[flash]

i have been approached about building a "chassis brace" similar to the one i did for the cab, but for the hardtop



the cab unit will not fit through the door, and the upper belt points are different in the hardtop, but i think i can come up with a unit that will work



like the cab unit, it would be a straight bolt in 6 point unit, with no cutting or drilling anywhere, and have the option of a harness bar



on the presumption that i go forward, i am going to be doing these in one-off fashion, as the batch process has proven to take entirely too long - there is a pile up spot that i cannot avoid in quantity, but is not a problem one at a time - basically the welder gets overwhelmed and doesn't get to my stuff - i have now solved that problem, but it means no more batches, which will definitely raise the price, likely to nearly a grand each



two questions:



1 - how important is it that the unit be race legal? i have 2 design ideas, one of which is easier and cheaper, but not race legal



2 - how much interest is there in such a unit?

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[JWahlsten]

Honestly, you'd be competing with the Redline Rennsport bar which is $550+shipping.



What benefit would the chassis brace create that the less expensive version doesn't? A thousand dollars is a lot for just a rollbar/chassis stiffener.



I am looking for something like you're contemplating, just letting you know my thought process...

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[flash]

no worries - i get that



i've looked at the bolt-in unit from redline, it only bolts in in 4 places, and it does not have rearward legs, therefore will not pass any inspections, and will not help as much in a rollover, as all of the stress is transmitted in sheer load to the bolts, and not the frame - it resolves the harness issue, but effectively eliminates the rear seat in the process



mine transfers the load to the frame via sheet metal landings, as required by both pca and scca



mine would have a removeable harness bar, so that the rest of the unit would not have to be removed to use the back seats



one benefit is chassis stiffening - the 6 points i use create a very real stiffening effect - on the cab, it reduces the chassis flex by about 60%



i understand about the price - that is why i was asking - i knew about the redline unit, and frankly if i had not been approached about it, i would not be asking - just thought i would poke around and see what folks thought

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[bob blackwell]

Thanks, but no thanks Flash. With the harness bar/brace, strut brace, and the lower front suspension brace I don't really see the need - but I am not going to race the car in wheel-to-wheel racing events either. Good luck, Bob Blackwell.

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[Cloud9...68]

[quote name='bob blackwell' post='39022' date='Jul 28 2007, 05:15 PM']Thanks, but no thanks Flash. With the harness bar/brace, strut brace, and the lower front suspension brace I don't really see the need - but I am not going to race the car in wheel-to-wheel racing events either. Good luck, Bob Blackwell.[/quote]



Bob (Blackwell) - Which harness bar/brace do you have? Brey-Krause, Redline, or another? As my speed in my DE events steadily climbs, I'm beginning to consider taking a big step on the slippery slope to the Dark Side, and getting racing seats and harnesses, which of course entail a harness bar.



Jim Child highly recommends the Redline roll bar/harness bar, and it does look like a very nice unit, but after seeing Flash's comments, I wanted to see your opinion, since you've been doing high performance/track day driving for awhile. I like the fact that the Redline unit seems like it would add some degree of chassis stiffness, though clearly not as much as a six-point unit attached directly to the frame, such as Flash's.



I've seen the Brey-Krause, and it looks quite nice as well, but doesn't look like it would add as much stiffness as the Redline, as I don't think its attachment points were separated as far as the Redline's (though my memory is a little shaky here). Also, the Redline can supposedly be removed in about 15 minutes, which is very important to me, since I carry kids in the back seat fairly frequently. I can't remember if the B-K is readily removable. The Redline was designed by John Hajny, who's considered a real guru in DE circles, so I'm sure it's plenty stout for non-competitive events, which is 100% certainly the only type of track driving I'll ever do with the 968. But I'm sure it costs quite a bit more than the B-K, and if as Flash says, its rollover protection is questionable, I'm not sure it's worth the added expense over the B-K. Thanks in advance.

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[Cloud9...68]

I found a site that carries the B-K bar, and it's only about a hundred bucks less than the Redline. Plus, the mounting instructions shown on the site say it's only a harness guide bar, and to not mount the harness directly to it. I don't understand what this means (I'm just beginning to learn about racing safety hardware, as my rate of improvement at my last two DEs sort of caught me by surprise), but it sounds like additional hardware needs to be purchased with the B-K bar to attach a harness to it, making the Redline unit look like a much better value.



I know this thread is moving toward belonging on the Racing forum, but the discussion here so far has been very informative.

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[flash]

bob - no problem - i'm not suggesting that anybody needs this, just asking how many might want such a thing - clearly if all you are doing is street driving or autocross, the need is very minimal - i was asked about making one, and wondered how many others might want it



the reason that the redline bar won't provide much rollover protection is simple - the threaded holes it goes into are in 90 degree opposition to the vertical load that would be applied - in a rollover, they would just rip out - that is why i added the landings on my cab unit - the load is then spread out across the frame rail - also, without the triangulating legs, required by all roll bar specs for any sanctioning body, it would be very easy for that bar to move forward or rearward in a rollover, and then collapse into the cockpit - that is why they even spec how far up the legs must be and at what angles



i'm not intending to slag the redline unit, just rather to say that if i was doing one, i would be looking to have it be more substantial - i'm not tryin to compete with that unit - i'm not even sure i want to get back into this - just testing the waters

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[bob blackwell]

I have the Weltmeister Harness Bar and it works fine. Bought it used for $75 so it was too good to turn down. I previously used the Brey-Krause in a 944S2 and liked it much better for the stainless steel finish (Weltmeister is just painted black) and the extra brace on each side (weltmeister just bolts in one place each side and probably does not give as much added strength to the chassis). Good luck, Bob Blackwell.

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[flash]

i think the question at hand extends beyond a mere harness bar - we are talking about something much more substantial - the unit i am proposing is not a ahrness bar - it has the option of adding a harness bar to it, but would really much more like the unit i did for the cab, which adds a LOT of rigidity to the chassis, and has the overhead hoop, rearward legs, and landings that are required for racing

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[Andre]

I am shopping for a harness bar for my 944 Turbo S coupe (likely same interior dimensions as 968), but $1000 brace is not something I would buy.



If I were looking to stiffen the car a lot and get a full roll-over protection for club racing, then a welded roll cage would be a no-compromise big bucks solution. For casual/beginner DE driver like myself a more economical harness brace, aka Bob Blackwell's Weltmeister, looks very appealing.



Perhaps some club racers may be interested, as a cheaper alternative to a roll cage?



Andre

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[Jason Judd]

"Perhaps some club racers may be interested, as a cheaper alternative to a roll cage?"

____________________



Andre,



No offense intended, but, there are some things you really shouldn't go 'cheaper' on...and I believe that your personal safety is one of them.



Jason

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[Cloud9...68]

Decisions, decisions. Flash makes some very good points. Adding rigidity to the chassis is certainly very appealing. Especially since between this, the strut brace, and the lower suspension brace, the car would achieve a level of chassis rigidity that would probably rival that of new cars, for far less that the cost of, say, a Cayman <img src="/forum/images/smilies/968/biggrin.gif" class="smilie" alt="" /> . Plus it would serve as a very stable platform from which to make further suspension mods. It all sounds great (and suddenly the Redline unit sounds decidedly less so..). I'm just not sure I can justify spending a thousand bucks on this right now. Damn those alternate priorities in life!



I need to do more research, but for now, maybe a simple harness bar like Bob B's would make sense, and if Flash is still in the mood to make a few of his super-braces when I get, say, a surprisingly large bonus, I'll consider it then...

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[Fox944]

[quote name='bob blackwell' post='39051' date='Jul 29 2007, 01:43 PM']I have the Weltmeister Harness Bar and it works fine. Bought it used for $75 so it was too good to turn down. I previously used the Brey-Krause in a 944S2 and liked it much better for the stainless steel finish (Weltmeister is just painted black) and the extra brace on each side (weltmeister just bolts in one place each side and probably does not give as much added strength to the chassis). Good luck, Bob Blackwell.[/quote]





Is there any noticable differance in rear chassis stiffness with the Brey-Krause or Weltmeister Harness Bars?



I'm looking into getting one (not for use with a harness so to speak, but rather to stiffen up the chassis). I have a KLA Strut Brace & Design 1 Chassis Brace up front.....so i would like to add a brace to the rear.



Also, who sells the the Brey-Krause Brace? and how much? Performance Products sells the Weltmeister Brace/Harness for $160. I actually prefer the flat black look & would paint the Brey-Krause. Also, from what it says on Performance products websight...the Weltmeister is now 1.5" thick rather then 1".

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[flash]

i think a lot of this back and forth, which is frankly a bit annoying, is due to a confusion in terminology - it is really sidetracking the basic question



let's be clear about one thing, i have to call this a "chassis brace" for reasons of legality and liability - calling it a roll bar opens up a pandora's box of potential litagation i am not interested in - it is built to every roll bar spec of both pca and scca



IT IS NOT A HARNESS BAR!!! can we please stop comparing it to those?



regardless of what they call it, the redline bar ("stealth" unit) is not a roll bar, does not meet roll bar specs, and will not provide much rollover protection - it's cute and convenient, and even ingenious in design, but it is not a roll bar



a harness bar is not a roll bar, is limited in chassis stiffening, as there is no triangulation anywhere, and does nothing for rollover protection



now, getting back to the original question, if i were to build a unit like the one i did for the cab, a bolt in design, requiring no welding or drilling or cutting, with full use of the rear seats, and meets all pca and scca regulations, what would be the interest level?



by the way, the only reason i ask, is that if i do one, i can expend the time and money to build a jig to be able to duplicate it if i thought there would be a need for more - otherwise, i'll do a one-off and everybody else can go about cutting, drilling, and welding their own into their car, at a much higher cost

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[JWahlsten]

I for one am interested in the extra protection and stiffness you're proposing. Your shear analysis makes sense to me, and actual engineering vs convenience is a good thing.



Whether I buy or not will be based on cost. I've had an Autopower bar and an OG racing version, but I really have no desire to cut this car. If you decide to press forward, and have a firmer cost in mind I'll make a more informed decision.

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[flash]

thanks



i guess one of the parts of the first question was answered in a round about way, or at least i could deduce the answer, which was in reference to race legality - it seems unlikely that there would be a lot of interest unless it did that - to do that means a continuous main hoop - there can be no breaks or couplings in it above the landing itself - i've seen other units that break in the middle - they would not be race legal



i do have a design that would meet those specs though, but it increases the cost just a bit (not a lot), though it should offset itself in reduced shipping



i'll be looking at it this week and let you know

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[bob blackwell]

"No worries" Flash, we understand exactly what you are talking about. I was replying to a direct question from Cloud968 and not intending to confuse your issue at all.



In answer to another direct question: Yes, a Harness Brace does stiffen the chassis and reduce flexing in the corners. (But of course, not nearly as much as a full roll cage or roll bar would).



Retired soldiers have to watch where our pennies go. Good luck, Bob Blackwell.

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[Cloud9...68]

Sorry to have sidetracked the discussion. I understand that Flash's design is a chassis brace, not a harness bar. This discussion is timely to me because I'm getting to the point that a harness (and the attendant bar) along with more supportive seats are worth considering. The Redline bar appeared to go that two better by adding additional chassis stiffening, along with (apparent) rollover protection, in addition to being a harness bar. Flash's analysis shoots some major holes into that idea, however. When Bob B. mentioned that he is happy with his harness bar, I was interested in what type he had, since, as I said, I'm in the market for one. Maybe a PM would have been a better way to ask...



So, getting back to the question at hand, Flash's brace sounds like something I would LOVE to add to my car, if it were available, because it appears to do everything I would need in my street/DE car (and to answer Flash's first question in his original post, being race legal wouldn't matter to me - how's that for bringing things back on topic?). It's just a matter of prioritizing the money, vs. other things, 968 and non-968 related. But this unit sounds so good, and so foundational to allowing the car to live up to its potential, that I think I would probably spring for one.

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[flash]

thanks guys - that's the kind of well thought out answers i was looking for - i just wanted to make sure that if i did one, that i looked out for others who might want it, and went ahead and made the jig fixtures if there was interest



as i said, i will look into this more closely this week when i can see a hardtop in front of me, and see if i run into any major snags, and figure out the cost - i needed to do some of that for the future cab units anyway



i am just about to finally wrap up the latest batch of cab units, and now that i have changed the way they will be built in the future, i can turn them around fairly quickly - the hardtop unit, being based on the cab unit, would share much of the tooling, so would not take any additional time - they would be done one at a time, to order, and take about 2-3 weeks from order to ship

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[Cloud9...68]

Sounds great; keep us posted.



I didn't follow the discussion on the cab chassis brace, but noticed that the thread generated a massive response. Just out of curiosity, about how many cab braces have been sold? I think you told me over the phone that the cab brace was so popular because it enables the cars to be tracked (but I can't remember if you meant DEs or competitive events). The brace for the coupe wouldn't have the same enabling characteristic, but will hopefully become a logical choice for people like me who are looking to combine added safety in DEs, and improved handling through significantly increased chassis stiffness, while maintaining streetbility, including useability of the back seat.

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