frame damage

Body-on-frame is an automobile construction method where a separate body is mounted on a relatively rigid vehicle frame or chassis carrying the powertrain (the engine and drivetrain). The original method of building automobiles, body-on-frame construction is now used mainly for pickup trucks and (mostly full size) SUVs.
In the late 19th century the frames, like those of the carriages they replaced, might be made of wood (commonly ash), reinforced by steel flitch plates – but in the early 20th century steel ladder frames or chassis rapidly became standard. Mass production of all-metal bodies began with the Budd Company and the Dodge Brothers. Mass production of all-metal bodies became general in the 1920s but Europe, with exceptions, followed almost a decade later. Europe's custom-made or "coachbuilt" cars usually contained some wood framing or used aluminium alloy castings.
In contrast, Unibody or monocoque designs, where panels within the body supported the car on its suspension, were developed by European manufacturers in the late 1920s with Budd USA (which had a number of large factories in Europe) and its technical knowhow; but not in USA until the 1950s and generally later. Because of the high cost of designing and developing these structures and the high cost of specialised machinery to make the large pressings required by this style of construction it is not used by low-volume manufacturers, who might construct an equivalent by welding steel tube to form a suitable space frame.

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