Reciprocating Engine Design and Construction

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Reciprocating Engine Design and Construction
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Reciprocating Engine Design and Construction

• Basic Parts
• Crankcase
• Cylinders
• Pistons
• Connecting rods
• Valves
• Valve-operating mechanism
• Crankshaft
• Head
• Spark plugs

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Reciprocating Engine Design and Construction

• Crankcase
• Foundation of the engine, containing the bearings
  in which the crankshaft revolves.

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Reciprocating Engine Design and Construction

• Crankcase
• Tight enclosure for lubricating oil.
• Support for attachment of the cylinders and the
  powerplant to the aircraft.
• Must be rigid, strong and light.
• Cast of forged aluminum alloy.

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Reciprocating Engine Design and Construction

• Opposed Engine Crankcase

Bearings
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Reciprocating Engine Design and Construction

• Crankshafts
• Transforms the reciprocating motion of the piston
  and connecting rod into rotary motion for the
  propeller.

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Reciprocating Engine Design and Construction

• Crankshaft
• Backbone of engine.
• Forged from very strong alloy (Chromium-nickel-mol
  ybdenum steel).
• Single or multi-piece.

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Reciprocating Engine Design and Construction

• Crankshaft
• Four-throw used on four-cylinder engines.
• Six-throw used on six-cylinder engines.
• Three Main Parts
• Journal
• Crankpin
• Crankcheek

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Reciprocating Engine Design and Construction

• Crankshaft Balance
• Dynamic dampers are used to reduce vibration
  during engine operation.
• Pendulum which
• is fastened to the
• crankshaft.

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Reciprocating Engine Design and Construction

• Connecting Rods
• Link which transmits forces between the piston
  and the crankshaft.

Master and Articulated
Fork and Blade
Plain
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Reciprocating Engine Design and Construction

• Master and Articulated Rod Assembly
• Commonly used in radial engines.
• One piston in each row is connected to the master
  rod. Others are connected to the master rod by
  articulated rods.

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Reciprocating Engine Design and Construction

• Fork And Blade Assembly
• Used primarily in V-type engines.

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Reciprocating Engine Design and Construction

• Plain Type Connecting Rod
• Used in in-line and opposed engines.

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Reciprocating Engine Design and Construction

• Pistons
• Acts as a moving wall within the combustion
  chamber.

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Reciprocating Engine Design and Construction

• As the piston moves down it draws in fuel/air
  mixture.
• As it moves up it compresses the charge.
• Ignition occurs, and expanding gases force the
  piston down.
• This force is transmitted to crankshaft through
  connecting rod.
• On the return upward stroke, the piston forces
  the exhaust gas out.

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Reciprocating Engine Design and Construction

• Piston Construction
• Machined from aluminum alloy forgings.
• Grooves machined for piston rings.
• Cooling fins inside for
• greater heat transfer.
• Piston pin (wrist pin)
• joins the piston to the
• connecting rod.

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Reciprocating Engine Design and Construction

• Piston Types
• Trunk Type
• Slipper Type
• Not used in aircraft

Slipper
Trunk
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Reciprocating Engine Design and Construction

• Piston Rings
• Compression Rings
• Oil Control Rings
• Oil Scraper Rings

Rings
Pin boss
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Reciprocating Engine Design and Construction

• Compression Rings
• Prevent the escape of gas past the piston during
  engine operation.
• Number used depends on engine design.
• Cross section of the ring is either rectangular
  or wedge shaped

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Reciprocating Engine Design and Construction

• Oil Control Rings
• Placed in grooves immediately below the
  compression rings.
• One or more rings per piston.
• Regulate the thickness of the oil film on the
  cylinder wall.

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Reciprocating Engine Design and Construction

• Oil Scraper Ring
• Installed in the groove at the bottom of the
  piston skirt.
• Installed with the scraping edge away from the
  piston head or in the reverse position.
• Returns surplus oil to the
• crankcase.

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Reciprocating Engine Design and Construction

• Cylinders
• The portion of the engine in which the power is
  developed.
• Provides a combustion chamber where the burning
  and expansion of gases take place.
• Houses the piston and
• the connecting rod.

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Reciprocating Engine Design and Construction

• Cylinders
• Either produced singly or cast in a block.
• Air-cooled engine uses
• the overhead valve type.
• Two major parts Head,
• Barrel.

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Reciprocating Engine Design and Construction

• Cylinder Heads
• Provides a place for combustion of the fuel/air
  mixture.
• Gives the cylinder more heat conductivity for
  cooling.
• Contains the intake valve, exhaust valve and
  sparkplugs.
• Contains fins for cooling.

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Reciprocating Engine Design and Construction

• Cylinder Barrels
• Made of a steel alloy forging with the inner
  surface hardened to resist wear. (Nitrided)
• Worn Cylinder walls can be ground out and
  re-nitrided or chrome plated.
• Chrome plated cylinders can be recognized by
  orange paint mark on cylinder.

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Reciprocating Engine Design and Construction

• Cylinder Numbering (Opposed Engine)
• Propeller
• (Front)
• Accessory
• (Rear)
• Left, right
• (Pilots view)

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Reciprocating Engine Design and Construction

• Cylinder Numbering (Opposed Engine)
• Numbering is by no means standard.
• Continental starts from rear.
• Lycoming starts from front.

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Reciprocating Engine Design and Construction

• Cylinder Numbering (Radial Engine)

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Reciprocating Engine Design and Construction

• Cylinder Numbering (Radial Engine)
• Numbered clockwise as viewed from the accessory
  end.
• Single-row, cylinder No. 1 is the top cylinder.
• Double-row, all odd-numbered cylinders are in the
  rear, and all even numbered cylinders are in the
  front.

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Reciprocating Engine Design and Construction

• Firing Order
• The Sequence in which the power event occurs in
  the different cylinders.
• Designed to provide for balance and to eliminate
  vibration.

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Reciprocating Engine Design and Construction

• Firing Order Single-Row-Radial
• First all odd numbered cylinders fire in
  numerical succession.
• Then the even-numbered cylinders fire in
  numerical succession.
• 1-3-5-7-9-2-4-6-8

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Reciprocating Engine Design and Construction

• Firing Order Double-Row-Radial
• Arranged with the firing impulse occurring in a
  cylinder in one row and then in a cylinder in the
  other row.
• Two cylinders in the same row never fire in
  succession.

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Reciprocating Engine Design and Construction

• Firing Order Opposed Engine
• Lycoming and Continental number their cylinders
  differently which gives us two sets of firing
  orders.
• But the firing impulses are the same.

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Reciprocating Engine Design and Construction

• Firing Order Opposed Engine

1-4-2-3
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Reciprocating Engine Design and Construction

• Valves

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Reciprocating Engine Design and Construction

• Valves
• Fuel/air mixture enters the cylinders through the
  intake valve.
• Burned gases are expelled through the exhaust
  valve.
• Mushroom or tulip type depending on shape.

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Reciprocating Engine Design and Construction
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Reciprocating Engine Design and Construction

• Valve Construction
• Intake valves, because of lower operating
  temperatures, can be made of chrome-nickel steel.
• Exhaust valves are made of exotic metals such as
  inconel, silicon-chromium or cobalt-chromium
  alloys.

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Reciprocating Engine Design and Construction

• Valve Construction

Stem
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Reciprocating Engine Design and Construction

• Valve Construction
• Valve head has ground face which forms a seal
  against the ground valve seat in the cylinder
  head.
• Valve face ground to an angle of either 30 or
  45.
• Valve face made more durable by the application
  of stellite (an alloy of cobalt and chromium).

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Reciprocating Engine Design and Construction

• Valve Construction
• Valve stem acts as a pilot for the valve head and
  rides in the valve guide.
• Surface-hardened to resist wear.
• Some stems are hollow and partially filled with
  metallic sodium.

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Reciprocating Engine Design and Construction

• Valve Construction
• The neck is the part that forms the junction
  between the head and the stem.
• The tip is hardened to with stand the hammering
  of the valve rocker arm.

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Reciprocating Engine Design and Construction

• Valve Construction
• Machined groove near tip receives the split-ring
  keys which form a lock ring to hold the valve
  spring retaining washer.

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Reciprocating Engine Design and Construction

• Valve-Operating Mechanism
• Each valve must open at the proper time, stay
  open for the required length of time, and close
  at the proper time.
• Timing of the valves is controlled by the
  valve-operating mechanism.

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Reciprocating Engine Design and Construction

• Valve-Operating Mechanism
• Intake valves open just before the piston reaches
  top dead center, and exhaust valves remain open
  after top dead center.
• At this particular instant both valves are open
  at the same time (end of the exhaust stroke and
  beginning of the intake stroke).
• This valve overlap results in better volumetric
  efficiency and lower operating temperatures.

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Reciprocating Engine Design and Construction

• Valve-Operating Mechanism (Opposed engine)

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Reciprocating Engine Design and Construction

• Valve-Operating Mechanism
• (Radial engine)

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Reciprocating Engine Design and Construction

• Camshaft
• Valve-operating mechanism is operated by a
  camshaft.

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Reciprocating Engine Design and Construction

• Camshaft
• The camshaft is
• driven by a gear
• that mates with
• another gear
• attached to the
• crankshaft.

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Reciprocating Engine Design and Construction

• Tappet Assembly
• Converts rotational movement of the cam lobe into
  reciprocating motion.
• Transmits this motion to the push rod, rocker
  arm, and then to the valve tip.
• Opening the valve at the proper time.

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Reciprocating Engine Design and Construction

• Tappet Assembly

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Reciprocating Engine Design and Construction

• Hydraulic Valve Tappets
• Designed to automatically keep the valve
  clearance at zero.
• Ball check valve traps oil in the pressure
  chamber and.
• Acts as a cushion as the camshaft rotates.

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Reciprocating Engine Design and Construction

• Hydraulic Valve Tappets

PUSH ROD SOCKET
HIGH PRESSURE OIL SOURCE
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Reciprocating Engine Design and Construction

• Push Rod
• Transmits the force from the valve tappet to the
  rocker arm.
• Tubular form used because of its strength
• Permits lubricating oil to pass through the
  hollow rod to the ball ends.

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Reciprocating Engine Design and Construction

• Rocker Arms
• Transmits the lifting force from the cam to the
  valve.

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Reciprocating Engine Design and Construction

• Valve Springs
• Function is to
• close the valve
• and to hold the
• valve securely
• on the valve
• seat.

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Reciprocating Engine Design and Construction

• Valve Springs
• Two or more springs used to eliminate spring
  vibration or surging during different engine
  speeds.
• Held in place by split locks installed in the
  recess of the valve spring upper retainer washer.

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Reciprocating Engine Design and Construction

• Bearings

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Reciprocating Engine Design and Construction

• Bearings
• Any surface which supports, or is supported by,
  another surface.
• Composed of material that is strong enough to
  withstand the pressure imposed on it.
• Permit the other surface to move with a minimum
  of friction and wear.
• Lubricated bearings.

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Reciprocating Engine Design and Construction

• Bearings
• Three types of lubricated bearings used
• Plain Bearings
• Ball Bearings
• Roller Bearings
• Bearings are required to take radial loads,
  thrust loads, and a combination of the two.

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Reciprocating Engine Design and Construction

• Plain Bearings
• Used for crankshaft, cam ring, camshaft,
  connecting rods, and accessory drive shaft.
• Subjected to radial
• loads.
• Made of nonferrous
• metals.

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Reciprocating Engine Design and Construction

• Ball Bearings
• Used in supercharger impeller shaft bearings and
  rocker arm bearings.
• Special deep groove ball bearings are used in
  some aircraft engines to transmit propeller
  thrust to the engines nose section.

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Reciprocating Engine Design and Construction

• Roller Bearings
• Straight roller bearings used where the bearing
  is subjected to radial loads only.
• Tapered roller bearings used where bearing is
  subjected to both radial and thrust loads.

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Reciprocating Engine Design and Construction

• Propeller Reduction Gearing
• Turns the propeller at a slower speed than the
  engine.
• Increases propeller efficiency.
• Three types
• Spur Planetary
• Bevel Planetary
• Spur and Pinion

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Reciprocating Engine Design and Construction
Spur and Pinion
Spur Planetary
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Reciprocating Engine Design and Construction

• Propeller Shafts

Spline
Taper
Flange