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LESSON 1
IDENTIFY COMMON AUTOMOTIVE TERMS AND
CLASSIFICATIONS OF WHEELED VEHICLES
TASK
Describe the common automotive terms and classifications of wheeled vehicles.
CONDITIONS
Given information about common automotive terms and general classifications of wheeled vehicles.
STANDARDS
Answer 70 percent of the multiple-choice test items covering common automotive terms and general classification of wheeled vehicles.
REFERENCES
Learning Event 1:
IDENTIFY COMMON AUTOMOTIVE TERMS
The maintenance and repair of wheeled vehicles becomes an increasingly larger job each year. New vehicles are being made, new types of systems are being used on the vehicles, and new words are becoming part of the language used by soldiers who perform the maintenance and repair of wheeled vehicles.
To become a good mechanic, you must keep up with all changes that pertain to your job.
In this lesson, we will discuss some of the terms and words that are commonly used when referring to wheeled vehicles, the various ways wheeled vehicles are classified, and where the major assemblies of vehicles are located.
The wheeled vehicle maintenance career field, like all other occupations, contains terms that are not often used outside the field. These words or terms make conversation among people in the trade much easier, because sometimes a single word or a group of two or three words can take the place of long sentences. Let's use the word "subcourse" as an example. If you happened to use "subcourse" in speaking to someone who does not know what it means, you would have to explain: "A subcourse is a bound book that contains training material on a specific subject. It is separated into one or more lessons, and each lesson has a short exercise or query at the end." You could go on for some time explaining the term. However, if the person you are talking to already knows what the word "subcourse" means, using that word is a quick way of communicating. This is exactly what happens in the language of vehicle maintenance. We use one word, or two or three words, to represent what could take many sentences to explain. Because you will hear these terms quite often, learn them well.
VEHICLE
A vehicle can have many shapes and can be large or small. Within your trade, vehicle means any type of equipment with wheels or tracks on it that is used to transport people, equipment, supplies, and so forth. It can be a sedan, cargo truck, wrecker, tank truck, trailer, semitrailer, or many other types. It may have its own power, or it may be a unit that must be towed by another unit. Vehicles are classified as administrative, tactical, or combat.
VEHICLE CHARACTERISTICS
Certain terms are used to express what a vehicle can do. These terms are vehicle performance characteristics:
All-wheel drive
As you know, most civilian vehicles have power to the rear wheels only, but some cars have power to the front wheels instead. Either design works fine for vehicles that travel on hard-surfaced roads most of the time.
However, cars do get stuck in soft ground or snow. If power could be applied to all of the wheels instead of just the front or rear, a vehicle could move much better in mud or snow. This is exactly what has been done to Army tactical vehicles. The operator can engage power to the front wheels when necessary, and then all the wheels on the ground can be driven.
You will commonly hear a vehicle referred to as a four-by-four (4x4), a six-by-six (6x6), or even a four-by-two (4x2).This means that, if a vehicle has four wheels and only the front or rear wheels are powered, it is called a 4x2. If all four wheels can be powered, it is a 4x4. If the vehicle has four wheels in back and two in front, it will be either a 6x4 or 6x6, depending on how many wheels can receive power.
All-wheel drive vehicles are needed in the Army because Army vehicles must travel cross-country in snow, mud, and sand as well as on hard-surfaced roads.
To understand "angle of approach," just think of driving on level ground and then coming to a steep upgrade. If the grade is too steep, the vehicle bumper will strike the ground. When we say angle of approach, we mean the steepest grade angle that a vehicle can come up to and start to climb with no part of the vehicle scraping or digging into the ground.
Angle of departure
"Angle of departure" is the opposite of the angle of approach. It is the steepest downgrade a vehicle can leave with no part of the vehicle except the wheels touching the ground.
This term refers to the distance a vehicle can travel on a full tank of fuel under normal conditions. This is important because, as you know, military vehicles cannot always stop at roadside gas stations. Therefore, you need to know how far the vehicle can travel on a full tank so that you can carry extra fuel if you are going to need it to complete a trip.
Drawbar pull
Most military vehicles have a device attached to the rear of the frame to connect a trailer for towing. This device is called a pintle, and it is merely a hinged connection that can be opened for hooking up the trailer and then can be closed in a locked position.
"Drawbar pull" is the amount of trailer load that can be safely handled by the vehicle and trailer connection.
Fordability
In combat situations, wheeled vehicles often have to cross streams and other inland waterways. When this is required, it is important to know whether or not the water is too deep for the vehicle to pass through without a special waterproofing kit. "Fordability" refers to the deepest water, measured in inches, that a vehicle can pass through without adding the special equipment.
Gradeability
Because Army vehicles are expected to travel cross-country, over rough terrain, they must be able to climb very steep hills. "Gradeability" refers to the steepest grade the vehicle can climb at a steady speed in low gear on a smooth, concrete road when fully loaded.
All tactical vehicles must be able to climb a 60° slope under their own power.
Turning radius
This is the distance from the center to the rim of a circle made by the outside front wheel of a vehicle when the front wheels are turned as far as they can go and the vehicle is moved in a circle.
One of your jobs as a wheeled vehicle mechanic will be to adjust the steering turning stops so that the vehicle turns in the correct circle prescribed by the manufacturer.
Ground clearance
This is the distance from the surface of a smooth parking area to the lowest component of the vehicle undercarriage.
As you know, when a vehicle is driven over rough ground, the oil pan, propeller shafts, or other components might be damaged. Therefore, military vehicles are designed with much greater ground clearance than civilian vehicles.
Traction
This is the ability of the vehicle wheels to hold to the road without slipping or spinning. Several factors determine the amount of traction a wheel has, such as the condition of the tire and the type of tire tread.
The road condition also has a lot to do with traction. On icy roads the wheels slip or spin easily, so the "traction" is poor. On dry, paved roads, the "traction" is good.
VEHICLE WEIGHT
Net weight
This is the actual weight of the vehicle only. It does not include the weight of the fuel, lubricants, water, crew, or cargo.
Curb weight
This is the weight of the vehicle with fuel, oil, and water added, fully equipped for operation. It does not include the crew and cargo.
Payload
This is the weight of the cargo or passengers, including the crew, that a vehicle can safely carry. It does not include the weight of the vehicle, fuel, oil, or water.
A vehicle can carry a greater payload when traveling on the highway than when traveling cross-country. The payload that a vehicle can safely carry on a good road is called the "on-highway payload."
Gross weight or fighting weight
This is the weight of a fully equipped vehicle serviced for operation, including the crew plus the full allowable payload.
DESCRIBE CLASSIFICATIONS OF MILITARY VEHICLES
ASSIGNMENT TO UNITS
All vehicles used by the Army are called "military vehicles." They serve many useful purposes but are made mainly-to carry the supplies, personnel, and equipment of the Army under combat conditions. All vehicles are classed as "organic" or "nonorganic" vehicles.
Organic vehicles
These are the vehicles that are permanently assigned to, and are part of, your organization or unit. This means they were issued to your unit and will be operated and maintained by the personnel of your unit.
Nonorganic vehicles
These vehicles do not belong to your unit, but your unit temporarily uses them.
An example of organic transportation is the movement of an infantry company using only its own vehicles. The same move using trucks from a transportation company is an example of nonorganic transportation.
MILITARY VEHICLE GROUPS
Military vehicles are divided into three groups called "administrative vehicles," "tactical vehicles," and "combat vehicles."
Administrative vehicles
Administrative vehicles are not specially made for the Army but are ordinary vehicles made for civilian use (trucks, buses, and sedans) that the Army has bought. They are usually repainted and are marked with Army numbers, but they differ very little from the ones you may have used as a civilian.
Tactical vehicles
These vehicles are specially made for the Army. They are made to operate off the highways under almost any type of weather condition and to travel cross-country through sand, mud, or snow. Tactical wheeled vehicles have all-wheel drive to give them more traction, and some have winches to help them through tough spots.
Combat vehicles
These vehicles are made for one reason only - to fight the enemy. These vehicles usually have armor and heavy guns.
Most combat vehicles use tracks instead of wheels. You will have no trouble recognizing a combat vehicle because it is specially made for fighting and not for hauling cargo or personnel.
TYPES OF TACTICAL WHEELED VEHICLES
There are three kinds of tactical vehicles:
General Purpose
Special Equipment
Special Purpose
General purpose vehicles are made to haul all sorts of things, such as ammunition, equipment, rations, and troops. They also tow trailers and artillery. All of these different jobs can be done without modifying or changing the vehicle.
You may sometimes see a general purpose vehicle that has a machine gun mounted on it, and maybe special steel plates (called armor) have been added; but its job is not to fight, but to haul: It is still a general purpose vehicle.
Special equipment vehicles
These vehicles have a general purpose chassis with special equipment mounted. The frame, wheels, axles, and so on are the same as on a general purpose vehicle, but the cargo body has been replaced with something else. Some special equipment vehicles are water-tank trucks, gasoline-tank trucks, and dump trucks. Remember, a special equipment vehicle has the same chassis as a general purpose vehicle; only the body has been changed.
Special purpose vehicles
These vehicles are made to do a certain job that a general purpose vehicle or special equipment vehicle cannot do.
One example of this is a wrecker. The frame of the general purpose vehicle chassis would not be strong enough to take the load. Another example is the truck-tractor that you see pulling a large cargo trailer on the highway.
Truck-tractors are made for towing and not for carrying cargo. The frame is shorter than a cargo-carrying truck.
TRAILER CLASSIFICATION
Some vehicles you will work with are made to be towed. These vehicles are trailers and semitrailers.
Trailers
These vehicles have a drawbar, or tongue, in the front, to be attached to the pintle or coupling mounted on the rear of the vehicle that does the towing. The eye at the end of the trailer's tongue that hooks into the pintle is called a lunette.
Most of the trailers in use today are two-wheeled. However, you will see some four-wheeled trailers (or "full trailers").
Trailers are made in such a way that their wheels support most of the weight of the cargo they are carrying.
Semitrailers
These are also vehicles made to be towed, but there is one big difference between a semitrailer and a tongue-type trailer. The front part of the semitrailer is supported by the towing vehicle. This means the towing vehicle carries a lot of the cargo weight.
The vehicle that carries some of the load and tows a semitrailer is called a truck-tractor. The semitrailer is connected to the "fifth wheel" of the truck-tractor or may be supported by means of a "dolly." A dolly is another set of wheels, a frame, and a fifth wheel.
When the dolly is placed under the semitrailer, it becomes a full trailer and can be towed using an ordinary truck.
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Lesson 2
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