[Hallicrafters] Blooming meter: my explanation (I think)

[Roger]

Although stress relieving would help, the problem is apparently a
manufacturing defect.

Be it steel, brass, copper, or aluminum the meter cups are basically
manufactured in the same way.

Basically:
They start with a billet (slug) of metal.  The metal is drawn, by being
forced into a die the same shape as the outside of the meter housing. (the
finished dimensions of the housing).  A ram with the inside dimensions is
driven down the inside causing the metal slug to flow up the sides forming
the cup.

I actuality, they do this in steps starting with a shallow cup and with
repeated steps the cup gets deeper and deeper until the final shape is
reached.  Often it is necessary to stress relieve the piece between steps.

IF they try to eliminate steps by increasing the amount extruded in each
step and/or eliminated stress relieving the work hardened material between
steps, the final result will be brittle (work hardened), possibly uneven
thickness, and prone to splitting.  In the case of brass those stress lines
will eventually separate giving the "blooming" effect.

I've gotten in a hurry with copper, aluminum, and brass and ended up with
the same effect without having to wait for age to take care of the piece. It
was a "blooming" failure when I finished.<sigh>

It appears to be a simple process but many variables have to be taken into
account when shaping a meter case/cup.

Roger Halstead (K8RI EN83 & ARRL Life Member)
WWW.RogerHalstead.com
N833R - World's oldest Debonair? (S# CD-2)


>
> I have had a few of these old meters "bloom" in my old rx's (and it's not
limited to Halli's either).
>
> You figure that the meter cases were made of cylindrically bent brass
pieces of metal. Well, as time progress (you know, 50 years plus), the brass
tends to crystallize and fracture. The case hasn't been stressed relieved
(i.e. put over a flame to soften out those stress points as a result of the
cylindrical bending). Well, the case now splits at various points which
results in the "petaling" effect you see (aka a "bloom").
>
> So....whadya think of that explanation? I did o.k. in my materials class
and did manage to pass Navy Nuke School before becoming "nuke waste" at
Arco, Idaho back in 1984. Let me know what you think. Cal. N6KYR.
>
>
>
> ---------------------------------
> Do you Yahoo!?
> Yahoo! Tax Center - File online, calculators, forms, and more
>
> --- StripMime Report -- processed MIME parts ---
> multipart/alternative
>   text/plain (text body -- kept)
>   text/html
> The reason this message is shown is because the post was in HTML
> or had an attachment.  Attachments are not allowed.  To learn how
> to post in Plain-Text go to: http://www.expita.com/nomime.html  ---
> _______________________________________________
> List Administrator: Duane Fischer, W8DBF **for assistance**
> dfischer at usol.com
> ----
> Hallicrafters Collectors International: http://www.w9wze.org
> ----
> http://mailman.qth.net/mailman/listinfo/hallicrafters
>