I'm going to be building a NHRA cage for my 280z starting the 26th of December. I'm looking for ideas of how to fit the 6X6 base plates nicely.

I will post a lot of pictures I've seen around here and I'd like feedback of whats is a Good -> Better -> Best Way.


The only thing that concerns me on the cage bellow is the main hoop contacting its base plate at an angle. Is there any way to get around this? Also, I've heard the bend C pillar bars aren't ideal. Should I keep them straight on my car?









Also,

For the A pillar bars I've been trying to decide how I'm going to mount them.

Option 1:




Option 2:



Regards,
Justin

 

i think option 1 would be stronger as long as you welded all the way around the tube

 

The first option would definitely allow much more weld area(assuming you weld the entire seam). It would provide more equal load distrobution to the mounting plate. NHRA legal or not, no idea.

 

Id go with #1....but with not as much of the tube notched out. maybe a 1/3rd

 

you could weld all the way up the tube in #2 as well.


i got stuck doing a cage in one of those cars, it sucked lol

 

Is this legal?



Regards,
Justin

 

im also thinking option 1, and not to thread jack but what material and thickness does nhra require for the 6x6 plates?

(sorry for the off topic question justin)


mike

 

They require 0.125" thick steel plate. I'm using cold rolled for the base plates.


Justin


Modified by Justin Olson at 1:57 PM 12/15/2007

 

As for the tubes contacting the plates on an angle, it really doesnt matter. Either is fine. As for rear down tubes...a bend in a tube is a weak point, some will argue, but its a fact, so straight is stronger and wont flex as much, BUT is it needed on a stock bodied type racecar? Probably not.
Kyle

 

My fear is the fact that welds are much stronger in compression then shear. I want to limit the shear loading of the welds as much as possible.

Justin

 

I'll go with two, in option one from what I see from the pics, your notching the pipe ? I would think it would weaken that small leg of the pipe thats still attached after you notched it. Unless your notching the frame, then its a different story.

 

Option one would notch the pipe. The thing is, the rocker is much stronger then the sheet metal. I'd like to load the rocker instead of the thing sheetmetal floor pan if I can. Both 1 and 2 I would weld the tube to the side of the rocker panel.

Regards,
Justin

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Justin Olson &raquo;</TD></TR><TR><TD CLASS="quote">Option one would notch the pipe. The thing is, the rocker is much stronger then the sheet metal. I'd like to load the rocker instead of the thing sheetmetal floor pan if I can. Both 1 and 2 I would weld the tube to the side of the rocker panel.

Regards,
Justin</TD></TR></TABLE>

Do number 2, put it close to the rocker/sheet metal, then weld that as well.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by RCautoworks &raquo;</TD></TR><TR><TD CLASS="quote">

Do number 2, put it close to the rocker/sheet metal, then weld that as well.</TD></TR></TABLE>

I agree, not to mention notching that out to make it fit tight to tig weld would be a bitch!

 

Ive personally done it as #2...but I don't think you'd lose any integrity by doing it the way #1 has it. Think of it as weld surface area.

 

I ordered 100ft of 1.625 X 0.083 CM and 40ft of 1.25 X 0.065 CM. That should be plenty for two cages I'd think

Its begun..




Another question, Do I need to do a bar that follows the rocker? Its shown here in the rule book:



Regards,
Justin

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Justin Olson &raquo;</TD></TR><TR><TD CLASS="quote">
Another question, Do I need to do a bar that follows the rocker? Its shown here in the rule book:
</TD></TR></TABLE>

I'm going to say yes since it shows it.

 

sorry for teh jack, but lets say for example this was a unibody car that had the bar going from rocker to rocker w/ d-bars going to it, and the main hoop welded to plates on the floor, would the bar that Justin Olsen is mentioning connect to the rocker bar or the main hoop? I am about to do an 8pt in my DC this weekend, i am thinking I should add this bar now instead of later. The above pic shows the main hoop but does not show the rocker to rocker bar, just curious if it does have to go to the main hoop, will there be enough room under the rocker bar to fit this bar in.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Justin Olson &raquo;</TD></TR><TR><TD CLASS="quote">I ordered 100ft of 1.625 X 0.083 CM and 40ft of 1.25 X 0.065 CM. That should be plenty for two cages I'd think

</TD></TR></TABLE>

if ya dont expletive any bars up! 11ft for a main hoop is a nice amount to junk...

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Justin Olson &raquo;</TD></TR><TR><TD CLASS="quote">

Another question, Do I need to do a bar that follows the rocker? Its shown here in the rule book:

</TD></TR></TABLE>

open the rulebook again and look to the bottom left corner where that picture is;

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by NHRA Rulebook &raquo;</TD></TR><TR><TD CLASS="quote">

Unless an OEM framerail is located below and outside of driver’s
legs, a rocker or sill bar, minimum 1 5/8-inch x .083 CM or .118 MS
or 2-inch x 2-inch x .058-inch CM or MS rectangular, is mandatory in
any car with a modified floor or rocker box within the roll-cage
uprights (excluding 6 square feet of transmission maintenance
opening). Rocker bar must be installed below and outside of driver’s
legs and must tie into the main hoop, the forward hoop, frame, frame
extension, or side diagonal. Rocker bar may not tie into swing-out
side bar support. If rocker bar ties into side diagonal more than 5
inches (edge to edge) from forward roll-cage support or main hoop, a 1 5/8-inch x .083 CM or .118 MS brace/gusset is mandatory
between the diagonal and forward roll-cage support or main hoop.</TD></TR></TABLE>

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 96 GSR-T &raquo;</TD></TR><TR><TD CLASS="quote">sorry for teh jack, but lets say for example this was a unibody car that had the bar going from rocker to rocker w/ d-bars going to it, and the main hoop welded to plates on the floor, would the bar that Justin Olsen is mentioning connect to the rocker bar or the main hoop? I am about to do an 8pt in my DC this weekend, i am thinking I should add this bar now instead of later. The above pic shows the main hoop but does not show the rocker to rocker bar, just curious if it does have to go to the main hoop, </TD></TR></TABLE>

The "rocker to rocker" bar you wont find in the rulebook for one reason; it doesnt exist. It's not a rule. You can add on any bars you want past the minimums if you like within a class's rulebook. Attatch the main hoop from side to side if you want.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 96 GSR-T &raquo;</TD></TR><TR><TD CLASS="quote">
will there be enough room under the rocker bar to fit this bar in.</TD></TR></TABLE>

make it fit!

 

So from reading, I believe the dash bar can be 1.25" X 0.065" CM. Can the cross bar that connects the A pillar bars also be 1.25" X .065" CM?




Regards,
Justin

 

Added the x brace.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Justin Olson &raquo;</TD></TR><TR><TD CLASS="quote">So from reading, I believe the dash bar can be 1.25" X 0.065" CM. Can the cross bar that connects the A pillar bars also be 1.25" X .065" CM?

Regards,
Justin</TD></TR></TABLE>

I'd keep the dash bar the same dimensions as the rest of the cage unless weight is a very, very big concern. NHRA and other sanctioning bodies are notorious for changes the rules and requiring different tubing year after year.

 

Won't this really depend on the type of collision or crash you would experience?
The primary purpose of the 6x6 plates is to have something of great surface area, so that the tube does not puncture the floor pan, which generally speaking, is like tin foil. I personally have done plenty of cages where I have joints intersecting the gusset plates at angles, I say the greater the weld area the better. As far as bends go... You will get hoop strength from a bend, and I suppose it really depends on how your loading the joint. But bends can also be a weak spot.

As far as the rocker bars... It has been my understanding from the rule book that they are only necessary if you have modified the OEM floor pan or rocker panel.

Dash bar can be 1.25"x.065" CM

 

So I'm cutting out some rust on the floor pan. I'm going to be welding in some more sheet metal and seat brackets. Does this mean I need the rocker panel

Justin