I need to make a new sway bar for my '37 LaSalle. The original was 5/8" and a Cadillac club member friend has a duplicate car. He had a 1" bar made and says it makes a very significant difference in handling. Thus, I need to know precisely what material to order. I shall have to bend the ends of the bar, then flatten, and drill so they'll fit the links. Thus I can't start out with heat treated material. Should I order normalized, annealed, then fabricate and have heat treated..or do I forget the heat treating all together?
No idea of where you are at so I have to ask, do you have a spring shop that makes/reworks springs close by? They should be able to tell you what steel you need and should be able to do the heat treating process to get it to work as a sway bar once you get it worked into shape. I don't know if any heavy trucks use a coil spring with 1 inch wire or not but looking at the process of making a coil spring it might be worth checking into
My first thought was 4140 but heard from an old fabricator friend who has made many sway bars that I should use 4340Ac and heat treat it to 38-42, so have my answer.
I have done them with 4140. On the 1", I was able to bend them cold in my Hossfield, using a 2-1/2" centerline radius. We weld the paddles on the ends, and had them heat treated, at a local spring shop. The shop moved locations, and doesn't have any plans on setting up the oven. They supplied the material, so I don't think I can get the absolute alloy. If I learn anything, I will post it here.
Wish I still had access to a Hossfield, so may have to bend the bar hot. But it's going to heat treat anyway. Thanks
If you don't have to weld to it, use 1144 stressproof. Similar properties to heat treated 4140 w/o having to heat treat it. Bend it cold
4340 would be a good choice. Start with annealed stock as that's the softest and easiest to bend. For heat treatment, I'd have it normalized. The part is brought up to the hardening temperature and then removed from the furnace and cooled in air. Normalizing 4340 will consistently result in a hardness of Rc 38-40 without any further treatment. The likelihood of warping or otherwise deforming during normalizing is much less than with quenching and tempering. It's worth mentioning that extreme increases in front sway bar diameter on an otherwise stock suspension can result in a car with a dangerous level of understeer. Going from 5/8" to 1" doesn't seem like a lot at first glance, but the torsional stiffness of a round rod varies with the 4th power of diameter. Doing the math shows the 1" bar is almost 7 times as stiff as the 5/8". Excessive roll stiffness at the front doesn't show up under normal conditions. Rather, one day you go into an unfamiliar curve a little too fast, the sway bar transfers too much weight onto the outer tire (and unloads the inner tire) and you find turning the wheel does pretty much nothing as the car plows into the ditch, over a bank, or into oncoming traffic. FWIW, compared to a 5/8 bar, a 3/4 is twice as stiff and a 7/8 is 4X as stiff.
I have made quite a few heavier anti roll bars over the years. I made them from 6150 because of the better fatigue life than 4340. If you need to weld on it go with the 4340. I bent the ones I did hot and flattened the ends, then drilled. I had them heat treated to 35RC. For your application, I would go with 3/4 diameter like metlmunchr says.
100% agree 6150 is the ideal sway bar material so long as no welding is involved. There's a reason it's called spring steel
I used Ford courier pickup sway bars on several vintage rods. they are clean with no crazy bends and easy to change the angle on the end bars in my Harbor Freight press. Get all the washers and rubber parts when you get the bar and all you need is the correct length bolts for the links.
The Courier bar looks like a good unit, but not many of these trucks in the junkyards nowadays. Another consideration with using a stronger sway bar is that it can put excessive loads on whatever it is attached to. I'm not familiar with your car, probably the suspension parts are built strongly enough.
Made front and rear bars for an autocross car using 1144, bent in a press, no heat. Worked well. If you are enlarging the front bar, consider a rear bar or the car will understear.
Oldest son used Ford F-150 REAR bars, with fasteners and bracketry off the same truck. Years differ, but bars are seemingly very similar. Measure and see, surprising fit for most fullsize cars...Nice stuff. (Ford)
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