Sway Bar Question

[JustThisOnce]

I plan to build some sway bars. I had decided on using 4140 but I've got a guy telling me that I should use 1045.

I am not an engineer but from what I have been able to find the 4140 is a better product for my application.

Any suggestions?

Thanks

[tobyaxis]

1045 is Spring Steel, which makes it better for your application.

Buy a Machinery's Handbook, it covers material applications.

[JustThisOnce]

Wel, it's obvious I need to do some more homework on this before I start making anything.

I know someone that has a Machinery's Handbook. I'll check that out tomorrow.

But I did find this in my searching tonight. I have not been able to find anything similar regarding the 1045 steel.

The ALTA performance Mini Cooper and Cooper S rear sway bar is a great upgrade for your Mini. Please note all bars are made from 4140 Solid Steel, for maximum performance and lifetime durability

[HuFlungDung]

5160 is the alloy grade they commonly use for leaf springs, if that is of any help. Perhaps 4140 would serve too, mainly because of what shapes are available out there, 5160 may only be readily available as flat bars. I have not compared the two, to see if there is a difference in fatigue life.

1045 I would think barely makes it into the spring steel category, 1090 would be more common in plain carbon spring steels. It needs to be heat treated and tempered, of course, to be of any value as a spring.

[tobyaxis]

Wel, it's obvious I need to do some more homework on this before I start making anything.

I know someone that has a Machinery's Handbook. I'll check that out tomorrow.

But I did find this in my searching tonight. I have not been able to find anything similar regarding the 1045 steel.

The ALTA performance Mini Cooper and Cooper S rear sway bar is a great upgrade for your Mini. Please note all bars are made from 4140 Solid Steel, for maximum performance and lifetime durability

Definitely do a bit of homework and as I recall now it could very well be 1035 Steel.

Look under Applications of Steels.

[JustThisOnce]

You guys are great! You're replies confirm 2 things.

1- This is not as simple as I thought it would be.

2- There are probably several materials that could be used to achieve my goal.

It may be nothing more than Good-Better-Best with the different products mentioned.

Manufacturer's are, understandably, not real eager to say what material they are using.

I'm going to hit the books, or in this case, book, and see what I can find.

[Gitman]

Not throw a wrench in the works, but I make sway bars for trophy trucks and off-road applications out of AL6061-T6. Some of them are almost 40 inches long. We spline them then put in a pinch bolt. These see the worst abuse and longest suspension travel, and hold up race ofter race.

[JustThisOnce]

Not throw a wrench in the works, but I make sway bars for trophy trucks and off-road applications out of AL6061-T6. Some of them are almost 40 inches long. We spline them then put in a pinch bolt. These see the worst abuse and longest suspension travel, and hold up race ofter race.

Interesting! Aluminum instead of steel. What kind of diameter relative to a steel sway bar do you need to achieve a reasonably stiffer product?

I have not looked into pricing on raw material yet, but I would assume AL6061-T6 would be more expensive than either the 1045 or 4140 that has been suggested so far.

[Gitman]

I meant the sway bar linkages are made from Aluminum. Sorry, my mistake...thought you were talking linkages.

[cgosnell]

In total, you will want a material that not only has good ultimate strength, but also has good elongation to break and a resistance to the environment it will be in. (Corrosion, low temperatures, etc...)

Check for a material that has a high enough yield strength (load required for a permanent bend), along with an elongation (amount of stretch until break) of better than 15% or so.
if you check matweb you can lookup the materials discussed so far.

One note about Aluminum. Over the long term two things can happen to Aluminum. One is 'creep', or the permanent set of aluminim under constant load over time, even at relatively light loads. Also increasing brittleness of the aluminum under constant load cycling over time.

I would also recommend that any bending of the steel sway bars be done after uniform heating of the area to be bent. If not, cracks can form due to excessive stretch (strain) of the material.

BTW, homebuilt Aircraft use 4130 steel and 2014 aluminum almost exclusively, The 4130 material is readily welded and formed, and retains good properties.

To get the best performance from the 4130, it should be hardened, quenched, and tempered. this is best done by a commercial heat treater. Especially if you have heated the bar locally to form it beforehand.

This isn't to say that sway bars aren't made of softer materials (say 1020/1035 normalized steel). But the dimensions of the sway bar required to avoid permanent set (yield) will be larger and heavier than a bar made from heat treated alloy steel.

[marksbug]

I think the sway(antiroll)bar on my racecar is mild steel tubing,alltho it is an econo version of the one that was on our nhra pro stock,(don ness chassie) they use 4130 exclusivly. the drag cars use straight tubing with either weld on ends or splined ends. I think some circle track cars also use tubing. on the other end of the spectrum my VW bug uses about 8, 1/2"wide 4' long about .060 thick each,stacked togeather for the torsion springs (not leaf bending, but torsion springs)to hold up the car in the frount,solid splined bar in the rear,the after market bars are Cromolly.probly 4130or 5110 not sure. I gess alot of it depends on the desigin/fabracation/load ,cycles,etc. good luck. I think the reason for bigger is with biger you get stiffer,you can make a small one stifer than normal with defrent heattreating/&materal but it will cut down on the life. so biger will last longer. a small car dosent need what a caddy needs.