Strut Tower Brace Design Revisited

[Peter Schulz]

Bernie:

Sorry that you feel that way, but remember one's "pot shot negatives" are 
another's opinion....
and we have not had to use disparaging terms such as "ill conceived", etc...

you could have easily avoided snide comments and kept this a thread on 
suspension design and engineering.
Instead, you started the panning of other people's efforts.

All we have stated is that what works well for you, in your environment, 
with your driving style, and your suspension components may not work well 
for others...I.e. what you term "engineered" , we think may not have 
covered all the variables...
and nothing that you have said in response has changed our opinions.

In lay terms, I think of the Benz brace this way - and yes, this is an 
over-simplification that does not take into account the vertical movement 
of the strut within the constraints of the strut tower and the lower 
control arm and anti sway bar mounting points....

take a box and remove the top and cut two opposing sides of the bottom - 
you are left with 4 sides connected to each other. Hold up the box so that 
you can see into it - the vertical sides are your struts, the lower side 
the control arm/sub frame and the upper side the benz bar.  Now distort one 
side - and the other side moves in the same direction with it - the box 
will maintain the shape of a parallelogram- but the bottom of the box ( the 
chassis) will move freely due to the two opposing sides being cut.

Great - your front wheels are now tracking together  - but what about the 
chassis behind it?...

So now tape the two cut sides on the box bottom to the box sides
.....the towers are now fixated to the chassis ( the back of the box)
Now do the same thing....

Our contention all along is that on the 200 20v, the front strut towers are 
not fixed to the chassis as rigidly as they could be. (need to address 
gross movement of chassis components - strut towers vs firewall (rest of 
the chassis)- audi addressed this issue on the V8 ( which btw carries about 
the same weight on the front of the chassis) with re enforcements around 
the strut towers to the firewall, and on the 1992 C5 S2, with re 
enforcements and the addition of the strut tie bar. - the evidence is there 
with the distortion on the passenger side tower to firewall gusset on the 
200s....

The Benz brace performs on the other hand, performs "fine tuning" in the 
deflection of the struts within their confines.

-Peter










At 11:15 PM 2/28/2005, Bernie Benz wrote:
>Scott and Peter,
>
>You of course have free choice to embrace my strut brace design or not.  If
>not and you wish to actively speek out,  you should have a constructive
>alternative that you can technically justify or, as you have done, show a
>preference for pot shot negatives in support of a do nothing posture.  My
>design and its justification has been offered for free use to the list, and
>I am willing to further discuss reasonable quiries of same, on or off list.
>
>George S. has implemented my design incorporating his (IMO ill conceived)
>"enhancements", and has acheived the intended improvement of my design, thus
>I am pleased that he apparently is a happy camper.   My only point in
>continueing this thread was to point out to other perspective followers that
>his design enhancements were unnecessary and contribute nothing to the
>intended and achieved strut brace performance.
>
>Insert humor here:
>I have discovered that when we upset our significant
>others, they nag us. If we upset them even more, we
>get the silent treatment. Personally, I think it's worth
>the extra effort.
>
>Bernie
>
>
>From: SuffolkD at aol.com
>
>Bernie:
>Strange you'd snip someone copying your "design", comedy or not.
>"Stick to your CEOing, George."
>
>While it may keep the strut inserts aligned when the bearings or other
>components are worn, there's deflection/twist in the chassis that your brace
>doesn't account for.
>
>As Peter says, your test conditions are far smoother than ours, and unless
>you drive by Braille ON the lane markers on the I-5, you'd never see the
>chassis flex which may show the potential short comings of the EMT in your
>design, or the design itself.
>
>I also seem to remember an engineer who also chimed in on the list a year or
>two ago telling how dangerous he thought your design was.
>
>Personally, I feel there is a reason the factory went with a tower brace
>(specifically) as Bernie you corrected me on my generalization of "strut
>brace."
>
>The twist of the chassis from pot holes, understeer/oversteer while in
>motion, elevation changes in mid turn, steep bisecting parking garage exit
>ramps (while turning) like in California, curbs and the like.
>This is easily duplicated by jacking the car up at a jack point then trying
>to open the door.  Chassis flex on an inferior design is evident when you
>try to open the door.
>
>This twisting of the frame is not addressed by your brace, but by every
>other suspension component (in line between your brace and the applied
>twisting force) until the last bit of strut movement which your brace
>bridges.
>Maybe IMHO that's why you haven't seen a failure in compression/tension of
>the EMT. Its the bushings, strut bearing and other components that have
>sacrificed themselves ahead of your EMT.  Either that or the sidewall of the
>tire is weaker that the EMT.
>
>IF I was to use your "intriguing" strut brace idea I'd go the George route,
>SOLID bar. but I'd also go "tower" brace ala Audi.
>
>If there was a design flaw in the VAG tower brace (next to cost) I'm sure
>they'd quickly adopt your brace idea as a cost cutting measure.  The
>accountants would push for it.
>-Scott by BOSTON
>
>From: Peter Schulz <>
>Sorry, but your design is engineered no more or less than Georges....
>Bottom line is that we all have our opinions - in the absence of the real
>science of suspension design with force measurements and analysis
>
>"If your rational were true, my strut brace designed for compression forces
>only, would have hammered itself to pieces by now, under your osculating
>tensile forces.  Rather, it shows no sign of the tubing ever leaving the
>jam nuts, the design intent."
>
>What does that mean in respect to the road environment where you live?  If
>your roads are relatively smooth, you would likely see alot less strain
>then on uneven, poorly maintained roads.
>
>-Peter
>
>
>
>
>
>_______________________________________________
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1991 200 20v Q Avant Indigo Mica
1991 90 20v Q Red
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Chelmsford Ma, USA