Piston engine construction, parts and materials.

1. Reciprocating engine components

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

5. Crankshaft

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

7. Crankshaft

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)

10. Camshaft

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

12. Sump

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.

14. Accessory gearbox

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.

16. Cylinder barrel

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

18. Cylinder head
• Valve
• Spark plug

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

21. Piston

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

23. Ring

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.

26. Piston Pin

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

29. 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