About to start my cage and need a quick question answered. I am buying a new die to bend 1 & 1/2" pipe but don't know how tight of a clr (center line radius) I need for my miata. They offer 4.5, 5.5 and 6.5"

 

You can do everything you need to do with the 4.5". Most people I know with Benders go with the tightest radius at or over 3x tube diameter.

 

Thanks! I need to look if anyone here has done a cage setup themselves but this phone is to slow to search. I have a harddog to go off of so it will help a bit.

 

Check the rulebook for your organization too. I feel like I remember seeing a bend radius min/max in one of the rulebooks.

 

In every rulebook I have looked at, nasa, scca, chump, lemons it says that the radius must be a minimum of 3x the diameter of the pipe. Consult your rule book for the group you intend to run with.

 

I'm not running a class, it will be a street cage but it will hit the track for fun. Still think 4.5" is what I need?

 

Even if you're not racing yet, I'd still look over the rulebooks that rharris mentioned and build to those specs. If you don't want to use all the bars they require, fine, but make sure the ones that you do use comply to those requirements. That way if you ever decide to move to some sort of w2w, you'll have a cage that's either ready to go or just needs a couple bars added. Or if you decide to sell the car, you'll have a much larger group of potential buyers.

And all that goes without saying that the current requirements are what they are because of previous trial and error. Stick pretty close to the rulebooks and you should end up with a cage that'll do it's job if you ever need it.

 

There's no such thing as a street cage. Build it to a ruleset (NASA/SCCA) or don't waste your time.

 

I have the 2012 SCCA rulebook in hand and have covered it, my local track (which is the only track I plan to get on) doesn't do much racing and does more member days than anything.

Blackbird Fab would argue with that, their cage is what I would like to get mine close to.

 

^ This.
1. A cage on a street car is asking for dents in your skull.

2. Depending on the intended organization, and discipline, your design will be radically different.


Ever seen video of the interior of a car during an accident, everything goes EVERYWHERE. Don't be a dummy and bounce your skull off your neat cage. That's a big reason that racers wear helmets.

For instance, the "cage" I'm planning for my autocross car will be VERY different from anything he needs. Not only because he runs NASA and I, SCCA, but because my car has no windshield, and safety is only a secondary concern.(I know I know, but when's the last time you've heard of an autocross car flipping?)

 

I have never been a fan of the street cage idea, but if you do it make sure it conforms to the following rule set for the forward hoops.



NASA Rules:
15.6.8 Forward Hoops (Option 1)
The forward hoops shall extend from the main hoop (in a forward direction) to the floor
by following the roof and the “A” pillar of the car. There shall be a bar connecting the
two (2) forward hoops at the top of the windshield mounted as close to the roof as
possible without violating CCR Section #15.6.20 Inspection. The forward hoops shall
incorporate no more than four bends each. Optionally a “15.6.9 Halo Hoop (Option 2)”
or “15.6.10 Front Hoop (Option 3)” construction may also be acceptable.

15.6.9 Halo Hoop (Option 2)
A “halo bar” extends from the main hoop (in a forward direction) following the roof line to
the windshield then following along the top of the windshield, then following the roof line
back to the main hoop, thus creating a “halo” over the driver’s head. A “halo” bar shall
be constructed of one (1) continuous piece of tubing. One (1) down tube following the
“A” pillar must support the “halo” on each side of the car. The down tubes shall
incorporate no more than two (2) bends each.

15.6.10 Front Hoop (Option 3)
A “front hoop” is a bar that extends up from the floor, then follows the “A” pillar up to the
roof, then follows the roof line across the top of the windshield, then back down the other
“A” pillar, and then terminates on the floor. There must be one (1) horizontal bar
(following the roof line) connecting the main hoop and the forward hoop on each side of
the car. The front hoop shall incorporate no more than four (4) bends.

This is convertible to a legal cage:

 

Maybe I should rephrase my definition of cage. I want a rollbar

My intentions:

 

That changes things 100%.

While I cannot give you a good answer I would love it if you did a write up on everything you do to build your roll bar. Sometime in the distant future I will be wanting to do the same thing.

 

Cage, rollbar, blah blah

I will be sure to take several pics during the build but it will most likely start next weekend.

 

No Dents, in my skull yet, finger crossed:

 

1.5" is too thin for a roll bar/cage. Go with 1.75" 0.095" wall

 

Unless you know what you're doing (maybe you do) don't mess with 1" tubing. Every tube you need in a basic cage for a miata should be 1.5". You might just be saying the die can do both even though you don't intend to use 1", but just wanted to clarify.


I have personally seen this happen.

And wouldn't you feel the fool (assuming you survived the incident) to be the guy who intentionally did his cage in a way that doesn't protect you in a rollover, when that's the primary point of a cage, if you're unlucky enough to have to find out how bad your design is?

-Ryan

 

Woah woah woah, I posted the above then read the rest of the thread and noticed you are not building a cage you're building a roll bar.

BIG DIFFERENCE - not just "blah blah, same thing" - not at all.

A roll bar should be 1.75" tubing.

1.5" Should ONLY be used in a roll cage

If you're looking at an SCCA rulebook you should already know this.

Just about every cage in miatas are done in 1.5", and this is absolutely acceptable. For a roll bar though, the only ones that meet NASA/SCCA are 1.75"

On the subject of thickness, I would agree that that is adequate, but SCCA requires .120 for roll bars, so which rule book you're following changes things.

-Ryan

 

double post.

 

I dunno about NASA but in SCCA land 1.5 is just fine for some applicationsSolo/Solo Trials at the very least(1.5x0.120, and 1.5x0.095 I think is good for GCR cages and the 1.5x0.120 is heavier per foot than 1.75x0.095