2. Crankcase
⢠The crankcase is that part of the engine block below the cylinders. It supports and
encloses the crankshaft and provides a reservoir for the lubricating oil.
⢠The crankcase holds all of the engine parts in alignment and supports the cylinders and
crankshaft
⢠It provides a place to mount the engine to the aircraft
⢠Constructed of aluminum alloy
⢠Divided into sections (radial)
3. Crankcase
⢠Nose section - Houses prop shaft and bearings
⢠Power section - mount for cylinders
⢠Fuel induction section - intake tubes, blower, manifolds (supercharger)
⢠Accessory section - mounts for magnetos, pumps, generators (magnesium)
4. Crankcase
⢠Opposed crankcase
⢠Sections are not as distinct as in the radial and the crankcase splits from front
to rear instead of in radial sections
6. Crankshaft
⢠Constructed of chrome-nickel-molybdenum-steel
⢠May be one piece or as many as three separate pieces
⢠The crankshaft rotates within the crankcase and is supported by main bearing journals
⢠Crankshaft throws or crankpins are off center and account for the reciprocating motion of
the pistons
8. Crankshaft
⢠Counterweights are used to reduce vibration but they are rigid
⢠Counterweights are used in piston engines because the power pulses and
movement of the pistons create large amounts of vibration
⢠Vibration shortens airframe and engine life and can lead to premature
component failure
9. Crankshaft
⢠2 Piece Crankshaft With Counterweights (Single
Throw, Single Cylinder)
11. Camshaft
⢠Used to open the valves for intake and exhaust
⢠Must be mechanically coupled to the crankshaft for timing purposes (gears,
belts, chains)
⢠The camshaft consists of bearing journals and lobes spaced along the shaft
⢠Each lobe is positioned to open and close a valve at a specific time
Lobe
13. Sump
⢠reservoir for the lubricating oil.
⢠A wet sump is a lubricating oil management design for piston engines which uses
the crankcase as a built-in reservoir for oil.
⢠Piston engines are lubricated by oil which is pumped into various bearings, and
thereafter allowed to drain to the base of the engine under gravity.
⢠A wet sump offers the advantage of a simple design, using a single pump and no
external reservoir.
15. Accessory gearbox
⢠The accessory drive gearbox is most often attached directly to the outside cases of the
engine at or near the bottom.
⢠The accessory gearbox is driven the crankshaft of the engine.
⢠The gearbox has attachment pads on it for accessories that need to be mechanically driven.
17. Cylinder Barrel
⢠Chrome-molybdenum or nickel-molybdenum steel
⢠Used to guide and seal piston and to mount cylinder assembly to head
⢠Barrel threads into head to form cylinder assembly
19. Cylinder head
⢠Cylinder heads
⢠Constructed of cast aluminum alloy
⢠Provides combustion chamber, and
mounting areas for spark plugs and
valve parts
20. Cylinder head
⢠The cylinder head is designed to transfer heat by conduction to the
fins and then from the fins to the air by convection
22. Piston
⢠Constructed of aluminum alloy
⢠Parts include top, ring grooves, ring lands, skirt, and piston pin boss
⢠Cooling fins on the bottom help the oil carry heat away from the piston top
24. Ring
⢠Provide seal between cylinder wall and piston
⢠Rings ride on a thin film of oil
⢠Conduct heat from the piston out to the cylinder and the fins
⢠Material is cast iron or chrome steel
⢠Piston rings (type)
⢠compression ring is to prevent gases from leaking by the piston during the
compression and power strokes.
⢠The oil ring, usually located just above the piston pin,it is an oil-regulating ring.
This ring scrapes the excess oil from the cylinder walls and returns some of it,
through slots, to the piston ring grooves.
25. Ring
⢠The gap at the end of the rings allows for expansion and contraction
and unevenness in the cylinder wall .
⢠Always place the end gaps during ring installation away from each
other to prevent losing compression.
27. Piston Pin
⢠The piston is attached to the connecting rod by the piston pin (wrist pin).
⢠Piston pins are made of alloy steel with a precision finish
⢠They are lubricated by splash from the crankcase or by
pressure passages bored in the connecting rods
⢠The pin is retained in the piston with clips or plugs to prevent cylinder wall scoring
28. Piston Pin
⢠Three methods are commonly used for fastening a piston pin to the piston and the
connecting rod
30. Connecting Rod
⢠Connecting Rod Assembly
⢠The link between the crankshaft and the piston
⢠Normally steel but some low powered engines use aluminum to save weight
⢠Types include : Plain Rod
Fork and blade rod
Master and articulated