Topic No. 2 Reciprocating Engine Construction

Crankcase, cylinders, pistons, connecting rods, valves, valve-operating mechanism, and crankshaft

Basic Major Components of Reciprocating Engine: CCPCR VVOMC

Crankcase

foundation of an engine

The two halves of crankcase

bearings and bearing supports

Crankcase

the _________ must provide a tight enclosure for the lubricating oil and must support various external and internal mechanisms of the engine.

sufficiently rigid and strong, misalignment

It must be _________ and __________ to prevent ___________ of the crankshaft and its bearings.

cast or forged aluminum alloy

used material for crankcase is made

it is light and strong

cast or forged aluminum alloy is used because?

nose or front

The shape of the _______ or _______ of the crankcase section varies considerably.

tapered/ round

The shape of the nose or front of the crankcase section

Cylinder Pads/Cylinder Mounting Pads

provides a suitable means of retaining or fastening the cylinders to the crankcase.

Cylinder Pads/Cylinder Mounting Pads

The machine surface on which the cylinders are mounted

opposed engine crankcase

crankcase that is consist of two halves of cast aluminum alloy that are manufactured either with sand castings or by using permanent molds.

radial engine crankcase

crankcase that are divided into distinct sections

nose section, power section, supercharger section, accessory section

NPSA: the radial engine crankcase separate into for main section

nose section

mounted in front of the radial engine crankcase bolts directly to the power section.

nose section

usually houses and supports a propeller governor drive shaft, the propeller shaft, a cam ring, and a propeller reduction gear assembly

main / power section

section of the crankcase where the reciprocation motion of the piston is converted to the rotary motion of the crankshaft

main / power section

supports crankshaft bearings, where cylinders are mounted.

crankcase diffuser supercharger section

located behind the power section and also called the fuel induction and distribution section

crankcase diffuser supercharger section

“fuel induction and distribution section”.

accessory section

section in the crankcase that houses the gear trains containing nothing spur and bevel type gears that drive various engine components and accessories

accessory section

It has mounting pads for fuel pump, oil pump, tachometer generators etc.

crank shaft

backbone of the reciprocating engine

crank shaft

main purpose is to transform the reciprocating motion of the piston and connecting rod into rotary motion for the rotation of the propeller.

chromium-nickel molybdenum steel

CNMS: very strong alloy material use for the crankshaft

journal, crankpin, crank cheek/ crank arm,

JCCA: three main parts of the crankshaft

journal

center of rotation of the crankshaft

crankpin

section to which the connecting rod is attached

crank cheek/ crank arm

connects the crank pin to the journal

crankshaft that is not balanced

excessive vibration is cause by the:

counter weight, dampers

usually attached to reduce vibration in the crankshaft

dynamic damper

consist of movable slotted-steel counterweight attached to the crankshaft

Cylinder

portion of the reciprocating engine where power is developed

aluminum alloy

cylinders generally made of:

cylinder head, cylinder barrel

two major parts of a cylinder

cylinder head

provides a place for combustion of fuel/air mixtures

cylinder head

contains the intake valve, exhaust valve, sparkplugs

sparkplugs

stainless steel heli-coil

Nitriding

is a thermochemical process in which the surface of a ferrous metal, such as steel, is enriched with nitrogen. Corrosion resistant

Chroming

is a process that plates chromium on the surface of the cylinder barrel and brings it back to new standard dimensions

valves

where the fuel and air mixture enters the cylinder

mushroom/ tulip

valves are also typed by their shape and are called:

chromic-nickel steel

material for the intake valve, operates at lower temperature

nichrome, silchrome, cobalt-chromium steel

material for the exhaust valve, more heat resistant: -chrome NSCCS

valve head, valve seat, valve face, stem

four major parts of the valve

valve head

ground face that forms a seal against the ground valve seat in the cylinder head

stellite

material made of by the valve faces

walve stem

acts as a pilot for the valve head and rides in the valve guide

metallic sodium

Exhaust valve stems are hollow and partially filled with:

the piston reaches top dead center on the exhaust stroke

intake valve open when:

after top dead center on as the cylinder begin its intake stroke

exhaust valve open when:

valve overlap

both valves are open at the same time

valve timing

this timing of valve is controlled by the valve operating mechanism

valve lift

distance that the valve is lifted off its seat

valve duration

length of time the valve is held open

cam rings

revolves causing the cam rollers to raise the tappet in the tappet guide

cam lobe

bump area

cam shaft

valve mechanism of an opposed engine is operated by:

tappet/ valve lifter

converts the rotational of the cam lobe into reciprocating motion

tappet spring

reduces the shock load when the valve is open

solid lifters/ cam follower

valve clearance

push rod

transmit the lifting force from the cam shaft to the rocker arm

rocker arm

transmitting the lifting force from the rods to the valve

piston

cylindrical member that moves back and forth within a steel cylinder

piston pin

joins the piston to the connecting rod, and sometimes called wristpin, gudgeon pin

piston rings

prevent leakages of gas pressure from the combustion chamber. Major components, Compression ring, oil control ring

compression rings

prevent the gases from escaping past the piston during engine operation

oil control ring

regulates the thickness of oil film on the cylinder wall

connecting rods

the link that transmit forces between the piston and the crankshalf

plain-type connecting rod
fork and blade rod assembly
master and articulated rod assembly
split type connecting assembly

4 types of connecting rod assemblies

Propeller Shaft/ accessory rear section

connecting the propellers from the crank shaft

Gear train

containing both spur and bevel type gears used in different types of engine

spur-type gears

to drive heavier load accessories

Bevel gear

permit angular location of short stub shaft

sumps

used to collect oil circulating the engine

wet sump engine

use the sump as storage tank for oil

dry sump engine

store oil in a remote tank

induction system

brings in are from the outside and delivers the fuel air mixture to the cylinder head where combustion occurs.

exhaust system

collects and disposes of high temperatures gases being discharged by the engine.