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Cage rule question, re: vehicle weight


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From the rules, it says to look at the car "as raced" but to exclude driver and fuel. Fine, I understand that part. My question is, do you look at the vehicle weight before the addition of the cage or assume the weight of the cage in the car?

 

The reason I ask is I am very close to the 2,500lbs limit and being able to use 1.5" .095 tubing. The car alone(wet minus fuel) was at 2,584 at last corner balance, but this would include 4 point roll bar in 1.75" .120 dom tubing. I want to add the front section and would like to keep the weight to the minimum up front. I know I could still go with 1.5" .120 at this point and the weight difference wouldn't be all that much, but I'd like to know.

 

The other question I have is in regards to chassis stiffening with the cage. Intent section of CCR under Roll cage. It's somewhat unclear what can or cannot be done. Any specific pointers? The car is 20+ years old and chassis is old and quite flexi.

 

Also, if I read the CCR correctly, tying into the front strut towers is not allowed if the bars would have to go past the firewall.

 

If there is someone I should email directly and ask, please let me know.

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"as raced" is pretty clear. Can you race your car without the cage? No...therefore you'll need the bigger tubing. If I had to do it over again, I'd go for the bigger tubing over the weight savings.

 

It is my understanding that the cage is free in GTS. Anything goes.

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The tubing specs are based on the weight of the "complete car" so if you finish the car with 1.5 .095 and it weighs 2499 it's okay or if you use .120 and it weighs 2501 it's also legal.

 

From the weight of the current car you'll probably have to use 1.5 .120 or 1.75 .095 unless you shed 100-150 lbs.

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As mentioned, the weight is based on the finished car, so you have to take into account the weight of the full cage.

GTS allows for additional cage reinforcing, including through the firewall.

Something to keep in mind, the heavier the tubing, the stronger the cage will be.

I could have gone with lighter tubing, but chose 1.75x0.120 for my cage, and I'm glad I did.

Petar, you've seen the pics of my incident at Putnam...

Only the required bars, per the CCR, have to be of the required size. You can go with smaller tubing for any additional bracing/reinforcing.

 

Feel free to give me a call to discuss your cage, or any other CQ stuff.

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It is my understanding that the cage is free in GTS. Anything goes.

For the record, GTS or not, the cage has to meet the NASA CCR requirements. As Mark says...

 

Only the required bars, per the CCR, have to be of the required size. You can go with smaller tubing for any additional bracing/reinforcing.

However, there is a limit. There is an extra penalty in the rules if you get to the point it would be considered a tube frame car (the definition of which is being debated in another thread).

 

Finally, you said...

 

From the rules, it says to look at the car "as raced" but to exclude driver and fuel. Fine, I understand that part...

I'm not sure where you are taking that from but since the only weight that matters in GTS is weight vs horsepower, I'm going to assume you're talking about what we use as your weight to determine whether you are legal. In that case, we DO include the driver and whatever fuel is in the car when you come off the track. So, if your target weight is 2,500 lbs and you weigh 180lbs with racing gear (don't I wish I did), the car would need to be 2,320 lbs (including fuel) to get you down to the minimum.

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Thanks for responses guys. Mark, I will talk to you about some car specific questions. I remember your crash well. I think the major issue was lack of A-pillar support, and I would plan to support that A pillar hoop with extra bracing.

 

Scott, read the CCR again, 15.6.18 Roll Cage Tubing Size: "For the purpose of determining roll bar tubing sizes, vehicle weight is as raced, but without fuel and driver."

 

http://www.nasaproracing.com/rules/ccr.pdf

 

- this is the confusion, as to me, "as raced" should also include driver and fuel. In any case, I think I will go with 1.5" .120 wall.

 

I understand that for classing in GTS full race weight is used, just like I did in TT when classing the car based on HP/wt.

 

Anyways, I think it's clear now - thanks again.

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CCR determines what the minimum level of stuff you need to race is.

Class rules may determine an upper bound on the level of stuff if there is any. Sounds like GTS sets one but it's way out there.

 

Also the way the legality for the class is determined may differ from how things will be checked when you're getting your logbook inspection or annual inspection done as you can tell.

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Scott, read the CCR again, 15.6.18 Roll Cage Tubing Size: "For the purpose of determining roll bar tubing sizes, vehicle weight is as raced, but without fuel and driver."

Peter...gotcha. I was guessing what you were referring to and got it wrong. I was talking about what we weigh for classing. You were talking about what you needed for the cage. Sorry...my bad.

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I have never heard a driver walk away from an incident saying "I wish I had less cage" - more in this case is always better. Error on the side of safety.

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+1. I went one size up on every cage I've ever had installed. All it takes is seeing one incident where you thought " That guy better buy his cage builder a case of beer".

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  • 2 weeks later...

I used 1.50 x .120 on my cage based on the car being around 2350 before the cage. To calculate weight I used around 115 ft of tubing for my car. Below are some specs on the various DOM tubing.

 

 

DOM Tensile Strength = 70,000 psi

Diameter (in) Thickness (in) ID (in) Cross Sect. Area (in^2) Tensile Strength (lbs) Weight (lb/ft)

1.75 0.125 1.50 0.64 44,668 2.169 lb

1.75 0.095 1.56 0.49 34,575 1.596 lb

 

1.50 0.120 1.26 0.52 36,416 1.769 lb

1.50 0.095 1.31 0.42 29,352 1.426 lb

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