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Engine Parts, Description, Function, Construction

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Engine Parts, Description, Function, Construction Cylinder Barrel Chrome-molybdenum or nickel-molybdenum steel Used to guide and seal piston and to mount cylinder ... – PowerPoint PPT presentation

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Title: Engine Parts, Description, Function, Construction


1
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2
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

3
Engine Parts, Description, Function, Construction
Cylinder Walls
Cylinder interior wall
4
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

5
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

6
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.

7
Engine Parts, Description, Function, Construction
  • Cylinder heads
  • Constructed of cast aluminum
  • Provides combustion chamber, and mounting areas
    for spark plugs and valve parts


8
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)

9
Engine Parts, Description, Function, Construction
  • Valve Guides
  • Made of bronze
  • Secured in the head by an interference (shrink)
    fit
  • Valve Seats
  • Made of chrome steel, stellite, or brass
  • Secured by interference fit

10
  • 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)

11
  • 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)

12
  • Opposed crankcase
  • Sections are not as distinct as in the radial and
    the crankcase splits from front to rear instead
    of in radial sections

13
  • Pistons
  • 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

14
  • 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)

15
  • Piston head designs

16
  • 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

17
  • Compression rings

18
  • 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

19
  • 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

20
  • 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.

21
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22
  • 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

23
  • 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

24
  • 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

25
  • Master and Articulating Rod
  • Used on radial engines
  • Uses knuckle pins to retain articulated rods to
    master

Master Rod
Articulating Rod
26
Master/Articulating Rod in Action
27
  • 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

28
Crankshaft Main Bearing Journal, Pin, Arm
29
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30
Crankshaft Ends For Mounting Propellers
31
  • 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

32
  • 2 Piece Crankshaft With Counterweights
    (Single Throw, Single Cylinder)

33
  • 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

34
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35
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36
1290 degrees F (typical)
37
  • 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

38
  • 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

39
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40
  • 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
41
  • 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

42
Valve clearance adjustment
Valve clearance measurement
43
  • 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

44
  • 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

45
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46
  • 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

47
  • Parts of a Ball Bearing

BALL
CAGE
INNER RACE
OUTER RACE
48
  • Ball Bearings (antifriction)
  • Used for both radial and thrust loads
  • Deep grooves in races allow thrust loads

49
  • 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

50
  • 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 21, .641, 3001
  • At what speed will the propeller be turning if
    the engine rpm is 2000 and the gear ratio is 21?
  • 1000 rpm

51
  • Which reduction ratio will provide the fastest
    propeller speed 101 or 41?
  • 41 (it is the closest to 11)
  • 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

52
  • Planetary Gears
  • Ring gear, Planet gear, Sun gear
  • Large gear reductions possible
  • Compact and versatile
  • Common in large radials and turbine engines
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