I decided to drain the tank completely. Had fans running to move out the fumes for a few days. Seems bone dry now. Sealed it up with new o-rings. Going to weld the support plates this weekend.


What is your opinion on removing the rear strut tower bracing and replacing with tubing vs leaving stock and or stitch welding stock bracing.
Tubing can be more sturdy than OE. Easier place to mount track accessories back there, also better access to strut tops. But, is it really worth the extra work, in your opinion?

 

I'd like to hear that too, if cutting the strut bar and putting tubing is better or leaving it?

 

Better in what way? Stronger? How strong does it need to be (what is the load and what is the load path)? Anyone done any FEA on the basic chassis to know what its load limits are along certain paths in the chassis?

Having done FEA on a couple cars (Datsun S30, BMW E36) I doubt cutting out an engineered structure and welding in a non-engineered (no analysis and design behind it) structure will improve anything. I suggest you augment the engineered structure.

 

Makes me rethink side protection

http://www.motorsport.com/v8supercar...emat-courtney/

 

FIA 253 Article 8 - Safety Cages.

 

The rule book is a great and very detailed resource no doubt. I have read it over, thanks for pointing that out to me.


I am also looking for feedback that's very Z specific and the rule books can be interpreted in various ways when we get to model specifics.

 

Not really. Having built cages in 350Zs, BMW E36/46s, Porsche 356/911/944s, Datsun 240Zs, Mustang SN95s, Toyota Celicas, Miatas, and a couple Loti I can say the basic cage design is the same. There are model specific concerns with attachment points but you're generally trying to attach the cage to the same general areas in any car. The idea is to protect the driver and FIA/SCCA have over 100+ years of combined experience in cage specification. What some cage builders do is out trick themselves by thinking of the cage as a chassis stiffening tool. In most cases that leads to a less then optimal cage from a safety perspective.

 

You wouldn't happen to have any pictures of the cages you built to put up on here, so we can see some of your ideas I think that would be helpful to all of us

 

Unfortunately no. I sold my shop last March and the web site was shut down at the end of October (I was never allowed to post a link here due to sponsorship rules). There is still a Facebook page for betamotorsports that has an album of pics for a M3 cage.

 

Maybe get some more discussion going about the optional bracing tubing. Rear down tube support V design instead of X design. "Backstay Diagonals" As seen here in green. (Taken from All Speed Innovations)

 

All of the additional green bars in the diagram above are listed in FIA 253 Article 8. They are essentially optional except for the roof "V" (or "X") and there is a vague discussion of the reasons for those bars in the technical document. The front bars going to the firewall are now a requirement with SCCA and NASA if you are building an 8 point cage.

Whether a "V" reinforcement is better then an "X" reinforcement is mostly a matter of opinion and personal preference. A customer's E36 went end-over-end 5 times at Buttonwillow and was 15 feet off the ground at one point according to the corner workers. The cage had just a diagonal in the rear braces and he walked away with only harness bruises - that's after leaving the track sideways at 95+ mph. That kind of accident is actually a best case scenario because energy is dissipated over time and distance. Worst case is a hit into a wall where the energy spikes over a few milliseconds. Crush zones and a safety seat/harnesses that flex/stretch somewhat help spread that energy spike over a longer period of time. In NASCAR they make extensive use of IMPAXX foam in the side and rear protection for just this reason.

BTW... The basic cage construction and chassis attachment is more important then any optional bars.

 

Nice topic, more into the cage B and cage C