Home Fabbed Strut Tower Brace And Subframe Connector Q&a

[Boosted92LX]

So I've been looking at MM parts, among others for the fox ever since I began DDing an SN95 car. It's brought to my attention just how dreadful the chassis is without help, now I just have to decide what to use. After visual inspection of MM parts, BBK parts, Kenny Brown, Stifflers, etc, etc. I've dawn a conclusion. I've produced x-ray quality welds, fabbed and done machine work my whole life and the only thing keeping me from building my own stuff boils down to two questions.

1-Are these parts made of mild steel, say 1018 cr, or a chromoly like a 4140 ht?

Question #1 leads to question #2

2- If indeed the more expensive 4140 mat'l is used, would it still be cost effective to buy and build my own stuff? (this is the tough one)

Keep in mind I've got a buddy close by with a shop that has Mig/Tig machines, band saws, plasma cutter, lathe, drill press, and latest hydraulic tubing bender... and I've got a key.

20 years ago I did moonlight welding for a guy with a fab shop that built dragster chassis, and he used 4140 chromoly, but that was for structure and this will be just to stiffen.. SO?

Any of you engineer types have any idea?
NIKwoaC
FastDriver
madmike1157

 

[CarMichael Angelo]

So I've been looking at MM parts, among others for the fox ever since I began DDing an SN95 car. It's brought to my attention just how dreadful the chassis is without help, now I just have to decide what to use. After visual inspection of MM parts, BBK parts, Kenny Brown, Stifflers, etc, etc. I've dawn a conclusion. I've produced x-ray quality welds, fabbed and done machine work my whole life and the only thing keeping me from building my own stuff boils down to two questions.

1-Are these parts made of mild steel, say 1018 cr, or a chromoly like a 4140 ht?

Question #1 leads to question #2

2- If indeed the more expensive 4140 mat'l is used, would it still be cost effective to buy and build my own stuff? (this is the tough one)

Keep in mind I've got a buddy close by with a shop that has Mig/Tig machines, band saws, plasma cutter, lathe, drill press, and latest hydraulic tubing bender... and I've got a key.

20 years ago I did moonlight welding for a guy with a fab shop that built dragster chassis, and he used 4140 chromoly, but that was for structure and this will be just to stiffen.. SO?

Any of you engineer types have any idea?
NIKwoaC
FastDriver
madmike1157

Sorry Allen, but I personally got no clue what the stuff is made from. I have only minimal experience w/ chrome moly, as all of my projects have been out of .125 (or thicker) mild steel, so I'm not the one to ask.

 

[RacEoHolic330]

Chromoly wouldn't be the best choice from a marketing standpoint as it requires TIG welding. People would be more likely to purchase something that they didn't need to have done at a shop. More people own MIG welders or know somebody with one.

All the commercially available SFC's I've seen are all mild steel.

 

[tannerc91gt]

In terms of cost to buy and build, I'd guarantee they're going to be mild steel.
Chromoly is ungodly expensive if you don't buy it in mass quantities and the time and skill it takes to build something with it is much higher than that of a steel you can mig weld.

Now since you're just making a one-off set for yourself, you can go either way. Chromoly won't break the bank but I'd still rather have ms sfcs just out of preference. Save the moly for cages and more important components. Plus I just never had that much fun tig welding the stuff. It burns through like aluminum (exaggerated a bit) but is stronger than steel when finished.
Boxed sfcs made from stock steel are going to be about the simplest part you'll make, which with your experience you probably already know. I have a friend who's built almost every susp. Component for his lsx rx7 himself, chromoly cage , but all the bracing and arms done in steel.
you'd be surprised what schematics and specs can be found online

 

[NIKwoaC]

Home built SFCs in Foxes are fairly common, IIRC my buddy built his own for both his street car and his race car (I'll have to ask to confirm). I would have to imagine that regardless of what steel you use, homemade ones could be better than OTS because you can focus more on fit and geometry and less on "manufacturability".

I have NO idea what the aftermarket guys use for steel. I think UPR's claim to fame is that they use cromoly in their control arms, but I don't know about SFCs.

As far as price goes, you'll just have to cost it out and see. I know that some of the nicer steels can get $alty when you're buying it piece-part.

 

[CarMichael Angelo]

I will say this,...the SFC's that I built for the red car were .1251 x 2 mild steel, notched then bent to follow the floor contours. Then dropped back down,...the notched "kerf" welded back closed, and buttressed. I added (3) 1" square "outriggers" on each sfc to tie a 1" square .125 jacking rail that I plug welded to the pinch seam at the bottom of the rocker.

All of that stuff combined cost me under 100.00. ( course it helps to live in a city that produces steel,............ cheaper, and very easy to get)

In the end, you will always get a better product for less money w/ your skill and similar access to whatever steel you choose to go with.

 

[Noobz347]

I sure wish I could remember where I saw it but there was a picture layout of a dude who made his own SFCs and tied them into the torque boxes. No idea if there was any real benefit to that but this thread made me think of it. Was a pretty cool looking project at least.

 

[RacEoHolic330]

What you need to do is create a STB that utilizes a mounting plate under the CC plates. The STB would be a 4-point design that uses heim joints to connect to the pinch weld and the plate on the strut towers. Much like the STB's on the market for the classic stangs. Being able to just unbolt heim joints is much easier when you need to remove the STB to do work on the car. I'm probably going to fabbing one of my own once I get my turd up and running.

If you use this idea and make millions, just remember me

 

[FastDriver]

Sorry man, I'm not able to give any advice on what you should use. It's clear you're already more read into this than I am. I'll only say that I've only ever had MS SFCs and they've always been good enough. My cage is chromoly, and my suspensions stuff is from UPR... don't know what it's made from, honestly.

All previous projects used only stock suspension stuff, and I have no other experience or knowledge to relate. But, I'll keep an eye on this thread for my own knowledge and insight.

 

[Boosted92LX]

Thanks for all of the replies, fellas. It has been very helpful! I think I'm going to make the SFC's like madmike1157 did.. by the way Mike, to be clear, you used 1 x 2 x .125 box tube for the main run on the SFCs... am I reading that right? I like the idea of a kenny brown style SFC with jacking rails and a matrix type design. And for the STB, probably 1.25 dia x .125 wall ms round tube with .125 or .187 flat bar for gussets and mounting brackets. I need to go price mat'l. Hopefully I can get it cheap enough I can knock out some for me and a few extra for friends and family.

BTW, I'm NOT planning on selling these and making millions.. I think UPR, MM and the others have it sewn up. I will look into a quick release STB, though.

 

[95BlueStallion]

If I had the tools and knowledge to fabricate such components, I would make them even if it cost me an extra $50 per piece than the aftermarket guys. I love the satisfaction of looking at something and knowing I built it and it functions and looks great. Only time I get that satisfaction is when people come to my house to see my remodels and deck, but it feels good to get those compliments.

 

[CarMichael Angelo]

Thanks for all of the replies, fellas. It has been very helpful! I think I'm going to make the SFC's like madmike1157 did.. by the way Mike, to be clear, you used 1 x 2 x .125 box tube for the main run on the SFCs... am I reading that right? I like the idea of a kenny brown style SFC with jacking rails and a matrix type design. And for the STB, probably 1.25 dia x .125 wall ms round tube with .125 or .187 flat bar for gussets and mounting brackets. I need to go price mat'l. Hopefully I can get it cheap enough I can knock out some for me and a few extra for friends and family.

BTW, I'm NOT planning on selling these and making millions.. I think UPR, MM and the others have it sewn up. I will look into a quick release STB, though.

It's tough when you have to look through 400 tiny thumbnails for the "right" pic to answer your question. Even then, I could only find a few to answer it w/ the benefit of an example to reinforce.

To answer your question: Yes 1 x 2 x .125 wall mild steel. And yes, I think that your Idea for the STB is the right way to go too

P.S. Click on the bottom pic to look at my high speed weld quality

 

[Boosted92LX]

That looks awesome. Almost exactly what I had in mind..good stuff! Thanks Mike!

 

[jrichker]

Hees's some help from someone who has done it before and has all the drawings and details...

http://www.oldwestracing.com/articles/subconn/subs.htm

 

[Boosted92LX]

Hees's some help from someone who has done it before and has all the drawings and details...

http://www.oldwestracing.com/articles/subconn/subs.htm

Good stuff! Thank you, sir!