined by experiment at the factory and the motorist does not have to regulate the oil feed to any extent. The operator's responsibility ceases when the oil container has been filled with a sufficient quantity of good engine oil. On some of the individual pump mechanical oilers the stroke of the pumps may be varied to alter the oil feed. Sight feed lubricators are often provided with needle valves to regulate the amount of oil passing through the orifice they control in a given unit of time.

Q. Describe some typical lubrication systems used on high grade cars.

A. The oiling system of the Packard six cylinder motor in clearly outlined at Fig. 124. In this the oil is carried in a sump formed integral with the crankcase and is taken from that point by a pump and delivered to a manifold pipe extending along the side of the motor crankcase. This manifold communicates with the main bearings, as well as to the timing gear assembly at the front end of the motor. The crankshaft is provided with drilled passages so the oil supplied by the oil manifold lubricates the connecting rod big ends after it passes from the main bearings. The cylinder interiors, pistons, valve plunger guides and other parts are thoroughly oiled by the oil spray always present in the crank

A manometer or pressure gauge is carried on the dash board and is attached to the end of the motor oil manifold. This indicates at all times if oil is being delivered to the bearing points. If the pressure of oil becomes too great in the manifold as sometimes occurs at high engine speeds, a relief valve is provided which permits the excess lubricant supplied by the pump to bypass back into the crankcase interior.

The system of lubrication employed on Packard trucks is shown at Fig. 123. In this the oil is drawn from a tank by an oil pump and forced through the sight feed on the dash, back to the crank

case.

[graphic][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed]

Fig. 124.—Lubrication System of Packard Six-Cylinder Engine.

case interior, where it collects in the front and rear crankcase compartments to a level indicated by the petcock screwed into the sides of the crankcase. The interior of the engine is thoroughly lubricated by the splash system.

In the Pierce Arrow cars practically the same arrangement as used in the Packard six cylinder and several other leading cars is used. This system is depicted at Fig. 125 and involves the use of a gear driven oil circulating pump having its suction side connected to the sump at the bottom of the crankcase and its delivery pipe to a manifold which goes to the main bearings of the drilled out

[graphic][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed][subsumed]

Fig. 125.-Oiling Method Used in Lubricating Pierce Arrow Six-Cylin

der Power Plant. crankshaft. A feature of this system is the use of an oil strainer or filter screen on both suction and delivery sides of the pump. Both of these screens may be readily removed for cleaning purposes and insure the delivery of only perfectly clean oil to the Fraring points. Two petcocks are provided on the side of the crank ase. The one at the bottom is a drain cock through which the sump may be emptied at any time while the testcock indicates if the oil level in the sump is sufficiently high.

Q. How can oil be introduced to the crankcase interior in emergencies?

A. Practically all power plants utilizing the constant level splash or manifold supply systems in which the oil is carried in a

container integral with the crankcase have a filler tube or funnel that communicates directly with the crankcase interior, through which the lubricating oil is poured. In some forms of power plant where the feed is by ind.vidual pump mechanical oilers that are set for normal operating conditions it is sometimes desirable to pro

vide a hand operated To Crank Case

pump of the simple plunger type that may

be used to draw oil from -From Auxiliary Tank an auxiliary tank and

force it to the crankcase interior in order to help

out the lubricating sysFig. 126.—Hand Pump Sometimes Used to tem under abnormal op

Inject Oil to Engine Base as an Auxil- erating conditions such iary to the Regular Lubrication System.

as speeding and long stretches of low speed gear work where the engine must run fast and pull hard. A simple form of oil pump adapted for this purpose is clearly outlined at Fig. 126.

LESSON THIRTEEN

COOLING THE GASOLINE ENGINE BY AIR

Q. Why is it necessary to cool the cylinder of a gas engine?

A. The rapid succession of explosions taking place in the combustion chamber, which means that temperatures higher than 2000 degrees F. exist at that point, temporarily causes the cylinder to become heated, and some method of absorbing the surplus heat must be provided.

Q. What part of the cylinder is hottest?

A. The combustion chamber or cylinder head is hotter than the rest of the cylinder because it is exposed directly to the hot gases at all times and is subject to the maximum temperature.

Q. What would be the effect on the valves, if the engine was not cooled?

A. If no provision was made for absorbing the excess heat present in the combustion chamber the inlet and exhaust valves would warp, the valve head seats would become burnt so these members could not hold compression and the stems would be liable to stick while in action.

Q. What would happen to the piston if cylinder was not cooled?

A. The piston would expand to such a point that it would have much friction in the cylinder and on account of the high temperature, which would burn away the lubricating oil, it would not be long before the piston would seize in the cylinder and perhaps become expanded by the heat to such a point that it could not move.

Q. Describe the possible methods of cooling.

A. Gas engine cylinders may be cooled by direct application of currents of air or by circulating water through a suitable jacket around the hot portions.

« НазадПродовжити »