The document summarizes various reciprocating engine components, including: - The crankshaft which converts reciprocating motion to rotational motion to drive the propeller. - Pistons made of aluminum alloy with rings to provide a seal in the cylinder. - Connecting rods which link the piston to the crankshaft. - The camshaft which uses lobes to open and close the valves via other components like lifters and pushrods.

1. Reciprocating Engine Components By Pat McCarty

4. 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 Changes reciprocating motion of pistons into rotating motion to drive propeller Constructed of chrome-nickel-molybdenum-steel May be one piece or as many as three separate pieces The propeller mounts to the front of the crankshaft using a spline, taper, or flange 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

9. Crankshaft Ends For Mounting Propellers

10. Dynamic Dampers can be mounted to the crankshaft to reduce vibration (floating) Counterweights are also used to reduce vibration but they are rigid and do not float Counterweights and dampers 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 The engine is also mounted in rubber bushings to absorb vibration

12. 2 Piece Crankshaft With Counterweights (Single Throw, Single Cylinder)

13. Crankshaft Main Bearing Journal, Pin, Arm

18. Engine Parts, Description, Function, Construction 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. Engine Parts, Description, Function, Construction Cylinder interior wall Cylinder Walls

20. Engine Parts, Description, Function, Construction Chrome cylinder walls use chromium plating to resist wear and provide a corrosion resistant surface. Cylinders may be chromed back to standard inside dimensions if they become worn Chrome is too smooth to hold oil without etching or channeling during the overhaul process

21. Engine Parts, Description, Function, Construction The cylinder head is designed to transfer heat by conduction to the fins and then from the fins to the air by convection The exhaust side of the head has the most fins as it runs the hottest The head also may incorporate a drain line fitting to allow excess oil to return to the crankcase (intercylinder drain lines on radials)

22. Engine Parts, Description, Function, Construction Cylinder Walls Inside surface of cylinder barrel is honed to a controlled amount of roughness Rough enough to hold oil film but smooth enough to minimize friction and wear Plain steel cylinder walls are not treated to prevent wear or corrosion Nitrided cylinder walls are hardened to reduce wear but still rust as easily as plain steel walls. Nitriding is exposing the cylinder wall to ammonia at high temperatures and it hardens the wall to a thickness of approximately .005”

23. Engine Parts, Description, Function, Construction Cylinder wall “CHOKE” The cylinder wall is tapered inward towards the top so that as the engine warms up, the hotter top of the wall expands more than the bottom, creating a round barrel at operating temperature.

24. Engine Parts, Description, Function, Construction Cylinder heads Constructed of cast aluminum Provides combustion chamber, and mounting areas for spark plugs and valve parts

25. Cylinder Valve Mechanism

27. Valve and Guide Head Tulip Mushroom Semi Tulip Flat Heat

29. Valve and Guide Stem Hardened Steel Metallic Sodium filled is a chemical element which has the symbol Na (Latin: natrium), atomic number 11, atomic mass 22.9898 g/mol, common oxidation number +1. Sodium is a soft, silvery white, highly reactive element and is a member of the alkali metals within "group 1" (formerly known as ‘group IA’). It has only one stable isotope ,

30. Valve and Guide Face Stellite alloy is a range of cobalt - chromium alloys designed for wear resistance. It may also contain tungsten and a small but important amount of carbon . It is a trademarked name of the Deloro Stellite Company and was invented by Elwood Haynes [1] in the early 1900s as a substitute for flatware that stained (or that had to be constantly cleaned).

31. Valve Tip Stellite Split Key Safety Circlet Spring Rotator

32. Valve Springs Inner and outer springs are used to prevent bounce, provide redundancy, and increase valve closing pressure Held in place by retainer washers on the top and bottom of the spring Split key or “keeper” holds the retainers and springs in place on the valve stem

33. Cylinder Valve Mechanism

34. Cylinder Valve Mechanism

35. Valves and the Valve System Valves control the flow of gases inside the engine Poppet valves are the most common and get their name from the popping open and closed during operation Intake valves are chrome steel and are cooled by the incoming air and fuel mixture Exhaust valves are also alloy steel but are often filled with metallic sodium for cooling. Valve faces may be coated with Stellite to reduce wear and corrosion Valve faces are ground to 30 degrees for intake (airflow) and 45 degrees (cooling) for exhaust

36. 1290 degrees F (typical)

38. Cylinder Valve Removal

39. Cylinder Valve Mechanism

40. Cylinder Valve Mechanism

56. Crankcase 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)

57. 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)

58. Pistons Constructed of aluminum alloy ALCOA132 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

60. Cam ground pistons diameter of the piston is greater perpendicular to the piston pin boss This compensates for uneven expansion during operation (becomes round at operating temperature)

62. Piston head designs

63. Piston rings (general) 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 rings are located at the top of the piston and seal the combustion chamber Types include rectangular, tapered,wedge

64. Compression rings

65. Oil control rings On bottom of piston below compression rings Regulates oil film thickness on cylinder wall Holes in ring and piston allow excess oil to drain back to crankcase Too much oil film and the engine will use excessive oil and too little oil causes heat and insufficient lubrication Oil scraper rings Directs the oil away from or towards the oil control rings depending upon the requirements of the engine

66. Piston ring end gap The gap at the end of the rings allows for expansion and contraction and unevenness in the cylinder wall Butt, step and angle types Always stagger the end gaps during ring installation to prevent losing compression

67. Piston Pins (wrist pins) Connects the piston to the end of the connecting rod Constructed of hardened steel The pin is retained in the piston with clips or plugs to prevent cylinder wall scoring Typical Lycoming and Continental pins are free-floating, meaning the pin is not secured to the piston or the rod.

69. Connecting Rod Assembly The link between the crankshaft and the piston Normally steel but some low powered engines use aluminum to save weight Cross section is an “H” or “I” Types include : Plain Rod Fork and blade rod Master and articulated

70. Plain Type Rods Used on inline and opposed engines Small bushing at piston pin end is pressed in place and reamed to final dimensions Large end of rod includes a cap, bolts, nuts, and plain bearing inserts Rods are numbered as to cylinder and for cap-to-rod alignment

71. Fork and Blade Connecting Rod Used on “V” type engines One rod inside another allows cylinders to be aligned and to share a common location on the crankshaft

72. Master and Articulating Rod Used on radial engines Uses “knuckle pins” to retain articulated rods to master Master Rod Articulating Rod

73. Master/Articulating Rod in Action

74. Valve Train Cam Shaft

76. Valve Train Cam Shaft

77. Valve Train Cam Shaft

78. Valve Train Cam Shaft

79. Valve Train Cam Shaft

80. Valve Train Cam Shaft

81. Valve Lifter or Tappet May be solid, roller, or hydraulic The lifter follows the cam lobes and pushes on the pushrod Solid and roller lifters require adjustable rocker arms Hydraulic type lifters fill with oil and lengthen to compensate for any clearances in the valve system

82. Continental lifter

84. Lifter Damage

85. Lifter Damage

86. Lifter Damage

87. Camshaft Turns at 1/2 the speed of the crankshaft 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

88. Pushrod transmits push of lifter up to rocker arm Hollow to allow oil to flow to the top of the cylinder for valve part lubrication Length can be varied to adjust valve clearance Valve clearance is the space between the top of the valve stem and the rocker arm. This clearance is to prevent a valve from being held open with the resulting heat build-up and loss of compression valve clearance increases as the engine operates due to cylinder expansion (solid lifters) Hydraulic lifters have a “0” clearance in operation

89. Valve clearance adjustment Valve clearance measurement

90. Rocker Arm Adjustable in solid lifter engines and fixed in engines with hydraulic lifters One end rests on the valve stem and the other on the pushrod Rocking motion opens and closes the valves Roller rocker arms incorporate a roller that reduces friction and are used in some radials and experimental engines

91. Bearings Must be able to withstand forces inside an engine with minimal friction and heat build- up. Must accept radial and thrust loads Plain Bearings A steel insert with babbitt (lead alloy) bonded to the bearing surface Plain bearings are keyed to keep them in place A lip or flange allows the plain bearing to accept thrust loads Commonly used as crankshaft and rod bearings in opposed engines

93. Normal Lycoming main bearing wear. Symmetrical pattern - side to side and end to end. Crankshaft is running true in bearing. I call such a pattern a "hour-glass" pattern.

94. Main bearing wear. Contact occurs only on upper half of bearing. Crankshaft is not running true in bearing. Either crankshaft is bent or crankcase journals are mis-aligned

95. Fatigue failed Lycoming 320 main bearing. Contact pressure from the crankshaft seems to be more concentrated and concentrated at the lower edge.

96. Damage or wiping at the center has to form before a hydrodynamic film is formed - an indicator of a dry start!

97. Breakdown of oil film Severe abnormal main bearing wear located at right side of bearing and the bottom edge. The pattern on the right is called "wiping"

98. early sign of bearing failure may be drop off of idle oil pressure or momentary loss of propeller control

99. Roller Bearings (antifriction) Hard steel rollers captured between an inner and outer “race” and held in alignment by a “cage” May be tapered to absorb radial and thrust loads or straight to absorb radial loads only

100. Parts of a Ball Bearing OUTER RACE INNER RACE CAGE BALL

101. Ball Bearings (antifriction) Used for both radial and thrust loads Deep grooves in races allow thrust loads

102. Bearing cleaning and safety Wash old grease and debris with solvent Blow dry with shop air but do not spin the bearing with the air blast Reapply grease or oil immediately to prevent corrosion Protect skin and eyes from solvent contact

103. Propeller Reduction Gearing Purpose is to reduce propeller rpm to its optimal speed and to increase engine rpm to its optimal speed Propeller always turns slower than the engine Gear Ratios: Expressed as 2:1, .64:1, 300:1 At what speed will the propeller be turning if the engine rpm is 2000 and the gear ratio is 2:1? 1000 rpm

104. Which reduction ratio will provide the fastest propeller speed 10:1 or 4:1? 4:1 (it is the closest to 1:1) Spur Gears Simple drive and driven gear system Number of teeth on gear and gear diameters determine reduction ratio Large gear would be mounted to propeller as it turns the slowest

105. Planetary Gears Ring gear, Planet gear, Sun gear Large gear reductions possible Compact and versatile Common in large radials and turbine engines