What's the better lower stress bar?

[amalventano1@comcast.net (Allyn)]

all of this truss talk, lets get down to whats really going on here. =
the
rear bar of that 4-point bar is doing effectively nothing. the rear b=
eam is
reinforcing a huge cross member thats already in place (no use). if t=
his is
the 4 point bar im thinking about, there is only a single diagonal be=
am and
no fore/aft beams. under hard acceleration, the a-arms exert huge for=
ward
forces on the a-arm mounting points (the parts extending from the fra=
me,
where the forward beam connects to). so this means that under hard
acceleration with mounting points flexing in the forward direction, t=
he
4-point bars diagonal cross member will result in CREATING SIDEWAYS S=
TRESS.
just imagine the letter "Z". pull up on the top of it, the "/" part o=
f it
will try to straighten like "|", ending up like "-|_" in the extreme.
    the factory bar does a better job of equalizing forces on the a-a=
rm
forward mount points under hard acceleration. it doesnt have a rear c=
ross
piece because quite frankly its useless. here is a pic of what its
reinforcing:
http://scirocco.dhs.org/vw/pics/0-allyn/project/imagepages/image81.ht=
m
that hollow beam runs all the way across. i seriously think that beam=
 isnt
going to give at all in the tensile/compressive area, its just fine o=
n its
own and needs no support.
    the 4 point bar may be slightly better than the factory bar from =
a
cornering standpoint, but i dont like the forces it tries to exert un=
der
acceleration. the only way the 4 point bar can truly be better than f=
actory
is if it was a boxed-x instead of a 'z'. heck, even adding a single b=
eam to
make a half-boxed-x would be better.

anyhow, just my ramblings (not trying to knock dan or anything like t=
hat). i
have considered all of these types of lower suspension stuff over the=
 past
3-4 months as i have been laying out plans for the twins rear suspens=
ion.
alot of my research has involved vector stress analysis using measure=
ments
=66rom the stock scirocco suspension mounting points (i actually trie=
d a z-bar
design for reenforcement and realized the twisting force it created).

Al

Allyn Malventano, ETC(SS), USN
87 Rieger GTO Scirocco 16v (daily driver, 170k, rocco #6)
86 Kamei Twin 16V Turbo Scirocco GTX ('it has begun', rocco #7)
87 Jetta 8v Wolfsburg 2dr (daily driver, 260k, 0 rattles, original cl=
utch,
driveshafts, wheels :)


----- Original Message -----
=46rom: "Scott F. Williams" <sfwilliams@comcast.net>
To: "Shawn C Meze" <skerocdriver@juno.com>; <type53@yahoo.com>
Cc: <scirocco-l@scirocco.org>
Sent: Saturday, May 25, 2002 9:47 PM
Subject: RE: What's the better lower stress bar?


'twas writting:
> >The factory bar and the TT bar are better than the
> >NoSpeed . . .

Mr. M=E9ze asked:
> OK. Why exactly?

The Neuspeed bar strengthens the chassis in one plane. The factory/TT=
 bars
are triangulated and resist twist in two planes. Surely one of the
mechanical engineer types can explain that more eloquently. Regardles=
s, what
makes me think that you're baiting us with this basic question, Shawn=
? :^)
--
Scott F. Williams
NJ Scirocco nut
'99 Subaru Impreza 2.5 RS
Mazda 323 GTX turbo "assaulted" vehicle
Golf GTI 16v "rollycar"
ClubVAC: "Roads found. Drivers wanted."




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