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Re: [Healeys] stub axles

To: allen c miller jr <acmiller@mhcable.com>
Subject: Re: [Healeys] stub axles
From: Michael Salter <msalter@precisionsportscar.com>
Date: Thu, 31 Dec 2009 10:13:18 -0500
Hi Allen,
Having suffered a stub axle failure while racing a Healey I can appreciate
your concern.
Many years ago I had every Healey and MG stub axle that I owned crack
tested. More than half the Healey ones (8 of the 15) tested were cracked. Of
the ones that I had to disassemble to have tested 3 of the 4 where the
spacer and shims had previously been removed were cracked. None of the MGB
ones (12), or for that matter late BJ8 ones (only 2), were cracked. I know
this is no where near sufficient quantity constitute conclusive study but
the trend is obvious.
Although Steve Byer disagrees with me on this I firmly believe that the
spacer and shims contribute significantly to the rigidity of the stub axle
and, as a result, limit the flexing at its root. This in turn substantially
reduces their exposure to stress related cracking.
I would definitely use penetrant or Magnaflux testing before shot-peening as
the compressive stress area just below the surface could indeed mask an
existing crack.
Although I've had only minimal experiance with it I would suspect that Xray
testing would still show a preexisting crack after shot peening but I would
deffer that to someone with more experience with Xray testing.
I had so little confidence in the strength of the Healey stub axle design
that I switched to MGB stub axles when I build AHX12 for rallying.
http://www.acmefluid.com.au/larry/ahx12.html
Hope that helps

Michael Salter


On Wed, Dec 30, 2009 at 10:21 PM, allen c miller jr <acmiller@mhcable.com>wrote:

> have heard a lot about big Healey stub axles showing latent flaws when
> tested.
> do you have them magnafluxed or xrayed? also, if magnafluxed, does
> shot-peening seal the cracks so they cannot be properly visualized (as i
> was
> told by someone who who restores healeys)? if so, is there an easy
> alternative
> to removing paint and leaving the cracks open? lastly, can you rely on
> micrometer measurements at right angles to determine whether there is wear
> in
> the bronze bushings, or is there another method to check for kingpin
> laxity?
> am going to race a bn2, so i want to take extra precautions.
>
> thanks. allen miller
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