a-arm bushing issues

[pboedker]

I am sure we had the same bushing issue, Joji. And had I added shims on the inside, like BDA has done, there might not have been any issue at all.

I plan to dismantle the a-arms again this winter and replace the rubber bushings with poly bushes. These will have shims on both sides if the long bolts allow it, otherwise only the front bushings. And I will make a jig for heating+bending the a-arms back into the proper dimensions before reassembly. 

[Grumblebuns]

Peter, is there a need to re-temper the steel after the heating process? I've heated and bent aluminum for non stressed applications so I didn't have to worry about the brittleness produced by the heating and cooling process. I've never worked with steel however. 

[EuropaTC]

Hi Joji,

The wishbone arms are, AFAIK, plain carbon steel. What's commonly called "mild steel" and usually has a low carbon content which isn't sufficient for hardening & tempering as you would do with a medium or higher carbon steel. So heating it to cherry red (700+C) and quenching won't do a lot for added strength.

Usually the best you can do with mild steel is stress relieve it, a process similar to annealing with copper, etc. Personally if I intended to straighten an arm I would simply warm it gently up to dull red heat, at which point it will move easily and without inducing new stress, then let it cool down slowly.  Mild steel starts to recrystallize about 400-440C, which is more or less the start of the annealing process. Dull red heat will be well above that, so you'll be in a safe zone for working.

see, that's what happens when you ask a question about metals with a retired metallurgist on the forum.....

[Grumblebuns]

Brian, excellent info and we have a metals expert on the forum to boot.

Any idea how long it will take a single propane torch to get a control arm hot enough to working temperature. I've been meaning to get an oxy acetylene rig for welding and cutting, this may a good excuse to hurry up the heating process.   

[EuropaTC]

Brian, excellent info and we have a metals expert on the forum to boot.

Any idea how long it will take a single propane torch to get a control arm hot enough to working temperature. I've been meaning to get an oxy acetylene rig for welding and cutting, this may a good excuse to hurry up the heating process.

metals expert ?        never in a million years, in fact the one thing I can guarantee is that I've never been an expert on anything.

I did qualify as a Metallurgist from Liverpool University in '71 and actually worked as one for a few years. But I joined ICI who recruited metallurgists and then proceeded to get them working as "materials engineers", which basically meant if it was a material you were supposed to sort it out. That was a great job and you never got bored, but of course your metallurgy drops back to "basic" as you struggle getting to terms with thermoplastics/thermosets/rubber/ceramics/etc.

So a "real" metallurgist would run rings round me !

I use a propane blowtorch to heat thinner sections up to around 1/4" on small items and it works reasonably well to dull red on steel.    For thicker sections or large items I use a carbon arc torch on the Arc welding set because the propane can't keep up with the rate of heat loss.  Or rather my patience can't keep up with the slower heating rate !

[jbcollier]

I am not a metallurgist, nor particularly good looking when wet*, but any evidence of a suspension component having been heated is an automatic fail in a safety inspection.  If you know what you are doing, excellent, remember to cover up your foul deed with a lick of paint.  If you don't, or you just saw it in a video on the internet, or have trouble toasting bread , do it right and replace bent components.

*Come to think of it, nobody raves about my looks when I'm dry either.

[Roger]

I'm  with the man from Lincs.  A dull red on mild steel destroys the paint, but allows you to straighten it, then you can paint it again.
Heating tempered components is definitely not for the amateur, though.

[EuropaTC]

but any evidence of a suspension component having been heated is an automatic fail in a safety inspection.

Oh, that's a harsh set of rules  John. I'm glad I'm not over there !

We have rules in our annual MoT test which fail things if they are "inappropriately repaired" but otherwise it's all about structural integrity. Checking for corrosion, physical damage, cracking, etc are the main ones.  I've a vague memory of reading about welding on steering components not being allowed but as a lot of home built cars use welded components I'm not too sure about that one. I suspect it was directed at welding on forged components and not worded very well.

Brian