Steering Arm routine bring up

[Ruairidh Dunford]

Thank you Dave - I hope it was not your drinking arm!

Your experience is similar to Steve’s, when I find a cracked one I will try to break it as well.

Do you khat type of steel were they made from?

[David Cochrane]

A professional chemical analysis was carried out in 1994, from which it was found that the material complied with the requirements of EN16B.

I think fatigue failures occur from the application of many relatively minor shocks to the component, rather than a massive thump!

[Ruairidh Dunford]

Thank you David.

The key is to key checking I guess?

[David Cochrane]

Yes, keep it clean and check it every so often (3000 miles perhaps?). If it's not cracked, it should be OK.

[Ruairidh Dunford]

Seems prudent David - thank you.

I have some time to sit and read (at last) and John Hopwood’s article on this very subject in the latest PWA7C Magazine caught my eye.

He makes reference to shrinkage cracks left on steering arms on cooling after forging. He details his method of magnetic particle crack-testing (my own kit employs this method) concluding that it is more effective than the dye kit ‘he’ had.

He found several surface cracks which he removed after grinding and polishing 40 thou of material away.

This is new information to me and raises the question as to the cause of cracks found to date? Are they in fact stress or perhaps manufacture related? Shrinkage cracks, if left, could cause future problems but appear to be easy enough to remove.

If anyone has a cracked arm I would be interested to receive it and undertake some tests as John did - then report the findings back here.

It may be that many (including me) have consigned arms to the scrap bin unnecessarily.