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Grooved Bobbins For Segmented Windings

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Patrick

Wed Mar 23 2011, 01:15AM

Registered Member #2431 Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639

Have you seen my insulators here on the forum?

jpsmith123

Wed Mar 30 2011, 01:36AM

Registered Member #1321 Joined: Sat Feb 16 2008, 03:22AM
Location:
Posts: 843

I thought I'd have the feed-through insulators completed by now, but I should've known better at this point.

Everything I've done so far seems to be just barely at the limit of what's possible and/or practical to do; between limitations with this lathe, limitations with materials, limitations with money for tools, parts, etc., it all adds up to a breathtaking PITA.

Maybe if I have some luck, I'll finally be ready to pot this thing in another week or so.

Patrick

Wed Mar 30 2011, 02:23AM

Registered Member #2431 Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639

jpsmith123 wrote ...

I thought I'd have the feed-through insulators completed by now, but I should've known better at this point.

Everything I've done so far seems to be just barely at the limit of what's possible and/or practical to do; between limitations with this lathe, limitations with materials, limitations with money for tools, parts, etc., it all adds up to a breathtaking PITA.

Maybe if I have some luck, I'll finally be ready to pot this thing in another week or so.

dont abandon your work, keep going, I have the same problems. Being so hard will make our victory even better.

See if you can find small cheap quantities of these for potting:

Henkel E1300 Common Electrical Epoxy, Potting.
Insulcast SET1-140 Thermally Conductive Epoxy, Potting
Quantum Silicones QSIL40 Common Electrical Silicone for small devices, Potting.

jpsmith123

Wed Mar 30 2011, 01:58PM

Registered Member #1321 Joined: Sat Feb 16 2008, 03:22AM
Location:
Posts: 843

Here's the stuff I was attempting to order...when they told me it was no longer available:

Excellent specs, I would say...best combination of properties I've seen so far.

The manufacturer, "Resin Technology Inc." is really "mysterious", and it's hard to talk to anyone directly at the company who can supply any information. They seem to always refer me to third parties who then have to "get back to [me]".

Anyway, I'm now looking at an epoxy marketed by Aavid Thermalloy "Ther-o-Bond 1500". It seems to have good specs (as far as I can see), but guess what, it's apparently also made by the mysterious "Resin Technology Inc.", and it's also very expensive.

At this point I'm still looking, so I'll check out the products you mentioned.

James

Wed Mar 30 2011, 06:01PM

Registered Member #3610 Joined: Thu Jan 13 2011, 03:29AM
Location: Seattle, WA
Posts: 506

You can get silicone potting compound from TAP Plastics. They have epoxy too, but it's cheaper to get that from US Composites or Aircraft Spruce.

For oil I like to use food grade mineral oil. It's nice and clear, easy to work with, and pharmacies sell it as a laxative. I'm still looking for a local place to get gallon jugs of it though.

jpsmith123

Wed Mar 30 2011, 06:30PM

Registered Member #1321 Joined: Sat Feb 16 2008, 03:22AM
Location:
Posts: 843

Hello James,

I've found that there are lots of places to buy relatively cheap RTV and epoxy. The problem is, they usually have no specs (or very limited information) on the material.

Afer having invested many hours of time, some money, and suffering lots of aggravation, I'm not inclined to take chances on the suitability of cheap generic products.

Basically I'm looking for something that has a relatively low viscosity, is at least moderately thermally conductive, has low loss (i.e., a low dissipation factor), high dielectric strength, and a CTE that's somewhere in the ballpark of the CPVC material I'm using. This seems to rule out most cheap, generic materials.

As it turns out, about 10 minutes ago I found a company that seems to have what I want, at a cost of $50 in a pint quantity. I think I'm going to try to order some and see what happens.

Regards,
JP

James

Wed Mar 30 2011, 10:07PM

Registered Member #3610 Joined: Thu Jan 13 2011, 03:29AM
Location: Seattle, WA
Posts: 506

I just looked at US Composites

and noticed that they sell rubber potting and molding compounds too. They have datasheets for many of the products.

jpsmith123

Thu Mar 31 2011, 03:37PM

Registered Member #1321 Joined: Sat Feb 16 2008, 03:22AM
Location:
Posts: 843

Can you provide a link to some of these data sheets?

Daedronus

Thu Mar 31 2011, 03:57PM

Registered Member #2329 Joined: Tue Sept 01 2009, 08:25AM
Location:
Posts: 370

Would white delrin be a good choice for a bobbin?
For something like a flyback transformer...

jpsmith123

Thu Mar 31 2011, 09:39PM

Registered Member #1321 Joined: Sat Feb 16 2008, 03:22AM
Location:
Posts: 843

I've never done anything with Delrin, but in looking at its properties, it seems like a potentially useful material for a bobbin.

Depending on how you use it however, one potential issue might be its low surface energy; i.e., most adhesives will not stick to it (unless the surface is corona treated or something).

One reason I decided to go with cpvc is because I can glue/epoxy the pieces together.

In looking at mechanical, thermal and electrical properties, and of course, cost and availability, CPVC seemed like a good choice to me. I wish it had a lower dissipation factor, but I guess you can't have everything.

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