The key phrase here is "injecting foam into the body". I was referring to Mike
Kerr's
statement regarding injecting foam into the frame (see quoted message below).
Since my '70
2000 is a California car, and therefore has a perfect body ;^ ) (not to
mention having
been garaged it's entire life), I have not had to do any body work on the car,
so I am not
too familiar with the body spaces where foam could be injected. Part of the
issue here is
the relative stiffness of the frame and the body. The Roadster's frame is a
relatively
stiff structure as it stands, and due to the size and shape of the cavities
would stand to
gain little or no additional structural strength from the foam. The body of the
car, being
fabricated of much lighter gage material, derives much of its stiffness from
its shape,
and from being rigidly attached to the much stronger frame.
Looking at the PDF files of the parts book as a reference to the body
construction, the
only areas I can determine might be candidates are the spaces in the fenders
immediately
fore and aft of the door openings. Filling these areas with foam might reduce
noise a bit,
but I don't see this contributing significantly to body stiffness. Unibody
designs can
benefit from this treatment because their multitude of cavities, forming a
continuos web
throughout the structure, are each made just that little bit more stiff when
filled with
the foam material, and it all adds up. The body structure of the Roadster, as
far as I can
tell, is not of the type that would lend itself to a profitable exercise of this
technique, but this is a point on which I would be more than happy to be proved
wrong.
As for cowl shake and Miatas, the cowl on the Roadster shakes because it has a
four-cylinder engine and the hood mounts and latch are not only not close
tolerance
interfaces to begin with, on most of our cars they are 30+ years old; the
Miata has a
tighter chassis because it's design is standing on the shoulders of the work
done in the
period between the Roadster's time and now. Modern cars are stiffer, lighter
and vastly
improved in the area of chassis and suspension design because engineers have
been
learning how to improve these structures, computer-aided design systems have
greatly
increased their ability to put that experience into practice and because
materials
engineers have developed improved materials and processes for fabricating these
structures.
Gary McCormick
'70 2000 (with gradually increasing amount of clear space around it in the
garage - woo
hoo!)
San José, CA
------------------------------------------------------------------------------------------
datsunmike wrote:
> Although I didn't actually drive the 300Z they used the foam in/on(?) they
> said that it provided a lot of extra structural strength, so much so that
> when they tested the Z after injecting the foam into the body "the chassis
> now almost feels like it has a roll cage."
>
> While the roadster is not a unit body design I can't see how this product
> would not stiffen the body and frame of our cars. Compared to my Miata, the
> roadster is fairly loose and has considerable cowl shake. Anything that can
> tighten it up for better handling would be greatly appreciated especially
> when no fabrication is needed.
>
> '66 Mike
>
> ----- Original Message -----
> From: Gary McCormick <svgkm@halley.ca.essd.northgrum.com>
> To: Marc Sayer <msayer1@concentric.net>
> Cc: Mike Kerr <mikekerr@innercite.com>; datsunmike <datsunmike@nyc.rr.com>;
> Roadster list <datsun-roadsters@autox.team.net>
> Sent: Monday, June 05, 2000 1:00 PM
> Subject: Re:
>
> > I question whether filling the interior of the frame members with this
> material will
> > significantly increase stiffness - the Roadster's frame members appear to
> be pretty
> > substantial already. A foam filling, even though the material itself, when
> set, is quite
> > stiff, is not going to contribute materially to either the torsional,
> lateral or
> > longitudinal stiffness of the car. The loads that affect the frame members
> are going to
> > subject a foam filling to shear stresses - stresses to which these
> materials are not
> > sufficiently resistant for them to be beneficial. Your best bet is to
> treat the frame for
> > external rust resistance to prevent corrosion from weakening it, rather
> than attempting to
> > use an ineffective means of attempting to strengthen it.
> >
> > Gary McCormick
> > San José, CA
> > ------------------------------------------------------------------------
> ------------------
> >
> > Marc Sayer wrote:
> >
> > > Mike Kerr wrote:
> > > >
> > > > one problem though if it traps moisture it can give you probems with
> rusting
> > > > out the body
> > > > there was this house that they used some new type of foam as
> insolation
> > > > that caused all the nails to rust that held it together , it had
> formed some
> > > > sort of acid that did the damage .. Would be a bummer if you pumped
> foam
> > > > inot your car only to have it rust away..
> > > > But if this stuff is safe it could be used in the frame of the roaster
> to
> > > > stiffen it ...
> > >
> > > Mike is absolutely right. Though the stuff is used for just this purpose
> > > in new cars and therefore isn't going to produce rust or corrosion in
> > > and of itself, if the box members being filled aren't properly prepared
> > > first, you are going to have problems. I haven't seen the instruction
> > > for these products, and they may give specific dos and don'ts But I
> > > would think that all rust should be treated first with an agent such as
> > > Rustmort or Ospho, which will convert the rust to a stable iron oxide
> > > that is not reactive and will not corrode any further. Then a coating of
> > > some sort might be in order, like a paint or something. As I say the
> > > specific product may well have instructions as to how to use it in an
> > > older car, once it is released for consumer use. Of course as it is used
> > > now, during production of a new car, the situation is completely
> > > different.
> > >
> > > --
> > > Marc Sayer
> > > Editor/Publisher
> > > Z Car & Classic Datsun Magazine
> > > http://zcarmag.com
> > > Voice 541-726-6001
> > > Fax 541-746-0863/726-6001
> >
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