Rage13

Looking for anyone running (or anyone with advice) a 14 pt., funny car or nascar type cage. I want to run in the silver state challenge, their rules for a 3500+ lb. car call for 1.75" OD x .120" wall tubing (this is for ERW tube). To me this seems a little thin.. I was thinking about steping up to .164" wall tube. What do you guys think?

AGood2.8

1st off, I would highly suggest you get the car under 3500lbs. Thats easily done if you strip it. Those figures are min. tolerances. Just remember that the cage adds weight also- Thicker the tube, heavier the cage. Just how fast do you thing your top speed will be on course? And what tires are you running?

Rage13

I want to beable to run 200mph thru the course, so thats what I'm building the car up to do. Tires I'm not sure of at this point..

Rage13

What would be the main reason for is?

AGood2.8

Not to be an ***- I am serious when I say this: So you don't die from tire delamination. At those speeds, with that weight, in the desert heat, say goodnight to your tires. Please learn some more about raicing physics before you try something over your head.

Rippin92RS

Get some tires that NASCAR uses. They are $389 a piece if I remember correctly. They race at 200mph in hot weather and have the inner-liner just in case. Good luck! What kind of hp will a 3rd gen need to reach 200?

-Rippin

Rage13

thats what i'm doing

Rage13

you guys know how heavy that 300 mph firebird was at bonneville? I've been looking for a while now and can't come up with any specs.
Also, what would be a good way to make down force on the front end of a car without adding weight?

AGood2.8

The thing about tires is heat and duration. If rated the correct speed, they can run high speeds, but the question is, for how long- that is determined by weight and temperature. Most NASCAR, and CART tires are top secret compounds. You cant buy the exact tires that the bigwigs are running. The tires are only loaned to the teams. And when they are worn, each tire is collected, the serial # cut off, the the tire is shreaded. Most land speed cars have the same- factory sponsored custom tires.

As for downforce, just eliminate as much air as possible going under the car. This will create a low pressure zone with air flow under the car at speed and will suck the car towards the ground. Channel the airflow out the rear so it can pick up volume as it travels back under the car. Theres alot that goes into a 200 mph car. Many have died at the SSC in Lamborginis (so called designed for hgh speed) and have delaminated tires on even them at 170+mph in the desert. The race has come along way though- they don't as far as my knowledge run it in the hot months anymore.

Darklord1987

I'm not positive about the rules for SSC, but why don't you run chromoly tubing. This way you can run a thinner wall (0.085 or 0.095), still have the same strength as the thicker mild steel, but have less weight. For an 8 or 10 point cage you will save about 80 lbs, so with what you plan on installing the weight savings will be over 100lbs. Also look into Carbon Fibre body panels if you want to lower your weight more. A few years ago, Hot Rod magazine had an article on a Grand National built for the same event and he had CF hood, fenders, doors, and trunk lid. Also think about getting rid of the glass and going with Lexan.

MrDude_1

umm not to be a ***, but..

to a tire, theres no diff in static car weight and downforce "weight" when you're going down the road....



also, for tires, i would be looking at what everyone else is running... seems to work well for them the past few years...

not this time, but eventually, i plan to run the silver state or some other race like that.... my prob is that i have a billion little issues to work out..... from PCV to tires to cage and downforce...


on a plus side... a 3rdgen camaro vert gets pushed DOWN at high speeds, while a 3rdgen camaro coupe gets sucked up.. hehe... im pretty sure its the hatch/roof line that does it to you guys

james_85Z28

Dude,

That statement and what you are trying to imply with it in regards to agood2.8's statements are so wrong, ignorant and just outright il-conceived that that statement alone displays your tech credibility.

I've never seen a tire on a heavy car delaminate its tires while it's parked.

Rage13

Pulled from the rule book: Chrome alloy tubing, such as 4130, is not recommended since the strength of the area adjacent to the welds will be impaired if the structure isn't normalized, and because of the difficulty in making satisfactory welds.

But I can use DOM tubing, the min. wall for that is .090.. So I'm probibly going to go with that, but with a wall of .120
I'm not to sure about the lexan windows tho.. it would save weight, but it also scratches easy and I'd assume after a run you probibly couldn't see thru it..
Any one know how well CF stands up to sand blasting?

AGood2.8

That is partially true- However- Whats it got to do with this conversation? You opened your mouth, so EXPLAIN?

Darklord1987

Didn't know they recommended against chromoly, oh well. As far as the Lexan goes though, why don't you run a search of nascar suppliers. I know that in Nascar they put about 10 layers of a clear sticker or window film that they just peel off when it gets marked up and they have another clear layer behind it to see through. Kind of like the clear film you can apply to the window of a sandblasting cabinet I would guess.

As far as the CF body panels, unpainted in the desert I don't think they would make it through too many races. Although properly prepped and painted they would be pretty durable. Just make sure that they would not be hung so low as to scrape the ground when you hit road undulations because if you do it will deteriorate pretty quick.

Rage13

Well if I used CF parts they would be painted.. only those clowns that don't need it and only do it for looks leave it out for the sun to eat.. There are some guys in a boat yard around here that do CF work, so I'm going to go talk to them and see what I can come up with. As for the lexan, I'm still not sure about it.. I know you can put layers of that coating on it, but 100 miles nonstop, I just don't know if it would hold up, and really wouldn't want to get droped from the race cause it got to scratched up to see out..

Darklord1987

Sounds like you're on the right track. Let us know how the car is turning out along the way. Good luck, hope I was able to help a little. Vader

MrDude_1

if a car that weighs say... 1500 lbs but had high downforce (open wheel formula car for example) is going down the road generating 500lbs of force on the front wing and 500 on the rear... the total weight on the tires is 2500, correct?

thats the same stress as a 2500lb car that doesnt have any downforce (or up) at that speed... right?


so waht i was just trying to say, is that on one hand the guy already has a extremely heavy car to be going at that speed... and then the downforce is going to be making it "heavier".


so what i didnt say but ment to imply is that when hes looking for load ratings for his tires, hes not looking for the weight of the car at a stop, but the weight of the car when its in motion....

athough as usual i phrase things wrong and come off as a dick...*shrug* not trying to insult you in anyway...

Rage13

on i will, i'm going to buy a good digital cam before i start, probibly going to make a site to follow every step of the way
and are you Vader as in Mod. Vader?

Darklord1987

Sorry, that was a slip-up. That's my name on a few other boards that I frequent more than here. Here it's Darklord1987.

AGood2.8

Well the problem here is your misinterpetation of my response to downforce-

Rage was asking about adding downforce to the front (to keep the nose from getting light and scary at speed. I responded that instead of adding downforce (which is drag), to mearly cut off airflow under the car and it will help the frontend stay planted and stable. Never implied adding downforce.

Back to tires and why your statement is only PARTIALLY true. At a stand still, the tire does not suffer from distrotion from centrifical force. at different levels of speed, tires will distort more or less based on their speed ratings (this is why you don't run an H rated tire at 150 mph- it will deform and cause excessive heat on the center contact patch of the tire rather than the entire tire evenly (plus speed increases friction, which increases heat) thus delamination occurs.

The same goes for a heavier car on a tire. The tire may be rated for the speed, but not for the weight of the car. The heavier car will produce more friction on the smaller contact area at speed (trying to flatten it back out, and creating more friction) than a tire with a lighter appropriate weight car.

Nascar tires are suject to pitstops with frequent tire changes and monitoring for problems. Even so, at the speeds they run, how many times do you see a car go into the wall because of tire failure? Enough to worry about it, It happens so commonly that NASCAR mandates the inner tire rule.

Hunter Motorsports

Only on the Super Speedways. And - yes they do mandate the rule because in those conditions of extreamly high speed a tire failure is even more catastrophic. Of course Goodyear does go to extreme lengths to make the tires as safe as possible, and most tire failures in Nascar are a result of a puncture - not de-lamination.

In any high-speed high-temperature situation the tires are going to be a major concern. That goes without saying. The less load on the tire the easier it is for it to stay together, hence the reduction of weight is a good plan. Choosing the right tires is also a good plan. Racing tires may or may not be the best idea. Nascar tires for example are probably not a good idea as they are made for circle track use, unless of course you can get your hands on a set designed for the road courses - and yes they are different. The most important thing to remember about real racing tires is that if you DO have a puncture - it is all over. The tire WILL fail almost immediately at those kind of speeds and it will give little or no warning before sending you spinning off the road into whatever may lie there - rocks, trees, use your imagination. D.O.T. tires that have a high speed rating are superior in this respect in that the carcass of the tire is stronger allowing it to stay together in the event of a puncture - and possibly allowing you to stay on the road. The tire is also stronger and thus less suceptable to damage from road debris. Finally in reference to D.O.T. approved tires - they must be able to sustain high speed operation for LONG periods of time at the LIMIT of their speed rating and also at the LIMIT of their weight or load rating. A properly chosen and properly inflated set of street tires can work just fine for high speed events. Shaving the tires to minimum tread depth is also recommended.

As far as the cage goes - stay away from ERW tubing. SCCA has now outlawed it - all new cages built for competition in SCCA MUST be made with DOM tubing. It is stronger. Any good fabricator will be using DOM tube to build cages. CroMo is also difficult because of the need to normalize welds - and in a production car this is not practical.

Have the main structure of the cage built with 1.75" X .120" tubing and it will be more than strong enough. Any non critical areas can be made with .095" wall tube to save some weight.

And make sure that the fabricator who is building the cage is reputable. Ask around to see who else has cages from him - and look at them. Just cause someone has a tubing bender and a welder does not mean they are able to build a good cage.

Do some research - talk to other people who have done the race, and make sure you are as well prepared as you can possibly be. That way you will have a better chance of finishing. Alive.

Rage13

I've decided to go with the DOM tube, so what are the non critical areas of a cage? As far as building the cage, I was planing to do that myself. I figured I could do all the cutting, palcing and tack it all together, then take it to a good welder and let them do that part. (After having a few of their welds tested.)
For being prepared, I plan on going to a few race type schools (probibly 2), and I'm going to set my target speed for the first few races at around 130 mph. So 150 mph DOT tires should do for now.