Unitized Construction

A unibody has no separate frame. It is a stressed hull structure in which each or the body parts supplies structural support and strength to the entire vehicle. The major advantage of unibody vehicles is that they tend to be more tightly constructed because the major parts are all welded together. This design characteristic helps protect the occupants during a collision. However it causes damage patterns that differ from those of body-over-frame vehicles. Rather than localized damage, the stiffer sections used in unibody design tend to transmit and distribute impact energy throughout more of the vehicle.

Body-over frame construction
In body-over-frame construction, the frame is the vehicle’s foundation. The body and all major parts of the vehicle arc attached to the frame. The frame must also be strong enough to keep the other car parts in alignmentshould a collision occur. The frame is an independent, separate component that is not welded to any of the major units of the body. The body is generally bolted to the frame. Large, specially designed rubber mounts are placed between the frame and body structure to reduce noise and vibration from entering the passenger compartment. Quite often, two layers of rubber are used in the mounting pads to provide a smoother ride. Body-over-frame designs are still used on many of today's pickup trucks, full-size vans,
and a few full-size passenger cars.

Body Shapes
Various methods of classifying vehicles exist. Vehicles may be classified by engine type, body/frame construction, fuel consumption structure, type of drive, or the classifications most common to consumers, which are body shape, seat arrangement, and number of doors. Seven basic body shapes are used today:
1. Sedan. A vehicle with front and back seats that accommodates four to six persons is classified as either a two- or four-door sedan Often, a two-door sedan is called a coupe. If the Vehicle’s B pillars do not extend up through the side windows, the car is called a hardtop. It can also be classified as either a two- or four-door hard-top.

2. Convertible. After an absence from the domestic market for several years, many manufacturers have offered convertible cars since 1985. Convertibles
have vinyl roofs that can be raised or lowered. Like a hardtop, the B pillar stops at the belt line of the car. It can be available in two- and four-door models. Some convertibles have both front and rear seats. Those without rear seats are commonly referred to as sports cars.

3. Sport utility vehicles (sws). This classification of vehicles covers a range of body designs. Compact and full-sized SUVs are available in two-wheel drive, four-wheel drive (4 x 4) ,or all wheel drive. suvs are best described as multi-purpose vehicles and, depending on their size and design, can carry a wide range of passengers.