Reciprocating Engine Construction Flashcards
foundation of an engine; usually made in two halves
crankcase
contains the bearings and bearing supports in which the cranshaft revolves
crankcase
Besides supporting itself, the crankcase must provide a _________ for the lubricating oil and must support various external and internal mechanisms of the engine
tight enclosure
Crankcase also provides support for attachment of the cylinder assemblies, and the _______ to the aircraft.
powerplant
A crankcase must be sufficiently rigid and strong to prevent _____________ and its bearings.
misalignment of the crankshaft
__________ is generally used for crankcase construction because it is light and strong.
cast or forged aluminum alloy
It is subjected to may variations of mechanical loads and other forces.
crankcase
Since the cylinders are fastened to the crankcase, the tremendous forces placed on the cylinder tend to _____________.
pull the cylinder off the crankcase
The unbalanced centrifugal and inertia forces of the crankshaft acting through the main bearings subject the crankcase to ______ which change continuously in direction and magnitude.
bending moments
The crankcase must have sufficient ______ to withstand these bending moments without major deflections.
stiffness
The shape of the nose or front of the crankcase section varies considerably, it is either _______ or ____>
tapered, round
The machined surfaces on which the cylinders are mounted are called ______ or ______.
cylinder pads, cylinder mounting pads
They are provided with a suitable means of retaining or fastening the cylinders to the crankcase.
cylinder pads, cylinder mounting pads
The general practice in securing the cylinder flange to the pad is to mount ______ in threaded holes in the crankcase.
studs
The inner portion of the cylinder pads are sometimes chamfered or tapered to permit the installation of a ________ around the _______, which effectively seals the joint between the cylinder and the crankcase pads against oil leakage.
large rubber O-ring, cylinder skirt
Types of engine crankcases
opposed engine crankcase, radial engine crankcase
A typical horizontally opposed engine cranckase consists of two halves of cast aluminum alloy that are manufactured either with ______ or by using ______.
sand castings, permanent molds
Radial engine crankcases are divided into distinct sections. The number of sections can be as few as _____ or as many as ______ depending on the size and type of engine.
three, seven
Four main sections of a typical radial engine crankcase
nose section, power section, supercharger section, accessory section
It is mounted at the front of a radial engine crankcase and bolts directly to the power section.
Nose section
It usually houses and supports a propller governor drive shaft, the propeller shaft, a cam ring, and a propeller reduction gear assembly if required.
nose section
It represents the section of the crankcase where the reciprocating motion of the pistons is converted to the rotary motion of the crankshaft; supports cranshaft bearings, where cylinders are mounted.
main or power section
It is located behind the power section and is generally made of cast aluminum alloy or magnesium.
diffuser or supercharger section
This section houses the supercharger and its related components; provides housing for attachments of induction pipes and manifold pressure lines.
diffuser or supercharger section
The diffues or supercharger is also called as “________.”
fuel induction and distribution section
It houses gear trains containing both spur- and bevel-type gears that drive various engine components and accessories; has mounting pads for fuel pump, oil pump, tachometer generators, etc.
accessory section
It is a shaft composed of one or more cranks located at specified points along its length.
crankshaft
The ____ or ____ are formed by forging offsets into a shaft before it is machined.
cranks, throws
Since crankshafts must be very strong, they generally are forged from a very strong alloy, such as ___________.
chromium-nickel-molybdenum steel
The crankshaft is carried in a position parallel to the _______ axis of the crankcase and is generally supported by a main bearing between each throw.
longitudinal
The crankshaft main bearings must be supported rigidly in the crankcase, usually accomplished by means of ______ in the crankcase, one for each main bearing.
transverse webs
The ________ form an integral part of the structure and, in addition to supporting the main bearings, add to the strength of the entire case.
transverse webs
A cranshaft may be of _____ or ____ construction.
single-piece, multi-piece
The _____ construction may be used either on four cylinder horizontal opposed or four-cylinder inline engines.
four-throw
The _____ shaft is used on six-cylinder inline engines, 12-cylinder V-type engines, and six-cylinder opposed engines.
six-throw
Cranshafts of radial engines may be the _____, ____< or _____ type, depending on whether the engine is the single-wor, twin-row, or four-row type.
single-throw, two-throw, four-throw
Three main parts of crankshaft
journal, crankpin, crank cheek/crank arm
_______ and _____, although not a true part of a crankshaft, are usually attached to it to reduce engine vibration.
counterweights, dampers
The ______ is supported by, and rotates in, a main bearing. It serves as the center of rotation of the crankshaft. It is surface-hardened to reduce _____.
journal, wear
The ______ is the section to which the connecting rod is attached.
crankpin
The crankpin is off-center from the main journals and is often called the _____.
throw
What makes a throw?
two crank cheeks and a crankpin
When a force is appiled to the crankpin in any direction other than parallel or perpendicular to and through the center line of the crankshaft, it causes the crankshaft to ______.
rotate
The crankpin is usually ______ which reduced the total weight of the crankshaft and provides a passage for the transfer of lubricating oil.
hollow
The outer surface is hardened by ______ to increase its resistance to wear and to provide the required bearing surface.
nitriding
It connects the crankpin to the main journal.
crank cheek
In some designs, the cheek extends beyond the journal and carries a _______ to balance the crankshaft.
counterweight
The crank cheek must be of sturdy construction to obtain the required rigidity between the ______ and the _____.
crankpin, journal
In all cases, the type of crankshaft and the number of crankpins must correspond with the _______ of the engine.
cylinder arrangement
The position of the cranks on the crankshaft in relation to the other cranks of the same shaft is expressed in _____.
degrees
The simplest crankshaft is the single-throw or _____ type.
360 deg
This type is used in a single-row radial engine and can be constructed in one or two pieces.
single-throw or 360 deg type
Two main bearings, one on each end, are provided when this type of crankshaft is used.
single-throw or 360 deg type
The _______ or _____ crankshaft is used on double-row radial engines. In the radial-type engine, one throw is provided for each row of cylinders.
double-throw, 180 deg
_______ in an engine not only result in fatigue failure of the metal structures, but also causes the moving parts to wear rapidly.
excessive vibration
In some instances, excessive vibration is caused by a crankshaft that is not ______.
balanced
Crankshafts are balanced for _____ and ______.
static balance, dynamic balance
A crankshaft is _______ when the weight of the entire assembly of crankpins, crank cheeks, and counterweights is balanced around the axis of rotation.
statically balanced
A crankshaft is __________ when all the forces created by crankshaft rotation and power impulses are balanced within themselves so that little or no vibration is produced when the engine is operating.
dynamically balanced
To reduce vibration to a minimum during engine operation, _____ are incorporated on the crankshaft.
dynamic dampers
A _______ is merely a pendulum that is fastened to the crankshaft so that it is free to move in a small arc. It is incorporated in the _________.
dynamic damper, counterweight assembly
In a dynamic damper, the difference in the diameter between the pins and the holes provides a ______.
pendulum effect
The portion of the engine in which the power is developed is called the ______.
cylinder
The cylinder provides a ________ where the burning and expansion of gases take place, and it houses the piston and the connecting rod.
combustion chamber
four major factors that need to be considered in the design and construction of the cylinder assembly
- must be strong enough to withstand internal pressures developed during engine operation
- be constructed of a lightweight metal to keep down engine weight
- have good heat-conducting properties for efficient cooling
- be comparatively easy and inexpensive to manufacture, inspect, and maintain
The cylinder head of an air-cooled engine is generally made of ______ because it is a good conductor of heat and its light weight reduces the ___________.
aluminum alloy, overall engine weight
Cylinder heads are ______ or _____ for greater strength.
forged, die-cast
The inner shape of a cylinder head is generally _______. This shape is generally stronger than other designs and aids in a more rapid and thorough scavenging of the exhaust gases.
semi-spherical
The cylinder used in the air-cooled engine is the ________.
overhead valve type
Two major parts of each cylinder
cylinder head, cylinder barrel
The majority of the cylinders used are constructed in the manner of gas-tight joint using an _____ head and a _____ barrel.
aluminum, steel
Its purpose is to provide a place for combustion of the fuel/air mixture and to give the cylinder more heat conductivity for adequate cooling.
cylinder head
The fuel/air mixture is ignited by the spark in the _________ and commences burning as the piston travels TDC on the compression stroke.
combustion chamber
The ignited charge is rapidly expanding at this time, and _______ is increased drastically so that the piston is driven downward on the power stroke.
pressure
The intake and exhaust valve ports are located in the _________ along with the spark plugs and the intake and exhaust valve actuating mechanisms.
cylinder head
__________ spark plug inserts are used in many engines currently manufactured.
Stainless steel Heli-Coil
The cylinder heads of air-cooled engines are subjected to ___________; it is therefore necessary to provide adequate cooling fin area and to use metals that conduct heat rapidly.
extreme temperatures
It is well adapted for casting or for the machining of deep, closely spaced fins, and it is more resistant than most metals to the corrosive attack.
Aluminum alloy
The ___________ is the hottest part of the internal surface; therefore, more fin area is provided around the outside of the cylinder head in this section.
exhaust valve region
This is where the piston operates; must be made of a high-strength material, usually steel; must be as light as possible, yet have the proper characteristics for operating under high temperatures and pressures; must be made of a good bearing material and have high tensile strength.
cylinder barrel
The cylinder barrel is made of a steel alloy forging with the inner surface hardened to resist wear of the __________ that bear against it.
piston and piston rings
The hardening in the cylinder barrel is usually done by exposing the steel to ______ or ______ while the steel is very hot. The metal is also said to be nitrided.
ammonia, cyanide gas
As the cylinder barrels wear due to use, they can be repaired by ________.
chroming
This is a process that plates chromium on the surface of the cylinder barrel and brings it back to new standard dimensions.
chroming
______ the cylinder walls is a process that brings it to the correct dimensions.
honing
Some engine cylinder barrels are choked at the top, or they are smaller in diameter to allow for _________ and _______.
heat expansion, wear
The valves used in aircraft engines are the ______________.
conventional poppet type
The valves are also typed by their shape and are called either ______ or _____ because of their resemblance to the shape of these plants.
mushroom, tulip
The valves in the cylinders are subjected to _______, _________, and __________; thus, the metal alloy in the valves must be able to resist all these factors.
high temperatures, corrosion, operating stresses
Because intake valves operate at lower temperatures than exhaust valves, they can be made of ________.
chromic-nickel steel
Exhaust valves are usually made of ______, ________, or ____________ because these materials are much more heat resistant.
nichrome, silchrome, cobalt-chromium steel
The valve head has a _____ that forms a seal against the __________ in the cylinder head when the valve is closed.
ground face, ground valve seat
The face of the valve is usually ground to an angle of either ____ or ____.
30 deg, 45 deg
In some engines, the intake-valve face is ground to an angle of _____, and the exhaust valve face is ground to a _____ angle.
30 deg, 45 deg
Some installations have the valves and valve seats ground ______ different to enhance the seal formed between the face of the valve and the valve seat.
1/2 deg
Valve faces are often made more durable by the application of a material called _________. About ______ inch of this alloy is welded to the valve face and ground to the correct angle.
stellite, 1/16
It is resistant to high temperature corrosion and also withstands the shock and wear associated with valve operation.
stellite
The _____ is the part that forms the junction between the head and the stem.
neck
The tip of the valve is hardened to withstand the hammering of the ______ as it opens the valve.
valve rocker arm
The ________ acts as a pilot for the valve head and rides in the valve guide installed in the cylinder head for this purpose. It is surface hardened to resist wear.
valve stem
A machined groove on the stem near the tip receives the _______. These form a lock ring to hold the valve spring retaining washer in place.
split-ring stem keys
The metallic sodium melts at approximately _____ and the reciprocating motion of the valve circulates the liquid sodium, allowing it to carry away heat from the valve head to the valve stem where it is dissipated through the valve guide to the cylinder head and the cooling fins.
208 deg fahrenheit
Some intake and exhaust valve stems are hollow and partially filled with _________. It is used because it is an excellent heat conductor.
metallic sodium
Intake valves for low-power engines are usually ______ headed.
flat
With the melted sodium, the operating temperature of the valve may be reduced as much as ____ deg Fahrenheit to _____ deg Fahrenheit.
300, 400
In some engines, the intake valve may be the tulip type and have a smaller stem than the exhaust valve or it may be similar to the exhaust valve but have a __________.
solid stem and head
Although these valves are similar, they are not interchangeable since the faces of the valves are constructed of _________.
different material
Under no circumstances should a sodium-filled valve be cut open or subjected to treatment that may cause it to rupture. Exposure of the sodium in these valves to the outside air results in _____ or _______ with possible personal injury.
fire, explosion
The most commonly used intake valves have ______, and the head is either flat or tulip shaped.
solid stems
The intake valve usually has a ______ on the tip to identify it. Also, the head of the intake valve typically has a larger diameter than the exhaust valve.
flat milled
