Tube Frame Questions- 1991 GTO RX7
Hello all,
I have just recently gotten my 82 Pr-7 car sorted and on the track and I'm going to start racing with gusto next year! In the meantime I've been (obsessively) thinking over what I want my next project to be. Since it'll take several years to build up both a faster car and the skill to drive it (not to mention the money I'll need!) I've decided that I'd like to build a tube frame FC! Because of that I've been searching doggedly for any info I can find on Mazda's 1990-1991 IMSA GTO RX7. I have plenty of pics of the car in the paddock with bodywork off, and some screenshots from taped IMSA races from the 90s found on youtube and that sort of stuff, hell I even know a guy who worked on the 89 Roush team with Pete Halsmer and if I ask him nicely he'll go talk to Pete about the car for me, but I can't find any info or pics or blueprints of the frame! Does anyone have any info on it? Anyone have any blueprints or pics of knowledge that I could have? All I really know is its a bespoke tube frame designed by Lee Dykstra. All that begging aside, if anyone has any tube frame pics or knowledge they'd be willing to share for either an FB or FC specifically, or about tube frames in general please chime in! I'm just resuming school for my engineering degree and I find it all fascinating! Also I hope to one day build a fast racer too :D |
you might see if you can find any blueprint from any car Lee Dykstra built, its probably somewhat similar.
having seen the car in person a bunch, i can tell you the only stock parts are the roof panel and taillights. |
Dude… after you start taking hits of the racing crack pipe next season, you’ll forget about building and just want to skip to the racing. :)
GT classes are usually tube frame cars but they are often $50-100k builds. Theres a decent tube frame build in the first gen section as a starter |
Originally Posted by j9fd3s
(Post 12498794)
you might see if you can find any blueprint from any car Lee Dykstra built, its probably somewhat similar.
having seen the car in person a bunch, i can tell you the only stock parts are the roof panel and taillights.
Originally Posted by gracer7-rx7
(Post 12498809)
Dude… after you start taking hits of the racing crack pipe next season, you’ll forget about building and just want to skip to the racing. :)
GT classes are usually tube frame cars but they are often $50-100k builds. Theres a decent tube frame build in the first gen section as a starter I can't wait to get racing properly, but I don't want to take the Pro-7 car to full tube frame. That car may get Group C or IMSA GTU bodywork and some small suspension upgrades, but I plan on keeping it 12a powered and low stress. I may have lofty aspirations here, but I'm totally committed to this silly idea. I'll check out the 1st gen section for that tube frame build tonight after work. Does anyone know if the current owners of any IMSA GT series chassis is active on the forums? I know there was a GTU 1st gen for sale years back in SD by me, and I know the Team Highball RCX7 was for sale a while ago too. |
i was going to say if he's still alive you could probably call him, but ran across this https://forums.autosport.com/topic/52866-lee-dykstra/
"All Dykstra's paper, designs, etc are now in the Watkins Glen library." https://www.racingarchives.org/the-c...ions/overview/ |
Well I'll definitely have to look at that! The only problem is that I'm in SoCal but the library is in NY :crying:
I guess I'll have to email the library and see if I can access the blueprints or designs online or be sent a copy. |
Originally Posted by IMSAaspirations
(Post 12498894)
Well I'll definitely have to look at that! The only problem is that I'm in SoCal but the library is in NY :crying:
I guess I'll have to email the library and see if I can access the blueprints or designs online or be sent a copy. |
also, fyi, there's a decent discussion in the GT3 group on FB about tube frame 'blueprints'. The context of the discussion is that the participation trends have been decreasing due to the expense of fab'ing a new chassis and people just aren't racing them as frequently as other classes presumably due to cost.
Judging by what I see turn up at regional races, the lower cost race cars are raced far more frequently and in greater numbers. |
Originally Posted by gracer7-rx7
(Post 12498965)
also, fyi, there's a decent discussion in the GT3 group on FB about tube frame 'blueprints'. The context of the discussion is that the participation trends have been decreasing due to the expense of fab'ing a new chassis and people just aren't racing them as frequently as other classes presumably due to cost.
Judging by what I see turn up at regional races, the lower cost race cars are raced far more frequently and in greater numbers. |
Originally Posted by j9fd3s
(Post 12498935)
or just ask Mazda if you can look at the car and bring your tape measure
Originally Posted by j9fd3s
(Post 12498968)
it seems like the trend is just to get track time, more than competing. some of my friends and i ran Lemons this year, and its a ton of track time, but its not a race, nobody wins...
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Hmmm "nobody wins"... A good day at the track with good friends is always a win in my book :)
You might be surprised by how much time, effort, learning is required to run up front in these competitive classes. It can get pretty intense. At least in Spec Miata. |
Originally Posted by gracer7-rx7
(Post 12499135)
Hmmm "nobody wins"... A good day at the track with good friends is always a win in my book :)
You might be surprised by how much time, effort, learning is required to run up front in these competitive classes. It can get pretty intense. At least in Spec Miata. second i have a couple of friends who have built front running Lemons cars (our Rx7 https://www.rx7club.com/build-thread...s-car-1150848/ needs better drivers, come drive it), and the work it takes to have a front running Lemons car is on par with a cheater Spec Miata. not only do you need to find a 77 fairmont, but you need to swap a 5.0 mustang under it, for $500 and then come up with costumes Edit, its just like the GTO Rx7, because um they both raced at Sears Point? sorry about the off topic stuff.... https://cimg3.ibsrv.net/gimg/www.rx7...aed2ab3539.jpg |
Originally Posted by gracer7-rx7
(Post 12499135)
Hmmm "nobody wins"... A good day at the track with good friends is always a win in my book :)
You might be surprised by how much time, effort, learning is required to run up front in these competitive classes. It can get pretty intense. At least in Spec Miata.
Originally Posted by j9fd3s;12499190
so two things, Spec Miata is racing, there is a winner, and a championship, and if you win that (and you're good at the PR stuff) you can move up. second i have a couple of friends who have built front running Lemons cars (our Rx7 [url https://www.rx7club.com/build-threads-293/lemons-car-1150848/[/url] needs better drivers, come drive it), and the work it takes to have a front running Lemons car is on par with a cheater Spec Miata. not only do you need to find a 77 fairmont, but you need to swap a 5.0 mustang under it, for $500 and then come up with costumes
Edit, its just like the GTO Rx7, because um they both raced at Sears Point? sorry about the off topic stuff.... https://cimg3.ibsrv.net/gimg/www.rx7...aed2ab3539.jpg |
i'm probably being too pessimistic about Lemons, if you wanted to work on your racecraft or just get lots of seat time in a car or track its probably great. with 150 cars on track, you have way more traffic to manage
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I've been told by Carl and Michael that Lucky Dog is actually a really good way to get a lot of seat time per weekend given that they're endurance races. I've heard that Lemons is less serious about the racing, but that it's still a fun time if you get a good team together. Frankly I'm just looking forward to getting on track as much and I can! I understand its definitely a good stepping stone, and I hope one day tp be able to move up to being able to build and race a gnarly tube frame race car.
Oh and Merry Christmas you filthy animals!! :lol: |
@j9fd3s We need to meet next season. I have probably walked by you multiple times at events over the last 10 years...
I'm not the biggest fan of LeMons. I've attended a few where friends were racing and needed someone to drink their beer but I've only raced one leMons event 12 years ago. @IMSAaspirations LD and Champ are definitely more racing oriented that LeMons. Better quality of drivers and cars usually in attendance. |
The tube frame build that gracer7-rx7 referred to may be mine : Tube Frame SA turbo 13B autoX/track car. There is a complete log on the LocostUSA forum in the non-traditional build log section. Since the Lotus 7 clones are all tube frame, it's a good source for the design and construction of any tube frame you can dream up.
For several decades I was involved in the design/construction and maintenance of multiple GT2 and GT3 RX7s running on the west coast from Laguna Seca to Seattle Raceway. I'd be happy to provide my two-cents on any tube frame questions that you have. https://cimg1.ibsrv.net/gimg/www.rx7...a6d3daf1c9.jpg The SA RX7 when it reached roller status. https://cimg2.ibsrv.net/gimg/www.rx7...e1e2b92b1.jpeg The first of the FD GT2 cars we fielded. https://cimg2.ibsrv.net/gimg/www.rx7...fc65cd213.jpeg Hanging the body. |
Super sick Build there.
I raced at buttonwillow last weekend and blew my trans, which turned out to not be such a bad experience. Sevens Only is based at the track so I got to meet Tom the owner who has heeps of knowledge with NA Tube chassis cars. I may look into something like this vs tracking my FD. I think it will save me money in the long run lol. |
I think it would be interesting to compare the construction of the 91 Mazda GTO car to the stuff being built and raced now. State of the art in the 90s may not be as good as the stuff being raced now. The level of effort to build a car like this would be the same no matter how it is built. So why build an obsolete car?
As far as GT3 (and GTL) are concerned, what the class needs are racers driving the cars that already exist. Both of these classes received a veiled warning from the SCCA regarding future Runoffs participation. They are included in the 2022 event at VIR but participation numbers need to improve if that is to continue. Currently GT3 is a rotary racers paradise with some interesting engine options in the rule book. Check out the race from Indy this year (it is on Youtube) Rx7s of all generations are represented. If is a spendy class but the cars are REALLY fast. I have first hand knowledge of this because my class shared qualification sessions with them at Indy. If a person really wants a tube frame car, a GTL build could be very wallet friendly. The SIR (Single Inlet Restrictor) for 12A and 13B engines is so small that guys aren't spinning their rotaries much past 7500RPM. So an engine could last 5-7yrs! With the right chassis and transmission a GTL car would be a really cost effective way to go national racing. Also, the GTL community on FB is really supportive because the elders in the class get it - building participation is key. If I was starting over, younger and wanted to race a tube frame car in the SCCA; GTL is where I would be looking. |
I agree with what Scott just said about the " state of the art in the 90's". All race car classes are subject to the rules published by the sanctioning body. SCCA Club, SCCA Pro and IMSA rules dictated some specific suspension designs that evolved, sometimes driven by "cost saving" logic. Specifically, rear suspension could only be live axle with 3-link trailing arms. The freedom to design your car with current concepts/parts would be very desirable.
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This is also a good thread to follow: https://www.rx7club.com/build-thread...oject-1116871/
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Here are some shots of a tube frame car in our shop. It is a pro-built chassis that has had some success in GTL/3 in the past. Front suspension is double A-arm coil over and the rear is a triangulated 3 link coil over. Fully clothed, it is a Nissan Sentra. I keep trying to talk him into a rotary with a Protege' body but he likes hand grenade piston engines.
https://cimg2.ibsrv.net/gimg/www.rx7...cf8d374bfc.jpg https://cimg5.ibsrv.net/gimg/www.rx7...b094c7cc50.jpg https://cimg6.ibsrv.net/gimg/www.rx7...d07efdf7fa.jpg https://cimg7.ibsrv.net/gimg/www.rx7...2c93ef010f.jpg |
I really don’t have anything to add but am enjoying following this thread. I also follow the GTL, GT3 & Prod FB pages. Some good humor but also lots of info and sharing. Keeps me motivated.
Scott, wouldn’t mind a JPM-esque shop tour. Just sayin’. |
Originally Posted by gracer7-rx7
(Post 12498809)
Theres a decent tube frame build in the first gen section as a starter
Originally Posted by gracer7-rx7
(Post 12498965)
also, fyi, there's a decent discussion in the GT3 group on FB about tube frame 'blueprints'. The context of the discussion is that the participation trends have been decreasing due to the expense of fab'ing a new chassis and people just aren't racing them as frequently as other classes presumably due to cost.
Judging by what I see turn up at regional races, the lower cost race cars are raced far more frequently and in greater numbers. So OK. Let's me kinda more specific... first off the GTO FC relied on a lot of custom parts. Diff housing is custom castings with Hewland internals, gearbox is custom casting with Hewland parts, suspension uprights are fabricated weldments, etc. Almost nothing off the shelf; the chassis is kind of the easy part. Having priced out stuff like centerlock spindles... there's just a whole pile of custom parts where if you add up the costs either you need a huge variety of tools and expertise or you need to spend a lot of money. Plus a 13J, which don't exactly grow on trees. The chassis is just tubing; triangulated tube structures were figured out in aircraft in the 30s or so; people since have done things right or not within various constraints (deciding how much stiffness you're willing to pay for in weight) since then. Lee Dykstra did it right but you don't have the resources he had to get stuff made so it'd be folly to copy him. Figure out what you actually want and where you'd race it. For example, if you made a 4 rotor fully independent suspension tube car... where would you race it? How will you afford consumables? How do you afford to fix things that break? I'm more than happy to provide guidance and stuff, just, do you want to dream or do you want to figure out how to build something that can be raced? |
Here's a link to the detailed build log on my SA 13B turbo with all of the questions and answers that came up as it progressed:
LocostUSA.com ? View topic - Tube Frame SA RX7 turbo 13B AutoX/Track Car If the answers that I provided at the time are too brief or lack the specific info you'd like to get, let me know. For a free suspension design/analysis program, vsusp.com is very useful and was created and is maintained by one of the locostusa users. |
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