Sway Bar Material & Heat Treatment

[CSXDreamer]

Are their any knowledgeable Mechanical Engineers or Metalurgists on this forum who actually know what the alloy and heat treatment of sway bars is?
I have some solid round bars of mild steel , 3/4" to 1", that can be bent into a "U" shape to fit. Of course something has to be done to the ends to attach the two vertical links. However, if a plus or minus 30 degree torsional rotation causes mild steel to yield, there's no use wasting time and material on it.

[Richard Hudgins]

CSXdreamer,

You cannot use mild steel.

The most commonly used material is Chromium-Moly 4130 for tubular bars.

For blades 6150 Chrome-Vanadium is the typical material.

Heat treat for both is RC35>38

[Silverback51]

Truthfully it's probably cheaper to buy them than to make your own.

[ZOERA-SC7XX]

Sway bars are about the least expensive part you'll ever buy for your Cobra. When you buy one, you'll know if it's close to the correct setup. If you try to make one, you won't know where you are until you try it...it may take you several sway bars to get it right, if ever. Let the experts do their job.

[Jon Miller]

Let the experts do their jobs!?!

If I had done that it might not have taken me 11 years, but I would not have the unbounded joy of being able to say I built the radiator filler, steering wheel adaptor, pedal assembly, headers, side pipes, etc, etc......... Also helps to justify the lathe and MIG welder!

I'ver got a Mustang II front and Jag rear and I would like to go with straight bars with aluminum end links for the adjustability and custom look. Seems like solid ends would be the best bet for attaching the end bars. Any idea what wall thickness and OD would work best for our cars? Seems like most of the fronts on the market about 1", but I think that those are solid......

Thanks,
Jon

P.S. Richard, what's a "blade" ??

[COBRANIP]

There is an interesting part in Mark Donohue's book "Unfair Avantage" where they had lots of problems setting up one of the race cars.... until they discovered the anti-sway bars had not been properly heat treated.....

[Ralphy]

Why couldn't you buy a few sway bars from a bone yard? Then cut them to the length you desire and mill the ends square. Then make up your own ends.

Just a thought.

Mild steel has very little carbon, it will not harden adequately.

[CSXDreamer]

Thanks for the technical advice guys. I've just found a way to mount front swaybar bushings on my LAX. There's no low frame forward of the front cross member. I've read many threads on this subject and there are two extreme views: 1. Springs are so stiff that a S.B. is not needed. 2. You need one but don't bother with a stock Miata that easilly fits. Miata racers and auctocrossers replace stock with a heavier bar. So, if Sway Bars are hardened and tempered alloy steel, I really can't modify somebody's stock bar by torch heating, welding, or an un-cooled cut-off wheel. Also, 30-38 Rc is too hard to cut threads into. I like Ralphy's idea of cutting a stock bar, milling flats on each end, and making my own arms to link with the lower controll arm through Heim joints.: I'll have to be careful with stock bars as many of them are hollow. 3DSMILE:

[Silverback51]

You can machine 30-34 RC material.

[Ralphy]

CSXDreamer
Tapping 34 Rc should be no problem. I've tapped 58 before more then once, takes a sh!t load of taps. You get maybe 1/4 turn.

If you do use a cut off sway bar, it might be better to hex the ends.

Also when your looking at steel the last 2 numbers represent the carbon content. Mild steel say 1020 has I think .20% carbon, 6150 would be .50%.

[scottj]

Originally Posted by Silverback51

You can machine 30-34 RC material.

Yes, we machine 38 RC 4340 and finish with nickel plating. But, threads are milled, not tapped. H13 is much tougher to machine so we machine that annealed. 4130 @ 30-34 is cake...

[CSXDreamer]

Like Ralphy said, tapping mid 30's Rc can be done, but uses up many taps. I have a guy who can mill this hard, and I've turned parts this hard in a lathe before. I'll just have to take measurements of the extensions for 2 S.B. bushings that are going to mount to the front of the front crossmember. This
will tell me how long the end "levers" of a S.B. have to be to line up with provision for the links on the lCA. I might get lucky and find one that will match.

I just remember that I do have a heat treated bar straight bar that's probably long enough. It's 52100 bearing steel that was hardened, then tempered at 1000 deg. F for a couple hours. I'll have to check its hardness. If this won't work, I'll be checking the boneyards, trying to do it when its not cold or wet, but before the snakes come out from hibernation.

[Silverback51]

Okay, try this.

Don't worry about forming or machining the sway bar. Use a straight bar and then just add fittings to the end.

In the picture you can see that they have splined ends, but you can work around that if you like. Two options. Grind two flats and use that to react the loads. Or you can drill it and dowel it. I would suggest that you use steel links, not aluminum. The bearing loads would be to great and would deform the aluminum.

Hope that helps.

[Richard Hudgins]

Originally Posted by Jon Miller

P.S. Richard, what's a "blade" ??

Jon,

Look at the JBL site and you will see the "Blades" in the chassis photos section.

They are the rotationally adjustable anti-roll bar components that are used in virtually every modern road racing chassis design.

Really quite simple and the JBL has been using them since 1993.

Look around the web a bit for adjustable anti-roll bars and you will see many examples.

[TButtrick]

I bought a rear sway bar from Vintage Performance. They make front and rears (IRS or Solid) and although specifically made for Factory Five cars, they are pretty straightforward designs and might get you 90% there. I have the rear only for solid axle and it works well. Don't see a need for a front bar on my ride. (street only)

Front



Solid Rear



IRS Rear

[Ralphy]

CSX Dreamer,
What size of a bar are you looking at? From what I have read here, it seems you need not use a massive diameter bar.

I like the look and function of a store bought setup like Silverback posted also.

Ralphy

[CSXDreamer]

Ralphy, I'm not sure what size bar would be functional and am looking for advice based on experience. I've got a 427 Windsor with aluminum heads and intake, and I gotta believe the weight and location of the engine influences chassis roll, which is what a Sway Bar is supposed to limit. Front suspension is a stock Mustang II setup with 400 lbs./inch springs and gas filled heavy duty shocks. Right now I'm switching over to tubular upper and lower control arms, and I'm trying to see if I can fit a sway bar in their someplace.

[Ralphy]

CSX are you buying tubular lowers with the sway bar mounts? As low as these cars sit it would seem you would not need a very large sway bar. Sure would like to see some pics when your done.

Also I have seen front end parts being sold at Ebay.

Ralphy

[CSXDreamer]

I began installing front tubular A Arms bought on Ebay by having 2 support blocks welded into the LCA bracket. This stiffens up the stock bracket and extends the rear pick-up point about 3 1/4" to allow for the wider spacing of the tubular LCAs. LCAs installed, then the spindle, and next the UCAs. When bolted into place, even with the mounting bar pushed to its maximum inward travel, I had 3 degrees positive camber and 3 degrees negative caster. Totally bad, as I need to set -.5 deg negative camber and about 3 deg positive caster(upper ball joint aft of the lower ball joint). I compared the new tubular A Arms by laying one on top of the other and using a grease nipple in one to slip into the nipple hole of the other. The new tubular A Arms look about 1/2" to 5/8" longer than the stock arm; hence, the bad camber value. I've seen advertised, 5/8" shorter Mustang II UCAs, so here's a quick fix, but they're not available now. So I decided to make new UCA locating brackets moving the mounting points 3/4" inward. I used a piece of 3/16" thick angle iron so I could cross bolt the mounting bar with horizontal bolts and shims. The bad thing about the Mustang II UCAs is they had vertical bolts and depended on friction to hold them in place. If you got caster set, then you had to move the cross bar parallel, which would mess up your caster. I think Heidts and Bethania garage sell conversion piece to do this, but I couldn't find them on their web sites. Anyhow, I have 2 1/2" Grade 8 bolts and 2 3/8" Grade 5 bolts holding the bracket in place. If it works well, I can come back later and weld it in. If not, I can remove it and try the 5/8" shorter A Arms. My bracket also shifts the mounting bars 1/4" rearward to move the upper ball joint in this direction. I'll be re-assembling this weekend to see how things shape up.

[Ralphy]

CSXDreamer,

Who made your control arms? It's always been my impression they should be geometrically the same. Unless you were to buy minus sizes. I have seen -5/8 and -7/8 on EBay.

Ralphy