Auto and Shop Information Review

Auto Information 
The Auto and Shop Information subtest covers automobiles and other vehicles  that use an internal combustion engine. 

Automotive Systems 
Cars, trucks, buses, and other vehicles all use literally  thousands of components, or parts. A combination of  several components that work together to perform a  specific function is called a system. There are several  main systems that perform key functions in the automobile:  providing power, transferring energy from the  engine to the wheels, keeping the engine cool, smoothing  out the bumps in the road, and more. You’ll learn  about the most important systems and components in  this section. 

The Internal Combustion Engine 
Internal combustion engines power many kinds of  machines, not just cars and trucks. In general, an internal  combustion engine operates by burning fuel to  produce kinetic energy. This energy causes the internal  workings of the engine to rotate. Ultimately, this energy  is transferred to the wheels of the car via gears and  other linkages—and the car moves. 

Kinetic energy: the energy of motion 
Internal combustion engines can be fueled by  gasoline, diesel fuel, natural gas, or other combustible  fossil fuels. A fuel pump moves fuel from the fuel tank  into the engine. Inside the engines are typically four, six,  or eight cylinders, each with one piston that moves up  and down. 
The fuel is injected into the cylinders by the carburetor  or fuel injectors. Each cylinder has one spark  plug that fires at regular intervals. (The energy for the  spark is provided by the electrical system; see page 162.) The spark causes a mini-explosion in the cylinder,  driving the piston downward. The tie rod to which  the piston is fastened is therefore also driven downward. 
The tie rod is attached to the crankshaft, which  converts the up-and-down motion of the pistons and  tie rod into rotational movement. The gears attached  to the crankshaft are connected to other gears on  the transmission system. Through the  transmission, eventually the power is transferred to the  wheels of the vehicle, the inner workings of the pump,  or whatever machine the engine is driving. 

The Transmission System 
The transmission is the link that transfers power from  the engine to the tires and wheels. It typically consists  of several shafts, gears, and joints. When the power  from the engine rotates the transmission shafts, the  car begins to move. The driveshaft between the transmission  and the axles is typically made of steel so it can  withstand the high torque of operation. 

Torque: twisting force 
As the speed of the car increases, the transmission  rotates faster and faster. In order to keep the transmission’s  rotation speed at acceptable levels, several gears  are used. That is why you must shift a car as your speed  increases and decreases. Some vehicles have transmissions  that shift automatically between the necessary  gear sizes. Others, including the heavy vehicles used in  the armed forces, have a manual transmission that  requires the driver to change the gears using the clutch  and the gear shift. The transmission is disengaged  when you press the clutch pedal to the floor. After you  move the gear shift into the gear you want, you slowly  release the clutch pedal. The transmission gears touch  and once again transfer the energy from the engine to  the wheels. An automatic transmission does all this  work for you. 

The Cooling System 
An internal combustion engine has many moving parts. 
As these parts slide past each other, the friction of their  movement against each other generates heat. The cooling  system dissipates this heat in order to prevent the  engine from becoming too hot. The cooling system  consists of a pump that moves cooling fluid, or coolant,  from the radiator through piping to the engine block. 
As the coolant passes over the engine block, some of the  heat from the engine is transferred into the coolant. The  fluid then flows back to the radiator, where it is cooled  by the flow of air across the radiator. The reason a  vehicle is more likely to overheat on a hot day than on  a cold one is that the air moving over the radiator can’t  cool the fluid effectively. 

The Exhaust System 
The exhaust system includes a system of piping connected  to the engine with welded joints. Several brackets  suspend the piping beneath the automobile. The  engine’s exhaust gases pass from the engine through the  piping to the muffler, which is an acoustical chamber  that reduces the engine noise and removes some of the  pollutants created when the fuel burns. 

The Suspension System 
The suspension is the system that attaches the wheels  of the automobile to its body. The wheels cannot be  directly attached with a hard connection because the  high forces of hitting bumps in the road would cause  structural failure—the connections would break. 
Instead, a combination of springs and dampeners are  used to “soften” this connection. The springs are typically  either leaf springs or coil compression springs. 
They provide a flexible link between the wheels and the  body of the car. 
The shock absorbers serve to dampen the bumps  in the road.Without shock absorbers, when a car hit a  bump, it would continue to bounce up and down on  the suspension springs for a long time. The shock  absorbers are movable but very stiff, so they quickly  reduce the movement of the springs. Shock absorbers  are typically oil-filled cylinders approximately 12 to 18  inches long. One end is bolted to the body of the automobile,  and the other is attached to the axle of the  wheels. A vehicle typically has one set of springs and  shocks for each wheel. 

The Electrical System 
The electrical system in an automobile is incredibly  complex. It provides the energy for the initial spark  from the spark plug that makes the engine run, so without  electricity you couldn’t go anywhere. It also operates  other systems and accessories, including headlights and  other lights as well as power windows and door locks. 
The electrical system is similar to your body’s cardiovascular  system. The heart of the system is the battery. The  wiring that runs throughout the automobile is similar  to your veins and arteries. The wires transfer energy  from the battery to the spark plugs and other devices  that use electricity. There are literally hundreds of feet  of electrical wiring in modern automobiles. 
The battery would quickly lose its charge without  a method of recharging. The component of the electrical  system that charges the battery is the alternator. 
The alternator rotates to generate electrical energy,  which then recharges the battery. 

The Braking System 
Automobile brakes are activated by pressing the  brake pedal. This action compresses a piston to force  hydraulic fluid through the brake line piping. In disc  brakes, the brake fluid presses against a set of mechanical  calipers, or levers, that squeeze the brake pads against  the rotors. The friction of the pads rubbing against the  rotors slows the rotation of the wheels. Springs are used to  return the brake pedal and the calipers to their neutral  position when the brake pedal is released. 

Miscellaneous Components 
Many other minor systems and components are used in  internal combustion vehicles besides the major systems  just listed. Gauges and pumps are used not only  on automobiles but also in other kinds of machines you  may encounter on the ASVAB. 

Gauges 
Gauges help operators monitor the condition and  performance of machines such as pumps and internal  combustion engines, as well as the surrounding  atmospheric conditions that can indirectly affect a  machine’s function. 
Gauges are usually marked with the units they  are measuring. A few examples of different types of  units are: 
- degrees Celsius or Fahrenheit for temperature  gauges (usually called thermometers) 
- pounds per square inch (psi) for pressure gauges 
-  gallons or liters for fuel gauges 
- amperage for battery gauges 

You must be very careful to recognize and understand  the units of a gauge that appears in a test question.For  instance, a temperature gauge could use either degrees Fahrenheit or degrees Celsius. Mistakes on units can  cause major problems, so be careful. 

AUTOMOTIVE PERFORMANCE GAUGES 
Gauge - What It Measures - Units 
Speedometer velocity (speed) miles per hour (mph)  or kilometers per hour (kph) 
Tachometer speed of rotation for pumps, engines, fans, etc. revolutions per minute (rpm) 
Pressure gauge internal pressure, such as oil pressure or pounds per square inch (psi)  water pressure or inches of water 
Ammeter electrical charge amps 
Fuel gauge remaining volume of fuel gallons or liters

Gauges are sometimes marked with warnings  about limits of safe operation. For instance, an oil pressure  gauge on an internal combustion engine may show  a maximum safe working pressure of 15 psi. If you’re  asked about the safe operation of a device with a gauge  on it, you should pay careful attention to any markings  that show such a limit. 
Gauges are also used for non-automotive  machines as well as to monitor conditions of various  mechanical and electrical systems.

Pumps 
A pump is a device used to transfer a liquid or a gas  from one location, through a piping system, to another  location. There are many different types of pumps,  including centrifugal pumps, positive displacement  pumps, metering pumps, diaphragm pumps, and progressive  cavity pumps. 
Generally speaking, a working pump consists of  the pump itself—case, bearings, impeller, seals, shaft,  base, and other components—and an outside energy  source. The outside energy source may be an electric  motor, an internal combustion engine, or a battery  and motor. The energy from this source causes the  inner workings of the pump to propel the liquid or gas  through the piping system. The flow rate at which the  liquid or gas is pushed through the piping system is typically  measured by a flow meter in units of gallons per  minute (gpm) or cubic feet per minute (cfm). 
Some automotive pumps include the fuel pumps  used to pump the fuel from a holding tank into your car  and the pumps that transfer coolant through the  engine’s cooling system. 
Pumps have many other uses besides automotive  ones. They can be used to move drinking water  from a reservoir to your house or business. Industrial  pumps are also used to move industrial fluids such as  chemicals or waste products from one tank to another  inside a plant. 

Automotive Tools 
Car maintenance and repair may require specialized  tools as well as some with which you are already familiar. 

Some of these tools are: 
- Wrenches to tighten and loosen nuts and bolts. 
Examples include vice grips and box end  wrenches, socket wrenches, crescent wrenches,  and pipe wrenches. 
- Screwdrivers to tighten and loosen the thousands  of screws in a car. Both regular head and Phillips  head screwdrivers are used. There are also screwdrivers  unique to particular vehicles. 
- A spark plug wrench to change the spark plugs. 
Typically a spark plug wrench is actually an  adapter that connects to a socket wrench. 
- A jack to lift a car so that you can change a tire. 
- A hoist to lift heavy objects such as engines and  transmission components in order to repair them. 
There are lots specialized tools used for repair  work, but you’re not likely to find them on the ASVAB. 

OTHER GAUGES 
Gauge - What It Measures - Units 
Thermometer temperature degrees Fahrenheit or Celsius 
Barometer atmospheric pressure inches or millimeters of mercury 
Hygrometer relative humidity percentage of water in air 
Flow meter volume of flow in a piping system cubic feet per minute (cfm) or gallons per minute (gpm)

Automotive Maintenance  and Troubleshooting 
Today’s automobiles are such complex machines that  explaining how to maintain and repair them can take  thousands of pages for each model of car or truck. 
Most automobiles are sold with a manual for that  model, and if you are assigned a specific kind of vehicle  in the armed forces, you’ll be trained on the specific  procedures for that vehicle. Some kinds of maintenance  and troubleshooting, however, are common to  almost all vehicles. 

Preventative Maintenance 
Any vehicle requires regular maintenance in order to  keep it operating properly and to insure a long, reliable  life. Some automotive components wear out and have  to be replaced. Also, an automobile has many moving  parts that require regular lubrication so they don’t wear  out before their time. 
Obviously tires wear out with use. Tires on a typical  car last 30,000 to 80,000 miles, depending on use. 
Car tires have wear bars that indicate when they should  be replaced. Worn tires can be unsafe, so replacing  them is a must. 
Tires also have to be rotated. The tires in the front  will wear more on the outside of the tread because of  extra wear from turning. Tires should be rotated, or  moved from the front to the back, every 3,000 to 5,000  miles. Tire pressure should also be checked regularly in  order to insure proper handling of the car and prevent  abnormal wear. 
Another part of regular maintenance is keeping  the engine and transmission lubricated. The engine  uses petroleum-based oil to reduce the friction between  moving parts such as the pistons and the cylinder wall. 
Over time, this oil becomes dirty and must be replaced. 
Most engine manufacturers recommend three months  or 3,000 miles between oil changes. Also, the rotating  joints in the transmission have to be lubricated with  grease in order to keep operating properly. 
Some automotive components that usually need  to be replaced during the life of an automobile include  the battery, belts and hoses, air filter, shock absorbers,  and spark plugs. Also, some automotive systems use  fluids that have to be replaced regularly. These include  the transmission, brakes, power steering, and cooling  system. The replacement intervals vary from vehicle to  vehicle. Again, if you are required to do this kind of  maintenance as part of your military assignment, you  will be trained on the procedures for the vehicles you  are responsible for. 

Troubleshooting 
An internal combustion engine requires three  basic items in order to operate properly: fire, fuel, and  oxygen.When an engine will not start, one or more of  these items is missing. 
Fire—a spark, actually—is provided by the electrical  system through the spark plug. If a vehicle won’t  start, you should check the battery and alternator, the  wires connecting the electrical system to the spark  plugs, and the plugs themselves. 
Fuel is pumped from the fuel tank to the engine  by the fuel pump through the fuel line. A lack of fuel in  the engine could be caused by a ruptured fuel line or a  broken fuel pump. Another possibility is a problem  with the carburetor or fuel injectors, which regulate the  amount of fuel going to the engine. 
Oxygen is necessary for the fuel to burn. If you  light a match and then place it under a glass, the match  will go out in a few seconds because the oxygen in the  glass has been consumed by the burning match. 
Oxygen—which is provided by the air since air is 21 percent oxygen—comes into the engine through the air filter, controlled by several valves. One possible  cause of lack of oxygen is a dirty air filter—a problem  you can diagnose simply by looking at the filter. 
Another common problem is that the engine runs  but the automobile will not move. This problem  typically indicates that something is wrong with the  transmission. Once you’ve determined that the transmission  is indeed in the correct gear, there wouldn’t be  much more you could do about this problem. Transmission  repair is one of those jobs that only trained  mechanics should take on, so you’re not likely to find  any questions about it on the ASVAB. 

Shop Information  (shop tools,  building materials, and construction procedures. )

Hand Tools 
Hand tools are defined as tools operated not by motors  but by human power. Often used in construction and  metalwork, as well as some lawn and garden tools. (Search online for 'carpenter's tools', or 'gardening and lawn care tools', for example)

Gardening and Lawn Care Tools 
You might be surprised  at how often these tools are used in the armed  services: shovels for latrines, trenches, or bunkers; post  hole diggers for fences; axes, hoes, and rakes for firefighting. 

Building Materials 
The materials used to construct residential and commercial  buildings, bridges, and roads are all commonly  used in the armed services. Some materials play structural roles by providing  support and load-bearing functions. A few of the  most important structural materials include steel, concrete,  wood, brick, and cinder block. Other materials  are used as decoration or insulation, including glass,  fiberglass, and stucco. 

Steel 
Steel is commonly used in construction because it is  relatively inexpensive and is available in many shapes  and sizes: I-shapes, channels, circular and square  tubing, and rods. Steel comes in several grades, or  strengths; the grade used depends on the requirements  of the particular application. Structural steel members  are typically connected using bolts and/or welds. 
One drawback of using steel in outdoor applications,  such as bridges, is that it must be painted regularly  to prevent corrosion and rust. Common uses for  steel include road and pedestrian bridges and large  commercial buildings. The use of steel studs in the  walls of houses is also gaining popularity. 

Concrete 
Concrete is a versatile, low-cost building material that  can be formed into any shape. Forms are constructed  at the project site, and the concrete is poured into the  forms. It takes several days or weeks, depending on  weather conditions, for the concrete to harden, or  cure, to full strength. Concrete is very strong for compression  loads; that is, it’s good at holding up things  that are pressing on it. However, it has poor tensile  strength; that is, it doesn’t hold up well under a pulling  force. So concrete is typically used in combination  with steel reinforcement bars (commonly called rebars)  placed inside a concrete beam or column to provide  adequate strength. 

Concrete offers the added benefit of low maintenance  since it does not need to be painted. Common  structural applications of concrete include road and  bridge surfaces, building foundations, and support  members on some structures. 

Wood 
Wood is used for both structural and decorative purposes. 
Structural applications include use as studs and  roof trusses in houses and as beams for light bridges. 
The decorative uses include moldings, floor coverings,  doors, and windows. Wood is also used to cover over  steel or concrete beams and columns. 

Brick and Block 
Brick is a decorative material typically used on the  outer surface of walls. Cement mortar is used between  bricks to construct a solid wall that is decorative and  also protects the inner wall from the elements. Brick is  also sometimes used as a paving material for roads  and sidewalks. 
Cinder blocks are similar to bricks but much larger. 
The walls of small buildings are often made of cinder  block because it is a low-cost material. As with brick,  cement mortar is used to connect the blocks together. 

Construction Procedures 
Constructing a building, road, or bridge requires  coordination and planning. Standard construction  procedures assure that projects are finished on schedule,  within budget, and according to specifications. 
However, specific procedures vary, depending on  what is being built and on local conditions. Some of  the common terms and procedures in building construction  that may appear on the ASVAB are discussed  below. 

Foundations 
The foundation is the base that supports a building or  bridge. Most foundations are made of concrete. Surveyors  stake out the locations of the corners and other  key areas of the building or bridge pier. Then the earth  is excavated so that the forms for the concrete can be  built on solid ground. A solid foundation is key to having  a long-lasting structure. The design engineer will  determine the size and thickness of the foundation  based on the anticipated load. 

Flooring 
There are many kinds of flooring materials and many  ways in which floors are constructed, but there are  common elements. The subfloor is the structural  portion of the flooring system; it transfers the loads  placed on the floor to the foundation. The design engineer  considers the loads that will be placed on the  flooring in determining what materials will be used. For  instance, a warehouse floor has to be much stronger  than the flooring in an office. The warehouse subfloors  would be made of concrete while the office subfloor  might be consist of wood joists or beams. 
The decking is the portion of the floor that lies on  top of the subfloor beams. Decking usually consists  plywood nailed to the beams. The final component of  the flooring system is the decorative covering such as  tile, vinyl, or carpet. 

Framing 
The term framing refers to the “skeleton” of a structure. 
In a house, the framing usually consists of wood or steel  studs and roof trusses. Larger buildings may use beams  and columns made of concrete and/or steel due to the  larger loads involved. The framing of a building is typically  built right on top of the foundation so that the  weight is transferred to the supporting soil. 
After it is put up, the framing is covered, on  both the inside and the outside of the building, with  decorative material. The outside covering might be  made of brick, wood, glass, or other weatherproof  material. The inside covering might be drywall, brick,  or wood. Insulation is normally placed between the  inside and outside cover layers in order to keep the  building at a constant temperature and to minimize  noise from the outside. 

Roofing 
Many options exist for roofing materials and designs. 
Roofs can be made flat or with a pitch, or slope. This  choice affects which materials and construction techniques  are used. The structural portion of the roof is  typically made of wood or steel trusses, which are simply  a collection of beams fastened together using special  connectors. Plywood sheeting is then attached to  the trusses, and some type of weatherproof covering is  placed on the plywood. Options for this covering  include asphalt, wood, tile, metal, or concrete shingles. 

Learn More About Auto and Shop Topics 
There are many real-life sources you  can investigate to learn more. A construction site is a  great place to visit for a day to learn more about hand  tools, cranes, pumps, and other devices. Visit an auto  repair shop. Internal combustion engines, lifts, levers,  and hand tools are only a few of the types of tools and  systems you could see in use. Visit a local  manufacturer in your town. Examples include a  foundry, a sheet metal fabricator, an automotive manufacturer,  or a pump manufacturer.