Re: Getting the bugs out- a little help, please...

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

Original poster: Bart Anderson <classi6-at-classictesla-dot-com> 

Hi David,

I think you'll be fine with the 480 BPS system. If we assume a 50 amp limit 
and ignore other aspects that relate to the transformer (for a rough 
guide), the cap will take 7.128ms to charge to applied voltage (typ. 
240/14.4kv potential). With the 480 BPS system, your electrodes will align 
every 2.08ms which ends up at about 77% charge on the cap when it fires or 
15.6kVp.  This really isn't bad in this situation if we look at the energy 
across the cap per second. This value calc's to 4843 joules per second.

Now, if you removed 4 rotating electrodes for 240 BPS operation, here's how 
the numbers go. Time to charge cap to applied voltage doesn't change. But, 
the firing rate is now every 4.17ms which puts the cap charge at 95% when 
it fires or 19.3kVp. This looks good eh? Well, if you look at the energy 
across the cap per second it ends up at 3675 joules per second.

I also looked at what breakrate this would peak at, and it appears to be 
around 4886 joules per second which would take around 558 BPS. As BPS is 
raised beyond that point, the energy across the cap begins to fall again.

I suspect the 480 will do a little better than the 240 in your case, say 
10" sparklength difference. Given 15 foot sparks possible at this power you 
may or may not notice the difference. (12 kVa, yea I'm pushing it)

I see no problem with either gap configuration. You'll have to experiment 
with it to see what holds true and what doesn't. Regarding the arcing at 
the strike ring. On my old 13.75" diameter coil, I periodically had arcing 
between ring and primary. I never realized until I looked at some photos 
that it was arcing at the RF to Ring connection. It was also an area where 
that was prone to strikes. Something to look at for what it's worth. BTW, I 
would definitely go to a larger toroid.

Take care,
Bart


Tesla list wrote:

>Original poster: Tesla729-at-cs-dot-com
>Hello coilers,
>
>I posted this letter about a week ago and got no response, so
>I thought that I would try it one  more time and see if I have any
>better luck this time:
>
>
>
>Hi all,
>
>I am in the process of rebuilding my piggie system and
>I fianlly got to start firing her up and tuning it in this eve-
>ning. I now only have a 9x30 toroid and I know that's a lit-
>tle small for my 12.75"x48.5" secondary coil as I'm think-
>ing more along the lines of a 12x48 toroid to properly
>utilize the avilable power from my coil. I did get a few
>8 to 9 ft. strikes to a metal ladder in my driveway this
>evening on just a rough tune-up.
>
>There are a couple of problems that I encountered
>though. First, my Wysock-built rotory gap is sync at
>480 bps and w/ .0825 uFD primary capacitance, I'm
>thinking that's a little too fast for the capacitor to ever
>be able to fully charge before discharging across the
>SG and that would definitely limit my sec. voltage gain.
>I haven't built a Freau phase adjuster yet either as I'm
>not sure that the phase angle would even be that big
>of an issue at 480 bps. I'm thinking about removing
>4 of the 8 rotory electrodes to go for 240 bps. Maybe
>some of you you more mathematically inclined mem-
>bers can tell me what the best bps rate range should
>be for this coil. My power supply is a 10 kVA, 14400
>volt PDT controlled through (2) paralleled 1256 variacs
>(up to 280 volts -at- 56 amps) and ballasted w/ a seriesed
>225 amp arc welder w/ the welding leads shorted. It just
>seems that I ought to be able get brighter,longer, more
>powerful sparks w/ my available power. Of course, like I
>said, I just roughly tuned it in tonight.
>
>The one other little problem that I did encounter when
>I really began to pour the juice to her was that the
>grounded strike ring would start flashing over to the
>outer turn of the primary coil. I thought that I had
>plenty of claerance here (about 3" or so) but maybe
>that autotransformer action is a little bit more of a problem
>than I thought. I'm tapped at just over 9 turns on the pri-
>mary, so I only have right at 3 more turns to build up
>voltage between the outermost primary turn and the strike
>shield ring. I have the 1/2" ID copper tubing primary secured
>w/ plastic cable tie-downs to 1 1/2" white PVC pipe through
>pre-drilled holes to run the tie-downs through. The ground ca-
>ble that connects to the strike ring is #6 green insulated
>stranded building cable and it runs though the bottom of one
>of the (8) 1 1/2" dia. PVC primary supports. Could the problem
>be here as the outer primary winding may be arcing to the
>grounding cable though one of the pre-drilled mounting holes
>in the PVC pipe? It was kind of hard to tell the exact location
>of the annoying bright flashover that was taking place when I
>turned the power up, but I could tell it was around the outer
>primary turn and the grounded strike ring. This annoying flash-
>over was what was causing EM problems in the house, too.
>As long as this flashover didn't occur, nothing electronic in the
>house (like the alarm system going off) was bothered.
>
>I just finished building my RF ground system today. It con-
>sists of (4) 5/8" dia. x 8ft. long copper-cald grounding rods
>driven all but about 3" worth into the soil. They are inter-
>connected w/ a bare #1/0 welding cable about 10" to 12"
>under the ground. I run an 18 ft. long piece of insulated
>#1/0 welding cable from the RF grounding post on the coil
>to the RF grounding rods and I think my ground is sufficient
>for my coil.
>
>On a positive note, I didn't have any trace of racing sparks
>on the secondary at any power level so I'm not overcoupled.
>The bottom-most secondary coil is about 1 3/4" above the
>top of the innermost primary coil. I could even try to increase
>the coupling a bit but I don't think that the secondary needs
>to be lowered much more relative to the primary coil on a coil
>of this magnitude. No racing sparks are good ;^)
>
>Sorry for the long post but I knew if anybody could help w/
>this, it would be you guys on this list ;^)
>
>Thanks in advance,
>David Rieben
>
>
>
>