Hi Tedd,
Cardboard tube works fine as a coilform by itself. As long as you bake the
moisture out, then seal it you're all set. Clear polyurethane varnish from
the hardware store works fine and requires no heat curing or special
processing to use. The amount of water paper can retain is rather
surprising. There was a capacitor factory here in Chicago that you could
smell from down the block. It was an odor similar to cheap paper towels
or wet paper bags and was just moisture being drawn from the capacitor
elements in vacuum chambers. Nothing went in soggy- it was just moisture
from the air they were removing from kraft paper and cardboard insulation.
Paper dielectrics were dried for days and there was even one company that
dried sections for something like 2 weeks (nobody knows why) before
impregnation. The cans would be soldered shut under oil- that is they
actually put large soldering irons into the oil tanks and soldered under
oil.
Transformer manufacturers can bake parts at higher temperatures and bake
stuff for less than a day, even if it contains paper. Final curing takes
place in an oven again. These temperatues exceed what most plastic parts
or any dielectric in a capacitor can withstand.
As for polyester resin as a choice, it sounds excellent. They even use it
in reconstituted mica capacitors, which are still by far the most rugged,
highest performing high voltage capacitors available.
On Thu, 19 May 2022, Tedd Dillard wrote:
> Is there any reason besides difficulty to use a cardboard tube or other
> material as an arbor and use fiberglass fabric and epoxy Resin to make a
> form?
>
> On Thu, May 19, 2022, 6:00 PM <pupman.com@xxxxxxxxxxxxxxxxxxx> wrote:
>
>> US plastics sells extruded 4" OD acrylic at $71.58 for a 6 foot piece,
>> which isn't too bad. A local plastics supply house if you have one can
>> chop it up if they have it in stock. 24" might fall into the scrap
>> category too.
>>
>> Acrylic is pretty, and solvent welds nicely. It's free of compounding
>> agents that leak out too.
>>
>>
>>
>> On Thu, 19 May 2022, Joshua Thomas wrote:
>>
>>> " It can be noticed that PVC isn't used in the electrical industry
>> outside
>>> of low voltage wire insulation. It's not a great choice, especially for
>>> high voltage applications. We just use is as it's good enough, and at
>>> least in north america, very available, and at a reasonable price as it's
>>> the cheapest of all plastics."
>>>
>>> No kidding! I tried pricing 4.00" OD acrylic and polycarbonate - yikes!
>> 24
>>> inches of acrylic was over $225.
>>>
>>> On Thu, May 19, 2022 at 9:12 AM <pupman.com@xxxxxxxxxxxxxxxxxxx> wrote:
>>>
>>>> In general, PVC cannot be epoxied.
>>>>
>>>> There is nothing wrong with mechanical fasteners on a PVC pipe. Anybody
>>>> with internal arcing on the inside of secondary is doing something else
>>>> wrong. The voltage at the bottom of the secondary is zero. There is no
>>>> reason to overcomplicate something as simple as a binding post.
>>>>
>>>> PVC pipes are not clean when you buy them.
>>>>
>>>> Wash and scrub them, including the bore before use. You don't know what
>>>> release agents or plasticizers are on those surfaces. PVC pipes (or
>>>> anything made of "PVC") is a complex mix of additives as pure PVC is
>>>> completely useless as a final product.
>>>>
>>>> It can be noticed that PVC isn't used in the electrical industry outside
>>>> of low voltage wire insulation. It's not a great choice, especially for
>>>> high voltage applications. We just use is as it's good enough, and at
>>>> least in north america, very available, and at a reasonable price as
>> it's
>>>> the cheapest of all plastics.
>>>>
>>>>
>>>> On Wed, 18 May 2022, Joshua Thomas wrote:
>>>>
>>>>> Hi Jim,
>>>>>
>>>>> It looked to be the copper side that failed. I had cleaned both
>> surfaces
>>>>> with isopropyl before using the epoxy; perhaps I needed to wait a bit
>>>> long
>>>>> for the iso to clear up.
>>>>>
>>>>> I really not have had any great results trying to use epoxy (Bob Smith
>>>>> brand, in this case) with plastic surfaces; but most of my epoxy
>>>> experience
>>>>> is with amateur rocketry, which uses material like phenolic and woods.
>>>>>
>>>>> Joshua Thomas
>>>>>
>>>>>
>>>>>
>>>>> On Wed, May 18, 2022 at 8:14 PM Lux, Jim <jim@xxxxxxxxxxxxx> wrote:
>>>>>
>>>>>> On 5/18/22 4:43 PM, Joshua Thomas wrote:
>>>>>>> Hello Mads,
>>>>>>>
>>>>>>> Thank you for reminding me of your site, I had used it before as a
>>>>>>> reference. I have been sticking to the ?rules? of not putting any
>> holes
>>>>>> in
>>>>>>> the secondary, but I see you?ve gotten away with it on occasion. I
>>>> might
>>>>>>> try using a nylon bolt threaded from the inside to outside as a place
>>>> to
>>>>>>> terminate the bottom of the coil.
>>>>>>>
>>>>>>> On that note, do you have any recommendations for adhesives for
>>>>>>> plastic-plastic (pvc) and metal-plastic bonding? The epoxy I used to
>>>>>> hold a
>>>>>>> piece of copper to a pvc pipe was a complete failure.
>>>>>>
>>>>>> Which side of the joint failed? The copper or the PVC? You have to be
>>>>>> scrupulously clean.
>>>>>>
>>>>>> I use silicone sealer (like for tubs or aquariums) for a general
>> purpose
>>>>>> "glue" - it sticks to most stuff pretty well. It's not good
>>>>>> structurally, but for something that's not seeing a lot of loads it
>>>>>> works ok - good epoxy joints are stronger than the material in some
>>>> cases.
>>>>>>
>>>>>>
>>>>>> _______________________________________________
>>>>>> Tesla mailing list -- tcml@xxxxxxxxxxxxxxx
>>>>>> To unsubscribe send an email to tcml-leave@xxxxxxxxxxxxxxx
>>>>>>
>>>>> --
>>>>> Joshua Thomas
>>>>>
>>>>> My new email address is: joshuafthomas@xxxxxxxxx
>>>>> Please update your information if you have not already done so.
>>>>> _______________________________________________
>>>>> Tesla mailing list -- tcml@xxxxxxxxxxxxxxx
>>>>> To unsubscribe send an email to tcml-leave@xxxxxxxxxxxxxxx
>>>> _______________________________________________
>>>> Tesla mailing list -- tcml@xxxxxxxxxxxxxxx
>>>> To unsubscribe send an email to tcml-leave@xxxxxxxxxxxxxxx
>>>>
>>>
>>>
>>> --
>>> Joshua Thomas
>>>
>>> My new email address is: joshuafthomas@xxxxxxxxx
>>> Please update your information if you have not already done so.
>>>
>> _______________________________________________
>> Tesla mailing list -- tcml@xxxxxxxxxxxxxxx
>> To unsubscribe send an email to tcml-leave@xxxxxxxxxxxxxxx
>>
>