I've been reading over the NASA roll cage rules and they specify the DOM tube size vs. car weight. From 1501-2200 lbs they require 1.500" x .095" tubing and from 2201-3000 lbs they require either 1.500" x .120" or 1.750" x .095" tubing.

My car as it stands is about 2200 without fuel and driver. Once the cage is done and the car is prepped for racing, I'm not sure what the weight will be.

If your car is on the cut off mark do most people just go with the heavier tubing just to be safe?

 

Always go heavier for safety.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 6ghatch &raquo;</TD></TR><TR><TD CLASS="quote">My car as it stands is about 2200 without fuel and driver. Once the cage is done and the car is prepped for racing, I'm not sure what the weight will be.</TD></TR></TABLE>

Well, you'll be over the limit, even without the cage, as cars are weighed as they come of the track (ie driver, leftover fuel, etc).

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Crack Monkey &raquo;</TD></TR><TR><TD CLASS="quote">

Well, you'll be over the limit, even without the cage, as cars are weighed as they come of the track (ie driver, leftover fuel, etc).</TD></TR></TABLE>

Really? That's not what the NASA GCR says.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote &raquo;</TD></TR><TR><TD CLASS="quote">For the purposes of determining roll bar tubing sizes, vehicle weight is as raced, but without fuel and driver.</TD></TR></TABLE>

When putting the cage in my EG, I went with the under 2200 tubing. If I were building an EK I'd go with the larger.

 

You will be over 2200 once the cage is in, so go with the thicker tubing.

NASA does measure weight as they come off the track with driver, fuel, but that is for class weight specs mostly.

The "empty" weight, if nessesary would be used to get the cars logbook.

 

This will sound like overkill. Our CRX has a "minimum weight" requirement of 2140. To insure that we were within the spec's for tubing and because the weight penalty is not that great (IMO) we used 1.75 x .120 DOM for our 8-point cage. Better to be safer.

 

were those tubing specs for chrmoly or mild steel?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by sol2nr &raquo;</TD></TR><TR><TD CLASS="quote">were those tubing specs for chrmoly or mild steel?
</TD></TR></TABLE>

Specs are the same for both.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by sol2nr &raquo;</TD></TR><TR><TD CLASS="quote">were those tubing specs for chrmoly or mild steel?</TD></TR></TABLE>

doesn't matter. in road racing you don't get a break on tube size or wall thickness if you use chro-mo like you do with NHRA.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by jc836 &raquo;</TD></TR><TR><TD CLASS="quote">This will sound like overkill. Our CRX has a "minimum weight" requirement of 2140. To insure that we were within the spec's for tubing and because the weight penalty is not that great (IMO) we used 1.75 x .120 DOM </TD></TR></TABLE>

Safety is very important, but just to give everybody an idea of how much weight you added.

1.5 x .095 = 1.426 lbs per ft (minimum for your car)
1.75 x .120 = 2.089 lbs per ft

A normal cage uses between 100 and 120 ft of tubing. so basically you added probably close to 75 lbs. To some people that is a lot, to others it's a drop in the bucket

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by metalworker &raquo;</TD></TR><TR><TD CLASS="quote"> A normal cage uses between 100 and 120 ft of tubing. so basically you added probably close to 75 lbs. To some people that is a lot, to others it's a drop in the bucket</TD></TR></TABLE>

Yea .. like those of us who are 100# under weight for H3 and 205# under for ITS. I will take more cage over 200# of lead bolted to the floor.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by SPiFF &raquo;</TD></TR><TR><TD CLASS="quote">

Yea .. like those of us who are 100# under weight for H3 and 205# under for ITS. I will take more cage over 200# of lead bolted to the floor.</TD></TR></TABLE>

IIRC, you're only allowed up to 50# of lead ballast to make weight (I may be wrong, don't flame me; it's been awhile since I read that portion). On the other hand, the ballast lowers your center of gravity, as opposed to the cage, which for the most part, raises it. Don't skimp on the cage, though.

 

15.5.18 Roll Cage Tubing Sizes
For the purposes of determining roll bar tubing sizes, vehicle weight is as raced, but
without fuel and driver. Note: There is an allowance of minus 0.010 inches on all tubing
thicknesses. Minimum tubing size for the roll cage is:
Up to 1500 lbs.
1.375” x 0.095” DOM/Alloy/Seamless
1501 - 2200 lbs.
1.500” x 0.095” DOM/Alloy/Seamless
(No issuance of log books for cars with ERW cages being certified after April 30th, 2003)
2201 - 3000 lbs.
1.500” x 0.120” DOM/Alloy/Seamless
1.750” x 0.095” DOM/Alloy/Seamless
(No issuance of log books for cars with ERW cages being certified after April 30th, 2003)
3001 - 4000 lbs.
1.750” x .120” DOM/Alloy/Seamless.
No ERW allowed.
Over 4000 lbs.
2.000” x 0.120” DOM/Alloy/Seamless.
No ERW allowed.