d'Arsonval Meter Repair

[Paul Hovnanian P.E.]

I'm putting a Weston wattmeter back together and I've run into a bit of
a puzzle.

The repair involved freeing the moving coil/pointer shaft and gently
moving it aside in order to fasten a few turns of the current coil
(stator) down. I managed to do all that without pulling the moving coil
out of the core, which would have involved disconnecting its (very tiny)
wiring.

Now, I've got to put the shaft back. In order to do so, I've got to set
the bottom point into its bearing (similar to a watch jewel) and get the
whole assembly to hold still while I align the top bearing and screw its
adjustment down. But due to the coil spring and wires, the shaft keeps
jumping out of the bottom bearing. Its so small that its difficult to
feel when the bottom bearing is seated (the change in shaft position is
barely perceptible when it drops in. And the bottom bearing is located
deep inside the stator core, so I don't can't see it to line things up.

Any ideas how to hold all this junk in alignment while I reassemble it?

--
Paul Hovnanian mailto:Pa...@Hovnanian.com
------------------------------------------------------------------
In theory, practice and theory are the same, but in practice they
are different -- Larry McVoy

[Dave M]

Paul Hovnanian P.E. wrote:
> I'm putting a Weston wattmeter back together and I've run into a bit
> of a puzzle.
>
> The repair involved freeing the moving coil/pointer shaft and gently
> moving it aside in order to fasten a few turns of the current coil
> (stator) down. I managed to do all that without pulling the moving
> coil out of the core, which would have involved disconnecting its
> (very tiny) wiring.
>
> Now, I've got to put the shaft back. In order to do so, I've got to
> set the bottom point into its bearing (similar to a watch jewel) and
> get the whole assembly to hold still while I align the top bearing
> and screw its adjustment down. But due to the coil spring and wires,
> the shaft keeps jumping out of the bottom bearing. Its so small that
> its difficult to feel when the bottom bearing is seated (the change
> in shaft position is barely perceptible when it drops in. And the
> bottom bearing is located deep inside the stator core, so I don't
> can't see it to line things up.
>
> Any ideas how to hold all this junk in alignment while I reassemble
> it?

I would use a small chunk of Silly Putty to do stuff like that. While I've
never tried to overhaul a meter movement as you are doing, I think it might
do the trick. Silly Putty is pliable and sticky enough to easily grab the
moving parts and hold them in place, while being cohesive enough that none
of the stuff will be left on the parts when you are finished. Dollar stores
still carry it; I have an "egg" in my toolbox now.

--
David
masondg44 at comcast dot net

[N_Cook]

Paul Hovnanian P.E. <pa...@hovnanian.com> wrote in message
news:4AE8D969...@hovnanian.com...

If you succeed, please post back here.
That's one of those jobs over the decades i'd like to have reason to have a
go at. A company in Totton, Hampshire , UK now called (probably not doing
that sort of stuff these days)
http://www.inmar.co.uk/about.htm
maybe just the same address, used to be called Totton Test Instruments
used to do those sort of jobs all the time. Other initially daunting ones
I've had a go at are rewinding magneto coils and guitar pick-up

--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/

[N_Cook]

Paul Hovnanian P.E. <pa...@hovnanian.com> wrote in message
news:4AE8D969...@hovnanian.com...

I'd not forseen that problem in such cases, seeing just the fine and
laquered-in wire on the frame, counting-off and rewind and problems removing
and resetting phosphor bronze hair-spring/s without upsetting them.

For the spindle reseating .
Can you drill out a piece of wooden dowel (as non ferrous),an axial hole the
diameter of the spindle, friction-fit slide over the open end of the spindle
and give you some more positional positivity to replace. If still awkward
then maybe a fine rigid wire in the dowel, felt into place in the jewel
bearing, dowel clamped off /glued to some temporary scaffold that you can
slide the dowel in and out in an alignment . Remove the wire and replace
with the movement spidle and lower the dowel and spindle into place, gently

[tn...@mucks.net]

On Wed, 28 Oct 2009 15:53:13 -0800, "Paul Hovnanian P.E."
<pa...@hovnanian.com> wrote:

>I'm putting a Weston wattmeter back together and I've run into a bit of
>a puzzle.
>
>The repair involved freeing the moving coil/pointer shaft and gently
>moving it aside in order to fasten a few turns of the current coil
>(stator) down. I managed to do all that without pulling the moving coil
>out of the core, which would have involved disconnecting its (very tiny)
>wiring.
>
>Now, I've got to put the shaft back. In order to do so, I've got to set
>the bottom point into its bearing (similar to a watch jewel) and get the
>whole assembly to hold still while I align the top bearing and screw its
>adjustment down. But due to the coil spring and wires, the shaft keeps
>jumping out of the bottom bearing. Its so small that its difficult to
>feel when the bottom bearing is seated (the change in shaft position is
>barely perceptible when it drops in. And the bottom bearing is located
>deep inside the stator core, so I don't can't see it to line things up.
>
>Any ideas how to hold all this junk in alignment while I reassemble it?
>

? Can you put one drop of melted wax onto one end of the shaft?
Melt it away when done?

[David Nebenzahl]

On 10/29/2009 6:58 AM tn...@mucks.net spake thus:

Far too messy, I'm guessing, and risk of damage from whatever heat
source you'd have to use.

--
Who needs a junta or a dictatorship when you have a Congress
blowing Wall Street, using the media as a condom?

- harvested from Usenet

[Baron]

Paul Hovnanian P.E. wrote:

> I'm putting a Weston wattmeter back together and I've run into a bit
> of a puzzle.
>
> The repair involved freeing the moving coil/pointer shaft and gently
> moving it aside in order to fasten a few turns of the current coil
> (stator) down. I managed to do all that without pulling the moving
> coil out of the core, which would have involved disconnecting its
> (very tiny) wiring.
>
> Now, I've got to put the shaft back. In order to do so, I've got to
> set the bottom point into its bearing (similar to a watch jewel) and
> get the whole assembly to hold still while I align the top bearing and
> screw its adjustment down. But due to the coil spring and wires, the
> shaft keeps jumping out of the bottom bearing. Its so small that its
> difficult to feel when the bottom bearing is seated (the change in
> shaft position is barely perceptible when it drops in. And the bottom
> bearing is located deep inside the stator core, so I don't can't see
> it to line things up.
>
> Any ideas how to hold all this junk in alignment while I reassemble
> it?
>

Have you tried using paper shims to support the rotor whilst you fix the
top bearing ?

--
Best Regards:
Baron.