Need some brainy cromo bar help.
 

I bought a 1” chromo round bar to make an anti-sway bar with. I had intentions of getting it heat treated. I found the spec sheet recently and it looks like it’s already been hardened?

https://uploads.tapatalk-cdn.com/202...78eab6cf78.jpg


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Yes. That is 4340 heat treat. The material is already hardened (quenched and tempered)from the mill.

So...I guess I can’t weld on it or I’ll have to re-temper it?


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I am not a welder, but am a machinist with 30+ years of experience working with metals, so I can't give you exact details.
Generally this material would be welded in an annealed(soft) condition. Proper welding includes preheating the material and maintaining temperature while welding (not too hot) and letting the weldment cool slowly. ( to keep metal soft, a weldment is sometimes buried in a pile of sand post welding that allows it to cool very slowly. ) if the metal gets too hot and cools too quickly it may crack at the welds. After welding the weldment would be heat treated as a unit to desired hardness.
(Your piece can be annealed, welded, and re heat treated, but it may not be necessary, and too many processes can have the tendency to warp the metal.)
Now that I scared you, I am sure some good welders can give you Proper advice to weld it in its current condition without it softening or cracking, or do an internet search on welding 4340 in a T1 condition.
Good luck.

I'd say spline the ends of the bar and then make the ends that connect to the control arms aka Detroit speed splined sway bar style. No welding ,no heat treat etc etc

Rear sway bars seem to be somewhat rejected by the majority of people I’ve interacted with on this site which seems plausible to me. If memory serves, good front bars are necessary, too much in the rear, and the car suffers, in corners. Straight line work, and it’s a different game, if you are struggling to put the power down and go straight. What’s interesting is how prolific they are on race cars, at least pictures I’ve seen of race cars. The guy that welded up the housing ends on my rear axle seemed to think I would never twist a 1” cromo bar and heat treating was a waste. His gig was drag, and he has many years of experience, so he said. My control arms are quite long so that minimizes the effect as well. I fabricated mine to avoid the $400+ price tag on a modular system. At this point, I’m just going to finish welding it up, hook it up and see how it works. Worst case, I hate it or twist it (hopefully that’s worst case) and it gets removed or replaced. At least I have the provision for it built in to my set-up. In time (a while out) I’ll update this post to let everyone know where it went, and how it worked. If I had to make a prediction, it will be disconnected on the street and for road courses and possibly hooked up for any 1/8 mile work, just to see if it makes a difference. My car isn’t going to be a monster so there’s a good chance it’s going to be insignificant either way. It would be cool to put a GoPro under there with one of the links disconnected to see what kind of input it would be getting.

Thanks for all the input.


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So, this bar is for the rear. 1" is a lot of bar in the rear. Let us know how it works out.
The strategy for my car is to use a rear bar. Mine is 3/4" diameter.
With the bar I can achieve the roll stiffness needed for cornering, and keep softer rear springs for ride quality, which is always a compromise with dual purpose vehicles.

There are many problems with the logic here. One is that you might be confusing a rear sway bar setup for a drag car with one that is for a regular car or one that corners. The motivations are quite different. A drag bar would be like putting your rear wheels on plastic trays . . .

Generally, from a handling perspective, most of the talk you've seen that is against a rear bar relates to leaf spring setups. The idea is that the action is redundant, given the leverage forces being applied between the axle, the body, and the springs. The sway bar just becomes kind of a redundant spring, and it will generally just add oversteer (which isn't always bad).

Linkage (three, four, five) setups will generally have rear sway bars. Modern independent setups will have rear sway bars. The factories are careful to balance spring rates between the bars and the coils, however, so as not to create an oversprung setup.

I'm not an expert, so I'll have my glass of shutup juice now.