Hi Tim,
As others have already stated, I think the main issue that's limiting your output to the 40" to 50" corridor, as opposed to 60" to 70", is the relatively small primary cap and the stationary gap that you are using. For NST driven systems, an SRSG, with an LTR primary cap, is the way to go to squeeze every last inch of output spark from the available wall plug power from your system (indeed 2 kVA, more or less, is pretty much the maximum output that you are gonna be able to glean from a standard 120 VAC wall outlet on a 20 amp circuit, in North America). As Adam stated, PFC caps can substantially reduce the actual wall plug draw of amperage if you are "running the razor's edge" on blowing fuses/kicking out breakers.
Now if you get to the point that 6 ft. arcs still aren't enough for you, then you should start looking into replacing those NSTs with a PT(s) or a pole pig transformer, along with an async rotary spark gap (ASRSG), and start tapping into a 240 VAC circuit, assuming that you're staying with the classic SG driven coil design. Of course, this much of an upgrade in power may very well require an upgrade to the physical parameters of your primary/secondary coil and topload, also - (depending on the extent of the "upgrade" that you desire). It is a definite advantage to have a much deeper well of raw power to draw from if you're just looking to make huge sparks, though ;-)
Happy sparking,
David (Rieben)
Timothy Gilmore <tdg8934@xxxxxxxxx> wrote:
>David,
>
>When I bought the tungsten spark gaps and fan I received this email:
>
>*Most folks use them in series and reduce the gap width on each one. For
>example for a ¼ inch gap (a good place to start) they use two gaps in
>series set a 1/8”. I have had excellent results using them in parallel. For
>the amount of current you are using I would use two gaps in parallel both
>set at 1/4 inch. It works great and is easier to line up with the fan.*
>
>Should I be using them at 1/8" gaps in serial then?
>
>Tim
>
>On Tue, Apr 7, 2015 at 8:26 AM, David <zipo@xxxxxxxxxxx> wrote:
>
>> Tim - Here is my take on spark gaps. First you say you have two gaps in
>> parallel, not series but parallel? Only one spark at a time can happen in a
>> parallel gap set up, maybe it will switch back and forth from one to the
>> other but only one at a time. A single gap can provide the least resistance
>> and more current in the primary circuit but does not quench and control
>> ring down very well. putting multiple gaps in Series seems to provide an
>> improvment in quenching and ring down control. To experiment with series
>> multiple gaps would seem to be a logical next step, two, four, maybe even
>> six gaps in series. A lot of people have had good results with the Richard
>> Quick multi gap and is not to difficult to construct. The next step up
>> would be a sucker gap, a lot of people like these and they give real good
>> results, there are examples on the net. But I believe the best and most
>> difficult is the Sync Rotary gap. my recommendation would be to experiment
>> with the progression of gaps above but keep an eye to words the sync
>> Rotary. Some thing I wish more people would do too, is cover your spark
>> gap, put a largish box over it to block the light from it and to quiet it
>> down a bit, doesn't have to be fancy, just a simple wooden box placed over
>> it wile your running. Nasty gasses build up inside but for the length of
>> time most of us run our coil it will be ok. For a 15kv NST the max voltage
>> it can handle is about 25kv +- a bit peak, so you want the largest cap you
>> can charge to 25kv. The Geek group capacitor chart is very good at
>> appropriate cap values for a type of setup/gap being used.
>>
>> Thanks
>> David
>>
>> On 4/7/2015 8:00 AM, Timothy Gilmore wrote:
>>
>>> David,
>>>
>>> 72" WOW as I have similar specs but only get 36-48" or so.
>>>
>>>
>>> Here are my specs:
>>> 15kv, 120ma <-- Same (2 15kv 60mA NSTs)
>>>
>>> 3 levels of 0.010uf in parallel for 0.030uf mmc (30kv) <--- Seems like
>>> your double of what mine is
>>>
>>> 2 parallel tungsten gaps "about" 1/4" separation each (with a squirrel
>>> cage
>>> fan blowing on them) <--- *Should these be tighter since there are 2 of
>>> them? (i.e. 1/8" inch each)*
>>>
>>> Secondary - 6"dia x 31"lg 1400 turns No. 24
>>>
>>> Top load - 6" x 25" aluminum dryer ducting and foil pizza pans with foil
>>> wrapped cardboard between and nylon toilet bolt <-- NOT wrapped in 3"
>>> aluminum tape
>>> (Would wrapping this improve the length significantly). I have the
>>> materials for an 8" aluminum dryer ducting, aluminum tape, 17.75" x 1"
>>> circular wood table (to be wrapped in foil and then glued and possibly
>>> aluminum taped). *Should I just wrap the 6" more flimsy version or go with
>>> the bigger 8" more solid heavier version (to construct) - OR use both on
>>> top (wrapped/unwrapped in aluminum tape)?*
>>>
>>> Primary 0.25" copper refrigerator coil in single layer tapped at 12.5
>>> turns
>>>
>>> I was thinking of the rotary gap motor version for the spark gap but have
>>> no idea where to even start on this. I was hoping to get everything the
>>> best I could first before and if I go down that route.
>>>
>>> *So what has the greatest impact on spark length - the rotary spark gap or
>>> the wrapped aluminum tape on the toroid - or are both necessary?*
>>>
>>>
>>> Thoughts?
>>>
>>> Tim
>>>
>>>
>>>
>>>
>>> On Mon, Apr 6, 2015 at 8:56 PM, David <zipo@xxxxxxxxxxx> wrote:
>>>
>>> Timothy, List - I too have recently put together a 15kv, 120ma coil. I'm
>>>> still tweaking for best out put. So far I'm getting 72" output and based
>>>> on
>>>> the way it was running and the way it was tuned I believe it will do at
>>>> least 80" after it's fully peaked. I can only run outside so I'm having
>>>> to
>>>> wait for good weather.
>>>> Here is a brief over view:
>>>> 15kv, 120ma
>>>> .0625uf mmc
>>>> sync rotary gap @ 120 breaks/sec
>>>> secondary - 7"dia x 27.3"lg 1500 turns No.26 wire
>>>> Top load - 5" x 20" spun aluminum toroid
>>>> primary - 10 turn 2 layer spiral
>>>> Tesla equi drive circuit.
>>>>
>>>> There are two aspects of tuning and peaking that seem not to get the
>>>> attention that they should (in my opinion).
>>>> First is that if tuning with a signal generator and a oscilloscope you
>>>> need to simulate the added capacitance of the spark. Adding a piece of
>>>> wire
>>>> the length of the spark your expecting to the top load and then tune with
>>>> sig gen and o scope. This seems to be overlooked a lot. Java TC shows
>>>> this
>>>> very well. If you ad an additional cylindrical top load, on JTC, .02dia x
>>>> length of spark (JTC will point it straight up) you will see a marked
>>>> reduction in res. frequency.
>>>> Second is that the safty gap or static gap width has a large impact on
>>>> output. There are way of setting these gap for safest operation. However
>>>> I'm guessing these gap widths get pushed a bit by savvy coilers but don't
>>>> talk about it. At least on a sync rotary safety gap width has a big
>>>> bearing
>>>> on output. I would find it very interesting to hear what gap width people
>>>> are using with what setup. And in full disclosure :) I have set both of
>>>> my
>>>> safety gaps at .22 using rounded brass draw pulls for electrodes.
>>>> It just seems to take a lot of time to get every thing tweaked to
>>>> Perfection.
>>>>
>>>> Carry on
>>>> David
>>>>
>>>>
>>>>
>>>> On 4/6/2015 9:34 AM, Timothy Gilmore wrote:
>>>>
>>>> Has anyone put together any sort of a listing of others Tesla Coils
>>>>> built
>>>>> with parameters listed such as:
>>>>>
>>>>> (for example): I have 2 NSTs (15kv, 60ma) each, 6" diameter, 31" high
>>>>> secondary, torroid is ....
>>>>>
>>>>> I am getting 3-4' sparks and wondering if I should be getting longer
>>>>> sparks. Is this normal? or should I add another NST or bigger Toroid
>>>>> (working on an 8" diameter ducting bigger one). How do I know since the
>>>>> Tesla Map software says I should get "ideally" 72.6 inch sparks and I'm
>>>>> getting about 1/2 to 2/3 of that. Just wondering if it's not tuned
>>>>> properly
>>>>> (but I think it is) - or making a larger toroid is worth the effort if
>>>>> I'll
>>>>> gain a foot or more sparks.
>>>>>
>>>>> How does one know they are getting close to the best they can get in
>>>>> spark
>>>>> length?
>>>>>
>>>>> I have attached my Tesla Map file of current settings.
>>>>>
>>>>> Thanks,
>>>>>
>>>>> Tim
>>>>> _______________________________________________
>>>>> Tesla mailing list
>>>>> Tesla@xxxxxxxxxx
>>>>> http://www.pupman.com/mailman/listinfo/tesla
>>>>>
>>>>>
>>>>> _______________________________________________
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>>>>
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>>>
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