[DeTomaso] Stress-relieving Rims

[Stephen Nelson]

I searched again, this time under "annealing magnesium".  Found two relevant
articles - which suggest J. Deryke is pretty much spot on in his
recommendations for stress relief.  If interested check out:

 

First
<http://news.alibaba.com/article/detail/metalworking/100188588-1-metals-know
ledge%253Apractical-heat-treatment-magnesium.html>  Article

 

Second Article <http://www.keytometals.com/Article93.htm> 

 

Note, annealing temperatures are quite a bit warmer than the 375F he calls
for, but that is not what we are going for - we want stress relief.  Here is
a table from the ASM handbook on annealing temperatures for wrought
magnesium alloys.  The previous two articles also reflect higher annealing
temperatures:  

 

Annealing <http://www.asminternational.org/pdf/HTSRefCharts/OMM051508.pdf>
Temperatures

 

Which means I will now be annealing my rims, then sandblasting them and
refinishing.  So, next question.  I suspect I will end up spraying them
myself to get a good seal on the metal.  Any recommendations on materials to
use?  It sounds like they originally had a zinc-chromate prime - and I have
some self-etching zinc-chromate primer - so suspect that would be a good
base material.  Providing it is compatible with what ever would make a good
finish.

 

And, yes, I could get them powder coated.  But, so far, the powder coaters I
have talked to are not aware of any special requ's for magnesium and don't
sound crazy about long cooling times.

 

 

Stephen Nelson

 

 

 

-----Original Message-----
From: detomaso-bounces at poca.com [mailto:detomaso-bounces at poca.com] On Behalf
Of JDeRyke at aol.com
Sent: Saturday, August 17, 2013 3:59 PM
To: michaelsavga at gmail.com
Cc: detomaso at poca.com
Subject: Re: [DeTomaso] Stress-relieving Rims

 

In a message dated 8/17/13 1:38:58 PM, michaelsavga at gmail.com writes:

 

> Please send your methods so we can all do it.

> 

Piece of cake. I've published this several times before, in both POCA pubs 

over the last 15 years, but....

 

* Preheat Mom's oven to 375F degrees some evening; take a clean, dry rim 

with no valve stem or center logo disc and put it in the oven. If the rim is


not clean & dry, there WILL be smoke and smells which will not gain points 

with the cook or the dog. Soap & water works just fine to clean Campys but
be 

sure the rim is dry. If the valve stem is left on, the heat will badly 

deteriorate rubber stems and the rubber grommet on metal stems. Leaks will 

follow.

* Bake for at least 2 hrs. Less time probably doesn't do as much while a 

little longer doesn't hurt. 

* Then remove the rim (gloves!) and wrap in a non-synthetic-fiber blanket 

and PUT IT BACK INSIDE THE HOT OVEN. Turn off the oven and let it alone
until 

Morning. The idea is, at least 2 hrs of 375F heat followed by as slow a 

cool-off as possible! 

This WILL cause stock Argent-Silver paint (or others) to turn tan. So have 

a rattle-can ready along with a new metal valve stem. It will do nothing to 

powder coated rims unless they have an overcoat or touch-ups of regular
paint

. 

 

Some owners contract with powder-coaters to coat cleaned, previously 

weld-repaired rims, then do a very slow cool-off in the power-coat oven as
above. 

Most powder coaters run about 350F- 375F to cure their coatings, so if 

they'll give you the slow cool-down afterwards, you get most of the
annealing 

service simultaneously. 

This is one of those mods where, if things work according to Plan A, 

nothing will happen, so it's diffcult to quantify as an improvement/upgrade.
But I 

suggest doing it every 10 years or so; I've heard of quite a few broken 

Campys in my 33 years with these beasts but none in the 1st 10 years of 

ownership, so I'm guessing on the safe period. Good luck- J Deryke 

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