The important questions are:
* how much strength does the box section add
* does it really need it
Very well stated. It would definitely matter on the intended use of the car and how it is built.
For example, one of my builds is really only for looks. Air suspension to be able to slam it as low as possible, modifications to the body work simply for for aesthetics, changes to the many of the vehicle's systems to allow for other "customization". On this one I definitely don't care about performance, handling, or functionality beyond getting me to the car shows. It will probably never go much over 40-50 MPH, only on local streets.
My other build will be a track day car. Completely gutted, full performance mods, all business and technically not road legal (but I will keep plates on it...we don't have inspections here). In time I may even go complete tube chassis with it, who knows.
So contrast those two examples and ask how much a little chassis stiffening matters on each. Very different answers. And there are others who use their X's for daily commutes, or some only for the very rare Sunday afternoon drive down Pacific Coast Hwy with the wife, or some are 100% original perfect show cars, or even the rough 'rat-rust' basher that gets thoroughly abused. All will have their own definition of how much structural integrity is needed.

So maybe there is no one right answer, other than "it depends".
 
.....Ooooohh, I like that rat-rust label, I now know what my Bertone is. Let's walk a fine line on this thread an not go into the dark web of whether the box is needed but OK to discuss alternatives. An under cage sounds neat and has the opportunity to be even stronger than the box.
 
Carl, I was tempted to use another label "sewer pickle", but decided something 'rust' related was more appropriate for the X. :)
Speaking of rust, there are X's on the road with so much chassis cancer that the structural "stiffness" is severely compromised. Yet they continue to be enjoyed by their owners with regular use. I guess it is another example of what I was saying, the importance of the coolant tube's box integrity 'depends' on the application.

but OK to discuss alternatives
I had a thought following Kevin's prior comment, "I just simply used a cutting wheel, and cut along the 2 corners running all the way from front to back, leaving the 2 sides in place, and the bottom open."
If the two lower corners were left in place, and the cuts were made along the bottom flat portion about .5 inch inside those corners. This would retain the structural benefit of the 90 degree bends along the corner portions. The coolant and heater tubes could still be removed/replaced. And a new bottom cover added with 90 degree corners bent along it's edges, doubling those portions. Once the new bottom panel is bolted in place it should be stronger than the original structure, due to the doubled corners and sides. Here is a crude illustration of what I'm thinking (sorry, not a good one, maybe someone can make a better picture to show this):
DSC08471.JPG

The red arrows are where the cuts would be made. The yellow lines are the new bottom cover with 90 degree corners. The blue arrows are the bolts securing the new bottom to the original sides. And the black lines show where the original 90 degree corners are retained.
This doubles the thickness of the side walls and doubles the number of 90 degree corners (a very strong structural shape). No drilling of spot welds. No re-welding. And it is removable for future services, should it need any. The bolts securing the new bottom are like the rivets on aircraft designs, offering a strong reliable attachment of the two pieces together.
 
No re-welding. And it is removable for future services, should it need any.
Exactly why I did it that way....plus, it was already butchered, and the cover I built went all the way up to the bottom of the car. Note to anyone doing this also, I found numerous missing body plugs in the floor of my "hump" over the cooling pipes, might wanna locate some beforehand, stopped a lot of heat transfer into the cabin. And oh BTW, my car still hasn't bent in half, even jumping RR tracks :)
Edit...I thought I had used sheet metal screws, as that was my original idea....forgot I had a flange added to the top edge, and tack welded 10mm bolts down thru the floorboard, like studs...man my memory, must be getting old as you guys
 
my car still hasn't bent in half, even jumping RR tracks
Well that pretty much settles the question...the box isn't needed to keep the car from bending in half when jumping RR tracks, therefore it isn't necessary. Only joking.
I think bolts are a better way to go than screws, nice job.
 
Note to anyone doing this also, I found numerous missing body plugs in the floor of my "hump" over the cooling pipes, might wanna locate some beforehand, stopped a lot of heat transfer into the cabin.

Yep, there are 4 oval access holes that aren't plugged:

UnderTunnel.jpg Front.jpg Mid.jpg Rear.jpg

I think these plugs are hard to come by tho. Rodger fabricated some.
 
For the access holes in a non visual area there are some very good aluminum tapes intended for actual duct work which will seal these off and stay on there for years to come. We use it as an acoustic seal for some of our products where we have a variety of difficult to close off holes.

They will seal off water, air and to a limited degree radiant heat. You will want to buy a tape rated for UL 181AP which is an aluminum tape. Great stuff and definitely not ‘duct’ or ‘duck’ tape...

https://www.tapeuniversity.com/2016/06/ul181ap-ul181bfx/
 
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Started the initial work on the open cage retro today but still have some welding left to do. Should be equally as sturdy as original if not stroner? Added some deflectors to scoop up passing air to help aid in cooling while in motion and dissipate heat while at idle.
 
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Forgot to send along the channel cut out. Still have to bend up new pipes.
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Curious to see that in place. It looks like serious overkill in terms of construction. I'm assuming you have no intention of the car ever seeing wet roads? What does it weigh?
 
Yes, it definitely does if only based on the cracked spot welds owners observe when servicing these. The important questions are:
* how much strength does the box section add
* does it really need it

The first question is answerable by testing and observation: you take an exxe chassis and hook it up to a torsional rigidity measurement device. Something like this:
View attachment 11163
For an exxe, I'd think the best way would be to somehow seize or fix the struts into place (or make a solid strut) so you are mounted to both the suspension arm pickups as well as the strut tower top. then attach the rear hubs to the floor. the front gets the balance bar with a deflection gauge. If I remember correctly, someone here did this with their exxe - or at least linked to it.

Anyways, test it with the cover then remove it and test without. It'll twist more, but how much is what matters. Actually, how much you care about torsional rigidity is what matters.

Here's a way to do a comparable test at home with basic equipment.

Baseline Setup:
Park the car on a solid level surface such as a garage floor, then raise the car and place on four identical jackstands, setting the height of the stands to equal positions but on the second from the bottom height stop. Position the jackstands: two at the rear, on the flat chassis pads located just forward of the front outer corner of the rear wheel arches; two at the front, under the vertical lip of the front radius rod bushing brackets. Lower the jack and take note of whether there is significant weight on all four stands--if the floor is level, this will be the case.

Trial 1:
Raise the front of the car, and on one jackstand, lower the stand one notch. Now lower the car until the vertical lip of the front radius rod bushing bracket rests on the taller stand. Next cautiously and carefully lower the jack until it is free. Allow 5 minutes of settling time, and take a measurement of the distance between the lip of he radius rod bracket and the shorter jackstand. This is your "reference" measurement.

Trial 2:
As the first step of replacing the coolant tubes, perform removal of the undercar coolant tube box. Before continuing with the tube replacement, repeat the measurement in Trial 1 above. If the box does indeed contribute to torsional stability, we would expect the measurement to be smaller, indicating some amount of "droop" due to a loss of strength/rigidity.

Trial 3:
After the undercar coolant tubes have been replace and the box restored to factory condition, once more repeat the measurement in Trial 1. Ideally the measurement would be the same or better than Trial 1.
 
Curious to see that in place. It looks like serious overkill in terms of construction. I'm assuming you have no intention of the car ever seeing wet roads? What does it weigh?
Actually weighs very little being made from 1/2” stock. My intention here is to satisfy the advice given by so many on this forum about structural integrity and at the same time keeping it light, allowing heat dissipation and provide a little cooling with the scoops while in motion. As far as driving on wet roads? “I’m assuming” you must think I would drive the car with holes in the floor? Thanks for the tip but already have grommets from a parts car to seal the openings. So far been nothing but impressed by the ingenuity and problem solving capabilities of members here but I guess everybodys entitled to their own opinion??
 
It’s yours, don’t worry about the rest of us, we are just the peanut gallery. Sometimes it cheers with you, sometimes against...

When I first saw your construction, I wasn’t clear as to what the function of it would be, its scale and the material thicknesses involved in it were. Lots of work in making it for sure. Care to explain how it will work with the original structure you have left as the remaining sides are curved inwards, do those legs of the original structure butt into and get welded to the sides of the ladder structure? Or are you cutting a bit more to get to a ‘flat’ surface farther up the sides and adding more to the sides of the ladder?

My only concern about it is how low it will be relative to road debris, manhole covers etc but thats conjecture without knowing quite what you are doing with it. I think the wet roads comment is about just how much water you will be driving up against the bottom of the car with the scoops.

As an aside, the Lancia Scorpion had a scoop that ran the length of the car to carry air to the engine compartment. An alternate approach to getting air along through there might have been to make an opening at the front of the box with a hose reaching in front of the radiator and then making a single port to allow the hot air to exhaust at the back of the housing by the engine area.

Thanks and sorry for adding more what ifs.

Always remember its yours, make it yours. You are the one who has to live with it. Keep up the great work.
 
My only concern would be hitting something on the road and snagging it into the cooling pipes and floor pan. At FFO Detroit (2016?) in the city as I was following another car I hit a section of angle iron on the road. It hit the jack point on the left side of the car and moved it back considerably. It rolled off and I kept going, heart pounding. Had there been this design, I think the angle would have gotten caught and either lifted the car or penetrated the floor pan.

TonyK.

Grimsby Ontario Canada.
 
Thanks Tony. Maybe I’ll shorten the scoops slightly for him but definitely going to give them a shot. I know these little cars are already low to the pavement and clearance is probably an issue but for the added inch and a half and possible benifits of cooling we’re willing to try it. I figured that after so many here dropping the chasis with modified springs why not?
 
Actually weighs very little being made from 1/2” stock. My intention here is to satisfy the advice given by so many on this forum about structural integrity and at the same time keeping it light, allowing heat dissipation and provide a little cooling with the scoops while in motion. As far as driving on wet roads? “I’m assuming” you must think I would drive the car with holes in the floor? Thanks for the tip but already have grommets from a parts car to seal the openings. So far been nothing but impressed by the ingenuity and problem solving capabilities of members here but I guess everybodys entitled to their own opinion??

We do all have opinions. I realize my post came over a perhaps a little harsh, however radical departures from stock designs will prompt significant questions as to the validity or value of the mod - I have received many such comments over the years :D. You clearly have invested significant time in the creation of the support. As Karl pointed out, it's unclear how this meshes with the existing box remnants. The pipes themselves preclude your creation from sitting much closer to the floor pan than the stock box lower surface, so it appears either the air guides or the bracing will sit lower than stock height. I was assuming the inner panel holes will be closed. I'd be concerned about moisture/dirt, etc being trapped in the inner box side and end seams, given the propensity for rust on these, which prompted the not driving in wet conditions remark.

I'd love to see pics of it placed as you intend it, that would help clarify one way or the other.
 
structural integrity and at the same time keeping it light, allowing heat dissipation and provide a little cooling with the scoops
As a self-proclaimed "customizer", who has modified every vehicle I've ever owned, I absolutely love the creativity and ingenuity of this. That's thinking outside of the 'box' (pun intended).
I am a firm believer that when any vehicle is designed/built at the factory they have to make considerable compromises for the sake of cost, production concerns, marketing parameters, construction limitations, government regulations, liability risk, etc.. All of which leaves plenty of room for improvement and redesign. Add to that the opportunity to enhance the appearance, restyle, or otherwise "personalize" the vehicle, and individual thinking to explore new ideas brings about unique concepts. Its what makes this hobby exciting for me.
Well done Cliff, excellent project. Please keep us informed with updates on it. ;)
 
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