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How to design a 968 Strut Tower Brace
#41

[quote name='Rap' timestamp='1346279711' post='131901']

Kum by ya. Let's be careful here or we will be doing a group kiss and AJG is not wearing a bra!

[/quote]

Eh! What are you saying Rap man! I was a passenger in a cabriolet just the other week and I thought since its such a nice day I'll put on me strapless bra, as you do.

Well we were driving along, and as we went faster and faster the wind blew me bra round back to front! I was nearly paragliding man! People were staring and I shouted out " Stop looking ye pervs" A policeman pulled us over and said to me " I need to take down your particulars" I said "Eh! Your on duty officer. Is that allowed"? He was probably a perv as well. You can't trust no one.
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#42

I always find looking in the mirror brings about a sense of reality! Although that can't be me in the mirror boy. Go to the mirror boy. Tommy can you hear me!
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#43

it doesn't happen much here, but on other sites it's truly amazing at how somebody sees something, doesn't understand it, yet continues to comment on it. the same thing is going on about the firewall brace. somebody saw a REV 1 unit, felt a little flex under clutch load, and thought it was useless. clearly it added strength, and would reduce the load on the firewall. REV 2 is so much stronger there is absolutely no movement on an undamaged firewall with a "normal" clutch. i'm pretty sure the guy commenting on the brace has not seen REV 2, and may not even be aware there is one, and that it's been the only one going out there now for over a year.



but he's the same guy who rubber bands and bubble gums pretty much everything anyway, and most people know it, so they ignore him. he's also the guy who tries to correct people's grammar and is dead wrong, like recently when he tried to tell somebody that it was "preventive" and not "preventative", when we all know that the words are interchangeable. but maybe his knowledge of english is as poor as his knowledge of engineering?



just the same, it's that kind of ignorance that abounds on other sites. there is no filter mechanism to ensure accuracy or reason. that's why you ultimately have to see things for yourself.
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94 Midnight Metallic Blue Cab Porsche 968 w/deviating cashmere/black interior and WAY too many mods to list - thanks to eric for creating www.968forums.com



"It isn't nearly as expensive to do it right as it is to do it wrong."
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#44

And who would've thought a strut brace that's too stiff could actually damage your car? You don't hear any mention of that anywhere else - where the issue is probably more likely to be considered a left-coast conspiracy.
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#45

the problem is partly due to a complete lack of sampling. there just aren't enough cars out there with braces, and being subjected to high stress loads, so as to provide a good sampling. braces aren't allowed in many racing classes. that leaves only street applications, and those would take a long time to have the problem show up, and even then, unless you understand stress loads, you would not know why the problem occurred.



i did quite a bit of reading before i put pencil to paper. i found a number of failed 944 towers (which are essentially the same as ours). i also already knew of a number of failed mounting hardware cases. a quick bit of calculation and testing, and bingo.



i was designing stuff for DOD long before a lot of the owners of these cars were even born. all of my applications had to undergo heavy shock load and stress testing. that put me in a great position to understand materials and stresses when it came time to design things for this car.
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94 Midnight Metallic Blue Cab Porsche 968 w/deviating cashmere/black interior and WAY too many mods to list - thanks to eric for creating www.968forums.com



"It isn't nearly as expensive to do it right as it is to do it wrong."
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#46

How could we tell which rev of the firewall brace we have? I'm pretty sure mine is a Rev 2, but Is there any way to tell? Thanks.
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#47

I believe Rev. 2 has a "gusset" at the bend. I just had my wife pump the clutch while I watched the firewall, and even shining a light down there I couldn't see any movement.
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#48

it does indeed have a gusset there. it's also thicker material, and the nuts are welded on.



the only thing that i could do to improve it would be to add a similar gusset on the other piece. the problem with that is there is no room for it without some significant changes in the harness.
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94 Midnight Metallic Blue Cab Porsche 968 w/deviating cashmere/black interior and WAY too many mods to list - thanks to eric for creating www.968forums.com



"It isn't nearly as expensive to do it right as it is to do it wrong."
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#49

OK, I must have the Rev 2, then, because the nuts were welded on. I'll haven't confirmed the firewall doesn't flex, because I installed the brace over six months ago, while the engine was still out of the car, and didn't think about checking it after I put the engine back in (especially since I don't have a driver's seat at the moment). It looks like a very solid piece, though, and my firewall flex wasn't all that bad before the brace install, so I'm sure it's fine.
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#50

yup - you're good to go. i doubt you will ever see any flex. the REV 2 is pretty darned stout. i looked at the amount of flex in my uncracked stock firewall, and then after the REV 2 was installed. it had a tiny bit without the brace. that amount was cut in half with the first brace. with the REV 2 brace it was zero!



i still do not recommend this as a repair, and i still feel that a real repair is warranted if the firewall is cracked. then installation of the brace will prevent that repair from failing.



i can come up with a repair item, but it would involve some changes in the harness. basically a lot of stuff would have to be unclipped and moved out of harm's way. the part would be pretty inexpensive though.
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94 Midnight Metallic Blue Cab Porsche 968 w/deviating cashmere/black interior and WAY too many mods to list - thanks to eric for creating www.968forums.com



"It isn't nearly as expensive to do it right as it is to do it wrong."
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#51

Thanks. I was wondering about that slight flex. All makes sense. I have run it for a few years now, without issue and the car hanldes very well and does get pushed along a little.
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#52

thanks for the lesson Bob. And to think I bought on experience and reputation alone...



Next time I'll ask for a full justification of each component.
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#53

yeah - gotta watch out for wikipedia - lol
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94 Midnight Metallic Blue Cab Porsche 968 w/deviating cashmere/black interior and WAY too many mods to list - thanks to eric for creating www.968forums.com



"It isn't nearly as expensive to do it right as it is to do it wrong."
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