On Mon, 20 Aug 2007 13:26:24 +0100, "Ron(UK)"
wrote:

Ross Herbert wrote:

The common GPO 3000 had the copper slug embedded into the
armature.

No Ron, the 3000 type relay armature was fitted with a small brass
residual stud to ensure the armature was not unduly held by
residual
magnetism in the core on releasing, NOT a copper slug.


You are probably correct copper/brass non ferrous anyway

Copper is too soft and quickly becomes thinned out requiring the
armature to be replaced too soon. Brass is much harder and takes a lot
longer to wear out.


impulsing relays used an adjustable residual stud (brass screw and
locking nut)
so that the residual gap could be set according to specific
requirements.

I imagined that was to adjust the throw of the armature to provide
and
also take care of the residual hang.

I don't understand the term "residual hang".

The travel of the armature was adjusted by bending it in a armature
bending tool. This was set to allow the specified travel and
functioning of all springsets fitted tothe yoke. The residual stud
adjustment on the armature was to allow release time adjustment
without unduly affecting the magnetic force attracting the armature to
the pole piece on operation while at the same time allowing periodic
resetting to compensate for wear.



Here is a pic of a 3000 type relay with a 1" heel end slug and an
adjustable residual stud.


I don't recall seeing one just like that, all the GPO types we used
had
the coil full length of the frame, some did have a D shaped shading
pole
set into the armature end of the pole.

We also used a later type of GPO relay, exactly the same in design
but
slimmer frame and coil.

Life was so much simpler back then: GPO relays, Bulgin microswitches,
Crouzet motors, Honeywell timers... Selenium rectifie... erm well
praps
not!

GPO relays are exactly what I have been talking about.

That relay in the pic was a 3000 type with heel end slug. The 3000
type relay was the standard relay used in all BPO Pre-2000 (later
issue), 2000 type SxS and SE50 exchange equipment from the 30's til
late 60's. The smaller brother to it was the 600 type relay but these
found only limited use in exchange equipment. None of the relays used
in exchange equipment that I worked on from 1956 - 1993 were fitted
with a D shaped shading pole. All 3000 type relays which required a
slugging effect were fitted with a cylindrical slug as shown in the
pic.