21st Century Overview - Body

Body encloses the engine, passengers and luggage.   It's called a cab on a pickup truck.   The body material is mostly sheet carbon steel with some aluminum, fiberglass, or plastic parts that are formed in hydraulic presses.   Galvanized steel is used for the underbody to resist corrosion.   There are 2 types of body construction: unibody and body-over-frame.

Unibody (unit-body, space frame) has no separate frame (see below).   Instead, it is composed of about 300 stamped-steel (occasionally, aluminum) parts that are shaped and welded together to provide body support and strength.   Weight is lower by as much as 40% and fuel economy is higher than in the body-over-frame construction, but its strength and crash-resistance are lower.

  Another view of the unibody construction.   Note that the body panels, which may be aluminum, fiberglass, or plastic, are attached to the body.   Most small and medium-size cars use the unibody construction.

  Body-Over-Frame (BOF) has a rigid frame to which are attached the operating components and the body.   The frame is an independent component that is not welded to any other component.   Components are bolted to the frame and rubber mounts are mounted between the frame and the components to absorb noise and vibration and prevent them from being felt by the driver and passengers.   Pickup trucks, full-size vans, and large passenger cars use the BOF construction.

Frame rails are usually made of stamped steel that are welded together.   Some frames are made by hydroforming, which is high-pressure shaping of the steel frame.

Chassis is the frame and all operating components.   It excludes the body.