smahaley
Established member
Question- how bad is this? Can I just leave it or should I replace it? NB I have not driven the car yet and previous owners put new tires on it so I can’t refer to potentially odd tire wear ….
Technical Bent trailing arm?
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Technical
Bent trailing arm?
Question- how bad is this? Can I just leave it or should I replace it? NB I have not driven the car yet and previous owners put new tires on it so I can’t refer to potentially odd tire wear ….
If damage not too bad it may be possible to put it in a press with suitable mandrels and square it up assuming a good replacement is unavailable.
I know the square root of nothing, but it occurred to me that it would be reasonably easy (for a non-hamfisted fool, which counts me out) to fabricate a replacement if the part isn't available. I'd not want to drive it as it is.
It does look like a fairly simple design, I suppose it depends on the extent of the damage. It is quite a common issue, you can put signs all over cars about where to jack them up, but some will still just chuck a jack in and start pumping.
We had a car delivered by the AA many years ago on a transporter and found they had secured it using chains and ratchets over the suspension but crushing the brake pipes.;(
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smahaley
Established member
Well - it looks like I could procure a new one for $56 + shipping... https://autoricambi.us/rear-long-trailing-arm-1969-78/?setCurrencyId=1
Ideal.
If a new one can be sourced for $56+shipping then what follows next may be more expensive.
1) The arm need to be rollered, not pinch, squeezed, etc. This will restore the original round profile.
2) Any metal manipulation can soften or work harden the metal being worked. If the intension is to put the arm under great duress (e.g. motorsport/rallying) then i would also get the arm sleeved and welded.
A good metal shop should be able to do the above in a hour but I suspect one hour is $65+ cost anyway.
1) The arm need to be rollered, not pinch, squeezed, etc. This will restore the original round profile.
2) Any metal manipulation can soften or work harden the metal being worked. If the intension is to put the arm under great duress (e.g. motorsport/rallying) then i would also get the arm sleeved and welded.
A good metal shop should be able to do the above in a hour but I suspect one hour is $65+ cost anyway.
Here's how I have straightened slightly bent axle trailing arms.
Support the arm at points indicated in green in above image.
Heat the area of the tube indicated in red, using an oxy-acetylene gas torch to a red heat.
Apply pressure at area indicated in blue. you may find the the area between the red and blue arrows has spread outwards slightly, if so, just squeeze slightly in a vice/vise or using pipe grips
To prevent further damage, the support and pressing should be done using 1/2 round formers that match the diameter of the tube. I've used short lengths of heavy wall tube cut in half lengthways. It may be possible to remove any trace of indentation in the tube by positioning the tube so that the pressure is applied applied from above and the area to be heated is at the bottom/underneath. In this orientation, heating the dent to a bright red heat will cause the metal to sag, effectively removing the dent. (Don't overdo the heating or you'll end up with a hole...). Allow to cool normally in air, don't quench.
These trailing arms are made from mild steel, nothing special. The metal won't be hardened by heating providing it's allowed to cool slowly. The metal won't be softened or weakened by heating providing it's allowed to cool slowly i.e. don't quench in water or force dry using e.g. a compressed air jet.
Clean the surface down to bare metal, carefully check there are no cracks. A home method for checking for cracks is to coat the surface with paraffin/light oil, clean off then dust with talcum powder, the powder will adhere to any residual oil remaining in a crack. There are also crack testing kits available.
If any cracks are found, they'll need to be welded and ideally sleeved but be very, very careful about where welds are applied. I prefer to attach any reinforcement by welding it to the tube along it's length - welding completely around a tube can be dangerous as any undercutting at the edge of the weld results in a weak point that can result in failure. If a tubular item being reinforced will be subject to any bending loads, it's advisable to chamfer the internal ends of any reinforcement pieces being attached - but this doesn't apply in the case of the above trailing arms.
Just be sure to order the correct side - some of those arms were sided left or right - the difference being the orientation of the parking brake cable support bracket....
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smahaley
Established member
Thanks again - and I did just receive the new replacement. Guess what? No parking brake support! So I suppose they just manufacture the one and leave it to us to figure out retention of the parking brake cable.
Which I will have to do.
Soon.
After the sleet and snow are done!