BC

My 78 is ready for interior and wiring, and I was looking at trying to make sure I don't want to weld in any subtle strengthening.

jeff jackson

Not sure I follow the question you have posted here. Interior and wiring, "shouldn't" require any "welding"...that would cause "undue" strengthening of the chassis ??? I don't think ! (But I may have just said it all, with the "I don't think" part of my statement...

BC

I'm saying that before I finish the interior, since it is BARE metal, where can or what can I do to strenthen the structure of the car. The project needs to move beyond this point, so I wanted to make sure.

Kaz

Besides a full Nascar roll cage you mean?

FlyingDog

How normal and daily driverable do you want the car? You could put a brace between the rear strut towers, brace the front strut towers to the firewall, and there are various tube options. I think unless you're racing, they're all over kill but somebody else would probably have a more informed idea of what to do.

Just out of curiousity, does your 78 have the battery box seperate from the body and bolted to the transaxle?

Bill51sdr

Oh, I dunno, give 'er a shake and see what flexes... Weld a full cage in there and cover all yer bases!! You're thinkin' too much Brendan, get that Shark on the road

BC

The car will be daily driven, but also have track duty. I'm trying to keep it light as well. Th eb attery box is gone, gone, gone. Heavy piece of pig iron if you ask me. Battery will go where I can fit it in the spare tire well. Small battery. The rear tower brace is something I have thought about, as long as its not close to my head.

BC

Spent the entire weekend fixing the wrong shark.

BC

Yeah, and then the 352inch engine goes in the front with a carb and restrictor plate, big meats and huge tide stickers.

FlyingDog

It could double as a harness bar.

PorKen

Don't the rear shock towers have a box frame connecting them already? Where would you put a brace?

Have you put gussets on the front sway bar mounts?

Who's race car was it that I read they jacked up the frame at different points around the car, and measured for movement, then strengthened what moved. It would be nice if that were written down.

I liked the other idea of using varnish(?) and checking for crinkling after hard driving and/or frame lifting?

SharkSkin

Brendan,

There was a thread awhile back where someone had done a finite element analysis with lots of cool diagrams, and a rennlister had bumped into the info and posted a link. Whatever the accuracy or applicability for you, it's interesting stuff. Thread here.

drnick

you could add a rollover bar in the rear for safety, but i thought the same as porken, the rear of the car is already quite stiff. if there is mileage to be gained i think its in connecting the front struts to the rear via tubular steel. i can hear my car flex when i run one wheel up a steep slope/curb. i like the idea of adding carbon fibre but i imagine that to be hard graft, what would you use to prepare the surfaces and what kind of resin will bond to steel?

GlenL

What problem do you think needs to be solved?

Check out what Mark A. has done to his car. It's like most of a tube frame chassis added inside the 928 unibody. That's a lot of work. It does address twisting of the frame especially in the front clip.

I really don't think there's any low cost with high benefit opportunities for stiffening. Also, consider that all the metal added will make your car heavier.

For racing you want a six-point cage where it extends to under the dash along the sides.

I did add a stiffener between the front skid plates.
https://rennlist.com/forums/928-forum/195178-frame-brace-installed.html

EB338

IIRC the under slung rear suspension crossmember takes almost all of the lateral forces of the rear suspension making a rear strut tower cross brace unnecessary. The front end is where bracing would be of the most benefit both by virtue of the 928s structure and the much wider range of stresses steering puts on any chassis