convertible question ?

Ok out there in tech land, we had our monthy race meeting and have become stuck on a subject. Is a t bucket a convertible or is it a dune buggy? under nhra rules
I side on convertible as i have one, then roll bar limit 13.5
A dune buggy needs a bar to even be on the track.
my other argument on this is there was no rollover protection built into any convertible until into the 70s, and that if a bucket is a dune buggy so are most early convertibles.
no one is really shure as there are opinions on both sides

I have seen t buckets at the tracks before with no roll bars but like mine they were not really fast down the 1/4

Open car, no bar. Nope, it'll never fly at Firebird.

Convertibles must run with the top up and afford at least s-o-m-e protection to the driver. You have no top, so it's an open car.

Richard, what are the exact requirements. Do you need a single hoop, or a 4 point, etc.?

Don

All dune buggy type vehicles must meet all 11.50 and quicker open car E.T. rules, regardless of E.T. or speed.
Minimum 5-point roll bar
SFI 16.1 belts with crotch strap
Arm restraints
SFI 3.2A/1 fire jacket
SFI 3.3/1 gloves
Minimum Snell 95 helmet

Thanks tech already went and ordered jacket gloves and belts
working on the roll bar stuff right now having trouble finding tubing.
I can find 120 wall tubing but have figured out that when one gets it bent the tubing actually goes well under 118 spec on the lage side of the bend
Am trying to find a hoop that is appox 56 inches wide but no one lists the hoops by width just by application. Have got the local speed shop looking to try to get a proper width for me.
I am thinking maybe a 55 hoop may fit but will have to wait and see.

It might be easier to just build a funny cage or side steer street roadster cage into the car. With a funny/roadster cage, you won't have to fool with the rear supports. If center steer, use a SFI 10.3 altered plan. If side steer, use SFI 10.4 street roadster plan. The dimensions and tubing required are in the rulebook or you can get specific plans from SFI.....
http://www.sfifoundation.com/drag.html

You can also modify a wider made-to-fit product by cutting the main hoop and the crossbar, narrowing them and inserting a slip tube inside that will be at least 4" into each side of the hoop and crossbar. Drill two 1/2" holes in each side of the hoop and crossbar and weld the bar to the sleeve tube inside (rosette). Summit has several kits that you could make work this way, but I still think a altered/funny/roadster cage would be the simplest. And the safest.

Thaks for the advice tech but i still want to keep the car as a street legal driver which i think i can even with the front downtubes. my biggest problem is finding a correctly shaped hoop that is wide enough for my cars body.
i measured a hoop from a mid 70s camaro 48 inches outside measusrement, need a little more than that.
I thought that the hoop had to be a single piece not spliced at any point?
i do agree that the alterd type cage would be safest as it would protect the driver the most, but it would make the car race only.
i wish someone would list the hoop dimensions.

I thought your car was narrower than the available hoops. Is there anyone in your vacinity with a tube bender? If not, I can have one bent for you from 1.750" x 0.134" and shipped. The rest of it, you could fabricate yourself. It's all straight tubing.

Dave Severson is closer to you than I am. PM him and ask if he can do it for you. If not, I can.

Thanks tech for the offer but the freight would make it not worth it. Called a cousin in law in calgary tonignt and got some names for some shops there that might be able to help.
Got someone here who can bend it up but cannot find any tubing.
Calgary is 300 m west of here and if it means i have to fuel up the wifes echo and go for a blast out there and take out the front seat to haul it home is shortened chunks so be it.
I would prefer to go to the heavier 130 vs 120

Getting steel today, will be here by the pm. just got to get the hoop bent up to start with.
got my rule book out and am wondering if the door bar has to be a straight member or can it have a slight bend to come right against the inner panels to give as much clearance as possible. i also would like to know if further braceing can be added to the door bar(as i dont have working doors) i was wondering if a can add a further vertical brace below the door bar to tie into the frame beside the seat
i cant see any harm in it and it would definitly reinforce the door bar.

answered ny own question went and looked at a kit that came with downtubes .

This may help you.......
http://www.metalgeek.com/static/cope.pcgi

wow im going to give that a try once i get going on this thing neat neat neat gotta find me a big protractor
thanks much

Quote:

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Originally Posted by canadianal

Getting steel today, will be here by the pm. just got to get the hoop bent up to start with.
got my rule book out and am wondering if the door bar has to be a straight member or can it have a slight bend to come right against the inner panels to give as much clearance as possible. i also would like to know if further braceing can be added to the door bar(as i dont have working doors) i was wondering if a can add a further vertical brace below the door bar to tie into the frame beside the seat
i cant see any harm in it and it would definitly reinforce the door bar.

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The whole idea of the door bar is to retain the driver in the car, so as long as it passes the driver between the shoulder and the elbow in normal driving position, you can tweak it any way you want to. You can also add any other bars you want to. Many door cars have the door bar bent into a lazy "S", with the afforementioned retention feature of the bar in place, but allowing more ease of entry and exit into and out of the vehicle by having the forward portion of the bar closer to the floor.

thanks teck i was looking at it also to give a little bit more protection to anyone in the car if you are hit on the side. i realise a hard t bone would probably be fatal but just a city fender bender accident may be helped by a reinforced door bar.
i have already changed the down tube design to go right down to the bottom of the frame kickup directly behind the body, this also gives a little side protection and allows me to have the hoop little wider.
I gots big shoulders and needs all the width i can get.
it looks like its going to work and i am planning on overbuilding past the nhra specs with gusseting and some exta tube bracing .
I keep thinking i am building a roll bar that guys put inside a regular car body and have the ability to compound the rollover protection of the cars roof structure and the roll bar,
Ive just got the bar so i better get it right the first time

getting my downtube tomorrow and am starting to mock some things up today. how heavy should a gusset be on a roll bar? i cut some right angle triangles out of some 1/8 by 6 wide plate. they look pretty good but wonder if i should be making them out of 3/16,
cant seem to find any real ideas on the net,

Triangles 1/8" thick by 4" on the long side will be fine.