Chassis/Cage Tech question

[BR3W CITY]

So this has had me curious since a while back when someone posted up a snippet from the NHRA rule book about cage specs. I don't need a full cage, but I'm approaching rollbar territory and it bothers me:

The rule was about position of the hoop and cross bar (belt bar?). It said that the bar had to be X number of inches above and Y number of inches behind the drivers helmet. (I don't have the current rule in front of me, I won't pay for the book )

Thats where the issue comes in. My cab is so tight, that it would be physically impossible to mount the seat in a way that could have enough space to fit a crossbar in the cab, as well as the hoop...and still have it "behind" my helmet.

What I need to know is.....is it OK to build 70's-style EXTERNAL main hoops? Its totally possible for me to get the 4-6" of room I'd need, but putting the hoop from the frame in between the cab and the bed...and the "lip" on the back edge of the 66 roof would tuck a bar nicely.

The best answers I've had so far are "well if it fits the rules"....but I don't wanna put that kinda time and work into something that will fail tech the second I show up.

[71Dragtruck]

The rule book is free online.

http://www.nhraracer.com/content/gen...000&zoneid=132


The 6" and 5" you are thinking is a max not a min distance, so I'm thinking outside the cab would be too high and far away??

[BR3W CITY]

Originally Posted by 71Dragtruck

The rule book is free online.

http://www.nhraracer.com/content/gen...000&zoneid=132


The 6" and 5" you are thinking is a max not a min distance, so I'm thinking outside the cab would be too high and far away??

Oh thanks man....thought you used to have to buy it for like $25, but its been a while.

My head is ALMOST against the glass. The distance between the helmet at the outside of the cab is only about the thickness of the back wall lol, so maybe 1-1/2".

I'll run out and take some measurements today for curiosity and see what it would end up at. I haven't seen a "blanket" statement about having to be IN the cab (t-buckets use sorta-external cages sometimes).

[BR3W CITY]

Originally Posted by 71Dragtruck

The rule book is free online.

http://www.nhraracer.com/content/gen...000&zoneid=132

Hmmm, they have links to buy a book, or join the NHRA....both cost $$$ lol.

found it here
http://s3-us-west-2.amazonaws.com/nd...A_Rulebook.pdf

[Oldtruckfanatic]

When I get into a situation like that I talk to a local shop that builds racecars. They build certed cages all the time so they stay abreast of the Rulebook. You might try that if its not easily answered but the book.

[slowtruck]

Page 16 in this may help.
http://www.nhra.com/UserFiles/file/G...egulations.pdf

[BR3W CITY]

I've read the whole thing, or at least as much of it as pertains to me as possible.
There is no mention of the word "external" or "Exo" pretty much anywhere in mentioning cage and roll bar requirements.

The "open top" and "sandrail" rules also don't mention anything specific to that (and since those would be the only other applications of an external cage, aside from a rockcrawler) I guess it should be ok.

To clarify; are supposed to interpret the NHRA rulebook the way Thomas Jefferson viewed the Rule of Law...that we CAN do something, unless it specifically says we CAN'T?

[71Dragtruck]

Just remember that your seat and harness have to attach to the back cross bar.

[BR3W CITY]

Originally Posted by 71Dragtruck

Just remember that your seat and harness have to attach to the back cross bar.

I know the belt would have to attach to the bar. Thats annoying, but I think doable, and I'm way more comfortable putting a 2" weathersealed slit into the cab wall, more than I am somehow modding the whole cab to find a way to put a bar inside it.

I didn't see the seat attachment thing tho, I may have to reread it. I didn't think you hard-mounted the seat in the back.

I'm looking at a few sections:

ROLLBAR
Roll are mandatory in all cars (includingT-tops) ning11.00 (*7.00) to 11.49(*7.35) ,in convertibles running11.00(*7.00) to13.49(*8.25), in all dune-buggy type vehicles running 12.00(*7.50) seconds ad slower. Permitted in all cars.

Roll cage mandatory incars running 10.99(*6.99)orquicker or any car exceeding 135mph.In ull-bodied cars, with unaltered firewall ,floor,andbody (from firewall rear ward ,wheel tubs permitted) ,running between 10.00(*6.40) and10.99(*6.99), rollbarpermitted in place of roll cage.

--------

Since my truck is full bodied with an unaltered firewall, I assume this means a regular hoop-only is enough for me. I don't expect to run faster than low 11's tops this year, so thats alright.

Adding rear-bars is easy with bedfloor and tubs, especially from an external hoop. The biggest thing would be needing a door bar at some point in the future, if I ever got to that point. And figuring out how to mount the harness. I have low-back buckets...which I have a bad feeling will become a problem at some point. The door bar is the only thing that would have to penetrate the cab, which is a shame that it can't be avoided, at least not the way I read it.

[71Dragtruck]

You will require at least a drivers door bar, plus if your seat back does not come up to the back of your helmet you will require a bar mounted pad behind your head.

Fun part about the rule book is you will find more than one section covering the same thing. Lots of the basics can be found in section 20 under general regulations.

[71Dragtruck]

Also if you read 4:10 in section 20 on roll bars to me it reads as the roll bar has to be within 1" of the roof 3" from the top of the helmet above the drivers head, to me that reads on the inside of the cab.

Reading it that way makes sense to me in a safety stand point as in you roll your vehicle on the track and the cab comes to rest on the guard rail and the bar is on the outside, the back of the cab will still crush down on you, with the bar on the inside it holds the back of the cab from crushing inward.

At least that my thinking on it, I would always want my bar on the inside of the cab.