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Re: torque conv./ inner tubes
>Message-ID: <199701111825.LAA31274-at-poodle.pupman-dot-com>
>X-Authentication-Warning: poodle.pupman-dot-com: bin set sender to tesla using -f
>Date: Sat, 11 Jan 1997 11:25:07 -0700
>From: Tesla List <tesla-at-poodle.pupman-dot-com>
>To: Tesla-list-subscribers-at-poodle.pupman-dot-com
>Subject: Re: torque conv./ inner tubes
>
>Subscriber: dbell-at-baygate.bayarea-dot-net Sat Jan 11 10:47:34 1997
>Date: Fri, 10 Jan 1997 08:50:22 -0800 (PST)
>From: Dave Bell <dbell-at-baygate.bayarea-dot-net>
>To: tesla-at-pupman-dot-com
>Subject: Re: torque conv./ inner tubes
>
>Kevin Nardelle (knardell-at-accesscom-dot-net) posted:
>
>> I have a bottle of CuS04 crystals but when I tried to plate something made
>> out of nickel, the Cu formed very very thin and took a very long time to do
>> so. I used 5,12,24 VDC 1.0A and the effect did not change much.
>
>Kevin, the problem here is that, once you have enough voltage
>to pass a given current through the plating solution, the voltage
>*doesn't matter*! It's all in the current and time. One Amp is
>also pretty low, if you want thick plating. I don't recall the
>exact values of Avogadro's and Coulomb's constants right now,
>but to within a few percent, it takes 10^5 (100,000) Amp-Seconds
>of current to transfer one Mole of mono-valent ions. Since you
>are dealing with reducing Cu++, it would take 200,000 Amp-Seconds
>to plate out 63 grams of copper. This would cover roughly
>7100 square millimeters of surface, 1 millimeter thick.
>
>A toroid one meter in diameter, with a 20 cm cross-section (not
>all that big, by standards of THIS group, at 40"x8"!) has a
>surface area of almost 1.8 million square millimeters, or
>something like 250 TIMES the above 63 gram surface, if
>one millimeter thick. This would take 1.6 YEARS at one Ampere.
>
>> I don't know what the amounts were that I mixed, water/CuSO4. Do you
>> think if the solution was strong enough you would get even 1/8" out of
>> it?
>
>The above (40"x8") toroid, one millimeter thick, would consume
>39 kilograms of copper. Ideally, your copper should come from
>the electrode you are plating from, not the electrolyte solution.
>You should only need sufficient CuSO4 to carry the ionic
>current from copper cathode (+ supply) to workpiece (- supply).
>
>> I very much like the idea and would like to hear how it comes out. I
>> might try to plate a rubber ball the same way just for fun and see if I
>> can get it thick enough. I'll let you know my findings.
>
>I think that's the way to start!
>
>Dave
As do I. Plating is a very good idea. Starting out small is an
excellent idea. One thing that we should remember is that plating
any object with pure smooth DC will likely result in uneven
thicknesses depending on the distance from the plating point or
plating surface to the opposite electrode. Unless you saturate the
solution electrically then the points closest to the other
electrode will plate thicker.
So, either very good dimensions of the plating tank are needed
(i.e., to plate a toroid the plating tank should be exactly
toroidal as well, with the graphite-coated inner tube suspended
inside the plating chamber it would be like a doughnut within a
doughnut), or else deliver the plating current in high-peak-current
low-average short duration pulses which saturate the
current-carrying capacity of the plating solution. This "saturation
effect" will make for a more even plating of copper all around. I
am not sure of the frequency of the pulses, I would imagine that
anything between 10 Hz and 1KHz would work. 60Hz sounds likely.
One drawback with this pulsing technique is that the resistance of
the graphite will be a big problem to high-current pulses at the
beginning of the plating job. So it would be best to start the
plating job with smooth DC until you get a thin copper plating all
over. To do this, you might have to change the position of the
other electrode often. Once you have an even thin coat of copper
all over the tube, then I think you can go over to pulsed DC for
more even thicker plating.
This experience is from back in my chem lab days. It is why
lead-acid cells charge better on rectified but UNfiltered DC,
rather than smoothed DC. The charge is distributed better over
the surface of the plates.
In some plating cells if you use pure DC in a very quiet
environment, the plating will even grow in long spiky filaments!
Why? Because this process displays positive-feedback upon itself.
The plating rate depends on the current, and as the filaments grow
from the plated surface to the other electrode, the resistance of
the liquid between the plating spike and the other electrode falls.
The current goes up in that part of the solution and
correspondingly DOWN in other parts of the solution (the spike hogs
the plating current), Thus the plating rate goes selectively up on
the spiky filament, and so the plating on the spiky filament grows
faster than the surrounding area. You can modify or ward-off this
annoying effect with with external magnetic fields to stir up the
ions in the solution, or by just by using a low-duty-cycle pulsed
DC source for the plating current. Instantaneously forcing the
solution between the electrode and the end of the spike into
saturation forces the current to move out and flow to other more
far-away places on the plating surface.
Does anyone else have any plating experience in this area? I know
the effects but I don't know the currents or duty cycles used with
the different strengths of CuSO4 solution. I suppose I could
calculate them. Off hand, my estimate of the duty cycle you might
need is between 1 an 10% , that is, the peak plating current would
be somewhere between 100 times and 10 times the average current.
I look forward to your results!
Fred W. Bach , Operations Group | Internet: music-at-triumf.ca
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