The Evolution of the Auto Body Frame

Automobiles were always built on a traditional body-on-frame model. That is, the two components were designed and built separately before being fused, welded and bolted together. This design was the widely accepted design concept for over 100 years, until the advent of unibody frame construction.
Through the early days of the automobile, frames were constructed from wood. This has many obvious disadvantages, including very rigid response- meaning a rough ride- and issues with longevity from exposure to elements, not to mention it was relatively easily damaged. In the 1930’s, however, the steel ladder frame design was introduced. With this came many advantages over the traditional wooden frame, including better resistance to wear and a safer ride.
Passenger vehicles, more and more, were increasingly designed employing a unibody frame construction. This design really took off in the 1970’s and had a second coming in the early 2000’s and has lapsed ladder frame as currently the most popular frame concept for the light passenger automobile.
There are numerous advantages to the unibody concept. For starters, it’s a lot cheaper for the manufacturer to produce and assemble. This makes it cheaper for the consumer- a lower sticker price. A unibody design is also much lighter for improved performance, acceleration and gas efficiency.
This increased performance is thanks in great part to better flexibility when taking turns, afforded through the frame construction. Most important is the increased safety, with designated crumple zones to protect from impact. These crumple zones divert impact absorption away from the passenger compartment as effectively as possible.