Re: Cornell-Dubilier caps (was salt water caps or buckets?)

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Mark Broker by way of Terry Fritz <twftesla-at-uswest-dot-net>" <broker-at-uwplatt.edu>


>
>>
>>
>> I noticed you're using Cornell-Dubilier caps.  I have a bunch of these
>> (.047uF 3000vdc) that I was planning on using for an MMC.  Then I found
>> a doc on one of Terry's pages (which I can't find now -  it listed
>> "good" caps and "bad" caps for MMC's), and the Cornell-Dubilier's were
>> the only "bad" cap listed.  I know somebody else on the list used these
>> and they blew rather easily.  Are they working for you?  Maybe the ones
>> you have are constructed differently - mine are pure metallized film, no
>> foil (I unrolled one).
>
> I believe Robin Coprini is using the same ones as we are, and he's got a Pig
> system on his. Ours came directly from CD (not a distributor) as part of
> their sponsorship of the Group. We've pounded the caps several times and
> never had a failure. They've been run below freezing, and moved dozens of
> times. Maybe our MMC is different. I've never seen one built like ours (and
> having spent 4 days drilling holes I know why) most of them are VERY
> different. I didn't read Terry's chart (good thing too) and we didn't pick
> CD, they picked us. We begged every cap producer out there. CD was the first
> to accept us for sponsorship. It took us almost a year to get a cap sponsor,
> and it has definately been worth it. After we got the company, Mark Broker
> speced the caps and designed the MMC electrically. We spent a month
> scrounging materials (Lexan, resistors, etc) then we all got together here at
> Little St to ! build them. On the first day we decided (I have no idea why)
> to radically change the design (we were gonna use the Coprini design) to the
> one you see on our site. 

We are using 942C series (2kV, .1uF)  caps.  I made this decision WHILE reading
the posts regarding Garry's 940C series failures.  After doing som e research,
the 940s are a metal film w/ polyester dielectric.  The 942s are metalized
polypropylene caps (probably identical to Terry's favorite Panasonic caps). 
These are the same caps the Robin Coprini is using, except he's using .033uF
caps, not .1uF.  They worked really well for he testing I witnessed.  Chris's
coil needs some work to really bring out the power of the caps (tuned at about
4 turns, used small hookup wires, crappy static gap....).  I think we were
getting about 36" using a pair of 12/60s.  At least the sparks were a purdy
light-blue :-)

Terry should update his good/bad list to specify that the 940C and 941C series
C-D caps are "bad" but the 942C and 943C series are "good".  (the "odd"
numbered series are oval, the "even" are round.)


>
> I designed the layout of having the caps held in place by their leads and 
> floating in open air, the resistors too. I mentioned it while we were 
> screwing around with the lexan and we all thought it would greatly help 
> cooling, completly elimate arcover, and look radically different than 
> anything else out there. The downside is they took FOREVER to build and were 
> WAY more labour intensive than they had to be. We wasted a lot of time 
> stuffing caps into little holes only to have them all fall out as you tried 
> to get the top piece on....ugh. 

I still won't discuss your mechanical design.........  (j/k - I think it looks
SWEET)


>
> lol....that's been an ongoing struggle for 2 years now. We made our site in 
> Frontpage and the CSS files are screwy. We are currently in the process of 
> recoding the entire site in Dreamweaver and Flash. Within 2 months (we have 
> a REALLY big site) it will be done and replace the code-nightmare that is 
> our current site. 

only 14 months.  As I recall, I first brought it to your attention Feb, 2k (I
have your reply here on my computer somewhere - I don't delete many Emails). 
So long ago, and so many Emails, phone calls, and visits later......


Mark Broker
Geek 1019
G-3 status