Material for front suspension

[davegt27]

Question

If you where building a front suspension from scratch that was bolt in like the original

What would you use?

Goal light and strong

I am thinking of aluminum but a friend says the thickness I would need to make it strong enough the weight would be to high


Thanks in advance
davegt27

[heimue]

Tubular high-strength steel, without thinking about it twice. BUT: You need to be able to calculate forces and torques on it just right, or you have to just make it beefier than necessary and lose the weight advantage.

Dieter

[jtb]

Your friend has a point there. I have heard with bicycle frames, the cheap ones are steel, then the good ones are aluminum, then the really good ones are steel (cro-moly) because to get the equivalent strength out of aluminum, the size becomes large and the cro-moly winds up being lighter! (Disclaimer: I am speaking in very general terms and have not considered materials like carbon fibre, titanium, etc.)

I would use steel, IMHO

jtb

[RallyBob]

On a 2000-lb car, I've used 1" x .095" wall DOM tubing (1018 or 1020 mild steel) with good luck for upper and lower a-arms.

You can use thinner chromoly instead to save weight and have a stiffer end product.....but the material is more expensive, is much harder to weld (TIG only with good heat control) and it tends to be more brittle. So it *may* break where mild steel will probably bend.

Bob

[davegt27]

Wasn’t there a GT4 racer that had a front end cross member made out of aluminum?



I got some aluminum A-Arms out of a mark III Supra (both front and rear are aluminum)

Or maybe the stock cross member that is lightened might be the ticket

Davegt27

[jeff denton]

I started doing some shopping for you today but then the phone rang and I had to go make some money...
Anyway when I was so rudely interrupted I was at speedway.com browsing through their lightweight generic a-arms, interesting, and then dug further there and found the totally tubular, adjustable every which way a-arm kits that we all use in our Limited Sportsman cars (uppers only, rules require stock lower) and Super Late Models (upper and lower).
Also noticed they offer a Mustang II (improved and legal at some tracks) complete spindle. Wow. Here we go!
Were I to wish to competitively race a GT again (which I might) and aftermarket/custom/non stock suspension were allowed (which it is in Outlaw Compact) I would go this way. I'd install it all with the car on the jig so we could get it right, that is, be able to get the geometry right as we go, according to the computer program we use (which works, why we got first in points for Super Late Model and second in the new Limited Sportsman). Ha! You cannot backyard guess/engineer the front suspension anymore and win a race. It's all about the computer taking you around the track and showing the changes that happen between static ride height and full bump.
You're a welder, right? It will be amazingly simple. If you don't want to tackle it yourself but want near perfect results, bring her up. There is no racing planned here this summer so our shop needs a little project. Bring her up.

[jtb]

On a 2000-lb car, I've used 1" x .095" wall DOM tubing (1018 or 1020 mild steel) with good luck for upper and lower a-arms.

You can use thinner chromoly instead to save weight and have a stiffer end product.....but the material is more expensive, is much harder to weld (TIG only with good heat control) and it tends to be more brittle. So it *may* break where mild steel will probably bend.

Bob

You're right, Bob. I wasn't actually suggesting to use chromoly, just citing an example of steel vs. aluminum. My front upper A arms are DOM (Drawn Over Mandrel - "seamless" if anyone is unclear) 1018.
With regards to aluminum suspension components on production cars, the few I've seen are cast, which is a different animal than fabricating something out of structural shapes.

jtb

[RallyBob]

You're right, Bob. I wasn't actually suggesting to use chromoly, just citing an example of steel vs. aluminum.

I hope my comments weren't taken out of context...I wasn't referring to your statement at all, just a general pet peeve I have about chromoly if it's not done professionally (not by me either, I'm talking about guys with far greater skill than I have!). Mild steel is just very forgiveable and easy to deal with, not to mention a lot cheaper!

With regards to aluminum suspension components on production cars, the few I've seen are cast, which is a different animal than fabricating something out of structural shapes.

Although *some* production cars (Corvette comes to mind) actually have forged aluminum arms. Pretty darn strong and light I might add. The cast aluminum arms tends to break, the forged stuff tends to bend a lot further before breaking.

[jeff denton]

Dave, it occurred to me today, my Parts GT could be very easily hauled over to Cory's Cut and Chop Shop (where we build race cars) and go on the jig according to measurements provided by you from your car (ride height, mainly) and a custom A-arm setup built on that crossmember. Other specs needed would be about the tires and wheels you plan on using, and how much travel you desire. Then it could be shipped to Colorado. I haven't run this by Cory yet, but I know he'd jump on it, there's no logging planned around here this year... he's so bored he's making a Bronco into a rock climber, but slowly, budget mandates strictly scrounged freebies for parts.
I wouldn't be all that involved since summer (busy-busy) is coming but I would then have a local shop experienced and ready to do the next one.
It wouldn't even cost much. Cory tends to work practically for free, something I keep having to talk to him about.
Anyway if this thought appeals to you, just PM me and I'll PM back his phone number. He's already pretty savvy on Opel GT front ends, well, one in particular. Converting to Chevette gear was his idea, he found the free Chevette, then fixed it when I refused to chop up such a cherry car. His mom still drives it every day.

[jtb]

I hope my comments weren't taken out of context...I wasn't referring to your statement at all, just a general pet peeve I have about chromoly if it's not done professionally (not by me either, I'm talking about guys with far greater skill than I have!). Mild steel is just very forgiveable and easy to deal with, not to mention a lot cheaper!

I couldn't agree more, Bob!

Although *some* production cars (Corvette comes to mind) actually have forged aluminum arms. Pretty darn strong and light I might add. The cast aluminum arms tends to break, the forged stuff tends to bend a lot further before breaking.

I was thinking about the rear trailing arms on my Porsche.. I think they're cast, but I never really looked that hard - nothing has ever gone wrong with them!
For an average joe building a suspension without the benefit of a team of automotive engineers behind them, mild steel seems to be the material of choice.

Cheers,

jtb

[davegt27]

Jeff PM sent

I was mostly thinking of the cross member portion of the front suspension

Not the A-arms (what are you guys thoughts on the cross member)

Here are a few PICs of what I have now (no laughing)






Can’t get a good side view on the rear



I have bought several upper A-arms but these look the best (have to be really short for the GT)

The first guy I hired went wild with a plasma cutter upper hole

The second guy I hired welded the cross member to the car (he installed the upper a-arms)







Davegt27

[jeff denton]

Yup it needs a little help. The workmanship could have been a little neater, no offense meant. It looks reasonably sturdy, and I don't think it's awful heavy.
Upper A-arms/ball joint is exactly how I'd do it except how they mount to the car. There should be a "cross shaft" (part of the kit) to attach the heim ends to, the cross shaft then should bolt to a fixture (part of the kit) welded to the car. Comes out super adjustable, yours presently isn't except for the length of the arms, which will adjust camber and caster at least but what about the "gain" at "bump"? The upper ball joint stud looks awful long, the angle of the upper A-arms is radical unless it's pictured in bump, which I doubt.
It's hard for me to guess what the geometry came out like. Did it work at all? Can you plot it out and see what the computer program thinks of it? As you mentioned before, the program doesn't tell you where things should be, but it lets you "adjust" settings to see if it "looks" better in theory. Trial and error, yup. We had a lot of fun with it when building the new Sportsman car last winter.

[davegt27]

Jeff what program are you using ?

some of the links i have collected

http://www.susprog.com/

http://www.rahul.net/dennisp/suspension/

http://www.lescanfield.info/rear_geometry.htm

http://www.lescanfield.info/DataFile...rd%20Link2.pdf

http://www.auto-ware.com/webbbs/WkndAutoRacer.htm

My favorite setup

http://www.home.earthlink.net/~roethler/front.html

http://www.auto-ware.com/index.htm


Davegt27

[RallyBob]

The upper ball joint stud looks awful long, the angle of the upper A-arms is radical unless it's pictured in bump, which I doubt.

Not too mention it looks like the upper ball joint is awfully close to binding in this photo. Any more bump travel and you may have bending/breaking issues with it. I can't imagine how radical the camber gain is in the last inch or so of travel...the roll center must be 10" below the ground!

[blancojp]

There is a front end setup I have used several times from Independent Technologies that might be the ticket for you. This is an all aluminum bolt on crossmember that uses mostly Mustang II mechanicals and can be used on vehicles with 20-22" rail spacing. The GT has 20 1/2" rail spacing at the crossmember mounting points so you should be able to use it on this application. It is also about 1/2 the weight of the stock crossmember so some gain it there.

This is a nice setup since the upper shock mount and the crossmember bolt on in the same place. And with the plasma redecoration that you did, should have no problems installing it.

I have all of the documentation at the office if anyone needs it.

[jeff denton]

I wanna see it, JB. I'll google the name you gave and see what pops up.
David, what are the weights of your car? Total, left/right, front/rear?
I'd be very surprised if the front of your car is, technically, too heavy. Also, do you need to meet a minimum weight? I don't recall the name of Cory's program but I'll find out, I'll be inspecting a rock crawler today. I think he's trying to get me into it, it's the rage here now that racing is out.

edit: Independent Technologies comes up second on the list at google.
Nice stuff, but other than the crossmember I'm sure it's just out-of-the- box hardware that's been blinged up. Perfect for simpler do-it-yourself hotrods. I wonder if they'd be willing to forego the prettiness for about half the price. I'd still rather go with very adjustable hardware, though, you just gotta be able to set the car up for different tracks and conditions.

[davegt27]

David, what are the weights of your car? Total, left/right, front/rear?

I don’t have weights --the motor and Trans are not in the car

Or the radiator

It was 2056 before the role cage (with driver)


Davegt27

[davegt27]

removed the front suspension yesterday
I found the bolts and nuts that are normally removed to take off the crossmember is welded to the chassis

here is a better look at the front A-Arms

wt is 30lbs per side







Davegt27

[davegt27]

wt of the cut down cross member is only 12lbs



crossmember ---surface rust is no big deal



rack is only 10lbs



David

[pw8penguins]

1. what is the car for?

2. skills and cost? got plasma cutter?

3. research?

4. personal i like the Modified front end. front spindle can be ford or Toyota then place Toyota rear end out back. Same bolt pattern.

5. look at the locost forum.. there's allot on custom suspension.

Just my .02

Myself looking at square tubing frame linking front suspension to rear end. so car can handle power. Think early Lotus Elan.