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Re: Why unibody?

To: mgs@autox.team.net
Subject: Re: Why unibody?
From: Keith Wheeler <keithw@sand.net>
Date: Wed, 22 Dec 1999 10:18:00 -0800
Tim Nagy wrote:

>Here's one I haven't seen...why did MG decide on a unibody versus a
>traditional chassis.
>
>I'm sorry if this is one of those "obvious things that every MG owner
>should know", but I just thought it would be alot easier to do the body
>work (sills) if it weren't structural.
>
>Well, flame suit on, if necessary.

No flame suit needed.

It's only obvious if you are in to mechanical engineering. Traditional
frame chassis cars are horrid. They're heavy, have no torsional
stiffness to speak of, and require more manufacturing steps.  If you're
going to be making body panels and welding them together anyway,
why not just make them structural?  The monocoque (or unibody) is
cheaper to manufacture, stronger, lighter, and makes a vastly
superior sports/race car.  Tis also a lot better in crash scenarios.
Structural body panels transfer and absorb load, a body just bolted
to a frame can shear mounts etc.

The downside?  Yes, it's harder to repair, and much harder to repair
properly.

If you are really interested, there are a number of good books
around that discuss such things, I think one "Race Car Chassis Design"
or something similar is easy to find in the book stores.  It discusses
the evolution of the chassis frame the old (read inherited from stage
coaches) ladder frame through spaceframes and monocoques, up to the
amazing carbon fibre things being built today.

-Keith Wheeler, dreaming of a carbon fibre MGB tub
Team Sanctuary                          http://www.TeamSanctuary.com/

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