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of lubrication. Medium bodied oils may be used successfully in summer while only light oils having a low cold test should be employed in winter.

Q. Outline main troubles with mechanical oilers.

A. The simplest form of mechanical oiling system is the constant level splash feed where an oil pump circulates the oil from the sump at the bottom of the crank case to the compartments in which the connecting rods dip. The main trouble with a system of this nature is failure of the pump or pump driving means or the filter screen mesh, that insures that the pump will only take in clean oil, becomes clogged with particles of lint, carbon or other substances,

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Fig. 290.—Top Half of Crankcase With Crankshaft in Place to Show

Main Bearings.

As these fill the mesh of the filter screen they prevent adequate quantities of oil passing through the system. When mechanical oilers of the individual pump type are used, a failure of the entire device to supply oil may be ascribed to a defect in the driving member, whereas if only one or two leads are at fault and the rest function properly the trouble is local and is probably due to faulty action of the inlet or discharge check valves on the small pumps supplying the leads through which no oil is passing. If the trouble is not in the pumps or their check valves, the pipe leading to the bearing should be taken off and cleaned out.

Q. What are main causes of overheating when thermosyphon cooling system is used?

A. If a motor employing a natural circulation system overheats, this condition can be ascribed more often to defective carburetion or lubrication than to poor cooling. If the trouble is due to the cooling system, practically the only thing that can occụr is constricting the bore of one of the rubber hose members interposed in the pipe line, as might be possible if the inner walls of the hose deteriorated and allowed particles of rubber or fabric to hang down into the hose. Sometimes the cylinders may be full of scale or rust or the radiator tubes may be clogged with similar material. The presence of scale or rust in the interior of the water jacket is not only apt to produce heating by impeding the flow of the cooling water, but it also lowers the efficiency of the cooling system because less heat is abstracted from the cylinder wall or combustion chamber sides if these members are coated with scale that keeps the water from being directly in contact with the heated metal.

Q. What are the main defects of a pump circulating system?

A. The main cause of overheating with a forced water circulation system of cooling is failure of the pump drive or some defect in the pump itself that prevents circulation. The pipes may be filled with sediment or scale or there may be accumulations of rust or sediment in elbows or similar connections included in the pipe line. One common defect that often causes overheating with either natural or forced circulation is failure of the fan driving belt.

If the radiator tubes are filled with scale, this material may be removed by filling the radiator with some solution adapted to cut the scale. In some sections of the country, hot washing soda solution will soften the accumulations, whereas the water in other districts makes it necessary to use some dilute acid instead. If the only running water available contains matter that will form scales it will be well for the motorist to use only distilled or rain water in the cooling system.

Q. How will defective lubrication cause heat?

A. If the cooling system is at fault and proper quantities of lubricant are not supplied to the cylinders, there will be much power absorbed in friction and wherever friction is present heat will always exist. An engine that is heating up unduly is generally one that is not lubricated properly or that is burning too rich mixture of gas if the trouble is not in the cooling system.

Q. How will defective mixture cause heat, and how is carburetor adjusted to overcome this condition?

A. A mixture that contains too much gasoline vapor will be slow burning and will have more heating value without producing correspondingly more power than one of proper proportions or having an excess of air. As combustion is not perfect, the engine will not deliver its full power and the surplus heat liberated every explosion must be absorbed by the cooling system. The carburetor adjustment varies with the type of instrument used, but as a general rule, the overheating may be reduced by either closing down the needle valve regulating the fuel supply so that less gasoline will be sprayed into the mixture or by opening the air valve to admit more air and thus dilute the rich gas.



Q. What are the main clutch troubles ?

A. The main clutch troubles are either harsh engagement, failure to release promptly, or slipping which means that the clutch will not transmit the full power of the engine.

Q. What is the main cause of slipping?

A. If a clutch is a cone type, as shown at Fig. 291, failure to drive properly is often due to a defective leather facing which may be either oil soaked so that it slips or glazed over so it does not have the proper amount of frictional adhesion with the female member. The spring holding the parts in contact may be weak or broken or the spring tension adjustment may have jarred loose and unscrewed so the spring does not exert sufficient pressure to keep the parts in proper frictional contact.

Q. What is the reason for harsh engagement?

A. If the clutch leather is dry or charred the clutch is apt to engage suddenly.

Q. What can be done to make the cone clutch engage easily?

A. If the leather facing is charred or worn too much it should be replaced with a new one, whereas if it has only become dry it may be softened by applying kerosene, neatsfoot or castor oil to the leather facing to soften it. Sometimes harsh engagement is due to defective or imperfect clutch design in which case it can only be eliminated by changing the clutch structure in some manner so that springs may be inserted under the leather or cork inserts may be applied in a clutch cone.

Q. What is an emergency treatment for slipping cone clutch?

A. If a clutch is slipping because of too much oil between leather facings and flywheel, the surplus lubricant may be absorbed

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Fig. 291.-Sectional View of Typical Leather-Faced Cone Clutch

Showing Points Where Deterioration Will Interfere With Proper
Clutch Operation.

by fuller's earth, talcum powder such as used for tires, or borax. Sand or gravel from the road should never be used because these substances are apt to cut the leather facing or destroy the smooth finish of a cast iron member.

Q. What should be done if a clutch fails to drive properly?

A. The first thing to look at is the condition of the leather surfaces and these should be brought to proper condition before anything else is done. The leather should be soft, springy and yet not too oily. If it is burnt or charred or glazed over, slipping is unavoidable. The clutch spring and fastenings should then be

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