turning down torsion bars (lathe)?

[sled]

has anyone ever played with machining down torsion bars to yeiled a softer suspension/more travel? Obviously done on a lathe with care.
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drive your split.

[Russ Wolfe]

If you try and turn one, it will probably break.
If you can find a diamond bit to turn it with. They are extremely hard.
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Society is like stew. If you don't keep it stirred up, you end up with a lot of scum on the top!--Edward Abbey

Gary: OK. Ima poop.

[baja72]

I would not do it! It would weaken the bar making it very unsafe. New torsion bars are fairly cheap compared to your health and safety.
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I suffer from a serious disorder : Volkswagenitis

[sled]

turning the bar is not an issue. was just wondering if people had done it.

of course it would make the bar weaker, that is what I am hoping for. I guess the trick is finding a point where the bar will flex more, but not break. Even a stock bar would break if it were forced to flex too much.

by the way this is in a bus, where the torsion bars are considerably larger than beetle. There are no new torsion bars available for buses that have a softer spring rate.

There is a guy who turned down some torsion bars for his trials-car with success. Said it was trial and error as far as how much to take off.

these 13mm bars shown did fail, but I guess he got bars with less material removed to work well.

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drive your split.

[Russ Wolfe]

You realize that VW pre-stressed the bars when they made them. That is why they are marked left and right. And, that is one reason that the one you show has the yellow stripe. That is to show what the rating is, IIRC.
_________________
Society is like stew. If you don't keep it stirred up, you end up with a lot of scum on the top!--Edward Abbey

Gary: OK. Ima poop.

[PhillipM]

The problem is there'll be surface stresses for cracks to propagate from after you've turned them, another temper session may sort that, but then you don't know exactly where that'll leave you with regard to the tensile strength, another tempering session might make them too soft and they'll bend.
Perhaps if you shot peened them after?

Actually turning them shouldn't be a problem though, most tooling will do, you certainly wouldn't want to use diamond on carbon steel though!

Just remember you don't need much off for a big change in spring rate - 13mm torsion bars must have been damn near useless, they'll have been soft as hell, I'm not suprised they broke! If they were ~30mm originally, then the 13mm bars are 28 times softer!

[jsturtlebuggy]

SwayAway grinds their bars to size.
I do remember seeing sprint car torsion bars being turn down for a short course car years in the race shops at the old Riverside race track. Car did work better but this was just for short term use.
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Joseph
Fair Oaks/Orangevale, CA
Elrod Motorsports
Motion Tire Motorsports
Having fun with Dune Buggies since 1970
Into Volkswagens since 1960

[takotruckin]

Airbags or coilover. You will be ahead in the long run IMO
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Member of the baja's that don't run club, for now!!

[joescoolcustoms]

[xirxious]

Usually anything with a spline is case hardened or gear hardened. You will most likely trim all that off. You may be able to anneal them and re-harden them, but I don't know alot about that. It would be easy to get one from the manufacturer pre-treated, but they probably won't sell them like that.

[joescoolcustoms]

[bdkw1]

It can be done, but be careful. Don't take to much off the first time. You can always make them smaller, a little hard to make them bigger. After turning I polish them with a flapper wheel on the grinder till the tool marks are gone. This will prevent stress risers and cracks. Do not get them hot!

Here is a good T-bar calculator to help figure out how much reducing the diameter will reduce the spring rate. http://www.proshocks.com/calcs/torsionrate.htm