How to bend torsion arms?

[PlanB]

I'm looking for specifics on how to bend B/J torsion arms to gain negative camber — on Type 3 torsion arms where there are no provisions for camber eccentrics.

I've read a number of recent posts here where people talk about "having done it", (see below) but can't find any details on the process.

I'm assuming an hydraulic press is part of the drill, but I'm looking for any insight into the "blacksmithing" portion of the process, where the heating is done. Have people built jigs to control the accuracy of the bend? Or is this strictly a 'freehand' exercise?

I'm also already aware of some of the other options (lower arm spacers, relocating ball joint mount hole on the torsion arm, etc).
I'm specifically interested in how the "blacksmithing" process of bending the torsion arms is done. What type of heating is done? How critical is the control of the heat source? Is the arm better bent with a press (cold)? How to control the angle and match it on the two arms, etc.

How have others done it?

Any feedback would be helpful.

Thanks!

Jul 09, 2012)
Bruce 2
"it is a hell of a lot more work than simply bending the top control arm a bit"

Tue Jul 10, 2012
buildabiggerboxer
"i run extra camber nuts, bent top arms and 9 degs caster"

Jun 14, 2012
FJCamper
"I've done blacksmith heat-and-hammer front suspension mods and I do not recommend them. It is a guessing operation."


Here's a pic of the Type 3 Torsion Arm:

Type3TorsionArm.jpg

[Marc]

You've already max'd out the adjustment on both ball joints and still need more negative camber?

[PlanB]

You've already max'd out the adjustment on both ball joints and still need more negative camber?

Yep... And got maybe a degree of negative camber, and this is on a dedicated road racing type 3 (not a street car).

[Marc]

One of my competitors back in my circletrack days ran a Type III front end; removed the upper swaybar (and ran an external one) and replaced it with what was basically a piece of all-thread. Trimmed the beam back slightly and used shims under the thrust rings to set the upper control arm position.
Might be worth considering before you start bending things. I've never liked bending control arms - I've done it, just didn't like it - one consideration is that when bent inward the arm also becomes effectively longer, which upsets the parallelogram geometry so that as the suspension cycles something must give so the spindle is forced to turn..."ball-joint-generated bumpsteer" is my term for this effect.

[Steve Arndt]

I bought a set of Thing arms for my baja and one of them was bent BAD. I put the curvy portion of the arm in a vice with the tube piece that fits in the beam oriented vertically. A big pry bar / breaker bar was inserted into the inside of the tube piece that fits in the torsion housing. I heated the arm with a torch and bent it back. It took one person to heat, and another to apply force. Something along those lines should work. Not exactly a scientific method for sure.

s

[DORIGTT]

[quote="Marc"] Trimmed the beam back slightly and used shims under the thrust rings to set the upper control arm position.
quote]

I was just thinking about doing this exact same thing! I would imagine the outer lip of the top torsion tube wouldn't have to be trimmed much in order to give a couple degrees of negative which would allow us to run the eccentrics in 'reverse' to dial out negative for road use and go back to more for track usage.

Thoughts, opinions?

[Marc]

For a super-light car (Formula Vee or buggy) the lower torsions might provide enough springing unaided but coillovers will probably be required for anything heavier. Once you replace the upper torsions with a through-rod there's nothing to control lateral location of the control arms except for whatever you insert for thrust washers. Simply removing the dust seals from the upper tube ends and substituting a thinner washer might be enough for a Type I, without shortening the tube.
Another idea would be to fabricate some slugs to go into the upper arms, threaded to go over the threaded rod. They'd have divots to allow securing with the stock grub screws. If you then anchored the through-rod at the center, the arms would be located by the rod (and how far the slugs were screwed on) rather than needing thrust washers. As the suspension cycles the slugs will move on the threads, causing a slight change in lateral position - not enough to be a problem over ~3" of travel.
Either approach would require periodic inspection for wear. If you remove the dust seals, dirt & water can get into the beam so you'll need to grease it frequently (especially if driven in wet weather).

[PlanB]

Still looking for specifics techniques for bending torsion arms???

(and thanks for all of the alternate approaches)

[Piledriver]

I like the "shim the bottom out" idea...

Hard to beat for consistency.

I picked up a spare beam awhile back out of a very low mile car, tempted to swap it in or something and get some measurements for spacers.

[Ol'fogasaurus]

Deleted

[fusername]

what about the opposite? can you shim out hte lower arm? I have only seen diagrams of these suspensions, so no idea how exactly it goes together.

as for heating and bending, since they are cast parts I would look around online for some blacksmithing resources. that should spell out what to do if you are willing to guess at what kind of metal was used to make them.
*edit*
I see pile beat me to that idea. and bending it is damn iffy, but if you are racing I assume ur all caged up and racing is quite iffy to begin with. on a street car I would be a bit more cautious. grandma on a street corner didn't sign up for our shenanigans.

[Steve Arndt]

The trailing arms are forged not cast.

[Bruce2]

Indeed. That means they are steel and not cast iron. Also, there's no heat treat to worry about.

Support the ends, centered under the ram of your hydraulic press and bend away. I wouldn't even bother with heat.

[Ol'fogasaurus]

Deleted

[PlanB]

Indeed. That means they are steel and not cast iron. Also, there's no heat treat to worry about.

Support the ends, centered under the ram of your hydraulic press and bend away. I wouldn't even bother with heat.

Thanks Bruce. That's what I was thinking. I have access to an hydraulic press and a bro-in-law/ shop-owner /engineer who can help set up a somewhat repeatable/accurate jig. I also have NOS trailing arms to play with.