Theories about coil-shielding

[Aziz]

I've been a few weeks ago at the art supplies (Boesner, http://www.boesner.com/suche?search=shellack ). They sell shellac flakes & dissolved shellac too.

This binder is really nice as it dissolves in alcohol. So you can re-dissolve your mixture again and again.
When dried, it is water resistant.

I for one would polish the graphite shielding surface further to lower the shield resistance.
Aziz

[DOOLEY]

How about an old 78 rpm record ???Anything from a junk shop or car boot sale,If alcohol dissolves it,Then you may have a life times supply with justOne record.....

[Skippy]

Shellac is still used to bond 'tubular' bicycle tyres onto wheel rims, so a specialist bike shop / mail-order supplier may have it. It's not used much, nowadays, there are more modern adhesives, and it doesn't stick well to carbon fibre rims, so an art supplier might be a better source.

[Paul99]

Shellac is still used to bond 'tubular' bicycle tyres onto wheel rims, so a specialist bike shop / mail-order supplier may have it. It's not used much, nowadays, there are more modern adhesives, and it doesn't stick well to carbon fibre rims, so an art supplier might be a better source.

Any half respectable paint shop carries shellac..

http://www.bunnings.com.au/feast-wat...lakes_p1567019

When used for wood polishing it is dissolved in methylated spirits or denatured alcohol which you will also get from any paint shop....

http://en.wikipedia.org/wiki/Denatured_alcohol

[Henrikras]

Okay.. Is this the recipe ; First take the graphite powder and mix with alcohol - find the perfect mix 2:10 / 3:10 / 4:10 !!!! (Like I did yesterday and made a utube) Then Paint this mix with a brush and let it Dry up. Then Measure the resistance and If and when you/I are saticefire, Then paint with the Shellac to make a protective layer. And Thats it ?
Or do you allso want to mix the Shellac in the first step with the alcohol and the Powder..? In that case I would say it would Be difficult to work with the lay, after it dryed up.. If the resistance is to low or to high.. The Shellac would make a hard surface don't you think.
Henrik.

[golfnut]

adhesion may be dodgy, as its just crushed beetles

[golfnut]

A lot of the shell plastics will surface melt in acetone.

If one dipped a shell for a short time, removed and plunge into graphite powder and allow to reharden that may be effective - you may burnish for lower R

worth a go on a scrap peice

[Henrikras]

Just working on a experiment... Velox one coil. Want to try a shielding at this wet grass problem coil outside. Found the connection to the inside shielding. It went to the cold side at the RX. Made some outside drainwires and to hold them, used som small piece of tape.
Then I made the mix with only powder and this alcohol I got... One hour paint with the brush, it was difficult to keep the mixture wet to keep a thin lay. Now I got to much and the resistance is down to 150-200 lowest. Tomorrow I will sand it or find a way to get a thinner lay.. Goal is 3-500 ohm, like I did at my sussecfull 7" Deus coil. Before the protecting lack, I will go out a do some test...
If this wouldn't help anything, It can Be taken off easy.
Picture shows the mixture is drying up.
Henrik.

[sinclairuser]

Any half respectable paint shop carries shellac..

http://www.bunnings.com.au/feast-wat...lakes_p1567019

When used for wood polishing it is dissolved in methylated spirits or denatured alcohol which you will also get from any paint shop....

http://en.wikipedia.org/wiki/Denatured_alcohol

not in the uk its not, all the kind of products derived from animal extracts are very specialist, and expensive.
for instance here a french polisher would only use it on a scratch on a piece of antique furniture, a complete panel or whole piece would be done with modern alternatives, solder flux is the same, i'm sure that in some parts of the world rosin pucks are cheaper than a tin of flux, but here only an idiot pays 30 quid for puck to soak there own flux, it only cost 5 quid for ready made tinned flux.
the uk is extremely expensive for some things, some things are completely unavailable, or strictly controlled, traditional yorkshire ham is made with flavoured sea salt as saltpeter is unavailable, some proper madness going on here.
the internet has remade some things available on paper, but try ordering such items in quantity, they either refuse your order or it dissapears in the post.

[DOOLEY]

Acetone eh ???
Interesting,
So could mix graphite with nail varnish remover from local
Pound shop,
And it'll stick like wonderfull stuff to coil casing,
Due to the softening effect of the nail varnish remover !!!!

[sinclairuser]

yes dooley i think its worth a try, i suppose the hard bit is softening up the plastic enough to key the graphite to it, but not so much that it turns to snot.

[green]

Has anyone documented the change in coil resonance using graphite for the shield?

[maikl]

http://en.wikipedia.org/wiki/Shellac quote from the link: "Shellac was once used in electrical applications as it possesses good insulation qualities"


On some Russian forums I read, people tried epoxy resin and graphite, did not get any good because the resin is a good resistor... while the lacquer (nitro and oil) get better results... it might better be some acrylic lacquers mixed with graphite...

[golfnut]

This looks like a good promise on low resistsnce 47 ohms / sq maybe too low??

http://www.mgchemicals.com/products/protective-coatings/emi-rfi-shielding/super-shield-graphite-839


Or this carbon one at 250 ohm / sq

http://www.mgchemicals.com/products/...e-coating-838/

[sinclairuser]

in a previous job we used good old aquadag (brandname,graphite powder you mix with water), and it used to work and stick.
i wonder if something like that would work for us, it may need a bit of liquid soap(washing up liquid), to stick to plastic, i'm just wondering if the lacquer is needed at all.