Aluminum used in chassis

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moreairguns@icqmail.com - 24 Dec 2007 01:14 GMT

I am interested in using aluminum tubing for building a tubular
chassis but most people say that aluminum does fatigue crack.
But I was thinking that it has been done and aluminum can be used for
a car chassis.

Audi uses aluminum for their monocoque chassis....

Is there anything I should know about this Audi chassis?

Isn't fatigue cracks also a problem with this Audi chassis since it's
also made of aluminum....or perhaps also with the Acura NSX?

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Scott Dorsey - 24 Dec 2007 13:32 GMT

>I am interested in using aluminum tubing for building a tubular
>chassis but most people say that aluminum does fatigue crack.
>But I was thinking that it has been done and aluminum can be used for
>a car chassis.

It does, but aluminum is more than one kind of thing. There are thousands
of aluminum alloys. Some have worse fatigue problems than others. Some
are easier to weld than others. Some are easier to machine than others.

>Audi uses aluminum for their monocoque chassis....
>
>Is there anything I should know about this Audi chassis?

Yes, you need to know what kind of aluminum alloy they use, first of all.
Secondly, you need to know how the chassis was designed to avoid flexing
and how they engineered welded joints to avoid flex points.

>Isn't fatigue cracks also a problem with this Audi chassis since it's
>also made of aluminum....or perhaps also with the Acura NSX?

I don't know. But I'll say that fatigue cracking can be a major problem
with aircraft, if you aren't careful. Aircraft designers work to distribute
flexure so all the movement isn't in one place. And aircraft maintenance
folks do regular inspections. Even so, sometimes things break like that
737 in Hawaii that had microcracking around rivet holes.
--scott

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"C'est un Nagra. C'est suisse, et tres, tres precis."

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HLS - 24 Dec 2007 18:06 GMT

>>I am interested in using aluminum tubing for building a tubular
>>chassis but most people say that aluminum does fatigue crack.
[quoted text clipped - 4 lines]
> of aluminum alloys. Some have worse fatigue problems than others. Some
> are easier to weld than others. Some are easier to machine than others.

> "C'est un Nagra. C'est suisse, et tres, tres precis."

Well said, Scott.

If you are not really an expert at design, welding, etc than one should
perhaps
not consider trying to develop a chassis from aluminum.

IIRC, the Norwegian aluminum producer (which name fails me at the moment)
spent a lot of money and worked closely with the automobile industry to
develop
a high tech aluminum chassis. It was a work of art.

For most people, fabrication with large diameter thinwall tubing would be a
lot
easier and very competitive. This was described in a book by Costin, I
believe,
if he is lucky enough to find a copy. It is supposed to be the prime
resource
for high performance chassis development. (He is the Cos in Cosworth).

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Bob Urz - 26 Dec 2007 04:05 GMT

>>I am interested in using aluminum tubing for building a tubular
>>chassis but most people say that aluminum does fatigue crack.
[quoted text clipped - 22 lines]
> 737 in Hawaii that had microcracking around rivet holes.
> --scott

Yea, you can visit a F15 jockey while most of the early F15 fleet is
grounded due to internal cracking of support structure....

Bob

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Bhagat Gurtu - 26 Dec 2007 15:24 GMT

On Sun, 23 Dec 2007 17:14:36 -0800, moreairgun wrote:

> I am interested in using aluminum tubing for building a tubular chassis
> but most people say that aluminum does fatigue crack. But I was thinking
[quoted text clipped - 6 lines]
> Isn't fatigue cracks also a problem with this Audi chassis since it's
> also made of aluminum....or perhaps also with the Acura NSX?

Before you start this job make sure that you have a degree in mechanical
engineering and are an expert in finite element modeling.

Of course it is taken for granted that you know how to use CAD software
and that you have the money and resources to produce a predictable safe
design.

HTH

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Scott Dorsey - 26 Dec 2007 16:20 GMT

>Before you start this job make sure that you have a degree in mechanical
>engineering and are an expert in finite element modeling.

Nah, FEM is for wimps who can't build real prototypes. Folks built big
structures out of aluminum for decades without FEM. The ME degree sure
wouldn't hurt, though.

>Of course it is taken for granted that you know how to use CAD software
>and that you have the money and resources to produce a predictable safe
>design.

The guys at Douglas sure did a nice job with the DC-3, with no CAD/CAM,
no FEM, and no CNC machining. And aluminum alloys were a lot poorer
controlled back then. Plenty of those aircraft are still flying with no
sign of fatigue failures. Of course, they had a LOT of guys with ME degrees
on staff.
--scott

Signature

"C'est un Nagra. C'est suisse, et tres, tres precis."

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