Tubular rear subframe - Input needed

[99gst_racer]

I can't use this thread to discuss pricing, and I won't even know a price until I get one built to see how much time and material I have into it.

I'm hoping to get started this weekend. I'll share some pictures as soon as I get one is finished.

 

[eviltsi]

The main reason people shy away from chromoly is the fact that it's brittle. I know a LOT of road racers that wont put anything but a mild steel cage in the car. Something like this that is not only structural but takes a lot of abuse, it's certianly something to consider.... All out drag car/trailer queen, sure chromoly would be great. Something daily driven hard by your atypical dsmer, steel may be a better option.


I too will probably do this this winter, or atleast something similar..... Marketing it to the masses will probably not be my intensions though. I just dont see the market really.

 

[99gst_racer]

That really depends on the state of the material. Heat treated 4130 is brittle but almost everyone in the motorsports world (myself included) uses normalized 4130, which is not brittle at all due to the normalization process (which is a type of annealing). Most people don't realize that 4130 chromoly is mild steel with an added bit of chromium and molybdenum. It's just a 25% harder version of mild steel, but with the same weight, elongation, and bend-before-break properties. We've been working with normalized 4130 tubing for a few years now and haven't had a single crack or break.

Mild steel is fine to use as well, but a thicker wall tube will be required to maintain the same strength, and will consequently add to the overall weight. I'm not apposed to using either by request, but I can say that my own personal subframe will be 4130 chromoly.

It's definitely a tiny market after a part like this. I don't have any intentions of making very many of these. But I figured that if I take the time to design and build one for my own car, I might as well knock out a few more in the process.

 

[tim3kgt]

3SI= 3000gt and Stealth International (club and website .org)
3/S = 3000gt and Stealth platform

saying "3si" in reference to a car/platform is like referring to a DSM as a "club dsm dot org"

/rant

 

[jw4free]

+1 on the explanation of cr- moly. vs mild steel. Will these components be normalized?

 

[99gst_racer]

^^^ The base material is already normalized, and I'll be tempering the weldments after welding.

 

[1997_GSX]

Paul were you the one that bought that jig off the ECMlink forums? I was wondering who bought it because it sold fast.

 

[FLASH1970]

Subscribed...

 

[99gst_racer]

Paul were you the one that bought that jig off the ECMlink forums? I was wondering who bought it because it sold fast.

I picked it up from a fellow NABR member.

 

[99gst_racer]

I figured it was time to share some progress.

For all mounting points, I'm using aluminum pressed into chromoly. This way it's solid, lightweight, and we can weld to it.

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And another weight saving option I'll have is tubular bolts. They're made from heat treated 4130 chromoly and have rolled threads and a zinc finish. These are very strong, affordable, and weigh about 40% less than a regular bolt. I forgot to take a pic of the ones I have, but this is what they look like:

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And here's a sneak peek of my progress:

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[97gst_spyder]

Hot damn, already looks good!

 

[bmoha7321]

love it!

 

[91stocker]

Looking good

 

[99gst_racer]

Thanks guys.

I had a solid plan for control arm and toe arm brackets, but it turns out that it won't allow for adjustable inboard pick-ups. So, back to the drawing board. Hopefully I can come up with a solution tomorrow.

 

[greengoblin]

Good work sir. Look forward to seeing more! What are you having problems with Paul?

Kevin

 

[gofer]

And here's a sneak peek of my progress...

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Where do I sign?

 

[99gst_racer]

How far raised are you guys wanting the pickups?

The reason I ask is because the inboard bolt size is probably going to be 3/4", so that will limit increment size between adjustments. So, I may only have two adjustment options (stock and one raised), and if I only have one raised option, I need to know a good average amount to raise it.

 

[bmoha7321]

putting money aside to buy one

 

[jw4free]

+1 for weight reduction.

This is what a 545lb rear end looks like....


Tires and wheels added up to 79lbs though.

 

[95eclipser]

The sneak peak already make me want to sign up.

 

[fjm9898]

If you toss in a bunch of adjust-ability, consider one already sold, no lie, cash in hand.... DO IT

 

[99gst_racer]

Bracket design has been sorted out. The lower control arm and toe arm pickups will have 3 available settings: stock, +1.00", and +2.00". Naturally, the control arms and toe arms will be adjustable in length as well.

 

[Dyesuperman]

I really hope I can somehow pull some cash out of nowhere for this! It's going to be sick

 

[bmoha7321]

Get this tubular cromoly rear subframe sorted out... And then onto a front tubular subframe buddy? Now that would be a sick sick setup.

 

[fjm9898]

this is getting me kinda excited. i thought i was going to have to make one, which i really didnt want to do, i have enough on my plate as is. i am going to have to make a custom front sub frame for my build already, so saving me the hassle of having to make a rear one as well is nice

that is if your piece turns out good enough