here's my idea if i understand your design right. bend the tubing just a little bit to get more contact area for welding.
thanks to whoever supplied the photo i used. very helpful.

 

thats basically what mine looks like. hacked into the floor and welded it into the rear subframe as well as the to the front point.

 

for that design though, you pretty much have to cut the floor? my drivers side rear floor is bad so it doesn't matter, but the passenger side is rust free. oh well, back seat of a camaro is already hell to sit in. lol. might as well cut it up.

 

I can take pictures and get dimensions of my sub frames, I wasn't the one who made them (buddy did) but it's made out of rectangular steel and they worked damn well on his old BBC third gen.

Email or message me if interested.

 

I would like to see those pictures and dimensions.

 

i agree with whoever said that the furthest out you can put the subframes would be best.

i wont get into the nitty details, but the stiffness torsionally can be calculated by the moment of inertia, and the parallel axis theorem which basically says that the farther away a beam is away from the axis of torsion/rotation/torque the stronger it is.


your first design is good, but im not sure how strong the metal you are welding to is.
i would try something more like this

the red stuff could be added if you wanted to go crazy with it





edit:
you could make the red bars on the outer side more parallel with the inner ones if you wanted... it would probably work better that way

 

That was me, and I'm glad at least someone is listening. Too many people with zero background trying to explain how things work.

For those who think that rear area of the car is a frame, maybe you'd care to explain to those who had the joy of their shocks ripping through it over time how strong it is. What that actually is, if you want to pay attention, is a built up POS of sheetmetal of various lengths (its not even one complete piece like a frame would be) spot welded at 3-5" increments to resemble an I beam but its basically worthless. Maybe if they had seam welded it so it had some actual structural value, it could be a frame. As it is, it uses every part of the rear body to give it any strength and therefore is not a frame but a member of a... Unibody.

 

Have you thought about using the alston SFC's with the spohn SFC's or umi or bmr doesnt matter, as the alstons run as though to make a full front to back sub frame (end of the front sub frame to beginning of the rear sub frame) , and spohn's bmr or umi run on the outside (where its said to work best).

But I think the alston + spohn, umi or BMR or global west would be the easiest way of getting something like what you want. Then everything else can be added afterwards for more contact points between the two sets. That or go for it and make some diamond type SFC's that would really be alstons with sponh units but connected.

 

Thanks RED DRAGON, like I said have the connectors furthest outward as possible under the rockers makes most sense. The further inward you go the easier the car will twist the connectors IMO.

 

madmax is correct. i think i might have stated that there was a rear frame... but when i stated that i mean that its the closest thing these cars have that resembles a frame. our entire cars are sanwiched peices of steel with spot welds. the strongest thing on our cars are the kmembers and engine blocks lol. i would have to argue that the rear "subframe" above where the rear spring perch is...is prob the strongest part of the whole rear of the car. its basically the thickest and the most pieces of sandwiched steel that is spotwelded. besides the front subframe.

run a perimeter type SFC that contects the front and rear subframes and then reinforce it with a roll bar. more leverage in a roll bar and u could ever get with a SFC. dual SFC (perimeter and inner) will suffice if your never gona need a roll bar or are never gona put a roll bar in... but plenty of 7-8-9sec cars run simple SFC and roll bars/cages and are fine.

some things would be overkill... like titanium pistons lol. or Gm producing the 3rd gen with an "actual" frame lol

 

I picked up some scrap steel peace in different sizes to get an idea. I'm thinking of now going with 2-1/2 X 1-1/2 for the outer peace that run next to the rockers and the other connecting peaces probably 2-1/2 x 1. but ould i be ok with just going with 2 x 1 on everything since im sticking to my organelle design? when you compare the (2-1/2 X 1-1/2) and (2 x 1 ) side by side there is a noticable difference between them on paper it doesnt seem like much and what should i go 11ga or 14ga ?

 

id go with the 2.5x1.5.... vs the 2x1. the larger steel will help more with the twisting motion. harder to twist larger steel. the 2x1 will give u more clearance... i kno by the rocker panels the 2x1 would fit nicely since thats where i planned on running 1x1 with my existing SFC. and the 2x1 u wouldnt even be able to see from the side of the car.

u could run the 2x1 as the perimeter and tie it into the 2.5x1.5 in the center but i think a 2x2 steel would be better suited and u could save the .5" of ground clearance.

go with the 11 gauge... thats 1/8" and is strong enough the 14 guage would be too thin.

 

That looks great!
i think im going with all 2.5" x 1.5" and i think i might even slim down to 14ga depending on my finally design. i was checking out the existing sub frames and in some places its pretty thin (16ga or 18ga) so i don't see how going with a smaller gauge would hurt especially when im connecting a lot more points then most sub frames
so i think i got that figured our finally

 

Based on my first one

 

i dnt think that one short peice of tubing would be needed. betweent he trans cross memeber bolts and the large hole in the stock subframe. delete that and weld brackets to the stock subframe.

looks good otherwise. good luck with running exhaust lol

 

Those look like mine, except you should add a crossmember brace/mount plate.

 

not really worried about the exhaust

 

?

 

My plan is to tie into the pinch seam along the rocker panel and go inward about 4-6inches, in the rear fan the box into the suspension mounts. in the front build them around the exhaust, I plan on using a y pipe from Jegs. yes the insides will be a pain do to the shape of the floor pans.
just my thoughts if some one has done this I would like to see it and know how it went
thanks

 

Update?

 

https://www.thirdgen.org/forums/fabr...al-design.html

 

Thanks.