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

[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.)

[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.