CONTENT A. LUBRICATION LUBRICATION SYSTEM 1. Lubrication Purpose The engine is comprised by many moving parts. Without lubrication, these parts will break
caused by heat from the friction. The purpose from lubrication is to compose oil coating on the surface which affected by friction to decrease friction and heat effect because moving of the parts, also to protect usage from damage. With existence of lubrication, the engine operated with smooth. 1. Anti-fr Anti-frict iction ion ffe ffect ct !f both of moving moving hard things be in contact, the surfaces which being in contact contact occur the friction. The surfaces which rub against are looked soft, but in fact both of the surfaces surfaces are crude if seen with microscope. microscope. ven if the surface which being in contact is very soft, the friction is caused by among both of hard things which being in contact directly. To decrease this friction, the oil coating is needed by the surfaces which being in contact. ". #oolin #ooling g ffec ffectt $riction is caused by heat. %ike cylinder and piston which doing combustion of gas and obtaining heat. %ubricant oil release heat and assisting to eliminate heat. &ot oil which to be made cool is used to cool down again. '. (eal (ealin ing g ffect ffect #ylinder is compressed by ring piston which attached at the piston. %ubricant oil is flowing to the ring piston to compose good seal between cylinder-wall and piston, so the gas and compressi compression on leakag leakagee can be preven prevented ted.. This This seal is very very effecti effective ve to rotating lubrication of oil. ). *uffer *uffer ffect ffect +ispersi +ispersion on ffect ffect *all bearing, roller bearing, and gear which sustaining heavy payload is concentrated on certain point. #onnecting-rod taking a heavy beat on the small and big back part. !f these these parts parts take take a beat beat repeat repeatedly edly,, the metal fatigu fatiguee will will happen happen.. %ubri %ubrican cantt oil is extending the pressure area to decrease the width of burden per unit and extending the blow. 5. ust-inhibiting ffect The oil is composing the flimsy coat to maintain the metal surface from air, water, and gas corrosive which causing rust.
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The oil pressure from pump is flowing to engine and maintain dusty metal, oxides, and hydrocarbon, so the friction surface can keeps cleaning. $or this lubrication, oil filter is needed. 2. Twostro!e En"ine Lubrication 0ot like four-stroke engine, combustion chamber and crankcase of two-stroke engine is apart with transmission. Therefore, engine and transmission system are lubricated separately. #. $ourstro!e En"ine Lubrication 0ot like two-stroke engine, four-stroke engine have separate crankcase from combustion chamber which each it is closed. *ut, crankcase chamber also used by transmission chamber. Therefore, the crankshaft is lubricated by same oil which used for clutch and transmission. il is given directly by oil pump. #ylinder and piston is lubricated by oil which lubricating crankpin and connecting-rod. At other side, the valve which attached on the cylinder-head also lubricated by oil which given by oil pump. After lubricate, oil is back to oil chamber. %. Oi& Lubricant The reason for lubrication at every parts of engine is to decrease and increase efficiency of engine, at the same time also preventing damage which effect from usage.
B. COOLIN' SYSTEM The temperature of engine will increase if engine in a working condition. The heat is emerged by combustion process and the frictions that happen caused by high engine rotation. !f lubrication or cooling is not functioning, then the expansion of parts will happen and stagnation is emerging. !n making design an engine, a calculation of material, parts form, and accepted burden is needed beforehand, so it2s can according to heat that happen by calculate on effectiveness of cooling system. The cooling system is classified by two method, air cooling system and water cooling system. (. Air Coo&in" S)ste* #ooling system which exploiting air, it construction more simple. There are two type of this cooling system.
1. 0atural Air #ooling (ystem The position of engine is at the open place, so the air is flowing freely. The surface of engine which will be made cool is added by fins. !n order that cooling more effective, fins is directed in the same direction of air stream. This system is usually used at motorcycle. ". $orce Air #ooling (ystem 2
!f position of engine is at the closed place, force air cooling system is more effective. This cooling system is using fan which moved by engine, and air is flowed from fan to the cylinder and cylinder head. $or cooling effectiveness, air is flowed in the same direction of fins direction. This system is usually used at scooter. 2. +ater Coo&in" S)ste* This system is using closed stream +water 3acket which flowing at part of cylinder and cylinder head. After the water taking heat from engine, water flowing back to the radiator to be made cool by air. $urthermore, it is flowed again to the cylinder head and cylinder body. There are two path of stream at this system4 first, water is circulated with water pump, other stream 50atural #irculation6 which water is only circulated without passing the thermostat path. The function of thermostat is to close water stream, so water not flowing to the radiator directly. !ts purpose is in order that heat of engine obtained 7uickly +Warming 8p. After heat of engine is fulfill, the thermostat opened automatically, so water flowing to the radiator to be made cool. The engine with big capacity is using this cooling system.
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