Chassis/Body/Frame types

The chassis is the main frame that holds the main body parts together.  It is very important that this piece is designed well, and breaks in a certain way during an accident. 

The most common chassis types would be monocoque (for typical road sedans, coupes, etc.),  ladder frame (many SUV and large family cars), backbone chassis and the least common, tubular frame chassis.

Here is some research that I have done. This is a commented posted on a forum with the topic of chassis types.  (reference: http://www.ultimatecarpage.com/forum/showthread.php?t=40386) It is very true, there are many cars that are monocoque but are also supported by a type of frame.  It is quite uncommon to find a car that is 'purely one type'. 

Types of chassis:

The most common is the unitised (monocoque) type body, which is a bunch of different shapes welded together into one piece, in which the engine components, suspension components and interior are bolted to the strongest parts.   The main advantage is that it is much stronger for the weight it is.  It also reduces squeeks and rattles as compared to having for example a ladder frame where the rest of the car sits on.

The space frame is a frame built of tubular steel or steel bar in which these are all welded together to create a frame.  crosses are used to reinforce the framing.  This is a type that would be found in DIY built vehicles or motor-sport vehicles.  This is because it is made from complete scratch, starting with just steel tubing which the tubes are bent, welded and hammered into place.  Mounts are built on for engine and transmission components, suspension components, etc.

 In this photo, the whole front (from the strut mount forward) has been completely cut off, and re framed with steel tubing.  All the mounts for the radiator, bonnet clips, etc. are welded onto this frame.  Builders will also do this to the rear, for extra strength and less weight.

The ladder chassis has a main purpose of being high in strength.  This type is found in commercial trucks and vehicles.  The ladder frame is a ladder shape of large steel bars that run length ways down the vehicle.  Other main components of the vehicle eg. the cab is bolted into this frame.