johnc

Ta Dah! Congratulations! But, one small suggestion, don't go down the paint path becuase it looks like crap after 6 months of use unless you use a good epoxy paint. Try lots of steel wool on the roll cage tubing and then wipe it down with Boeshield T9.

I'll toot my own horn, but i won't be "cheap"... http://www.betamotorsports.com

Hey! I see a place for a gusset! Brace the door jamb to the roll cage using... a gusset!

What size tires?

Maybe I'm ignorant when it come to turbo charged engines, but 30 degrees of ignition advance at idle sounds crazy.

IMHO, FWIW, the stiffness gain from a small taco gusset is more then offset by the additional weight of the gusset, the weld filler, and the extra paint needed to cover it.

In the few roll cage failures I've seen, the tube junction failures (which were rare) were all caused by poor welding. At the Lincoln Electric welding school they had a roll cage out of a Joe Gibbs Winston Cup car on display. Three tube junctions in the driver's side door bar failed from lack of penetration and almost impaled Tony Stewart. Every fabrication team member from Joe Gibbs racing was sent through the two week Lincoln Electric Motorsports welding school after that incident. They also go back periodically for a refresher course. If the tube junction is fit up properly and welded correctly, its unlikely to fail before the joined tubes themselves fail. A gusset won't help in that situation. A gusset can work as additional insurance against a poor welding job, but if the welder screwed up the joint weld, what's to keep him from screwing up the gusset weld?

If a single impact exceeds the design strength of a roll cage (with or without gussets), how do you predict the failure? Given an accurate prediction of cage failure from a single impact, how do you control that failure?

A roll cage should not be designed to crumple in any way. The rest of the car can and should crumple to the cage structure, but the cage itself is the last resort and should not give. A cage is designed to transfer load through itself to other areas of the vehicle. It should not absorb load by buckling, bending, or compresing.

A gusset is probably needed if a bar in a cage is spanning a failry long opening in the chassis. The upper cage bars that span the top of the door opening in a BMW E36 chassis is a good example. Be careful about blindly copying what Pro teams do. They are usually building cars to handle much higer speed impacts then the typical SCCA regional racer encounters. Our cage designs should focus on a 70 to 90 mph impact, not 140 to 160.

I've used 3M Bushable Seam Sealer 051135-08656 on probably a dozen different cars over the last 5 years without a problem. Maybe it has trouble with colder climates but its worked great for me here in SoCal. EDIT: its important to clean the seams after welding with Acetone and then use air to blow out and dry the seams after cleaning. Just putting seam sealer over welded seams invites cracking and peeling.

I'm on the fence regarding gussets. Roll cages have worked well for decades without them especially if the tube junctions are a tight fit and welded properly.

You need to get a shop manual or the Haynes manual for your car. There are pictures that show the factory rear anti-roll bar installation.

No kidding. Hopefully you learned from it.

Street cars use the big ARB, small spring paradigm. Race cars have almost all moved to the big spring, small ARB paradigm unless rules get in the way. A serious racing 240Z runs spring rates 275 lb. in. and above. FYI... my definition of a race car is pretty hard core - you wear a helmet every time you drive it. Anything else is a street car pretending to be a race car.

Each was fine for the particular track and event I was running. I sometimes switched out the ARBs between sessions at the track to adjust the car. I did less of that once I got the Penskes installed. Low speed compression and rebound valving takes care of a lot of the things an ARB does without reducing the independence of the suspension. I finally settled on a 23mm front and 16mm rear ARB and used the shock adjustments to fine tune.

At various times I ran: 1. Suspension Techniques 25mm fromt and 19mm rear. 2. Nissan Competition 23mm front and ST 19mm rear. 3. ST 27mm front and 22mm rear. 4. Custom 25mm front and 16mm rear.

Thanks for the support guys regarding my brother. I'm not the subject of this thread and don't want to hi-jack what someone else is going through.

In road racing, yes and no. It depends on the sanctioning body. SCCA and NASA both require FIA certified seats unless you build a seat back mounting brace that attaches the seat (just below the shoulders) to the roll bar/cage.

Probably fine for the street but until they get FIA certification don't race with them.

Whomever it is, my condolences.

That's what I remembered, but when I saw this picture today I got scared. Why? Because a rollover load would put the welds on the side of the tube in shear and they could peel away from the plate from something as simple as a little dirt in the weld, a gust of wind blowing the shielding gas away for second, or any number of other little things. Adding a box underneath to handle rollover loads in compression is a good idea. EDIT: When I use the term "compression" I'm referring to how the load moves through the tube. Roll bar tubing works well in comrpession/tension and not as well in bending or shear.

For the fourth year in a row Bob and Tina McKean at Vintage Motors are holding their Christmas open house, car show, and toy drive in La Habra, California. All Z guys are welcome and Bob is an ex-Nissan/Infinity Master Tech and has owned a number of Datsun and Nissan Zs over the years. The show is Saturday December 8th from Noon to 4pm. Bring a new unwrapped toy to the show and receive a t-shirt and a raffle ticket. Beta Motorsports is a show sponsor and I'll be donating some stuff to the raffle. Its a good, low key family show and there's no marque arrogance. More information here: http://www.vintageride.net/events/index.html

Man, I wish I was your tubing supplier.

Perfect reply! Thanks for listening and trying to improve.