Tractor Engine Parts

Tractor Engine Parts:

 Base or Frame
 Cylinder
 Cylinder head
 Piston
 Piston rings
 Piston pins
 Connecting rod
 Crankshaft
 Fly Wheel
 Valve System
 Fuel supply System
 Ignition System
 Cooling System
 Lubrication System
 Governing System

BASE or FRAME
 Made up of cast iron
 Other parts of engine are attached directly or indirectly
 Equipped with holes by which engine may be firmly anchored to its foundation
CYLINDER
 Made up of high grade gray  cast iron and may be attached with engine base or some time separate. In small size engines usually cylinders are attached with the base while in large size engines cylinders are detachable.
 Attaching a cylinder and base together produces a rigid construction but require greater outlay if cylinders are to be replaced when worn or damaged.
 If cylinders are not a part of the base but bolted to it, care should be taken to keep the bolts tight and retain the proper cylinder alignment all the time, it reduces breakage and wear.
 Cast iron: excellent heat retention iron
 Gray cast iron: Has graphite in its chemistry, auto-trop of carbon with high thermal conductivity
PISTONS:
 Made up of cast iron but aluminum alloy pistons are frequently used in multiple cylinders engines.
 Aluminum alloy offer the advantage of being lighter in weight and has greater co-efficient of thermal expansion.
 Piston move back and forth in cylinder owing to the explosion of the fuel mixture, this back and forth movement of the piston is transmitted through connecting rod and cranckshaft to the belt pully and thus power is generated.
 Piston clearance is the space between piston head and cylinder head, for cast iron pistons clearance is about 0.001 in. of the cylinder diameter.
 Too much clearance cause loss of compression
 Too little clearance cause the piston to seize in the cylinder as the engine gets hot
 A piston may seize in a cylinder even though it has the proper clearance but owning to lack of cylinder lubrication
Co-efficient of thermal expansion:
It is the change in the size of the object with the change in temperature

CYLINDER HEAD
 Made up of cast iron
 They are detachable from the cylinders but some time cast with it
 The detachable type of cylinder heads allow better accessibility and is more convenient to get to the valves and clean the carbon from the cylinder piston
PISTON PINS:
 Made up of hard steel
 It contact the connecting rod with the piston and provide a hinge like connection between the two
A hinge is a type of bearing that connects two solid objects, typically allowing only a limited angle of rotation between them

PISTON RINGS:
 Made up of cast iron
 The number of rings per piston varies from three to seven depending upon type of engine and the compression desired
 Ordinary type of engines seldom have three or four rings, but five or more rings are present in tractors or heavy duty engine
 Piston rings retain compression and reduce the cylinder wall and piston wall contact area to a minimum, thus preventing fraction losses and excessive wear
 Piston rings are classified as compression rings and oil rings depending upon their function and location on the piston

 Compression pins are plain one piece rings and are always placed in the grooves near the piston head. Oil rings are present in the lowest groove above the piston pin or near the piston skirt. It controls the distribution of the lubricating oil to the cylinder and piston

CONNECTING ROD:
 Connecting rod are made up of drop forged steel, it must be of some material that is neither brittle nor ductile
 The I-beam type is prevailing connecting rod shape, it gives strength with less weight and material
 That end of the rod fastened to the piston pin is known as the small end and the other end which is attached with to the crank shaft is spoken as large end of the connecting rod
 Drop forged: Motion of dropping hammer onto the hot steel or referred to the process in which super heated steel is formed into items such as tools etc
 



CRANKSHAFT:


 Made up of drop forged steel and carefully machined,  ground and polished at the journals.


 The journals that support the crankshaft and hold it in position are called main journals, whereas the part to which the connecting rod is attached is spoken of a crank journals





















FLYWHEEL:
 Made up of cast iron
 Assist in maintaining a uniform engine speed and provide a mean of balancing the engine properly
 Uniformity of the speed is maintained by the inertia of the heavy flywheel
VALVE SYSTEM:
 Each engine cylinder has at least two valves an intake and an exhaust valve.
 Intake valves are usually larger than the exhaust valves. The reason is that when intake valve is open the only force moving air fuel mixture or air is atmospheric pressure.
 The intake valve opens just before the intake stroke begins and allows the air fuel mixture to enter the cylinder.
 When the exhaust valve opens on the exhaust stroke, there is still high enough pressure in the cylinder to exhaust the gases outside the cylinder.
 The exhaust valve opens just before the exhaust stroke begins so that the burnt gases can escape the cylinder. For the Exhaust Valve, Chromium or Silicon is used which makes it resistant to corrosion due to high temperature and hot gases.
 Some engines have three valves per cylinder two for intake and one for exhaust, while in some engines four valves per cylinder two for intake and two for exhaust are present.

VALVE COOLING:
 The intake valve runs relatively cool. This is because the cool air-fuel mixture flows around the head of the intake valve. However, very hot exhaust gases flows around the head of the exhaust valve. As a result exhaust valve may become red in operation with temperature of upto 16000F.
 The engine cooling system cools the valves seat and stem. Coolant circulates through the water jackets in cylinder head. For the cooling purpose of exhaust valves some have hollow stems partly filled with metal sodium that keeps the exhaust valve cool.
 Valve Seat: The valve seat is a machined surface upon valve face rests when the valve is closed.
COOLING SYSTEM OF ENGINE:
 Temperatures in the combustion chamber of the engine can reach 4,500 F (2,500 C), so cooling the area around the cylinders is critical. Areas around the exhaust valves are especially crucial, and almost all of the space inside the cylinder head around the valves that is not needed for structure is filled with coolant. If the engine goes without cooling for very long, it can seize. When this happens, the metal has actually gotten hot enough for the piston to weld itself to the cylinder. This usually means the complete destruction of the engine.
 One interesting way to reduce the demands on the cooling system is to reduce the amount of heat that is transferred from the combustion chamber to the metal parts of the engine. Some engines do this by coating the inside of the top of the cylinder head with a thin layer of ceramic. Ceramic is a poor conductor of heat, so less heat is conducted through to the metal and more passes out of the exhaust.