2. 2
INTRODUCTION
WHAT IS MECHANICAL ENGINEERING?
Understanding Of Core Concepts Mechanics,
Thermodynamics, Materials Science, Mechanical
Design and Structural Analysis.
Use of Computer-aided Product Engineering
Lifecycle Management, Design And Analyze
Manufacturing Plants, Industrial Equipment And
Machinery, Heating And Cooling Systems,
Transport Systems, Aircraft, Watercraft,
Robotics, Medical Devices And More.
3. 3
One of the broadest of all engineering
branches
Mechanical Engineering
• Involved with “Machines”:
– Design tools, engines,
machines
– Design and develop power-
producing machines,
including…
• internal combustion
engines
4. 4
– Design and develop
power-producing
machines, including
• Steam and Gas
turbines
TurboFans from Jet Aircraft
Turbinator Gas Turbine
Engine Race Car
Mechanical Engineering
5. 5
Mechanical Engineering
- Jet and Rocket engines.
Jet Engine powered Truck
NASA next-generation
rocket engine powered
spacecraft
6. 6
- Design and develop power-using
machines such as
• Heating, Ventilation, Air-
conditioning (HVAC) systems
Mechanical Engineering
19. 19
Work (W): Work is the result of force (F) moving an
object linear motion a distance (S).
W = F x S
Power (P): Power may be
defined as the rate of doing work, or
work over time (t).
P = W/t = F x S/t
Where Velocity V = S/t
Linear Motion
P = F x V
20. 20
Torque or moment (T): Is the
twisting force, or torque is the generated work (W) rotating
an object, tangent a circle of radius (r) about the center.
Rotational Motion
P = F x V
T = W = F x r
Power (P):
P = T x ω =F x r . ω
Where:
V = r . ω
Angular Velocity ω = 2 𝝅 RPM/60
22. Some Types of Simple Machines
(components)
Lever
Gear
Bearing
wheel and axle
pulley
Screw
Shaft
MACHINE THEORY
23. A compound machine is ...
a combination of two or
more simple machines.
MACHINE THEORY
24. 24
Power can be…
Power (ENERGY)
• Electrical.
• Mechanical.
• Chemical.
• Thermal.
• Fluid.
25. 25
Distance between drive and driven
shafts.
Operational speed.
Power to be transmitted.
MECHANICAL POWER TRANSIMISSION
26. 26
Means of power Transmission
Mechanically:
• Hi power & speed: by COUPLINGS,
CLUTCHES OR GEARS.
• Medium Power & Low speed: by
CHAIN & SPROCKETS.
• Low & Medium power & Hi speed : by
BELTS & PULLEYS.
MECHANICAL POWER TRANSIMISSION
27. 27
Rotating device is utilized to transmit the
power between two shafts on alignment
without reduction.
• From prime mover to machine.
• From one shaft to another.
Couplings
MECHANICAL POWER TRANSIMISSION
29. 29
REGID COUPLING
Flanged coupling
Muff coupling
• It is used for heavy power
transmission and low speed.
• It is used to connect two shafts
which are perfectly axial alignment.
• Any misalignment causes high
vibration, then failure.
Split Muff coupling
MECHANICAL POWER TRANSIMISSION
30. 30
• Permitting some parallel
misalignment up to 0.762 mm
and angular misalignment up
to ±30
• can drive in either direction,
absorb impulses, shocks and
vibrations.
FLIXABLE COUPLINGS
MECHANICAL POWER TRANSIMISSION
35. 35
MECHANICAL POWER TRANSIMISSION
GEARS
Straight Gear [spur gear].
Helical gear.
Bevel gear.
Worm gear.
Rack and Pinion.
• Are used to transmit power from one shaft to another shaft in
closed contact.
• The rotation direction of the driven opposite to the drive shaft
• Are used to control the output speed (reduction is common).
• Are used to control the output torque (increasing is common).
• Are classified according to location of the shaft, position of the
tooth and types of tooth shapes to:
39. 39
Chain = sequence of inner link and pin link articulated to form a
flexible device for power transmission
Main parameters:
- Pitch: distance between two consecutive pins
- Roller diameter: dimension of the outside diameter of the chain
rollers
- Inside width: distance between the two opposite inner sides of
the inner link plates
CHAIN & SPROCKET
MECHANICAL POWER TRANSIMISSION
41. 41
MECHANICAL POWER TRANSIMISSION
• Used to transfer the power,
and control the speed, so the
torque between the drive
sprocket and driven sprocket.
• This system is very similar to
that of the gear system, but
the relative motion of both
shafts is IN THE SAME
DIRECTION.
CHAIN & SPROCKET
42. 42
MECHANICAL POWER TRANSIMISSION
CHAIN & SPROCKET
speed Ratio (SR) (Reduction Ratio common)
Speed Ratio = D1 / D2 = N2 / N1= T1 / T2
As Driven sprocket Diameter increases, speed
decreases and torque increases .
Where:
D1 : Drive sprocket Diameter or No of teeth.
D2 : Driven sprocket Diameter or No of teeth.
N1 : Drive sprocket Speed.
N2 : Driven sprocket Speed.
T1 : Drive shaft Torque.
T2 : Driven Shaft Torque.
43. 43
• This system is very similar to that of the chain and sprocket
system : in this case, the RELATIVE MOTION of both shafts is IN
THE SAME DIRECTION.
• Belts are used to connect two rotating item.
• Usages are as source of motion (conveyors system) or as a high
efficiency power transmission.
• The demands on a belt drive transmission system are large.
BELTS & PULLEYS
MECHANICAL POWER TRANSIMISSION
45. 45
The "V" shape of the belt tracks in a mating
groove in the pulley (or sheave), with the
result that the belt cannot slip off.
The belt also tends to wedge into the groove
as the load increases — the greater the load,
the greater the wedging action — improving
torque transmission and making the vee belt
an effective solution.
For high-power requirements, two or more
vee belts can be joined side-by-side in an
arrangement called a multi-V, running on
matching multi-groove sheaves.
Good resistance to overloads
Timing between sheaves may not be
accurate
MECHANICAL POWER TRANSIMISSION
47. Diesel Engines Eng. Mohammad Embaby
- PROGRAM OBJECTIVE :
• INTRODUCTION
• UNDERSTAND DIFFERENT TYPES OF ENGINES.
• UNDERSTAND HOW DIESEL ENGINES WORK .
• UNDERSTAND CYCLE THEORY OF INTERNAL COMBUSTION ENGINES.
• UNDERSTAND THE DIFFERENT SYSTEMS OF DIESEL ENGINE.
47
48. 48
INTRODUCTION
The diesel engine is used as a source of power for thousands of
applications.
WHO INVENTED THE DIESEL ENGINE?
• In 1895 – RUDOLPH DIESEL successfully invented an
engine that burned coal dust injected by pressurized air.
• The diesel engine was born.
WHO DEVELOPED THE FIRST MASS PRODUCED INJECTION PUMP?
ROBERT BOSCH IN 1927
49. Eng. Mohammad Embaby
INTERNAL COMBUSTION ENGINES
CLASSIFICATION:
Internal combustion engines can be classified according to the
following:
FUEL TYPE: Into Diesel engine and Gasoline engine.
OPERATION CYCLE: Into four stroke engine and two stroke engine.
IGNETION: Into self ignition engine and spark ignition engine.
CYLINDE CONFIGURATIONS: Into line engine, Vee engine
horizontal engine.
COOLING SYSTEM: Water cooled engine and air cooled engine.
NUMBER OF CYLINDERS: 4, 5, 6, 8, 10, ………Cylinders.
ENGINE CAPACITY: 1000 cc/rev, 1300cc/rev, 1600cc/rev, …...and
so on.
Diesel Engines
49
51. Heat Engine
The Internal Combustion engine that produces
power by burning fuel inside a combustion
chamber within the engine.
A heat engine is a device which converts heat
energy into mechanical energy to do work.
Diesel Engines Eng. Mohammad Embaby
51
HOW INTERNAL COMBUSTION ENGINES WORK
BASIC CONCEPTS
52. Three Elements produce heat energy
◦ To produce heat energy, it is mainly required
air, fuel and combustion. The heating of
air and spray fuel together produces
combustion and explosion, which create the
force required to run the engine.
Diesel Engines Eng. Mohammad Embaby
HOW INTERNAL COMBUSTION ENGINES WORK
BASIC CONCEPTS
52
53. ◦ Air
Air contains oxygen. Oxygen is required to
burn fuel
◦ Fuel
Fuel produces heat and force. When atomized,
diesel fuels ignite easily and burn efficiently.
◦ Combustion
Combustion occurs when the air fuel mixture
heats up enough to ignite. It must burn
quickly in a controlled fashion to produce the
most heat energy
Diesel Engines Eng. Mohammad Embaby
HOW INTERNAL COMBUSTION ENGINES WORK
BASIC CONCEPTS
53
54. Combustion Chamber
◦ The combustion chamber is the volume
inside the cylinder at the end of compression
is formed by the cylinder, piston, intake and
exhaust valves, and cylinder head .
Diesel Engines Eng. Mohammad Embaby
54
HOW INTERNAL COMBUSTION ENGINES WORK
BASIC CONCEPTS
55. Factors that control Combustion
◦ Combustion is controlled by three factors
How much the air is compressed
The type of fuel that is used
The amount of fuel mixed with the air
55
Diesel Engines Eng. Mohammad Embaby
HOW INTERNAL COMBUSTION ENGINES WORK
BASIC CONCEPTS
56. Compression
◦ Air can be compressed or squeezed into a
smaller volume. When air is compressed, it
heats up. The more you compress air, the
hotter it gets. If it is compressed enough, it
produces temperature above the fuel’s ignition
temperature.
Diesel Engines Eng. Mohammad Embaby
56
HOW INTERNAL COMBUSTION ENGINES WORK
BASIC CONCEPTS
57. Type of Fuel
◦ The type of fuel used in the engine affects combustion
because different fuels burn at different temperatures,
and some burn more thoroughly.
Amount of Fuel
◦ The amount of fuel is also important because more fuel
produces more force. When injected into an enclosed
area containing sufficient air, a small amount of fuel
produces small amount of heat and force.
Diesel Engines Eng. Mohammad Embaby
57
HOW INTERNAL COMBUSTION ENGINES WORK
BASIC CONCEPTS
58. Combustion Process: Diesel Engine
◦ In a diesel engine air is compressed inside the
combustion chamber until it is hot enough to self
ignition the fuel about 415Co. Then, fuel is injected
into the hot chamber and combustion & explosion
occurs.
Combustion Process: Gasoline Engine
◦ In a gasoline engine, a mixture of fuel and air is
compressed and a spark ignites the mixture within
the combustion chamber.
Diesel Engines Eng. Mohammad Embaby
58
HOW INTERNAL COMBUSTION ENGINES WORK
BASIC CONCEPTS
59. Transmitting Heat Energy
◦ In both engine types, combustion produces
heat energy which causes the gases trapped
in the combustion chamber to expand
pushing the piston down.
◦ As the piston moves down, it moves other
mechanical components that do the work.
Diesel Engines Eng. Mohammad Embaby
59
HOW INTERNAL COMBUSTION ENGINES WORK
BASIC CONCEPTS
60. Engines use two kinds of motion to convert the
heat of combustion into useable power.
◦ Reciprocating Motion
Reciprocating motion is up and down or back and forth
motion
◦ Rotary Motion
Rotary motion means circular motion around a fixed
point.
Rotary Motion
Crankshaft
Reciprocating Motion
piston & connecting rod
Diesel Engines Eng. Mohammad Embaby
60
HOW INTERNAL COMBUSTION ENGINES WORK
BASIC CONCEPTS
61. ◦ Components that Transmit Motion
The piston, connecting rod and crankshaft
convert reciprocating motion into rotary motion.
As the piston moves up and down, the
connecting rod transmits the reciprocating
motion to the throws on the crankshaft. This
turns the crankshaft, producing rotary motion
which provides power to the equipment.
Diesel Engines Eng. Mohammad Embaby
61
HOW INTERNAL COMBUSTION ENGINES WORK
BASIC CONCEPTS
62. Top Dead Center (TDC)
◦ Top Dead Center (TDC) describes the piston at its
highest point in the cylinder. The piston reaches TDC
on the compression and exhaust strokes.
Bottom Dead Center (BDC)
◦ Bottom Dead Center (BDC) describes the piston at its
lowest point in the cylinder. The piston reaches BDC
on the intake and power strokes.
Stroke
◦ Stroke is the distance the piston travels from TDC to
BDC.
Diesel Engines Eng. Mohammad Embaby
62
HOW INTERNAL COMBUSTION ENGINES WORK
BASIC CONCEPTS
64. DIESEL ENGINES CARACHTERSTICES
Diesel Engines are Heavier
◦ Diesel Engines are generally heavier than gasoline engines because the
diesel engine must withstand higher combustion pressures and
temperatures.
Compression Ratios
◦ Diesel Engines generally use higher compression ratios to heat the air
to combustion temperatures. Most diesel engines generally have a
13:1 to 22: 1 compression ratio. Gasoline engines generally use
compression ratios between 8:1 and 11:1.
Diesel Engines can perform more work
◦ Diesel Engines can generally perform more work at a lower rpm during
any given time. In general, diesel engines usually operate between 800
and 3000 rpm and provide more torque, and more power to do work.
Diesel Engines are more Fuel Efficient
◦ Diesel Engines are generally more fuel efficient for the amount of work
output than gasoline engines. It requires relatively small amounts of
fuel to produce the rated horsepower output in a diesel engine.
Diesel Engines Eng. Mohammad Embaby
64
65. 4-STROKE ENGINE
Four events of Combustion
◦ Combustion requires four events
Intake of air into the combustion chamber
Compression of the air
Injection and ignition of the fuel
Exhaust of spent combustion gases
Diesel Engines Eng. Mohammad Embaby
65
66. 4-Stroke Cycle
◦ Each event requires one stroke. The four strokes are
called:
1. Intake Stoke
2. Compression Stoke
3. Power Stoke
4. Exhaust Stoke
◦ The combustion chamber components work together in a
precise way during each step of the cycle. During the
four strokes, reciprocating motion is changed into rotary
motion.
Diesel Engines Eng. Mohammad Embaby
4-STROKE ENGINE
66
67. 1- Intake Stroke
During the intake stroke the piston
moves down from TDC and the intake
valve opens to allow the air inters to
cylinder from air filter.
The connecting rod turns the
crankshaft a final 180°.
When the piston reaches BDC the
intake valve closes and the exhaust
valve remains closed.
Diesel Engines Eng. Mohammad Embaby
4-STROKE ENGINE
67
68. 2- Compression Stroke
◦ During the compression stroke both
intake and exhaust valves close in
order to seal the combustion chamber.
◦ The piston moves up within the
cylinder liner to its highest point in the
combustion chamber, top dead center
(TDC).
◦ The connecting rod turns the
crankshaft another 180°.
◦ The piston motion compresses the air
in the cylinder.
◦ The amount the air is compressed is
called the compression ratio. Most
diesel engines have a compression ratio
between 13:1 and 20:1
Diesel Engines Eng. Mohammad Embaby
4 STROKE ENGINE
68
69. 3- Power Stroke
◦ Near the end of the compression
stroke diesel fuel is injected and
combustion occurs.
◦ The rapidly expanding gases force
the piston downward. This is the
power stroke.
◦ The intake and exhaust valves remain
closed to seal the combustion
chamber so that force is exerted on
the piston.
◦ The power stroke moves the piston
down, which causes the crankshaft to
turn 180°.
Diesel Engines Eng. Mohammad Embaby
4 STROKE ENGINE
69
70. 4- Exhaust Stroke
◦ During the exhaust stroke the piston
moves up and the exhaust valve opens to
remove combustion gases.
◦ The connecting rod turns the crankshaft a
final 180°.
◦ When the piston reaches TDC the exhaust
valve closes and the intake valve opens
again.
◦ The combustion cycle occurs over and over
as long as the engine is running.
◦ Each event corresponds to one stroke of
the piston.
Diesel Engines Eng. Mohammad Embaby
4-STROKE ENGINE
70
72. Firing Order
◦ The sequence in which each cylinder comes
to the power stroke is called the firing order
of the engine.
Crankshaft Rotation During 4 Strokes
◦ At the end of the exhaust stroke the
crankshaft has completed the cycle, per two
revolutions (360° rotations) we get one
power stroke.
Diesel Engines Eng. Mohammad Embaby
4-STROKE ENGINE
72
73. Eng. Mohammad Embaby
Every two events require one stroke. The two strokes are
called:
1. Compression Stroke.
2. Power Stroke.
Inlet Air & Exhaust Events
The combustion chamber components work together in a
precise way during each stroke of the cycle. During the
two strokes, reciprocating motion is converted into rotary
motion.
Diesel Engines
2-STROKE ENGINE
73
74. Eng. Mohammad Embaby
1. Compression Stroke:
• The piston moves up to TDC and compresses the
trapped air in the combustion chamber.
• The air pressure and temperature are raised too
much.
• Just before TDC the injector atomizes diesel in
the combustion chamber, self ignition and
explosion occurs .
Diesel Engines
2-STROKE ENGINE
74
75. Eng. Mohammad Embaby
2. Power Stroke:
• Due to explosion, very high pressure force
pushes the piston downward from TDC to
BDC.
• The exhaust valves and air ports are closed,
just Before the piston reaches to open the
cylinder air ports the exhaust valves are
opened.
• The exhaust leaves the cylinder, thus the
internal pressure is dropped.
Diesel Engines
2-STROKE ENGINE
75
76. • Air Intake & Exhaust Event
• The piston continues moving down from
TDC to BDC.
• The exhaust valve and air ports are
opened.
• The air is pushed by the blower into
cylinder through its lowest air ports and
scavenges the remaining exhaust out the
cylinder.
• The piston moves up, Just before the
piston closes the air ports, the exhaust
valves closed.
Eng. Mohammad Embaby
Diesel Engines
2-STROKE ENGINE
76
77. Eng. Mohammad Embaby
Crankshaft Rotation During 2-Stroke
At the end of cycle the crankshaft has completed one
revolution (360° rotation), i.e. we get one power stroke
per one revolution.
For the same size of cylinder bore and stroke, the
produced power from 2st engine equivalent to twice
that from 4st engine.
Diesel Engines
2-STROKE ENGINE
77
79. 79
Eng. Mohammad Embaby
• At the operation beginning the engine must be
started running by outer starter.
TYPES OF ENGINE STARTERS:
1- Electric Starter.
2- Air (pneumatic) Starter.
3- Hydraulic Starter.
4- Mechanical Spring Starter.
5- Manual Starter.
Diesel Engines
METHODS OF ENGINE STARTING
80. 80
1- Electric Starter:
• The system consists of electric motor (of 12V or 24 V – DC
and required amperes) and automatic magnetic coil, electric
battery 12V – DC (one or two), electric switch (Contact),
wiring and dynamo for battery recharging.
• The more current and the more wire, the higher the
magnetic field and the stronger the motor.
• The drive gear (Bendix) that is attached to the motor
meshes with the flywheel gear.
• The flywheel gear then moves the pistons in the cylinders,
setting the engine in motion.
Diesel Engines Eng. Mohammad Embaby
82. Eng. Mohammad Embaby
2- Air (pneumatic) Starter: The system consists of:
1. Pneumatic motor (vane type) attached with drive pinion gear
which will mesh with engine flywheel gear.
2. Air compressor (reciprocating type).
3. Air tank.
4. Air service unit (Drier, lubricator, manometer and Regulator).
5. 2/2 way Pilot operated air start valve.
6. 2/2 way Pilot pushbutton air valve.
Air starter
Diesel Engines
METHODS OF ENGINE STARTING
82
84. 3- Hydraulic Starter: The system consists of:
1. Hydraulic Pump.
2. Check Valve.
3. Accumulator.
4. 2/2 way valve.
5. Hydraulic motor.
6. Connecting hoses.
METHODS OF ENGINE STARTING
84
Diesel Engines Eng. Mohammad Embaby
(2)
(3)
(4)
(5)
(6)
(1)
85. 85
4- Mechanical Spring Starter: The system consists of:
1. Mechanical spring motor.
2. Spring charging handle.
3. Spring lock & release knop.
Eng. Mohammad Embaby
Diesel Engines
METHODS OF ENGINE STARTING
86. 86
5- Manual Starter:
1. handle is connected directly to
crankshaft, It is unsafe to use.
2. Recoil start usually on small
machines the starter consists
of a rope with a grip at the
end, coiled around an end of
the crankshaft.
Eng. Mohammad Embaby
Diesel Engines
90. Eng. Mohammad Embaby
2- BREATHING SYSTEM:
Air intake & Exhaust System
The system consists of:
1. Air suction filter
2. Air manifold.
3. Air valves.
4. Exhaust valves.
5. Exhaust manifold.
6. Spark arrestor.
7. Exhaust piping.
8. Exhaust muffler.
9. Turbocharger increases the air
intake, so the output power by
30%.
Diesel Engines
ENGINE SYSTEMS
(8)
(2)
(3)
(4)
(5) (7)
(9) 90
91. Eng. Mohammad Embaby
3- COOLING SYSTEM
• Remove Heat Generated from Fuel Combustion
Burn Temperatures Can Reach 3,500°F (1927°C)
Cooling systems are designed to keep an engine operating within
a desired temperature range.
Temperature of the coolant must remain high to allow the engine
to operate efficiently, however, temperature must stay low enough
to prevent the coolant from boiling.
A cooling system regulates temperature by transferring heat from
the engine to the coolant &eventually, into the air.
A major factor of heat transfer is the difference between the
temperature of coolant inside the radiator & the temperature of
surrounding air.
When the difference coolant temperature & the ambient
temperature increases, the rate of heat transfer increases.
Diesel Engines
ENGINE SYSTEMS
91
92. 92
• Increased engine wear
• Improper lubrication
• Increased fuel consumption
• Increased sludge formation
• Increased engine corrosion
• Moisture condenses if below 140 degrees in the
engine crankcase
SOME EFFECTS OF OVERCOOLING
• Cylinder head and block can crack or warp.
• Rings and valves may seize or stick due to gums and
varnishes forming from overheated oil and carbon formation.
• Bearings may be damaged causing excessive wear.
SOME EFFECTS OF ENGINE OVERHEATING
THE IDEAL OPERATING TEMPERATURE FOR MOST DIESEL
ENGINES is 165 – 185 DEGREES F (80-90 Co).
COOLING SYSTEM
93. Two types:
I.Water Cooling System
II.Air cooling system
I. Water Cooling System
• Water Is the Most Efficient Heat Transfer.
The system consists of:
1. Water pump.
2. Radiator.
3. Thermostat.
4. Piping and hoses.
5. Radiator cooling fan.
(2)
(5)
(4)
(3)
(1)
93
Diesel Engines Eng. Mohammad Embaby
COOLING SYSTEM
95. Eng. Mohammad Embaby
COOLING SYSTEM
II. Air cooling system
The system consists of:
1. Air Cooling fan.
2. Belt and pulleys.
3. Cylinders fins.
Diesel Engines
ENGINE SYSTEMS
95
96. 96
• LESS WEIGHT.
• LESS MAINTENANCE.
• LESS DOWN-TIME.
• NO CAVITATION EROSION.
• NO COOLANT CONCERNS.
• MORE EFFICIENT USE OF POWER.
• LESS VULNERABLE TO DAMAGE.
• LESS BULK.
• QUICKER WARM-UP.
SOME ADVANTAGES OF AIR-COOLED ENGINES:
• LENGTH OF THE ENGINE.
• LESS TEMPERATURE CONTROL.
• HIGHER OPERATINGTEMPERATURES.
• GREATER NOISE.
• MORE FREQUENT CLEANING.
DISADVANTAGES TO AIR-COOLED ENGINES:
Eng. Mohammad Embaby
Diesel Engines
98. Eng. Mohammad Embaby
LUBRECATION SYSTEM
The system consists of:
1. Oil pump (gear type).
2. Oil filter.
3. Oil sump.
4. Piping & hoses.
5. Suction oil strainer.
Diesel Engines
ENGINE SYSTEMS
(5)
(1)
(3)
(2)
(4)
Oil drain plug
98
99. 99
• Reduces shock, wear, and friction
• Seals compression.
• Provides some cleaning.
• Helps cool the engine.
• Quiets the engine operation
FUNCTIONS OF THE LUBRICATION system:
• OXIDATION INHIBITORS.
• CORROSION AND RUST INHIBITORS.
• DETERGENT DISPERSANTS.
THE THREE MOST COMMON OIL ADDITIVES:
Eng. Mohammad Embaby
Diesel Engines
101. 101
USES OF DIESEL ENGINES
Today, diesel engines are used to provide power in a variety of
applications in many industries.
THERE ARE SEVEN MAJOR USES OF DIESEL ENGINES
TRANSPORTATION.
MARINE.
OIL FIELD.
ELECTRICAL GENERATION PLANTS.
CONSTRUCTION.
AGRICULTURE/FARM.
FORESTRY.
