Making my own sway bar, have questions about welding it

[traut811]

I try to support the forum sponsors as much as I can. I am running ridetech coilovers/front sway bar on one vehicle and a Schwartz chassis with ridetech coilovers/splined sway bar on the camaro. I know off the shelf proven is probably best, but I really enjoy trying to make as much as I can and am playing around with making a rear sway bar (with welded arms, not splined).

From the research I have gathered, 4130 is a common material for sway bars.

I purchased some 1" OD, 5/8" ID 4130 tubing from McMaster. I cut out some arms (A36) on the water jet. Went to Oreillys and got some Energy 1" sway bar bushing mounts. I don't remember what brand end links I bought. Basically the arms will slip over the tubing, then I will need to weld them together. Splining isn't an option as I can't do that myself.

I need to weld it together and that's where I'm in the dark. I see a lot about 4130 being tough due to superheating and supercooling, and wanting to crack at the edge of the weld. One way around this is pre heating and post heating. My plan was to : Pre heat the tube and arm with a regular propane campfire torch, then just MIG the arms as a "get in-get out" method instead of TIG. As soon as I am finished welding I would lightly keep the propane heat on it to try to slow cooling. I don't know if it's bad to think of it this way, but if it were to fail (other than around a corner where it would pop back) nothing should drop down and drag as the bar itself would still be contained.

Has anyone else done the same and is there any concern with what I am trying to do?? Thank you in advance for any help or advice!


I don't know if the whole thing needs to be heat treated before or after, or if it is fine as is. I also need to check I suppose to see if it has been normalized. Material specs are:


Material
4130 Alloy Steel


Shape
Round Tube


Shape Type
Round Tubes


Wall Thickness
0.188"


Wall Thickness Tolerance
-0.028" to 0.028"


Tolerance Rating
Standard


OD
1"


OD Tolerance
-0.005" to 0.005"


ID
0.624"


ID Tolerance
Not Rated


Yield Strength
70,000 psi


Fabrication
Cold Worked


Hardness
Rockwell C20


Hardness Rating
Hard


Maximum Hardness After Heat Treatment
Rockwell C49


Heat Treatable
Yes


Appearance
Plain


Temperature Range
Not Rated


Specifications Met
AMS-T-6736, MIL-T-6736B


Straightness Tolerance
0.030" per 3 ft.


Coefficient of Thermal Expansion
7.6 × 10-6


Elongation
26.5%


Material Composition



Aluminum
0.039%


Carbon
0.27-0.34%


Chromium
0.80-1.15%


Copper
0-0.25%


Hydrogen
0-2 ppm Max.


Manganese
0.35-0.60%


Molybdenum
0.15-0.25%


Nickel
0-0.25%


Niobium
0.05% Max.


Phosphorus
0.011-0.035%


Silicon
0.15-0.40%


Sulfur
0.002-0.04%


Titanium
0.03% Max.


Vanadium
0-0.035%


Iron
Remainder


Warning Message
Physical and mechanical properties are not guaranteed. They are intended only as a basis for comparison and not for design purposes.


Length Tolerance
-1" to 1"


RoHS
RoHS 3 (2015/863/EU) noncompliant

[Alwhite00]

Not sure a propane torch will get it hot enough. Subscribed for answers

[jetmech442]

Love the ambition, heres a few thoughts.

The rate of cooldown is the key player right? I assume your trying to stay out of the martinsite range(but I havn't done this in a looong time). Maybe having a steel box to roughly contain the heat could help. a hole in one side for the bar to enter and another on the other side for the propane(MAP?) torch to enter. Perhaps heating the bar an inch or two in from the weld zone would help keep heat in the joint for those few crucial seconds after the weld stops. Then you could close the box and try to dial back the torch. (this is all my hillbilly way of approaching, so if this sounds like crap then please disregard).

Be aware if you are using a non-contact IR gun to take temp readings. The emissivity of the steel will change after welding and most guns guys like us get cannot change that value(they are usually set to .95 which is correct for duct tape). So you can use it for a change in temp, but not absolute values. Also, most cooldown charts I think are referencing the weld location, not air temp.

Is it possible to get an extra 4 inches of tube and run it through the intended process and see how it turns out?


I'd love to see how you do this, keep us posted.

[traut811]

Thank you for the replies!
Jetmech442, good thinking on the "hot box". I do have an old truckbed toolbox that I don't mind cutting up. I wasn't originally planning on doing something like that, but I'm sure it would help. I do not know if heat up or cool down is worse, or both from what I understand. If I could get it warmed up with a MAP torch (Benzomatic), I figured it would help. What the key temp here is I am not sure of, and don't think I will have near enough to get it extremely warm but it should help.

I could throw the A36 arms in the oven to heat up before they weld, but I think the problem lies within the chromoly. Lots of questionable items, as I don't know which MIG wire would be best as well. I was going to TIG it, but could run a MIG bead around much quicker and think it may help out.

I'm also unsure if there needs to be any sort of post heat treatment once the whole assembly is welded.

I have all of the components I need, just need them to stick together and not bust at the weld joint halfway around a cone ideally!

[Kenova]

For preheat and post heat/cool down you could use a BBQ. Most lids usually have an opening for the rotisserie that you can stick the tube through. It would also give you some control over the heat.
If you think you can do a better weld with TIG you can reheat the end between beads. It may take a while to do both ends but I would think there would be a little less guess work.

Ken

[Alwhite00]

How much $ are you going to have in this thing?

[WOLF1732]

In my ISMA days I welded and built many sway bars and adjustable blade arms. The only thing I would tell you is to stay with all 4130 parts and weld with ER-80S-D2 tig rod. I would not get wound up on preheat. Just sent to your local heat treater and have your parts stress relieved and heat treated to 33 to 36rc when you are done.

[traut811]

How much $ are you going to have in this thing?

The energy Bushings were $22, end links were $7/ea, 4130 tubing was around $55. A36 I had but say $15. Stainless rod for link arms I also had but figure another $15. I'll have a few bucks more if I need to buy Tig rod or might wire if recommended differently than I have. I'll have another $30 in powdercoat probably, so around $160-170 in materials. I have a mill and lathe so am fortunate to not have to pay anyone to do any of it
Yes I could buy a low budget sway for that, but I don't care for any of them. It might sound like a lot but I really want to do this myself.

I put together my rear suspension setup and had to machine several of the components to make it work, and am extremely happy with how it turned out. I like making little things on my truck if I can, but of course buy things I shouldn't tackle myself.

[traut811]

For preheat and post heat/cool down you could use a BBQ. Most lids usually have an opening for the rotisserie that you can stick the tube through. It would also give you some control over the heat.
If you think you can do a better weld with TIG you can reheat the end between beads. It may take a while to do both ends but I would think there would be a little less guess work.

Ken

Ken
My only concern with TIG is the amount of time it would take the actual welding process vs. MIG. I would think the MIG would leave surrounding less time to heat up than the TIG, and less chance of "shocking" it.

I'm not a pro welder by any means if no one picked up on that. I really should try to find my metallurgy books from college but figured I'd check with some of the experts here.

[traut811]

In my ISMA days I welded and built many sway bars and adjustable blade arms. The only thing I would tell you is to stay with all 4130 parts and weld with ER-80S-D2 tig rod. I would not get wound up on preheat. Just sent to your local heat treater and have your parts stress relieved and heat treated to 33 to 36rc when you are done.

Perfect!! Thank you very much.

The a36 arms are already cut on the waterjet. If it's strongly recommended against them, I will see if I can buy some 4130 sheet and try again. I will also need to find a local heat treater who could do it. Anything special need to happen like normalizing or anything else before? Our oven at work would not be big enough to fit it.

I do have some er80sd2 in 1/16, 3/32, and 1/8". Would you have concerns with MIGging it with er70s6 or er70s3?

Thanks again.

[WOLF1732]

mig not recommended for 4130. 4130 is available at stock car steel or aircraft spruce co. Spruce is my fav less hassle to buy from . How thick are the arms and how long? Also 4130 does not move like mild steel does when welded. For some of the formula cars we use to weld a plug in the end of the tube that was milled to a hex or splined so the arm could be removed. the arm had a bolt clamp setup never saw one fail. If you need I can draw you something up.

[traut811]

I made the arms 3/8" thick and they're probably 12" long or so. I got 1" od tubing because my front ridetech is 1.25".
I reamed the 1" hole in the arms so it fits really well. It isn't the end of the world to redo them though, just have to go backwards a bit. I will check out Spruce

[Alwhite00]

This kit it looks like they just pin the arms to the bars. Would that be an option?


https://www.jegs.com/i/JEGS+Performance+Products/555/60570/10002/-1?gclid=CjwKCAjwguzzBRBiEiwAgU0FT4TQ-lAAvvQNlvxfdcYzenpiJ0WC8ClxlJmQob0HMVsMyvTJt4iQuho CrDMQAvD_BwE

[79T/Aman]

I used to make rear bars, 7/8" solid hi carbon steel, can be welded, the arm would be 3/4" thick steel and milled to reduce weight, multiple holes drilled for adjustability.
, the weight savings is negligible especially that low.

[traut811]

This kit it looks like they just pin the arms to the bars. Would that be an option?

https://www.jegs.com/i/JEGS+Performance+Products/555/60570/10002/-1?gclid=CjwKCAjwguzzBRBiEiwAgU0FT4TQ-lAAvvQNlvxfdcYzenpiJ0WC8ClxlJmQob0HMVsMyvTJt4iQuho CrDMQAvD_BwE

That is fairly cheap for what you get it seems like. It wouldn't work for me as I have all dimensions I need already, but a pretty cool kit they put together.


I used to make rear bars, 7/8" solid hi carbon steel, can be welded, the arm would be 3/4" thick steel and milled to reduce weight, multiple holes drilled for adjustability.
, the weight savings is negligible especially that low.

I wonder how .875" solid high carbon would compare to my 1" od, .1875" wall current tube as far as torsion? How were you welding something like that?

There has to be a way these things are figured or rule of thumb instead of blindly pulling any material, I just haven't found it yet.

[Twentyover]

If I recall correctly, the Miller website has some instruction on welding 4130.Another resource may be the EAA (Experimental Aircraft Association) in Oshkosh WI. Thy have several publications and may prove helpful

[Alwhite00]

That is fairly cheap for what you get it seems like. It wouldn't work for me as I have all dimensions I need already, but a pretty cool kit they put together.



I wonder how .875" solid high carbon would compare to my 1" od, .1875" wall current tube as far as torsion? How were you welding something like that?t.

I only showed the link to sho they pinned the arms wondering if that could work for you.

[raustinss]

So why not a splined bar and make your own ends ... or did you already answer this and I missed it

[traut811]

If I recall correctly, the Miller website has some instruction on welding 4130.Another resource may be the EAA (Experimental Aircraft Association) in Oshkosh WI. Thy have several publications and may prove helpful

I did see the Miller one, and have done a ton of reading on this. All make me second guess trying it myself lol


I only showed the link to sho they pinned the arms wondering if that could work for you.

Ah I see. Yes that would make it much easier. A pin would make it the point of failure if something were to happen. I would think a weld joint could be much stronger but I agree a pin I could do messed in a mill.


So why not a splined bar and make your own ends ... or did you already answer this and I missed it
I have no way to make an internal or external spline myself. I have splined on my Schwartz chassis and I wish I was able to do that.

I've got a couple people I need to talk to and can hopefully get a game plan this weekend. I'll keep in touch with how it goes.

[BBPanel]

Paul Horton Welder Series has splined bars in 36" and 45" - if you asked they might make whatever exact length you need:
https://welderseries.ecwid.com/Sway-Bar-Kit-Trim-to-Fit-p49762034
I used their kit - just so happens the 36" was what I needed.
I'm sure there are others that would make the length of splined bar you need.

[79T/Aman]

That is fairly cheap for what you get it seems like. It wouldn't work for me as I have all dimensions I need already, but a pretty cool kit they put together.



I wonder how .875" solid high carbon would compare to my 1" od, .1875" wall current tube as far as torsion? How were you welding something like that?

There has to be a way these things are figured or rule of thumb instead of blindly pulling any material, I just haven't found it yet.

the arem had a trough hole for the bar to fit into, it was welded around on one side and plug welded on the other side with a mig welder.