Street Roadster Roll Cage

[frnkeore]

I just got a Austin Healey kit car and I need to build a roll cage for it. Has anyone done a street roadster roll cage?

The NHRA drawings are a bit confusing and I'd like to discus it with some that has built one.

[SSdynosaur]

I have never built one but, perhaps, some of the confusion comes from the fact that the rule book pictured street roadster cage (roll bar) design assumes a single occupant oriented in the center of the vehicle chassis; contrasted to an offset driver.

[frnkeore]

Yes and I did a search for pictures. In that search, I found some 2 seaters (like Cobra's), saying they they ran at the drags but, with regular type roll bars or cages.

Are there any NHRA Cobra competitors on the forum, if so, what are you using?

[Rory428]

Back in the 90s, my buddy drag raced a Shell Valley bodied Cobra. When he originally built the car, it was a street car, with the common chrome single hoop roll bar, but when he decided to make it a drag car, he needed to make a NHRA legal roll cage for it. Technically, the cage is supposed to be welded to the frame, but John came up with an interesting idea, he welded up a double hoop roll cage, which ran through the fiberglass body, with a drivers side door bar, and since welding the cage solidly to the frame would mean if he ever wanted to remove the body in the future, he would have to cut the bars from the frame. So he welded stub tubes, about 3" tall each, to the frame, and then the legs of the bar slipped over the stubs, and with 2 bolts per tube, at 180 degree to each other, bolted the cage to the stubs. The local tracked let that pass Tech, and a couple of years later, John really put the cage to the test, when during a typical high wheelstand, the car went right, flew up over the concrete guard wall, and flipped over , hitting the top of the wall with the main hoop, and eventually landing on its tires again, on the spectator side of the wall, with only a dent to the main hoop. I have some photos of Johns Cobra, but I can not seem to be able to post them here, maybe TomP has some as well.

[SSdynosaur]

Currently, the only Cobra I'm aware of that is running NHRA SuperStock and SS/GT belongs to John Stock, based out of Ohio and his cage/roll bar resembles a funny car-type enclosure around the driver's upper body. I believe John's car is a Kirkham, prepared for NHRA racing by Pat and Andy Kronenbitter of PK Race Cars, based near Columbus, OH.

[thatdarncat]

I’m not sure exactly what type of roll cage you are looking to build. Left hand drive open top roadsters of various body types are very common in the NHRA Super Gas category, for example. But they of course generally run a complete fabricated chassis. We have a local Minnesota racer and race car builder who has a Cobra replica bodied Super Gas car, although I couldn’t turn up a picture with a quick search, I’ll keep trying. As mentioned by SSdynosaur, John Stock runs a Cobra in NHRA Super Stock, and my understanding is the same, it’s based on a Kirkham body & chassis. Here’s a picture from the Internet of John’s car. A few years back, one of the years I ran Hot Rod Drag Week, there was a competitor running a Cobra replica, with just the typical Cobra style hoop roll bar, and they were allowed to run, but I don’t know what ET they were tech’s for.

[frnkeore]

I found a pic of the RT side but, I for sure can't do it that way. I'd pay hell if my wife couldn't ride in it.

Actually the NHRA drawings are very vague. They don't give min/max tube angles for any tubes and only give one length, in the middle of the structure. Some of the required tube sizes are very small @ 5/8 or 3/4" for diagonal tubes. The load paths aren't very good either.
 

[machoneman]

I’m not sure exactly what type of roll cage you are looking to build. Left hand drive open top roadsters of various body types are very common in the NHRA Super Gas category, for example. But they of course generally run a complete fabricated chassis. We have a local Minnesota racer and race car builder who has a Cobra replica bodied Super Gas car, although I couldn’t turn up a picture with a quick search, I’ll keep trying. As mentioned by SSdynosaur, John Stock runs a Cobra in NHRA Super Stock, and my understanding is the same, it’s based on a Kirkham body & chassis. Here’s a picture from the Internet of John’s car. A few years back, one of the years I ran Hot Rod Drag Week, there was a competitor running a Cobra replica, with just the typical Cobra style hoop roll bar, and they were allowed to run, but I don’t know what ET they were tech’s for.

Cool car and great pics!

[thatdarncat]

I found a pic of the RT side but, I for sure can't do it that way. I'd pay hell if my wife couldn't ride in it.

Actually the NHRA drawings are very vague. They don't give min/max tube angles for any tubes and only give one length, in the middle of the structure. Some of the required tube sizes are very small @ 5/8 or 3/4" for diagonal tubes. The load paths aren't very good either.

Another one of our local friends, JC, wanted to build a two seat, side by side, rear engine dragster. The idea was to build something he could run at the track, driver only of course, but also put another seat in and use at fairgrounds cruise events, and have a passenger. He wanted it to be NHRA legal, although I don’t believe he’s ever bothered to get the chassis sticker. He sent away for the SFI specs to build it to a NHRA legal spec. If I remember it was an involved process to get SFI to get him the proper blueprints, since what he wanted to build wasn’t “normal”. But in the end it was possible, and he built it. Here’s a picture below from when he was building it, and without the body work. Even though it is a rear engine configuration maybe that will help give you some ideas for the cockpit? As far as what’s in the NHRA rulebook, I think NHRA now days is figuring if you’re building a cage or chassis beyond something basic you will send away to SFI for the blueprints.

[Falcon67]

The John Stock cage and the one for the two seater are basically the same as most dragster cages around the driver.  Pretty much identical to my dragster cage.  Whichever, you'll want to allow 1~2" wider than your shoulders for fit.  If it's run down to the frame/lower rails like most others, consider "pull up" lap belts vs the "pull down" style, much, much easier to hook up and cinch. 

[frnkeore]

This is what I have to work with.

The body in front of the doors, come off pretty easy. The back body work is a little harder.

[frnkeore]

Update:
I got hold of the Division 6 inspector, that lives in Madras, OR (very nice guy and tries hard to help you) and he said that if I only run Summit and Lucas sanctioned events, I can run a 1 3/4 roll bar IF I don't break out of 10 sec flat.

He's doing a chassis certification on the 19th & 20th of March, here at the Medford/White City track and tell me exactly what I need if I take my car to him.

I guess that's why I had seen pics of that type roll bar saying they run NHRA.

I'm now very happy, I can at least get the hoop made.

We talked for a long time and I guess there are hard nosed, inspectors that rule subjectively in this area. He told me about a CA inspector that won't let a guy run his car in a lower class because it had run in a lower ET class, even though he had replace the 460 cube engine, with a 383 engine, after he bought it. He never ran it as a BBC, at all. He just wanted to learn the car before he reinstalled the 460.

[thatdarncat]

I assume this Austin Healy is a “convertible”, with no top? If you are planning on running a hard top on this car then that could effect the interpretation. I would contact that Division 6 inspector again (or another) and clarify exactly what you are building, and that you both understood each other correctly. What you just said is not NHRA legal, even for just Summit & Lucas events, in fact they would be even more likely to enforce the rules, compared to a casual bracket race. Summit events are just bracket race events that are eligible to be counted as qualifying to participate in the season ending division Summit ET finals, Lucas events are divisional and national events that include Super Stock & Super Gas class vehicles like we posted above, and even vehicles running 10.00 & slower have to meet the rules. I’m  just trying to save you putting work into this project, just to be turned away, or limited to a slower ET than you intend. In this case it doesn’t have anything to do with a particular inspector being “subjective”, the rules are clear. I’ve included a picture of the pertinent rules in the ET bracket section of the rulebook. What he described, a 1 3/4” roll bar, is legal down to 10.00 ET, in a full body vehicle with stock firewall, but that bar in a convertible will only be legal to 11.00, and is required quicker than 13.50. Now what could be “subjective” is if some particular tech inspector deemed your Austin Healy kit car a “dune buggy type”, then it’s only legal to 12.00. Again, just trying to help. Now if you just intend to run at an unsantioned track, or a track that generally ignores the rules on their weekly events, and there are plenty of those, then you might get by. Check the both the sections here on Roll Bars & Roll Cage. You might also want to check the section on Wheelbase, not sure what the wheelbase on an Austin Healy is.

[frnkeore]

Kevin,
You could be right. I down loaded the 2022 rules and just finished looking through them. He was confused at the start, not knowing a AH is a roadster but, I made sure he knew it was a convertible type, early on.

WB is no problem, it's 92".

I'll know more, when I take it to get it looked at. There will be two inspectors there. I'll hold off on getting the roll bar bent.