Racers,

Im putting an 8-point cage in my 914 and I have a few questions about roll cage gussets:

- Are there rules about what the gussets should be made from? Must be DOM? Pipe ok?
- Id like to triangulate my joints with smaller diameter 1" OD pipe than what the cage is made of.
- Are there regulations on where the gussets can and cannot be located? Im thinking of adding to the halo area above the driver, and the connection point of the halo to the main hoop.

Id hate to add a bunch of gussets only to have it flagged for removal by SCCA or another racing org.


Something like these:

Have you studied the rules?

Email the SCCA.

Ditto - suggest downloading/buying the SCCA GCR book and also cross-check PCA and any other orgs you may want to drive the car with. If any doubt remains, ask the "the person in charge" (chief scrutineer, competition director or whatnot).

I don't recall seeing this sort of detail covered in the rules I've studied, but you don't want to go by my memory!

I thought I had, but a quick search revealed this PDF: http://www.nasarallysport.com/rules-forms/...-Appendix-B.pdf

Rules say "round tubing" under 4.2 Gusset construction. Seems pretty clear.

I felt the same way...I'm adding two more gussets this Spring. Also, I've found that if you have any questions whatsoever, SCCA is very accessible. I have the direct email from the gentleman at SCCA headquarters if you'd like it - PM me for the address.

Tony

I am an aerospace structural engineer. Been doing this stuff for 30+ years. I have designed a lot of flight hardware and also welded ground support equipment. I have also been involved in a ton of static and fatigue failure analysis

I have also met a lot of welders who think they know structures and they don't. If they try to argue with you, just walk away and find someone else.

Your tubing should be DOM and not seam welded..even for the gussets.

So that it uniformly transfer the load to the pipe to which it is welded, a gusset should be the same diameter. This way, the load is transferred to the outside of the neighboring tube by shear. If the gusset is smaller in diameter, under compressive load it can punch through the thin wall of the neighboring tube. Under tensile load, It will pull itself from the neighboring tube.

If you are to use plate stock, it is better to use two triangles, on on either side of the joint. A single triangle in the middle of the joint like the one shown in your lower photo will cause a stress riser and can punch through the thin wall of the tube and also will eventually lead to a fatigue crack.

As mentioned above, use DOM for everything. 1020 DOM, specifically.

Scott

whatever you choose to do..take heart - most 914's (historic 4's & 6's) can barely muster enough speed to cause major damage.

maybe so, but having a faster car come up from behind in traffic on a fast straight away and have no where to go except to push you head on into a wall can make a well designed roll cage all the better.....

Bill - True. For some reason...that phenomenon isn't an issue I'm generally dealing with - good thinking. In all seriousness, I get it...you're an engineer. This means a basis of an opinion usually accompanies a brief on one's career. Sometimes I just need to walk away...

Back on track: ONE of my greatest concerns on track is another driver losing brakes or having a major medical into a high-speed braking zone (anywhere in my vicinity). Based largely on that potential event - I have chosen to build and retain a full (intrusive) cage. Is it convenient for an aging driver? Not really. Is it safe-r (and help the flimsy chassis? Yep.

Tony

I guess my greatest nightmare is not what I do to my self in a race car at speed but what someone else does to me even when I am just stalled on the track standing still on the backside of a blind turn...Event though a 914 may not be the fastest on the track, they usually lump us in with a lot faster cars...so the reason why track days can be equally dangerous when I am out in my Miata at Willow Springs practicing with the big bore Porsches that have 40mph over me through turn 8.....for example watch this video. I have driven Road Atlanta in a Formula Ford and know turn 12 all too well.....The guy had no place to go.

https://www.youtube.com/watch?v=RIdGGjMhL4M

Yep. It can be dangerous out there - you can die. However, the last three fatal accidents at Road Atlanta have been isolated, car specific events. The likely hood of multiple cars barreling into one-another is low (but possible).

T

I was at that IMSA event at Road Atlanta and was watching from the outer paddock area near turn 1. I did not see the initial impact, but I did see Jeremy Dale's car roll to a stop afterwards. It was a very scary accident.

You can never predict when you will have a fatal accident....I guess that is why they are called "accidents". I prep my cars for the likelyhood of that one worst possible scenario, not just the lesser ones that may happen more often.

I wouldn't be afraid of using 1"od dom or flat triangular gussets.
However, IMO it's unlikely that gussets (of any style) will provide increased driver protection over good basic roll cage construction in a 914.
My race car has very few gussets. They are made with 1 1/2" od DOM and none are in the upper greenhouse structure.