* Original msg to: Esondrmn-at-aol-dot-com

Quoting Ed Sonderman:

 ES> Richard,

 ES> I was doing some more testing last night and I think I       
 ES> learned something.  I was using 2 12kv 30ma neons, one       
 ES> static gap and my large 33" discharger. Performance was good 
 ES> with 30 to 34" discharges.  Then I replaced the static gap   
 ES> with the rotary and fired it up again.  Now I got worse      
 ES> performance than I just had with the static gap.  I slowly
 ES> decreased the speed of the rotary and found a point where    
 ES> the performance was better than with the static gap. I had   
 ES> discharges in excess of 36" and they were hot.  

OK, you learned about the need to achieve the correct break rate
for maximum efficiency. Break rates will vary between circuits
and systems, and there is no one speed that works well with all
circuits (or coils). When you start messing around with Tesla
Magnifiers and the balanced tank circuit (equal value of
capacitance on both sides of the primary) you will find the need
for those high RPMs, but on a smaller 1/4 wave coil, the lower
break rates frequently work best.

 ES> This is about the time I lost my last tank capacitor.  


 ES> I thought I was being careful to keep the voltage at about   
 ES> 10,000v - I must have screwed up. 

It is more likely that the duty cycle was exceeded and a hot spot
formed on the dielectric.

 ES> I apparently have been running the rotary WAY too fast.  

Without someone experienced to stand there and look over
everything, it would be very difficult to know these things. 

 ES> I noticed that I did not get any loud pops (kickbacks?) out  
 ES> of the rotary with the neons. When that has happened before  
 ES> it has always been with the pole pig and when the rotary was 
 ES> running at low speeds - at least speeding it up always made  
 ES> it quit.

It may simply be that the sweet spot of RPM has a very narrow
range. By revving the gap up you avoid the possibility of
discharging a fully charged capacitor, but you also avoid

 ES> I talked to Condenser Products this morning.  My capacitor   
 ES> is back in the oil.  They expect to test and ship it next    
 ES> week.  I hope so.  

In my dealings with Condenser Products they have been very
conscientious about their product quality, reliability, and
testing. Their products are sold with the understanding that
every unit is custom made, and tested, to order. Though it may
take longer, you should be pleased with the results.

 ES> I asked them what the dielectric thickness was and was       
 ES> surprised to hear it is only .025. They are using poly-      
 ES> propylene where I used polyethylene .065 thick.  If I am     
 ES> blowing my caps with more than twice the dielectric          
 ES> thickness, how can I expect theirs to hold up?  Is this
 ES> the difference between having the dielectric fully           
 ES> impregnated with oil and not? 

There is a huge difference between commercial clean room
constructed capacitors and a homemade unit. These commercial
capacitors are generally built up from several high value stacks
that are wired in series. The thinner dielectric offers per-
formance advantages, including higher breakdown strength; higher
voltage ratings are achieved by wiring precisely matched stacks
together until the correct value and voltage rating are obtained.
This is before they are pumped down by commercial vacuum
equipment and back filled with oil.
 ES> Let's talk again about fixing my capacitors since I now have 
 ES> two to fix. I am thinking about pulling the rolls out of the 
 ES> cases and hanging them up for a day or two to get most of    
 ES> the oil out of them. 

That's fine.

 ES> Then unroll them until I find the puncture and put the       
 ES> patches in. Do I need to fully unroll them and wipe all the  
 ES> dielectric and flashing off?  Is there contamination in      
 ES> there that I need to get out?  I will flush out the          
 ES> canisters and refill with clean oil.

This all depends on the sooting. As I am sure you noticed, a
plume of soot usually rises out from the roll after the unit
failed. It is best to remove failed units from the oil as soon as
possible to prevent spreading the conductive soot around.
Assuming the worst, here is what you will have to deal with:

Unroll the cap, and at the breakdown site you will find a sooty
oily mess. You will need a roll of high quality paper towels or
lint free wipes, and some petroleum distillate solvent: I have
always recommended PrepSol by Dupont, available where Dupont
finishes are sold. My second choice would be lighter fluid or
white gas. You will also need a sharp cutter, some scissors, and
some medium grade sandpaper.

First wipe away as much soot and oil as possible with dry towels.
Then use a solvent damped towel to remove most of the oil film at
the breakdown site. Cut out and remove the burned and melted
plastic dielectric where the breakdown occurred, and be sure to
check both sheets; I have seen punctures go through both plates
and both layers of plastic.

Sand out the burnt and pitted plates at the breakdown site.
Plates may be holed, or sharply dented. If dented, it is best to
push the dent out with a metal tool or coin, then sand as smooth
as possible. All sanding grit, soot, metal particles, etc.
must be removed with solvent dampened towels. 

Clean the entire repair site twice with solvent dampened towels. 
Cut out the required number of patches, two per dielectric
failure. Make the square patches about 3 inches per side. Place
the patches over both sides of each dielectric failure, and
carefully roll the cap back up as tightly as possible.

Richard Quick

... If all else fails... Throw another megavolt across it!
___ Blue Wave/QWK v2.12