I wish there was a way to know how much stronger this is
I think its beautiful,..I'd just lay under the car and look at it if I did it.
But I wonder...I really wish there was a way to see if the extreme that you have went to with regard to the frame rail stiffening is warranted. I think your work is top notch, but how many bars does it take before the extras just become just added weight?
Trust me, I am the poster child for " Why make it so hard on yourself" comments so I get it.....But even I have a limit...
I am not a fan of through the floor SF connectors, especially when adding all of the cross bracing to tie the rocker pinch weld jacking rail to it. Everytime I see somebody go to the extent that you have, I wonder to myself "what does he gain by this?"
It'd be a really cool science experiment to do a comparison with a car that has that matrix welded under the car versus what has been done to see what if any stiffening was gained.
Your car IIRC has every seam welded additionally...What is the intended goal here? I think you told me, but I'm crotchedy.
Appreciate the kind words, and yes, I have sat underneath the car and stared at it.
Not too long though, I have plenty of work to get done still.
I agree with you, I wish there was an easy way to measure how much stiffer this whole setup is. I wish I had a test rack that would be able to test rigidity of the chassis before and after the modifications, but, then I'd probably be working for a manufacturer or a well funded racing team. The only real-world measurement I have is the difference in corner jacking the car, which is quite significant. Makes me wish I had taken some measurements of chassis rigidity before I started cutting in the floor. I remember an article By MM&FF back in, oh, 2009 I think, that tested the difference in chassis rigidity before and after subframe connectors. All they did was measure critical points of the chassis and jack the vehicle in certain areas to see how much the chassis deflected. Surprisingly, the MM subframe connectors they installed didn't effect torsional rigidity much, but increased floor pan stiffness significantly which is what they attributed to the "seat of the pants" feel you get when you install connectors. My design is obviously a little more involved than just welding in a set of external connectors, which is by design.
One thing I did before I started cutting was design the entire reinforcement setup in CAD and perform some half-assed analysis of the rigidity of my design. To be clear, this analysis did not factor in the vehicle chassis itself, it just looked at the reinforcement setup as a whole, outside of the car. I really have no numbers as to how this setup performs welded into the car, I am just assuming from my experience that the design will augment the rigidity that is already in the chassis. By looking at my design in CAD, I was able to trim down metal thickness and the amount of bars to maximize the strength of the design. I went with .083 thickness rails and tubing, where most people go with .120. I found no benefit with going with .120 in my design, which would have added some significant weight. I also stuck with 2x3 for the main rail where most people go with 2x2. The increase in vertical height of the main rail helps to increase torsional rigidity in the design, much more than a 2x2 .120 main rail. I'm not trying to justify my design, you give you a perspective of what I looked at and why I went with what I did.
The cross bracing I did was originally based on Stifflers x-brace design. Their design is pretty good, so I didn't have to modify much to incorporate it into my design. Yet again, I have no way to quantify the benefits on the actual car, but the increase in lateral rigidity in CAD was huge. You don't have to deal with lateral rigidity in the chassis much with drag cars, but it's very important for road race cars. Torsional rigidity is important in both types of racing. Since most of the strength in a Fox chassis is in the rocker panels, I wanted to tie the subframes and cross bracing into the rocker panels so everything would work together as one unit. Plus I can fab jacking plates for the tube I welded down the rocker panel to make jacking that car up easier.
Other considerations I had:
1. The rocker to subframe corner pieces were added to give me a good spot to tie my cage too. They had the added benefit of increasing lateral rigidity of the chassis and adding safety into the wheel well.
2. I wanted the seat mounts to be as strong as possible, and probably overkill. I really want to feel the car and road, and don't want any flex in the seat mount.
3. Safety. I don't plan on running a full cage with a halo (since this will be driven on the street), so I'm trying to build as much strength in other areas as I can. This is also why I am stitch welding the entire car. Some of it has to do with rigidity, but most of it has to do with staying alive in the off chance I smack a wall at 100+ mph.
I can go on and on about all the other things I looked at, but in the end, I really have no way to quantify the increase in stiffness in the actual car at this point. I just know I can now jack three corners of the car up by putting the jack in a strategic location, something I could not do before the install. There are still many other reinforcements I plan on doing to the car still that will tie together with everything else I am doing. In truth, what I have done so far does not increase torsional rigidity all that much. Adding more reinforcements in the vertical plan will really help with the torsional rigidity. Also, stitch welding the transmission tunnel and firewall area will also help with this.
After all that being said, the main reason my setup is so involved is I wanted this to be integrated in the car as best as possible. I never really liked the add on subframes hanging below the car and other reinforcements being "tacked" on. I want people to really have to look closely to notice what I did. I'm not building this car for attention, but I do appreciate when someone notices the amount of work that must have went into making this all happen. Is this setup for everyone? Definitely not. There are much faster and easier ways to accomplish what I did, but I do believe my design is very strong and will benefit what I'm trying to do with the car. Plus by integrating this all through the floor, I'm cutting weight out of the car being I start putting stuff back in. I finally got around to measuring the weight of everything I have cut off and everything that I have welded back in (including welding wire). In total, I added ~65 pounds with this whole setup.
Need it for my 230 pounds, though hopefully I'm in the drivers seat...
Not fun at all! Ever since that time I wear ear plugs while welding overhead.
