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Phenolic discs for whimshurts? Answered

So recently I found a webpage about someone using Phenol for a rotary spark gap for a Tesla, I had never heard of this material and don't know too much about it. For a while now I have wanted to make a whimshurst that is larger than the one I currently have (bought online, a gift from my family) but with my current one i have an issue with the acrylic discs not only not being balanced but also warped causing them to start vibrating on their shaft making it harder to turn the handle. I figure that because every piece of acrylic i have ever worked with has been warped that is would be best to find an alternative. My question is, would it be easier to keep phenol flat and balance or would it be best to stick with acrylic? another thing im curious about is this a material that would even work for this application?

Lastly i would like to say that i did try doing a little research on this and didnt come up with anyone trying it for this purpose, i know that in some cases static can act a little differently than normal high voltage arcs (say, from a microwave oven transformer) which brings me to this question.

P.S. im not sure what category this should go in, if anyone thinks there is a better one let me know and i will change it.

Discussions

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Jack A Lopez

Best Answer 3 years ago

I think this material you call, phenolic, or phenol, is this stuff,
https://en.wikipedia.org/wiki/Phenol_formaldehyde_...

The word "phenolic" is probably a good generic name for it, although I humbly suggest you stop referring to it as "phenol", because that is a completely different chemical,

https://en.wikipedia.org/wiki/Phenol

and that could confuse, or annoy. Maybe. Maybe I'm just being pedantic, and everyone except me, just totally knows what you mean regarding this plastic you call "phenol", like that's the same word as "phenolic".

Also the stuff you probably want is a composite, sheet material, made of phenolic reinforced with fibers, the same composite material they use to make circuit boards. This page,
https://en.wikipedia.org/wiki/Novotext
calls it Novotext(r), Harex(r), Tufnol(r), Micarta(r), and those might be the names people actually recognise it by, or use to sell it. I dunno. Steve calls it Tufnol(r), like he's actually familiar with it.

In contrast, that stuff they call Bakelite(r) is phenolic mixed with wood powder, or some cheap filler, which probably makes it weaker. I mean that's in contrast to this Tufnol(r), phenolic mixed with fibers, which I would expect makes it stronger.

That is if you actually want it. I don't know if that's the best material for your Wimshurst machine or not.

By the way, there are other electrostatic machines besides Wimshurst. For a long time I have wanted to build a dirod machine, ever since I read about them here,
http://www.cavemanchemistry.com/dirod.html

Some time later, I discovered a huge collection of electrostatic machine designs, here,
http://www.coe.ufrj.br/~acmq/electrostatic.html

Coincidentally, the author of that page built a Wimshurst machine, described on this page,
http://www.coe.ufrj.br/~acmq/wimshurst.html
and he says he made the disks for his Wimshurst machine out of acrylic. He also claims vinyl (PVC) LP records will work too, but "the result is rather ugly".

I wish I had some firsthand knowledge about building Wimshurst machine, but I don't because I've never built one. However, I am hopeful some of these links will be useful to you.

Regarding, category, I think electrostatic machines belong in "Science", in the "Technology" category.

In contrast, if this were a more practical kind of electrical generator, like for powering LED lighting, or recharging batteries, then I think it would belong in "Energy", in the "Workshop" category.

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pmk222Jack A Lopez

Answer 3 years ago

if your interested in dirods you should check out this book:

http://www.amazon.com/Electrostatics-Exploring-Con...

i considered building something like a dirod, van de graaff, or a bonetti and though they would probably be easier to build i have always liked whimhursts more and they are where i started my research on electrostatics so i guess they have a bit of sentimental value in my eyes. thank you for the information.

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Jack A Lopezpmk222

Answer 3 years ago

I'm glad I could help. Also, thank you for the link to that book.

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Kiteman

3 years ago

I've seen Whimshursts built with old LPs for the discs.

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Downunder35m

3 years ago

You might have some luck with old DVD's...

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Downunder35mDownunder35m

Answer 3 years ago

After another round of thinking:
Back when I was young and played with my first tesla coils I used the distributer from some old V8 engine for the rotating sparks.
Bit big and needs work to fit a motor on it but lasts much longer than anything I tried, including the nails on a board...

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steveastrouk

3 years ago

Tufnol would be the best material for this. Its highly insulating, and very stiff and flat, a perfect material for a Whimshurst machine

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rickharris

3 years ago

I think these days it might be quite hard to get phenolic plastics. Many of the Phenol based materials are unpleasant and potentially carcinogenic

Possible Bakelite would have been used and is fairly stable although brittle and hard to find . Tufnol is a form of Novotext a phenol based plastic with high insulating properties. You should be able to find that in engineering suppliers.

If you wanting some modern equivalent try an old vinyl record 45 or LP.