Stewart Warner Amp gauge short circuit?

1941 - 1945, MB, GPW Technical questions and discussions, regarding anything related to the WWII jeep.
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Chuck Lutz
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Re: Stewart Warner Amp gauge short circuit?

Post by Chuck Lutz » Wed Jun 20, 2018 10:45 am

Bertrand:
The 50-0-50 Amp Gauge with the "F" at the bottom of the face has FOUR threaded "studs" attached to the body of the gauge. The TOP and BOTTOM use a "C" shaped bracket to hold the gauge to the back of the dash. The LEFT and RIGHT posts are insulated from the body of the gauge and are for mounting the wiring harnesses.

I can see that the bezel has been removed/replaced on the body of the gauge. If you mean there are only THREE studs on the body then the body is not original to the gauge. If you mean it has four but one is broken off then the body is probably original to a SW gauge. If you can post another pic of the back of the gauge, we can confirm what I just posted above.
Chuck Lutz

GPW 17963 4/24/42 Chester, PA. USA 20113473 (USA est./Tom W.)
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Division Leclerc
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Re: Stewart Warner Amp gauge short circuit?

Post by Division Leclerc » Wed Jun 20, 2018 11:05 am

Thanks Chuck

I have restored this gauge myself, and it seems to be untouched for a very long time, rusted and dirty in and out.
But you're right, maybe one is broken off......I have taken some pics :

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Bertrand
GPW 01/19/1945
Restoration Thread : viewtopic.php?f=4&t=284126

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Re: Stewart Warner Amp gauge short circuit?

Post by Chuck Lutz » Wed Jun 20, 2018 11:17 am

Bertrand….

Yes, you are missing altogether one of the mounting studs and I believe the one still present is too short. If you had an opportunity to find another BODY for a SW AMPERES gauge, I would suggest you swap out that body for one that is in better condition with good mounting studs on it.
Chuck Lutz

GPW 17963 4/24/42 Chester, PA. USA 20113473 (USA est./Tom W.)
Bantam T3-C 1947

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Re: Stewart Warner Amp gauge short circuit?

Post by Division Leclerc » Wed Jun 20, 2018 11:41 am

Chuck Lutz wrote:
Wed Jun 20, 2018 11:17 am
Bertrand….

Yes, you are missing altogether one of the mounting studs and I believe the one still present is too short. If you had an opportunity to find another BODY for a SW AMPERES gauge, I would suggest you swap out that body for one that is in better condition with good mounting studs on it.

OK Chuck, many thanks for your help.
Bertrand
GPW 01/19/1945
Restoration Thread : viewtopic.php?f=4&t=284126

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Re: Stewart Warner Amp gauge short circuit?

Post by YLG80 » Sun Jun 24, 2018 11:04 pm

@ Bertrand
ammeter.jpg
ammeter.jpg (48.73 KiB) Viewed 1460 times
I'm wondering if the parts pointed by the arrows are insulators?
If not, your ammeter is in short-circuit with the ground (housing), for sure.
It would produce a big short-circuit if you connect that ammeter !

There are ammeter gauges without the 2 additional studs perpendicular to the terminals like this one.
I don't like that design more prone to short-circuits but it can be used providing that the bracket insulators are of a good and durable quality.
ammeter_no_studs.jpg
ammeter_no_studs.jpg (42.58 KiB) Viewed 1460 times
Yves
Ford GPW 1943 - Louisville - DoD 12-7-43
serial 164794

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Re: Stewart Warner Amp gauge short circuit?

Post by YLG80 » Thu Nov 15, 2018 5:01 am

The picture here above shows a dangerous assembly which is not correct vs the original drawing!

For those interested in the repair of the ammeter gauge GPW-10850/ A-440047, here is the drawing showing the assembly and particularly the insulator positions in color.
Too bad that the link shunt GPW-10837 has no ohm value mentioned on that drawing.

Does anyone have an information about that "TANK AUTOMOTIVE CENTER BULLETIN n°3" mentioned on the drawing?
Yves
Drawing
THF403905_GPW-10850_GTBS_10850_AMMETER_ASSY-color.jpg
THF403905_GPW-10850_GTBS_10850_AMMETER_ASSY-color.jpg (222.19 KiB) Viewed 1408 times
Ford GPW 1943 - Louisville - DoD 12-7-43
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Re: Stewart Warner Amp gauge short circuit?

Post by dinof » Thu Nov 15, 2018 6:00 am

Getting back to the original post, I was using a 30+ / 30- amp gauge for 45+ years in a street rod. When I had the gauges restored recently, the gauge shop asked me why it was only a 30 max gauge. I said because I was 17, and didn't know any better. He told me to run a "shunt", or in other words, a small wire across the poles as this might not be totally accurate in reading, but will stop the needle of the gauge from "pegging out".

But also, never, never, hook the gauge up to a battery alone.
Dino Falabrino
On the "G" since 1998.
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Re: Stewart Warner Amp gauge short circuit?

Post by YLG80 » Thu Nov 15, 2018 7:03 am

You can calculate a shunt value so that the reading will simply be doubled and you write X2 near the gauge..
Just carefully measure the original shunt and make another one with the same value.
Connect the new one in // with the original.
a small wire across the poles
. I guess you are talking about the length not the section :lol:

As the ohm value of an original shunt is very, very low, you should ask to someone to measure it in a lab, i.e in a local school.
That's an excellent exercise for a student ! They could even build the second shunt to be placed in //.
The Wheatstone bridge: https://en.wikipedia.org/wiki/Wheatstone_bridge
Yves
Ford GPW 1943 - Louisville - DoD 12-7-43
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Re: Stewart Warner Amp gauge short circuit?

Post by Schelvis » Wed Nov 21, 2018 10:18 am

For what it is worth: I used ceramic "hat" insulators or spacers.

They go over the poles/studs and contain a narrow section which fit in the hole of the housing. So you never have any contact between the electrical poles and the housing. I also used a ceramic spacer to make sure that there is no contact possible between the shunt and the housing.

I want to avoid any contact between the positive charges on the poles and the negative/ground on the housing.

Image
Image
Image

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Re: Stewart Warner Amp gauge short circuit?

Post by mdainsd » Wed Nov 21, 2018 11:02 am

Ceramic is the way to go. No worries about heat from the shunt.
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Re: Stewart Warner Amp gauge short circuit?

Post by YLG80 » Wed Nov 21, 2018 12:46 pm

Yes elegant solution.
But do not over tighten the nuts .
I've turned my insulators in Ertalon or Teflon (don't remember exactly) with my mini lathe.

Electronic components distributors have similar pass through insulators of various sizes like these in Nylon or PET up to M8:
https://benl.rs-online.com/web/c/fasten ... nsulators/

Yves
Ford GPW 1943 - Louisville - DoD 12-7-43
serial 164794

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Re: Stewart Warner Amp gauge short circuit?

Post by Schelvis » Thu Nov 22, 2018 12:06 am

Impossible to over tight them. The thread is so fragile after 75+ years that it tears off before you can break the ceramic.

Don't ask me how I know... :shock:


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