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Last year in September I ordered my new 2022 Camaro LT1 for my daily driver to split with the company car. It's now a 2023 and finally on its way to my dealer! I haven't been this excited since I ordered my 1996 SS SLP car. Kind of crazy I'm so excited over this, it's my last new Camaro / sport car I will order before I retire.


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You know the last sports car old retired GM car guys buy is a Vette. When you are old enough in another ten years to retire those Vettes will be electric and merely 1200 hp to use as a cruiser.

Just funnin.
Bob

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Originally Posted by mmc427ss
You know the last sports car old retired GM car guys buy is a Vette. When you are old enough in another ten years to retire those Vettes will be electric and merely 1200 hp to use as a cruiser.

Just funnin.
Bob



Hi Bob, I could never afford paying a mortgage payment on a car regardless of the quality at my age. I'm actually selling the last of my Pontiac toys to pay a good chunk of the 37K it costs after my employee discount. I've been very fortunate in my career but by no means could I afford anything north of 40K in a payment form. Cash is king and this G body has rung me dry after the LS7...LOL


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Hi Ron,

So if for a given length we take torsional stiffness ~ t*phi^3, and weight ~ t*phi, and we assume:

1. Scenario 1: an inner tube of outer phi = 1.75", t = 1/8", PLUS the (now closed) outer box with an average outer phi = 4", t = 1/8".
2. Scenario 2: a maximally-expanded tube based on the existing frame rail with average outer phi = 4.75", t = 1/8".

It's easy to compute their relative torsional stiffnesses and weights.

For torsional stiffness, the second configuration is 58% stiffer than the first.
For weight, the second scenario is 16% lighter.

Diameter completely dominates. In the first scenario, the inner tube has only 7.4% of the torsional stiffness of the outer tube, but 42% of its weight, so its presence represents a net loss.

If we form a ratio of torsional stiffness to weight, then the second scenario is 88% better than the first.
So it's not even close - the second scenario wins.

HTH,
MAP

Last edited by MAP; 08/27/22 10:57 PM.
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Mark,

Your killing me, the result is better performing than the math. It's how the new tube is integrated into the existing tube rail that makes it work well. I have to dig the frame out of the weeds in a month and at that time I will decide what I will do and how I will do it? I want a car holding the factory vibe. I have two good sources for frame modeling software that I will visit. Maybe we get out in the weeds and drop another chunk of cash into it's chassis?



Regards,
Ron


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Hi Ron,

Well, I wish you all the best. When I had my '78 Malibu I added 1" x 3" rectangular steel tubing to the underside of each frame rail to stiffen it up. You could see a small difference in the car's appearance from a distance, but if you weren't looking for it, you'd probably miss it. But the added stiffness was very noticeable and welcome.

Ultimately you'll decide what holds the factory vibe and what doesn't, of course. Have fun!

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Last edited by 1 Slow SS; 08/28/22 01:46 AM.

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Hi Ron,

I wish I had a G-body to measure but don't, so I can't comment about that rack. My general recollection is that the front LCAs are too long, and thus their inner pivots in the frame are too close to each other, to permit a rack of more than insufficient length to fit. I'm also guessing that unless the rack is specifically made for an A/G body, the odds of it creating negligible bumpsteer are low.

Hate to say it but I think you're probably better off coughing up the coin and getting an entire front-end that's dimensionally and structurally compatible with the car, and that has good R&P steering. I haven't checked vendors for this in a long time but you can always start with the usual suspects. Detroit Speed is certainly a good one but they're usually pretty pricey - if you're up for it, in your shoes, I'd call them and ask to speak to an engineer and not a salesperson, and talk through the whole situation in exhaustive detail.

Best,
MAP

Last edited by MAP; 08/28/22 10:35 PM.
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Hey Mark,

I did a cutlas with a rack about 6 years ago, it's doable and works well with some significant surgery. The bump steer is the easiest part and was almost non existent, I'll make measurements this time around. This mod will be a bit close to my heart as I'm not a fan of the gear box. I won't invest a lot of time with writing though, generally what I did and the values for steering radius and bump steer.

As fare as my frame... I will add the external support on the inside of the rails near the floor pan area with a X brace! Oh, and two loops over the front suspension. cool

But for sure find everything in theory wrong with the retrofit and I'll put up values to counter it to the best of my ability. beer

Last edited by 1 Slow SS; 08/28/22 11:52 PM.

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Hi Ron,

Well, whether you go with the tube-in-a-tube approach or not, the one sure thing is that it will be a very big improvement over the stock wet-noodle frame. Do take torsional stiffness measurements before and after for all to read, please! One possible methodology: put rigid jack-stands under the frame right above where the CL of the rear axle resides. Then, support the front of the frame on a knife-edge that sits under the center of the engine cross-member. Get something to measure angle from the vertical with high accuracy and use this to measure frame transverse orientation. Then, apply a known longitudinal moment to the frame, and determine the angular change. One stock frame I tested years ago, which was coupled to the body with factory bushings, measured a positively lousy 2,100 (ish) ft-lb/degree.

Me, I always sweat not only the improvement in rigidity but its increase in relation to weight. Inertia is the sworn enemy of acceleration, and hot-rodding is all about acceleration.

And when you talk about a loop over the front suspension, would that be the triangulating brace from the windshield base of the A-pillar down to the frame by the UCA?

Last edited by MAP; 08/30/22 03:35 AM.
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Hi Ron,

I forgot a critical part of the torsion-measuring methodology: apply the upsetting moment to the frame at the front axle CL.

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Hi Mark,

After much thought I have decided NOT to build a frame. Two reasons, MAP you have pointed out several issues, among a cobbled together frame. Secondly is my time is slim and too valuable. I want something new and the best in the industry poke ! I want this car to be the first off of the best, in a series of G body builds that it gives G body owners a new option! I have reached out to the best suspension and chassis builder I know of in the business and proposed a first off build of a G body frame and suspension kit that can be marketed to the masses.

I hope I can pull this off!

Regards,
Ron

Last edited by 1 Slow SS; 08/31/22 12:28 AM.

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Ron - really love to see such a frame/suspension (steering?) kit.
Others have invested and built (Schwartz for example) How would it be different or just more approachable economically for us, or ....?
Dearly wish I had that as an option when I started.
Would it enable/anticipate EV conversion at a later time?
Your thoughts at this point if you can share?
Gordon


1987 Aerocoupe. Frame-off, notched/mini-tub, 383 with AFRs @ 535HP/487TQ, March Serpentine, 304 SS headers (Jet-Hot) & 304 3" dual exhaust w/ Borlas, Janis 200-4R, TrueTrac w/ girdle and Moser 28, Hydroboost, computer delete, lowered, every part replaced or messed with (several times).
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Hi Gordon,

At this time it's only a proposition to a very capable custom shop. Schwartz is a awesome option 'that I might have to visit" but that has been done, I want a different flavor.

EV conversion isn't on my mind and for sure not on theirs either at this point, as I have no gas powered commitment.

Economical is subjective, for a complete chassis at Schwartz your in the 11k - 30K range, I can't say this option would be any cheaper. Especially if you mini tub and buy top of the line options in brakes, wheels, tires, shocks, and many other areas. A build could easily climb close to or more than 6 figures with guys doing much of the work?

Regards,
Ron


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Wow! Big news! All the best!

Ron, you know I like to attack an idea from all angles. If we extend the idea of a tube's torsional stiffness going as the cube of its diameter, we have to arrive at the conclusion that if we can integrate the frame with the body into a rigid whole, then this will give us the lightest structure possible for a given torsional stiffness. I return to my soda can analogy.

If you only rely on the frame for torsional stiffness, you'll be adding weight - maybe something like 100lb.

But, if you want something that would appeal to a wider market than the near-insane customer or two who would consider a unibody conversion (like myself,) then this is probably the next-best thing. But may I make a suggestion? Whoever designs this beastie should do extensive FEA 3-D modeling to ensure it's as light as possible in relation to its stiffness. I've seen some dubious attempts by well-known chassis builders - including Schwartz.

Maybe you can get some weight back (50lb?) by making the front end lighter than the stout factory design. (Just add some lightweight crash protection like energy-absorbing foam, however.)

Best,
MAP

Last edited by MAP; 08/31/22 04:20 AM.
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After waiting a couple days and talking with two frame shops nobody is interested as of yet to build a G body frame. I even offered the first choice of mine a premium to build it and the owner has no interest. I will try two more shops and then replan.


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Last edited by 1 Slow SS; 09/04/22 12:59 AM.

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Hi Ron,

My quick opinion is that I think that frame has a lot of fat in it. Guessing from the photos, it might weigh about 150lb more than the factory frame. That rear also looks prone to binding in roll. If I got that frame, I'd ask them to delete some sections or at least leave some sections unwelded. This frame looks overbuilt versus the Schwartz frame which looks underbuilt. Not sure which makes the better starting point. Btw, $19k? Wow.

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Hey Mark,

I would think any 4 link with bushings would bind? If I were to build the frame with them the rear would be addressed with rotating joints.

The 19K wouldn't do it, I would be into the rolling frame for 30K all day long and additional chunk too widen the wheel wells for an additional 4" track width.

One other point folks miss. When considering the cost of something you must consider how long it takes you to make that much money and how long it would take completing the project plus materials.

Regards,
Ron

Last edited by 1 Slow SS; 09/04/22 02:13 PM.

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I have friends that are very close with the peeps at Roadster Shop. They make a fantastic product. I don't have any direct experience with their G Bosy frame but can vouch for them as a Company overall.

If you found something there that fit your build, I'm certain you'd be happy with it Ron.


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Good news Lance, Thanks.

I’m looking to build a sweet looking car that performs very well but yet drives great.

Regards,
Ron

Last edited by 1 Slow SS; 09/04/22 09:18 PM.

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Hi Ron,

That Roadster frame does look good, and really if you make any frame stout enough and heavy enough, it will also work well.

But the real trick is making it stiff and light too. And it's on that count that the Roadster frame falls short IMO. It's got a lot of fat situated under the floorboards. The junctions of the front and rear narrowed sections with the side rails look needlessly overdone. I would ask them the weight of that frame in its bare form (no suspension or rear attached,) and compare it to the stock frame in the same state. Again, I'm guessing the Roadster frame has 150 lb over the stock frame, which would make the car about 4% heavier. 4% heavier means 4% slower as well, so you'll want to consider the tradeoff carefully. After all, you bought a big engine to go faster. More weight would be taking you in the opposite direction.

I know a unibody conversion is lots of work, but it's unbeatable for stiffness in relation to weight. It would probably save you huge coin as well. If anything, just buy the front end as an assembly with R&P steering. Maybe the rear as an assembly too. (Art Morrision? Detroit Speed?) Of course, in saying all this, one must have very solid mechanical engineering and fabrication smarts to bring it all together successfully...

About binding: the factory C4L doesn't geometrically bind. I could be wrong, but a parallel-link rear with shorter arms on the top could bind in roll. In your shoes, I'd build a scale model first to be sure.




Last edited by MAP; 09/04/22 09:30 PM.
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Mark,

I would have the rear control arms made with a pivot joint. As fare as the weight I would have some of the bulk trimmed out. I know exactly where I would take it as you mentioned.

As fare as making a unibody out of this thing, no way, I have F bodies for that. Yes I could do this, but I have too many other cars and property to take care of. I'm getting old and this car is another project that I really shouldn't be diving into. But I have committed too both sons and my mother of getting this car back to it's former glory plus some. That's the main reason I will consider opening the check book. I could build the stock frame and let it roll boxed with a complete Speedtech suspension. If I do that it's major flaws won't be so bad. And I can say if I had Lance or Bernie driving it, I'm sure it would be as fast as any G body out there in that form given they had some seat time dialing it in. In all honesty I don't see that much performance to be had with any set up over what these cars can bring worked over. The gains are more for bragging rights with marginal improvements following IMO. I look at times, cornering pictures and much better unibody, IRS engineered cars still fall victim to the G body. A top contender would be a 150 - 200 K build and I'm not doing that either. This car was bought new and all options checked by me with my father. We liked the MCSS because it was a cheap resemblance of older muscle cars of the day and very good looking.

Regards.
Ron

Last edited by 1 Slow SS; 09/04/22 11:17 PM.

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OK, I get all that, but a 4% weight savings can only help you. Now what that 4% is worth to you is your call to make, naturally. Maybe you can negotiate with the Roadster shop to save some weight and coin by removing all that fat? And no matter what you do to modify that frame, it will move your COM rearwardly compared to the stock frame, which will certainly be a plus. Btw, can you use your stock bumper mounts with that frame by deleting or modifying the end caps?

IRSs on a flat road course buy you essentially nothing. In fact, you'll probably lose because IRSs give you little anti-squat compared to a live axle. It's in street driving with irregular surfaces where they shine, but even there, for RWD, the car should be rear-heavy if the engine has strong output.

Last edited by MAP; 09/05/22 04:34 AM.
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Originally Posted by MAP
OK, I get all that, but a 4% weight savings can only help you. Now what that 4% is worth to you is your call to make, naturally. Maybe you can negotiate with the Roadster shop to save some weight and coin by removing all that fat? And no matter what you do to modify that frame, it will move your COM rearwardly compared to the stock frame, which will certainly be a plus. Btw, can you use your stock bumper mounts with that frame by deleting or modifying the end caps?



As fare as weight goes, I would have to inquire the actual number. I'm not sure if they're focused on factory comparisons to promote sales.

Yes, all you have to do is open the capped ends to allow the shock body to enter the rail.

Last edited by 1 Slow SS; 09/05/22 10:17 PM.

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