Cage building question

Build to minimum spec for intended purpose (1.5 x 0.095 or 1.625 x 0.080) or over build to 1.75 x 0.120 regardless of intended venue, sanctioning body,  or class? 

1987 VW Scirocco 16v

Track days with SCDA, COMSCC and the like. Eventually some "low cost" endurance racing. Probably an autocross or 10.

I feel that this will be the last car I build. My intention is to make it track only. Most of the drivetrain and suspension is done. Brakes are next. But I want to start thinking about the cage. 

Thoughts?

for mostly non-competitive stuff, I would say just build for safety. A few lbs won't matter at track days, and likely won't matter for enduro racing either, in the grand scheme of things. 

Our rally cage is a combination of 1.75 (primary bars/hoop) and 1.50 DOM, all .120 IIRC. Some bars should be stronger than others, so you don't have to use the same for everything. 

I am a firm believer in building a cage that meets as many different racing series as possible.

At some point when you contemplate selling it, it will help.

The downside, is that many different series, have major differences. Many Rally groups required FIA type cages, but some series require "Nascar Bars", that you will never see in an FIA cage,

In reply to vwcorvette :

When I redid my car I had the cage built  to pass SCCA specs even though Comscc does not require us to have them built to a particular spec. Do you still run with COM regularly. If so what car and # are you? I have a silver 2nd gen RX7,  #714.

An engineer friend recommends the over built cage too. And yeah the weight isn't an issue. I'm not trying to win anything. 

imgon, I only ran once last year at Palmer. Was in blue and purple rabbit GTi. I think used some combination number with 77 in it somewhere. I before that I hadn't done COM since the late nineties. Silver rabbit GTi. 

I like COM. 

I don't foresee any rallying in my future either. Was thinking some form of x door bars that reach into the door cavity.  Something similar but with a more positive connection perhaps at the meeting joint. 

If for some reason you feel like going fast in a straight line, 1 3/4 .120 is nhra/ihra size.  Nobody else is going to fail you in tech for overbuilding a cage.  I do all mine that size because it’s easy to get, and now I have a bender i only need one die set

Overbuilt will be safer.  I'm always a fan of safer if I'm starting from scratch.  I see no reason not to overbuild it.

Short of an actual tubing notcher  what's a more Grassroots means of notching tubes easily?  Was there a story in the Mag? 

The only downside to using 1 3/4 tube in a low roof car like a Scirroco is head room.  The diameter of the tube generally means you cannot bend as tight a radius.  Small car, tall guy is trouble, for me.

Is the car going to be faster in the quarter than 11.50?  If not, NHRA won't care what the cage is made of, as long as its properly padded.

Built to SCCA rules, and most everyone will be happy.  

vwcorvette said:

Short of an actual tubing notcher  what's a more Grassroots means of notching tubes easily?  Was there a story in the Mag? 

Order up an Ol' Joint Jigger.  They are cheap, ans work remarkably well.

vwcorvette said:

Short of an actual tubing notcher  what's a more Grassroots means of notching tubes easily?  Was there a story in the Mag? 

I have always used a grinder, but I recently bought a notcher and anticipate life getting easy.  

vwcorvette said:

Short of an actual tubing notcher  what's a more Grassroots means of notching tubes easily?  Was there a story in the Mag? 

angle grinder and a lot of grinding discs. We used a notcher for my cage, but I had to change a few bars later, when I didn't have access ot the notcher, and used a grinder. What a pain in the ass, and I'll never do it that way again, even for just a couple tubes. Unless you have a LOT of experience (or really, really take your time) you'll end up with tubes that just don't fit all that well and/or will have to re-do some. 

Buy a notcher or borrow one.

I got really good at plasmaing or torching out the fishmouths and quickly hitting them with the grinder to clean it up

but just using a grinder works well too

i used the chop-saw method i saw this guy use on youtube. SUPER efficient, highly recommend. 

tube notching w chop saw

Go_Gators said:

i used the chop-saw method i saw this guy use on youtube. SUPER efficient, highly recommend. 

 

tube notching w chop saw

Thats how i did my jeep cage and it worked great. Try it on some scrap first to figure out your angles and after you do a couple you will be knocking out joints quick.

I built a few cages for SAE Baja in college with a JD squared notcher, bench grinder, chop saw and a TIG Welder.  A good notcher isn't necessary but it makes for quick work. Most of the budget notchers are limited on the shallow angles so it's kinda guess and check. 

I found this site,Cope template generator, one night after getting frustrated with the shallow angle joints. Input the size of each tube and the angle they meet at and it spits out a profile that you print out and tape onto the tube.  I would trace the edge with a paint marker and use the angle and bench grinders to make the cope.