do cage support "boxes" count as mounting plate area?

[tom91ita]

i have seen many cage pics lately with a "box" that supports the hoop, etc. this looks like a good way to get better access to weld the bottom of the hoop, front tube down by the A piller, etc.

not sure what part of the rules allows this. if it is the reinforcing plate then does the box count as part of the area? and for those that do this, is there anything "in the box" to prevent it from being "crush-able"?

correct section right?


9.4. ROLL CAGES FOR GT AND PRODUCTION BASED CARS




3. Mounting Plates
a. Mounting plates welded to the structure of the car shall not be less than .080 inches thick nor more than 0.25 inches thick. The maximum area of each mounting plate in
the Improved Touring, Showroom Stock, Spec Miata, and Touring classes shall be 144 square inches. Plates may be on multiple planes but shall not be greater than 15 inches on any side.

[DoubleXL240Z]

It has been my understanding that all of the material used in "box" is subject to the area limits.
That being said, while it does make it easier to weld I don't believe it is as strong of mounting configuration as a flat plate, plates mounted at more than one plane. To me it is like welding knives edge down to the floor of the car. As opposed to a much larger flat surface that is supporting the load in a roll over scenario. YMMV

[tom91ita]

i am thinking about the following method (sizes approximate for discussion purposes);

roughly a 4" by 4" plate welded to the floor of the car.

make a 2.5" "cube/box" to support the main 1.5" OD hoop. this will be made by welding the four sides to the plate leaving the "top" of the box open until the next step.

the "top" will have a 2.5" long piece of tubing welded to it that will be inside the "box" when done.

now the 4" by 4" plate will have any roll-over impact spread across the both an area equal to what the tube would have had due to the "insert" plus the "box"

[Flyinglizard]

First, I have never seen any SCCA tech person measure the plates.
The square in rule, is the area covered by the plates, IMHO. not the plate area.
Most of the current vertical plates/boxes, are designed to tie into the sill plates and the floor. Keep in mind that the floor has almost no structural value on most modern cars.

The above box is a good idea, but way too small,of course. The improvement would be to build the multi sided plate, up the sill, insert the tube as described but leave a 1/2 gap to the box bottom. I consider any more than 1/2 in to be too much movement.
This now forms a "crush box", allowing the hoop to crush and move the impact loads to the rest of the cage before hitting the bottom of the box. The sole intent is to reduce the punch through potential , by spreading the loads to the other members.

[Greg Amy]

It has been my understanding that all of the material used in "box" is subject to the area limits.
Concur.

[DoubleXL240Z]

[QUOTE=Flyinglizard;339455]First, I have never seen any SCCA tech person measure the plates.
I have!

[betamotorsports]

I measure them. IMHO, if the box (normally called a plinth) is wholly contained within and welded onto a plate (or plates) that are welded to the chassis of the car, then I do not count the plinth area in the mounting plate square inches. If the plinth is welded to the mounting plate and/or some part of the chassis directly then I count the plinth area as part of the mounting plate square inches.

[Ron Earp]

Our tech measure the area of the various plates that make the plinth. It isn't easy in all cases, but it can be done.

The rules clearly allow for creation of these structures:

"Plates may be on multiple planes but shall not be greater than 15 inches on any side."

And I think you'd be remiss in not using them. A box structure welded on three sides to strong portions of the chassis is far better than a single plate welded to the floor.

[Flyinglizard]

The contact area of the car's structure, should be the only measured area of the square in rule.
" shadow".
It was designed to keep the cage plates from stiffening the car.
What you do inside of the 144 in , is only regulated by the 15in max side rule.
If you have guys measuring and adding the sides of the hoop/ base plate/box, etc, contacting the car structure, than I really think the rule is misinterpreted.

[seckerich]

If you trace the total area of the plates on paper and lay it out flat it must fit in the required area. Up 6', over 6' and down 6' is 18 per the rules. You can get creative with the bends to gain room.

[CRallo]

i am thinking about the following method (sizes approximate for discussion purposes);

roughly a 4" by 4" plate welded to the floor of the car.

make a 2.5" "cube/box" to support the main 1.5" OD hoop. this will be made by welding the four sides to the plate leaving the "top" of the box open until the next step.

the "top" will have a 2.5" long piece of tubing welded to it that will be inside the "box" when done.

now the 4" by 4" plate will have any roll-over impact spread across the both an area equal to what the tube would have had due to the "insert" plus the "box"

generally good thinking, but take full advantage of the plate area that you are allowed! You should see some of the plates in my car, even Kessler thought I was crazy!!

[timo944]

Check the web for good ideas on box design. There are a couple of forums out of Australia (VW racing I think) that have good concepts on proper design to avoid "kinfe" problems etc. IIRC they actually have a requirement that these are used.

As for the original question, I assumed it's the area of the plates that attach to the car. I think that would be hard to prove wrong. But I'm under the 144 sq in either way - that's a lot of room.

[Spinnetti]

i am thinking about the following method (sizes approximate for discussion purposes);

roughly a 4" by 4" plate welded to the floor of the car.

make a 2.5" "cube/box" to support the main 1.5" OD hoop. this will be made by welding the four sides to the plate leaving the "top" of the box open until the next step.

the "top" will have a 2.5" long piece of tubing welded to it that will be inside the "box" when done.

now the 4" by 4" plate will have any roll-over impact spread across the both an area equal to what the tube would have had due to the "insert" plus the "box"

Tom, what problem are you trying to solve? If its ability to weld the top tubes easier, there's two approaches that work well.
1. Use a hole saw, and cut holes in the floor. Drop the cage through, weld the top, then raise back up and weld in your floor plates
2. Do like we did in the lex, and bend the top tubes a touch to bring the tube end lower on the hoop.

[tom91ita]

thanks for all the comments.

i do plan on using most of the allowed area. the dimensions noted were for discussion. i will likely "count" any box support area as part of the allowed area since it will not be that much and better safe than cutting out part of it....

i like the idea of any "inner" tubing section being a 1/2" shorter for some allowable deflection/crushing.

Dave, one area of welding would be for the landing by the "A" pillar where i want to get very close to the rocker. if i "build" that up a bit with a "box" then that weld would be much easier. i really kind of liked what Greg (i think?..) had done with landing that support on the rocker panel as well.

if the reason we can build the "box" is because of the allowed area, i don't see how i cannot count it.

question just for grins, if i built it up to be 5" high under the main hoop, would anyone think that would pass tech? it could still meet the area requirements etc. but i do not think it would pass tech. bascially, at what point does a "box" stops being an attachment point and becomes part of the support structure?

[Flyinglizard]

Please do this. Call SCCA and talk to club tech. get names.
Verify that the sq in is the shadow cast on the car structure.( as I read it)
The "box" is not currently addressed in the rules . Many boxes are as tall as the sill top to floor size. . 5-8 in, is not uncommon.

I have a patent pending on the "crush box" for bolt in cages.

[Greg Amy]

...bascially, at what point does a "box" stops being an attachment point and becomes part of the support structure?
The moment it becomes a rollcage tube.

There are only two GCR-allowed basic elements in the rollcage design: the tubes and the mounting plates. If it's not a tube, it's a plate, and the plate is subject to area limits.

GA

[Flyinglizard]

The plates are( should be) measured by shadow, not the sq in of the multi sides.

[Greg Amy]

The plates are( should be) measured by shadow, not the sq in of the multi sides.
They are not. If they were, then they could be three feet tall.

The "boxes" are measured by total surface area, just as if they were plates mounted flush to the vehicle's structure. Any other way is contrary to the regulations.

GA

[seckerich]

As Greg stated, see post 10. That is the way it has been explained when the new rule was crafted. The idea is to limit the area away from the attachment point that can be used to structurally reinforce the chassis. If the SQ inch rule was gone we could legally seam weld the entire car to the cage and run 1/8 wide plates down every seam of the car. Rule is well written and does what it is intended to do. Not so hard to do a very safe design within this allowance. If you went by a shadow I could run all the way up the down tubes so you can see how it goes crazy quick.

[betamotorsports]

Greg is right regarding how the mounting plate and plinth square inches are calculated. My post above was mistaken.

[Flyinglizard]

The rule was written before anyone used boxes. It was, and still is, the shadow of the plates upon the car structure. Per Ryan MIles @ SCCA tech 8/9/12.
The 15 in(?) longest side rule counts.
Basically if you make a crush box, place it on a 12x12 plate , you are good to go. As the rule is written today and clarified by SCCA tech.

Maybe the crush box needs a max side size also. As long as they are less than the 15 in rule, up the sill plate, they should be very safe.
I am sure that if you built a fancy box over about 6in from the floor plate/level , you may have some valid safety issues.
You should avoid the potential to crush the box more than you have room to the roof, minus 2in, IMHO. I like 1/2 to 3/4 in before it all loads up .
Short story is that there is very little stiffness gain, as long as the cage sits inside of the 12x12 rule. (Not much even as the cage gets really tied, either.)

[seckerich]

We used boxes on the Speedsource cars long before this rule, but for conversation lets say it is some new innovation. Good to hear you got the opinion of the day from the latest person in the tech office. Lets see which way the wind blows next week. For reference you received an opinion that is only good after it passes CRB muster. That might have changed too, but that is how the system works. They are the only ones who can clarify and give a rules interpretation, and there is a form on the SCCA site to have that done if you want. I know it is hard to tell tone on a post, but not being a jerk, just giving information as it has been all for the years I have been a National Tech.

[Greg Amy]

The rule was written before anyone used boxes.
This ain't nuthin' new. We've been doing this for over a decade. And we've always followed the plates size rule.

In fact, for the 2006 ARRC (for reference, that was six years ago) on a cage we built in 2004 (for reference, that was eight years ago) we kept cardboard cutouts of all the plates to hand to Scrutineering to make it easier for the Tech guys to measure the plates.

What's old is...old again.


Maybe the crush box needs a max side size also."Crush box" definition does not exist in the GCR. In fact, I don't think anyone on this forum has the engineering degree and testing experience to be designing "crush structures". As such, all parts of...whatever you want to call it...is subject to the plate rule.

And in fact, if one wants to get technical, remember that the GCR baseline is "if it doesn't say you can, then you can't". Ain't nuthin' in the GCR about "crush boxes", thus they don't exist...and if you're doin' 'em - whatever they are - you're not compliant.


...For reference you received an opinion that is only good after it passes CRB muster....

Ding.

[Flyinglizard]

This is a common problem with SCCA tech. The local tech person has to have an opinion of what the rule means. And it varies..
The IT guys themselves will beat the thing to pieces, regardless of the head of tech opinion, at the national level.
And, it is just not that important.. IMHo.

FWIW I have the testing for the Crush box from 10yrs ago and we are in the process of running it on INEX next week for the patent stuff. So yeah, I have a lot of time in research both the theory and results of cage failures and improved design areas.

I really dont care about compliant on safety issues. I have seen way too many SCCA cars with crap cages. ( no cross bars, small welded floor plates without any tabs. )
All of my VWs now run HP, the only IT spec car is the SM and that runs NASA.(NASA checks the cars at regional races).

[Spinnetti]

thanks for all the comments.

i do plan on using most of the allowed area. the dimensions noted were for discussion. i will likely "count" any box support area as part of the allowed area since it will not be that much and better safe than cutting out part of it....

i like the idea of any "inner" tubing section being a 1/2" shorter for some allowable deflection/crushing.

Dave, one area of welding would be for the landing by the "A" pillar where i want to get very close to the rocker. if i "build" that up a bit with a "box" then that weld would be much easier. i really kind of liked what Greg (i think?..) had done with landing that support on the rocker panel as well.

if the reason we can build the "box" is because of the allowed area, i don't see how i cannot count it.

question just for grins, if i built it up to be 5" high under the main hoop, would anyone think that would pass tech? it could still meet the area requirements etc. but i do not think it would pass tech. bascially, at what point does a "box" stops being an attachment point and becomes part of the support structure?

Tom,

I think I did the lex cage kinda how you mention... I'm about at 50% overlap to the rocker on a couple tubes, so I just boxed the rocker to extend it out, with small flanges on the bottom of the box to act as load spreaders. The primary load transfer is in shear to the rocker box as extended by the box... I'll take a couple snaps and post later to see if that's what you mean... Honestly, I think some of these cage rules are goofy. With all the crazy insurance rules anyway, I'd think we should build the cage with as much tube and plate as we want. So what if it stiffens up - it gets heavier too!

[tom91ita]

Dave,

you guys in for Chicago in October? we submitted again for AutoBahn...

[seckerich]

Always loved the early cage rules for the Grand Am series. Cages must be built to accepted industry standards. That was it.

[Spinnetti]

Dave,

you guys in for Chicago in October? we submitted again for AutoBahn...

Yep, we'll be there - #77... with some fatter tires on wider wheels to keep that beast in check a bit better.... gunning for FTD :)

Steve - definately like those cage rules :). Our Lemons cage is very conventional SCCA, but I did tie it to the shell in more spots.

[seckerich]

When the updates to the cage rules were done a few years ago it was discussed to leave out the pad area rule all together. That would be fine if you did not have the high number of classes that had so many cars built to the early regulations. You would essentially make them obsolete overnight without a lot of extra money and time. Some would argue that you do not really add that much stiffness with a cage confined to the passenger compartment, but data show otherwise. I have seen the difference in flex on a surface plate and it is substantial.

[Spinnetti]

When the updates to the cage rules were done a few years ago it was discussed to leave out the pad area rule all together. That would be fine if you did not have the high number of classes that had so many cars built to the early regulations. You would essentially make them obsolete overnight without a lot of extra money and time. Some would argue that you do not really add that much stiffness with a cage confined to the passenger compartment, but data show otherwise. I have seen the difference in flex on a surface plate and it is substantial.

That said, I've had to update my cage twice since it was orginally built, at some cost. I've had many costly upgrades in that time, with more to go.... changes in shock rules, cage, ECU, Hans etc. and almost always more expensive... Rules they are always a-changing; Only peoples time horizion varies.... I've been running SCCA events of one kind or another since 1987 so not much sympathy for worrying about the cost of an optional change when I've borne plenty of non-optional ones.

[lateapex911]

Spin, while a plate change rule SEEMS innocent, it is much more complex. Allow anything, and you will get EVERYthing. As Steve points out, seam welding will become legal. That's fine you say? I disagree, it will mess with the competitive balance. You might have a light car thats easy to make weight with. So you go nuts, your firewall gets stiffened where some suspension subframe attaches, stiffening an Achilles heel issue with your car: lower A arm geometry movement under load. Another guy with the same model car but a bigger engine has to run at a lower weight. Guess what, he cannot make the same mods you can, because hes over his minimum with all the tweaks he can come up with as it is.

And that kind of thing will happen all over the 300 plus model ITCS.

The current plate rule is FINE, and leaves PLENTY of room for proper structure and creativity.

[Spinnetti]

Spin, while a plate change rule SEEMS innocent, it is much more complex. Allow anything, and you will get EVERYthing. As Steve points out, seam welding will become legal. That's fine you say? I disagree, it will mess with the competitive balance. You might have a light car thats easy to make weight with. So you go nuts, your firewall gets stiffened where some suspension subframe attaches, stiffening an Achilles heel issue with your car: lower A arm geometry movement under load. Another guy with the same model car but a bigger engine has to run at a lower weight. Guess what, he cannot make the same mods you can, because hes over his minimum with all the tweaks he can come up with as it is.

And that kind of thing will happen all over the 300 plus model ITCS.

The current plate rule is FINE, and leaves PLENTY of room for proper structure and creativity.

Gotcha.. Rules stability is important to maintain the status quo. I'm ok with the cage rules as they are, though would love to tie the cage to the roof and pillars purely from an engineering standpoint.

[Ron Earp]

Gotcha.. Rules stability is important to maintain the status quo. I'm ok with the cage rules as they are, though would love to tie the cage to the roof and pillars purely from an engineering standpoint.

Me too.

It'll be interesting if the NASA rules evolved to make it mandatory (you can do it now in NASA) to see what the SCCA's stance would be. I know folks here will trot out all sorts of reasons why not to do it from basic expense to claiming you'll need more expensive shocks due to chassis stiffening.

[Greg Amy]

...would love to tie the cage to the roof and pillars purely from an engineering standpoint.


Me too.
You can do it now, in Super Touring, Production(?), and GT.

The default Improved Touring/Touring/Spec Miata/Showroom Stock cage provides sufficient safety margin for the level of performance and prep that these cars are allowed. Anything else is performance-enhancing desirability.

GA

[Ron Earp]

Anything else is performance-enhancing desirability.

GA

Yes sir. I am a racer. I like to enhance performance.

[Greg Amy]

Yes sir. I am a racer. I like to enhance performance.
...and that's why we have rules.