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ExPeNsIvE HoBbY
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Discussion Starter #1
Hey guys, figured I'd post this where people know the answers.

I've got a 2000 mustang and am in the early stages of installing my Chris Alstons Chassisworks 8 point roll cage for 94-04 mustangs.

I've read thru the general regulations in the NHRA rull book and it is rather confusing.

My basic questions include:

1. How should I mount my main hoop(vertical)? Should it be 90° to the rocker panels, or should it lay rearward slightly to match the B-pillar angle? Is there an allowable angle range to meet cert?

2. To follow up number 1: how for forward or rearward should the base of the main hoop go in relation to the rear seat structural brace directly underneath the rear seats? I know the top cannot be any further than 6" behind the rearmost portion of the drivers helmet but what about the seat brace bar? Distance from rear of seat?

3. On the cage sides(the part connecting from the top forward edge of the main hoop continuing forward along the A-Pillars down to the floorboard by drivers feet) how far inward/outward from the main hoop bends should it be? As far outward as it can be on the flat top section?

4. Rear braces. Mine has bent rear struts to clear the rear seat area and drop through where the package tray would normally be. I read they must be parallel to each other. Is that in both axis?

5. Floor plates for main hoop. Can they be bent to match floor contour and the main hoop welded wherever it lays? Does it HAVE to be centered on the floor plate?

Basically the cage is supposed to be compliant up to a 8.50+ET and want to install the cage legally. Any help greatly appreciated.

Any photos to help even more appreciated!!!




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Isn't MustangMatt putting a cage in his car. I would PM him with your questions.
 

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ExPeNsIvE HoBbY
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Discussion Starter #6
Anything more guys? I need my fellow mustang family to pull thru for some help. I've got the main hoop tacked, and working on the bent rear struts. I'm confident I can do all of this, just not sure how to do all of this lol.


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I mounted mine so its parallel with the b pillar. The struts going back didnt find any regs so i just made them symetrical and then put an x brace on them. I still need yo put my door bars in but im going to install swingouts. All the floor plates i bent them to form so i could weld them in. My car passed tech so i guess everything is fine. Just make sure you arent using flux core welding wire. It burns hotter than normal and causes weak spots on the edge of the weld
 

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ExPeNsIvE HoBbY
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Discussion Starter #8
I mounted mine so its parallel with the b pillar. The struts going back didnt find any regs so i just made them symetrical and then put an x brace on them. I still need yo put my door bars in but im going to install swingouts. All the floor plates i bent them to form so i could weld them in. My car passed tech so i guess everything is fine. Just make sure you arent using flux core welding wire. It burns hotter than normal and causes weak spots on the edge of the weld
Thanks Froush. I bent up my floor plates, tacked em in, and set my main hoop centered on the plate, and laid it back 8° which followed my window angle(vert so no real B pillar) and it looks pretty good there.

I got started on my bent rear struts last night as well, got one floor plate in(sits in the rear corner of the shock tower and fender well joint on the trunk floor. They sit at a slight outward angle from the edge of the horizontal portion of the main hoop(just before the bend) toward the mounting point of the trunk floor. The vertical portion of the bent rear strut sits square at 90°.

Hopefully that will work ok for spec. I read somewhere that technically you could write your name in cursive with the rear struts as long as they connect on the horizontal or no more than 5" below the main hoop, and mount SOMEWHERE on the truck floor as long as it isn't the fender itself. Lol




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Proud American
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Hey guys, figured I'd post this where people know the answers.

I've got a 2000 mustang and am in the early stages of installing my Chris Alstons Chassisworks 8 point roll cage for 94-04 mustangs.

I've read thru the general regulations in the NHRA rull book and it is rather confusing.

My basic questions include:

1. How should I mount my main hoop(vertical)? Should it be 90° to the rocker panels, or should it lay rearward slightly to match the B-pillar angle? Is there an allowable angle range to meet cert?

I normally match the angle of the window or lay it back about 5-10 degrees.

2. To follow up number 1: how for forward or rearward should the base of the main hoop go in relation to the rear seat structural brace directly underneath the rear seats? I know the top cannot be any further than 6" behind the rearmost portion of the drivers helmet but what about the seat brace bar? Distance from rear of seat?

I normally try and make it as far back as possible. In a new edge car the restriction is going to be the rear seat bottom. 3 inches forward of the sheet metal that is vertical will work.

3. On the cage sides(the part connecting from the top forward edge of the main hoop continuing forward along the A-Pillars down to the floorboard by drivers feet) how far inward/outward from the main hoop bends should it be? As far outward as it can be on the flat top section?
I would put the a pillar bars as widest as possible. It helps to get in and out of the car and gives more room once in it.


4. Rear braces. Mine has bent rear struts to clear the rear seat area and drop through where the package tray would normally be. I read they must be parallel to each other. Is that in both axis?

I make them as uniform as possible. Makes the car look much better, and being a convertable it will be easy to see if they are not straight to each other.

5. Floor plates for main hoop. Can they be bent to match floor contour and the main hoop welded wherever it lays? Does it HAVE to be centered on the floor plate?

Does not have to be centered on the plate, but don't put it right on the edge either.

Basically the cage is supposed to be compliant up to a 8.50+ET and want to install the cage legally. Any help greatly appreciated.

Any photos to help even more appreciated!!!




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Thanks Froush. I bent up my floor plates, tacked em in, and set my main hoop centered on the plate, and laid it back 8° which followed my window angle(vert so no real B pillar) and it looks pretty good there.

I got started on my bent rear struts last night as well, got one floor plate in(sits in the rear corner of the shock tower and fender well joint on the trunk floor. They sit at a slight outward angle from the edge of the horizontal portion of the main hoop(just before the bend) toward the mounting point of the trunk floor. The vertical portion of the bent rear strut sits square at 90°.

The spec says no less than a 30 degree angle and within 5 inches from the top of the cage.

Hopefully that will work ok for spec. I read somewhere that technically you could write your name in cursive with the rear struts as long as they connect on the horizontal or no more than 5" below the main hoop, and mount SOMEWHERE on the truck floor as long as it isn't the fender itself. Lol




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Its fortuneate that you have a convertable, you have to cut the holes in the floor where the plates will weld. Then you have to drop the tacked cage down through it. Weld the tops of the bars, and then push it back up and put the plates in, and then finish the rest that way. Convertables are easy to do.

If you click the links in my signature, it has a link to my build either on facebook through the never lift race cars page (my own page). Or the 25.3 sfi will show you too.
 

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ExPeNsIvE HoBbY
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Discussion Starter #10
Very thorough reply thank you very much.

I have the rear struts finish welded(not as purty as I wanted dammit) and the main hoop 80% finish welded now. Everything is symmetrical now, and tomorrow I will try to finish the whole thing up.

I can tell I'm getting good penetration on my welds, but they are a little proud. I understand you cannot grind them at all as per spec? Or can you knock down the proud points a bit and be ok?

Btw the floor plates are just tacked in, to keep everything square, but I don't wanna weld them in until I do the front half in case I have to pull it out to reach any hard to reach areas...


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Proud American
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No grinding of any of the welds.


You need to clean the tube really well before welding. Also where the plates are welded to the floor needs to be cleaned of paint.

Are you using a flux core welder? Theoretically you shouldn't use flux core to do chassis work either.
 

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ExPeNsIvE HoBbY
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Discussion Starter #13
No it's a gas shielded Lincoln 180. I'm using .023 wire, little smaller than I normally am comfortable, but my buddy said to try it and ill like it. I don't.

I cleaned the tubes with acetone before welding, just a little proud on my start stops. It doesn't look great, but it will hold. I guess if I really can't live with it, I can grind it out and use a wire I'm more familiar with. Finding temp and feeds that worked good with this stuff was like pulling teeth.

Ugh. Do you know how thin the damn floor pans are on our cars?? I would swear it was like .010" lol. Burned thru so easily even using all the tricks. I'm most likely gonna make some outriggers from the FLSFC'S because I'm not to sure about the strength of the floor pan even with a 6"x6" plate...

Here's after today...





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Proud American
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Doesnt look too bad. First cage work is always tough to learn how to weld.

The bars dont look paralell to me, but they may be and its just a bad picture angle.

Floors are hard to weld to, no doubt. The plates will be strong enough if welded properly, but it isnt a bad idea to tie into the FLSFC too.
 

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ExPeNsIvE HoBbY
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Discussion Starter #15
Doesnt look too bad. First cage work is always tough to learn how to weld.

The bars dont look paralell to me, but they may be and its just a bad picture angle.

Floors are hard to weld to, no doubt. The plates will be strong enough if welded properly, but it isnt a bad idea to tie into the FLSFC too.
Thanks for the replies man. The floors were hard but I did get a good tie in on the thicker rocker panels so that's strong. Got the seat brace in today:


and sized up the cage side bars(not the door bars) and that was a pain.

I will tie directly into my FLSFC's from the main hoop just under the seat brace bar. I think they call it a "D" bar? Anyhow it will go thru the floor down to the FLSFC's at an angle both downward and forward. More triangulation.

The bad part about doing all this and my welds turning out ugly, is I know how to weld, and I weld very well. But that's at work, with $10,000 welders, with the best wire available, and not much round work...

The stress of this being my own project, on my own car, with an unfamiliar welder, with situations I'm not used to, it's not spelling out B E A Utiful.

Here's some of my WORST welds that I did at work. It's round work, but flat.


And a quick little storage rack I made:


I can weld, and they are strong, I just can't make them look good at home lol.


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Bo Baustin
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^^ I love making storage racks and such like that. At my old job, my boss told me to build a small powersprayer setup, that is easy to work on and I had to make 5. So I got to spec the power sprayers, electric motors and tanks, then build and paint it afterwards. I love that stuff.

Back on topic, that weld was sexy btw, and that cage looks good.
 

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ExPeNsIvE HoBbY
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Discussion Starter #17
^^ I love making storage racks and such like that. At my old job, my boss told me to build a small powersprayer setup, that is easy to work on and I had to make 5. So I got to spec the power sprayers, electric motors and tanks, then build and paint it afterwards. I love that stuff.

Back on topic, that weld was sexy btw, and that cage looks good.
Ya that type of work is hella fun! Being our lead machinist now(at 26 no less) they throw me on a lot of prototype projects, where I get to order the equipment, design different parts, and make everything. It's fun because its not our normal inventory parts day in and day out...

I just machined a new shaft for our right angle drive unit from the 600hp Diesel engine, which powers our bladeshafts and blower drive belts. It took 3 days of machine work and it came out tits. It was cool turning a shaft that long, with as many intricate radius's and keyways it had.

Back to the cage, I'm hella happy I have one to put in finally. That is all lol.


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