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replacing inner insulators of GE 42D6G series edgewound grid
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Author:  JeffH [ Tue Nov 20, 2018 10:56 pm ]
Post subject:  replacing inner insulators of GE 42D6G series edgewound grid
Anyone have any success with ordering replacement parts similar to what is pictured?

These are the "comb" insulators that are inside of GE elliptical edgewound resistor units in the 42D6G series.
The particular part shown is 12D535, an 11-groove insulator.
These insulators are made of a refractory material to withstand heat, and support the individual edgewound coils. A sheet metal plate slides through the center of them.

I see that Ohmite purchased this product line as their WLRD6G series, but it isn't clear if they sell the individual insulator combs. We have an application where these combs are deteriorated but the resistance ribbons themselves are perfectly fine. Don't want to spend big bucks replacing the entire thing.

I have successfully taken the center steel plate out and replaced a few insulators with the handful of new old stock spares we had. But we need a bunch more.

Attachments:
12d535-small.jpg
12d535-small.jpg [ 110.76 KiB | Viewed 6972 times ]
Author:  bum_401K [ Fri Nov 23, 2018 6:01 pm ]
Post subject:  Re: replacing inner insulators of GE 42D6G series edgewound
Previously at the Pennsylvania Trolley Museum we had a GE Edgewound bank have a failure in that sheet metal rusted out that held ceramic cores you are asking about.

Yes, Ohmite will make replacement resistors but at that time they were over $900 each with minimum number of pieces and the bank took several part numbers $$$$. Fortunately some gently used units were found and a sigh of relief was shown.

Fast forward to 2016. I had to design a reproduction headlight resistor for West Penn 832. The Electric Service units used two ceramic parts, the insertable bushing at the end of each tube and a terminal block that also feed through the sheet metal. The number needed varied depending on the size of the resistor needed. I made drawings and also had a couple of samples. I contacted quite a number of possible sources and finally found one that could and did produce the parts. We bought extra has we have five or six future restorations that need the parts. They were very reasonable and the part quality was excellent and they fit well.
Contact info is below.
Dennis Bockus

Andy Higgins
International Ceramic Engineering
235 Brooks St.
Worcester, MA. 01606
Ph: 508-853-4700
Fx: 508-852-4101
ahiggins@intlceramics.com
http://www.intlceramics.com
Author:  NYCRRson [ Fri Nov 23, 2018 7:16 pm ]
Post subject:  Re: replacing inner insulators of GE 42D6G series edgewound
Have you tried carving them out of firebrick;

https://www.mcmaster.com/9355k2

With a masonry saw;

https://www.mcmaster.com/6914a61

Maybe clean them up with diamond files;

https://www.mcmaster.com/diamond-files

Might take a bit of patience, but it could be cost effective.

They make machinable ceramics that can be cut on lathes, milling machines etc. They are more expensive than firebrick.

Good luck, Kevin
Author:  kew [ Fri Nov 23, 2018 8:26 pm ]
Post subject:  Re: replacing inner insulators of GE 42D6G series edgewound
NYCRRson wrote:
Have you tried carving them out of firebrick;

https://www.mcmaster.com/9355k2


I was thinking the same, except I'd try a stone cutting blade in an angle grinder or powered bench saw. Have to rigidly mount everything and watch out for the dust!
Author:  bbunge [ Sat Nov 24, 2018 12:17 am ]
Post subject:  Re: replacing inner insulators of GE 42D6G series edgewound
Country and city parks agencies in some locations have pottery and ceramic classes and facilities with kilns. So do some middle and high school art departments. Out of season, but you might find an interested ceramic worker at a local arts and crafts show. You might get lucky and find a teacher who has some knowledge of molding or an interest in exploring how to hand form something like that. There are many types of "mud," some research might even point to varieties meant to be used as insulators.

Unless there is more complexity there then I'm realizing from the photo...
Author:  Tony Pignaloni [ Sat Nov 24, 2018 12:50 am ]
Post subject:  Re: replacing inner insulators of GE 42D6G series edgewound
Or contact Ohmite and see if they cell the ceramics seperately?
Author:  JeffH [ Sun Nov 25, 2018 12:47 am ]
Post subject:  Re: replacing inner insulators of GE 42D6G series edgewound
Thanks for the replies. If I can find someone at Ohmite who can answer the question of whether they will sell the insulators, I'll let everyone know.

I may also contact the custom ceramics place that Denny from Arden recommends, if the OEM
pieces are not obtainable.

Regarding various ceramics, remember, it must be a good electrical insulator too!
Author:  JeffH [ Thu Nov 29, 2018 10:33 pm ]
Post subject:  Re: replacing inner insulators of GE 42D6G series edgewound
FYI Ohmite will not supply the internal parts. Perhaps this is because they do not make them but rather purchase those parts from another vendor.
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