Safest Auto Frame/Chasis Style?

http://en.wikipedia.org/wiki/Crash_test

I have a feeling that your question in its present unrefined form cannot be correctly answered. Are you going to build a "one-off" just for yourself, a small series say less than 1000 or are you going to mass produce maybe 1000+ ????

Firstly you have to assess what building methods can you support, then build a frame, using these methods, under software control and then "crash it" many times in the software to achieve the safety you are looking for, then build it for real and then crash it some more for real.....

Remember the following, say for example Tube is best, but you build or design it badly, then a better built hexagonal would be better than a badly built tube.....etc etc..

I personally feel that square tubing has most of the efficiencies of round tubing, but with fewer building problems....crash safety has to be designed in to any contruction.

Have fun...

Abrahams A1 Battletank selfsupporting chassis-body protects you quite well against most guns, handgranades and morters.

And it gets quite well through a head-on crash with a Mercedes S-class at 80km/h.

Randolph

As others have noted, you have not defined the problem very well. One could easily design a cube shaped cage made entirely of steel I-Beams. This could easily weigh tons. While this cage would be safe it would require a huge engine to overcome drag, were you to want to actually MOVE the cage. So you now must begin the set of compromises that define a design.

A mentioned before, how many will you build? What is your budget? How many crashes does the cage have to withstand? Taking the last point, you can create a cage with excellent survivability, but you would require the replacement of the vehicle for any crash.

Too, what tools and techniques do you want to use in the construction of the cage? Steel is heavy and easy, but you must decide if you want the frame welded or bolted. But again we loop back to the issue, what do you want the vehicle to do? How fast does it have to be? What kind of mishaps are expected?

From any perspective, the vehicle should be designed for its intended use. For example, a downhill mountain bike may have a full suspension, a wide range of gears, and a near disposable frame, but this same "bicycle" would be useless on a velodrome and may even be prohibited from entering the track. If your vehicle will ever see a public thoroughfare, then you have to comply with local laws, which is yet another set of design criteria.

It is going to depend heavily on the application, but generally speaking a chrome-moly tubular chassis is usually used in severe duty applications such as rock crawling and stock car racing, where a vehicle impact and/or rolling is all but guarenteed, and many of its drivers walk away after the most serious looking of accidents (all without the use of airbags no less). The key is in the design though. I'm sure with the right design you should build a frame out of wood and it would be perfectly safe in most conditions (might weigh a ridiculous amount though). Unfortunately many of these applications mentioned before do not have working doors.

I'm making a LOT of assumptions, but:

For a one-of-a-kind, low budget automotive, square chrome-moly tubing. Round tubing might be a little stronger for the same weight, but square wins for easy fabrication.(Off road racing, stock cars)

For a high budget vehicle as above, molded carbon-carbon fiber. (Indy and F-1 cars)

For medium production, formed sheet "tray" type chassis, fiberglass body (Corvett)

In any case, plenty of FEA and simulated crash testing followed by crash test actual chassis if possible.