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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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