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Re: torque conv./ inner tubes



 
On Tue, 7 Jan 1997, Tesla List wrote:

> Subscriber: SSNSanders-at-aol-dot-com Tue Jan  7 22:30:48 1997
> Date: Tue, 7 Jan 1997 18:33:48 -0500
> From: SSNSanders-at-aol-dot-com
> To: tesla-at-pupman-dot-com
> Subject: Re: torque conv./ inner tubes
> 
> In a message dated 97-01-07 03:33:06 EST, you write:
> 
> << 
>  	I used this idea last year in constructing the small toroid that I
>  have.  I used a 15"(?, not sure) wheelbarrow tire and stuffed it with
>  newspaper for rigidity.  I then covered it in Al tape, then smoothed.  It
>  works fairly well, but I have since moved on to a Duct toroid, as this one
>  wasn't large enough for my six inch coil.  I plan to wind a 4" sometime
>  soon, and then the wheelbarrow tire will again see service.
>  
>  Stan Harle
>  Alamogordo, NM
>   >>
> I want to rub down a tire of this size with graphite and somehow keep it
> under a solution of CuSO4 and plate it with copper to a thick coating. I just
> dont know how to keep it covered with solution with air in it and it has to
> have the air to maintain shape. Any ideas?  Stephen

I have a few. I've been working on this and some related problems since 
around springtime, though I've gone about it in some very different ways.
Now, if you want to try for a very thick copper coating, you may come up
with something, but there may be easier ways. I'll give a real rough
summary of what I've been trying (and been quite pleased with) and you
can take or leave it, or maybe find something useful therein.

I've been working on several processes to produce rigid shapes from 
polystyrene. I can then make a polystyrene laquer by dissolving polystyrene
scraps in tolulene or tolulene/acetone mixtures. The laquer is then loaded
with a mix of powdered graphite and conductive lampblack. Both materials 
conduct well, but their particle size is radically different, with the
smaller particles (conductive lampblack) filling in the spaces between the
graphite. This produces a conductive laquer that adheres well to other
polystyrene forms and can be plated reasonably well. By the way, you'll 
find that if you try to just rub graphite on the inner tube without some
sort of binder to hold it on, it will come off in large quantities, forming
a conductive layer that will float on the top of your plating vat. You're
also likely to get the graphite distributed unevenly on the surface of the
inner tube, causing some spots to be more conductive than others. Getting 
a nice, even, solid plate that doesn't flake off is difficult 
even when everything is well controlled; 
you're asking for extra variables that you don't need.

One other post mentioned using aluminum powder. I don't think it was in
relation to plating, but if anyone should try it, the aluminum will very 
quickly react with the copper sulfate, producing a copper powder that
won't adhere. Plating copper on aluminum is a difficult problem, usually
using an intermediate layer of plated nickel. (But don't use nickel plate
just yet! more on that in a bit.)

One of the most promising processes for forming the polystyrene involves 
making a papier mache' negative mold of the shape, (say, a half-toroid) 
that then gets its inside painted with several layers of the conductive 
laquer. Further layers of non-conductive laquer are added, and possibly 
the layers are bulked up with thin layers of a gum made from 
polystyrene and acetone. This gum has a number of problems, however.
In some cases, I've worked with laquer that uses both acetone and tolulene
as the solvent, because tolulene evaporates very slowly, but dissolves 
polystyrene well, while acetone doesn't dissolve it at all, but softens it
to a gum, but it evaporates (frighteningly) quickly.

By the way, the tolulene/polystyrene laquer at the right concentration, is
essentially identical to airplane glue, according to an older edition
of "Toxicology of Commercial Products". Newer glues have extra additives to
keep kids from sniffing it, but are basically the same.

I mention this because I thought I'd let you know what you're
dealing with if you want to experiment before I get the processes cleaned
up (which may be a long time). Also, the styrofoam we throw out by the 
ton is a fine source of polystyrene. Many specialized solvents at the 
hardware store are largely acetone and tolulene, though what you pay for
a pint of the stuff, I can pay for a gallon of tolulene at a large, well
stocked home center. 

I should point out that both the solvents mentioned are highly flammable,
and not at all healthy to breathe. I use a NIOSH-approved respirator, with
filters designed to remove organics, and work outside; it should be 
tragically easy to build up an explosive cloud of vapor indoors. Don't
even think of doing this.

Anyway, once the polystyrene form is thick enough, it's soaked in water, 
which softens the papier mache' mold, which is then scraped away. The 
conductive laquer is then sanded to a fine finish, and the plating is done
with a fairly standard CuSO4/H2SO4 solution in water. Since we're not 
plating metals, no cyanides should be needed as complexing agents. 

I should also mention that I've made some really nice polystyrene tubes
using various sized oatmeal boxes, glued together in-line,
as the negative mold for the polystyrene
laquer. There are a number of tricks that need to be played to keep them
from going out-of-round while the whole thing is curing. These should make
some nice hi-Q secondary forms, once the paper is removed.

I've not built any coils with them yet; I'm still fine-tuning the processes
I'm working with, trying to get something that's not too time consuming and
yet produces an excellent result without cracks or voids. 

I'm expecting to write up something 
eventually for the TCBA newsletter, but I'm looking to produce a process
that has a lot of margin for error. Right now, little changes can make the
difference between an excellent result and a mediocre one, and a lot of
coilers seem to like to make changes and substitutions without first 
following the directions exactly. This may lead to a lot of poor results,
and some discrediting of some techniques that work really well if done
properly.

Right now, I'm doing precious-little with the laquers, because it's 
wintertime, and I can't work outdoors very well. When the weather got
colder, I got a little more involved in the plating end, though that's
not really going very fast now, as I have very little spare time. If you
want to experiment with plating, start with a number of very small items, 
work with various current densities, and compare the results. If you just
hook up the workpiece in the tank with the current density varying all 
over the surface of the workpiece, and you're expecting a nice, solid, even
plate, you're gonna be disappointed. Getting it right will take some time.
Do pilot parts first, and take a lot of data. 

Also, if you look through the plating literature, you'll see that it's 
just about as easy to nickel plate as it is to copper plate. I'd strongly
discourage this right now for anything that might get make contact with a
discharge. Besides the nickel salts being toxic, there's an unimaginably
toxic compound called nickel-carbonyl that seems to form easily in 
certain energetic situations, and might possibly form on contact with a
discharge. (I don't know for sure, but wouldn't risk it for the world). 
Nickel-carbonyl's toxicity makes cyanide look like potato chips, and is a
liquid that's very easily vaporized so that you don't need to touch or
taste it; you only need to breathe. The CO2 in the air seems to be all 
that's required to form the stuff with the nickel. Again, this may or
may not be a possibility, but there are many manufacturing processes where
there's great care used not to form the stuff, and it would be wise to
follow suit.  

Well, that's an extremely crude summary of some of my work last summer; it
may be of interest to some of the more adventurous/inquisitive/insane (take
your pick) members of the list. Right now the whole thing is very messy, but
can produce some really nice parts. Hopefully, the process will get 
cleaned up in the months to come.

Wes B.