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Re: larger than resonant (fwd)
Original poster: List moderator <mod1@xxxxxxxxxx>
---------- Forwarded message ----------
Date: Sat, 02 Jun 2007 14:48:16 -0700
From: Barton B. Anderson <bartb@xxxxxxxxxxxxxxxx>
To: Tesla list <tesla@xxxxxxxxxx>
Subject: Re: larger than resonant (fwd)
Hi Scott,
It sounds to me that as you are using bottle caps for this coil, the C
value of each cap makes a big change in L. Using the same primary for
changes in C may just be going from one extreme to the next. If you can,
could you provide me some details on this coil. Things like height to
base of secondary from the floor. Same with the primary. Toroid cord and
OD. Center height of the toroid to the floor. Primary ID and OD
dimensions, tube diameter, spacing center to center. You know, all the
details. Have you ever measured a single bottle caps capacitance? Each
bottle will vary a little from the next, but not a lot if their all
similarly filled. Shouldn't be too difficult to look at your coils
relationships with good data. We might be able to help with some decent
advice, but without those details, all of us just guess off of our own
experiences. With details, the guesses are less prone to error.
This week, I managed to get a little table top small coil working well.
This was difficult. Small coils have such a drastic change in L because
of short lengths (a little L makes a big inductive change in frequency).
This coil did not have taps, so I had to be very precise to ensure start
to end of primary was modeled correctly. But it worked out well. I find
large coils so much easier to build from a tuning standpoint. This coil
I built for a neighbor (friend from childhood). He's been wanting me to
build him a coil forever. I just wanted him to have something small. I'm
using a 12/30 NST which I got from Hal Krohn.
Here's a couple pics of that little coil:
http://www.classictesla.com/temp/smallcoil_1.jpg
http://www.classictesla.com/temp/smallcoil_2.jpg
BTW, if coilers are looking for NST's for their coils, Hal is your man!
Take a look at what he's got available:
http://www.halice.com/physics/ad.html
Take care,
Bart
Tesla list wrote:
>Original poster: List moderator <mod1@xxxxxxxxxx>
>
>
>
>---------- Forwarded message ----------
>Date: Sat, 02 Jun 2007 10:06:40 -0400
>From: Scott Bogard <teslas-intern@xxxxxxxxxxx>
>To: tesla@xxxxxxxxxx
>Subject: Re: larger than resonant (fwd)
>
>Bart,
> For the small coil, I always used salt water caps, Pickle jars, the
>calculated capacitance of which is about 1.2 nf. I use 3 of them to get the
>coil in tune, with only 2, I believe my primary is entirely too short. With
>4, it seems less than 2 turns is required to put it in tune, and
>performance is kind of lousy compared to just 3 capacitors. I think the
>primary is 8 turns, tapped at about 6, I have to check. The top load is
>3-15, it looks big for the small secondary, and will usually only produce 1
>or 2 streamers at a time regardless of whether a breakout point is used.
>Any thoughts would be appreciated.
>Scott Bogard.
>
>
>
>
>>From: "Tesla list" <tesla@xxxxxxxxxx>
>>To: tesla@xxxxxxxxxx
>>Subject: Re: larger than resonant (fwd)
>>Date: Sat, 2 Jun 2007 07:31:26 -0600 (MDT)
>>
>>Original poster: List moderator <mod1@xxxxxxxxxx>
>>
>>
>>
>>---------- Forwarded message ----------
>>Date: Fri, 01 Jun 2007 21:57:00 -0700
>>From: Barton B. Anderson <bartb@xxxxxxxxxxxxxxxx>
>>To: Tesla list <tesla@xxxxxxxxxx>
>>Subject: Re: larger than resonant (fwd)
>>
>>Hi Scott,
>>
>>Sync operation is different. Best bet is 120 or 240 bps and the
>>difference is negligible between the two other maybe the sound of the
>>break rate you might personally prefer. 250mA is a decent amount of
>>current and in the PT category. You really could head either direction.
>>Your in that borderline area. The MOT's may will probably due better
>>nearer to resonance than an NST. Since were not sure of resonance, you
>>would have to make some MOT measurements to find our (short and open
>>circuit test).
>>
>>The 3" coil will run at various primary cap configurations, regardless
>>of what you have experienced. The primary resonant circuit can be made
>>to resonate at the secondary's resonant frequency with various L and C
>>values. If you had problems running at other values of C, maybe you
>>could detail those particulars? If the C value was larger, then L would
>>have had to be smaller to make up for it (and the tranny would need to
>>be beefy enough for the size). Almost any value can be made to work,
>>it's just a matter of making sure the primary L and C are resonant to
>>the secondary and that adequate charging current is available.
>>
>>Take care,
>>Bart
>>
>>Tesla list wrote:
>>
>>
>>
>>>Original poster: List moderator <mod1@xxxxxxxxxx>
>>>
>>>
>>>
>>>---------- Forwarded message ----------
>>>Date: Fri, 01 Jun 2007 23:40:53 -0400
>>>From: Scott Bogard <teslas-intern@xxxxxxxxxxx>
>>>To: tesla@xxxxxxxxxx
>>>Subject: Re: larger than resonant (fwd)
>>>
>>>So, what would be best if using a sync spark gap, on a MOT powered 6-in
>>>coil, LTR or STR? I still am unsure as to the exact amount of current
>>>
>>>
>>going
>>
>>
>>>through my MOTs, but I think 200-250 mA is a good estimate, at around 8
>>>
>>>
>>kV.
>>
>>
>>>I currently use 75 nf, which I believe to be close to "resonant" sized,
>>>which may be a bad thing according to what I am hearing. Also, I have a
>>>small coil, a three incher that will ONLY run in tune with a small 2.9 nf
>>>capacitor, I have tried lots of other values, but it always stops working
>>>
>>>
>>at
>>
>>
>>>higher or lower values, regardless of where you tap the primary. It is
>>>
>>>
>>10
>>
>>
>>>kV at 92 mA. It has a 3-in secondary wound 12 inches with 20AWG (300
>>>
>>>
>>some
>>
>>
>>>turns, which is low, but it is what I had at the time). Any more
>>>
>>>
>>thoughts
>>
>>
>>>would be appreciated.
>>>Scott Bogard.
>>>
>>>
>>>
>>>
>>>
>>>
>>>>From: "Tesla list" <tesla@xxxxxxxxxx>
>>>>To: tesla@xxxxxxxxxx
>>>>Subject: Re: larger than resonant (fwd)
>>>>Date: Fri, 1 Jun 2007 20:43:02 -0600 (MDT)
>>>>
>>>>Original poster: List moderator <mod1@xxxxxxxxxx>
>>>>
>>>>
>>>>
>>>>---------- Forwarded message ----------
>>>>Date: Fri, 01 Jun 2007 19:20:25 -0700
>>>>From: Barton B. Anderson <bartb@xxxxxxxxxxxxxxxx>
>>>>To: Tesla list <tesla@xxxxxxxxxx>
>>>>Subject: Re: larger than resonant (fwd)
>>>>
>>>>Hi Scott,
>>>>
>>>>Smaller transformers like NST's will almost always run LTR. Larger
>>>>transformers like PT's and PIG's will often run STR. Gary mentioned bang
>>>>size. This is a big deal for both NST sized transformers and large pigs.
>>>>If you were to run STR with an NST, the cap would be small and the bang
>>>>energy would also be small. Your better off from a spark length
>>>>standpoint to run LTR with one of these smaller transformers. The reason
>>>>has to do with a transformers ability to charge the cap which is based
>>>>on the cap value and the current available from the transformer. That is
>>>>the reason why we only go "so far" with LTR sizes. Thus, each
>>>>transformer rating has it's own LTR value.
>>>>
>>>>Larger transformers like pigs, if run LTR, would have an incredible bang
>>>>energy that could be devastating (and expensive). There is some limit to
>>>>transformed energy for every coil before the coil turns into a blaze of
>>>>glory, but one we almost have to blow it up before we actually find that
>>>>limit. In most cases, large transformers are better off running STR to
>>>>keep the bang energy within a coils abilities.
>>>>
>>>>In both cases, the spark gap, when running without a failure, will limit
>>>>the breakdown voltage. If a static gap, it's a constant limit that
>>>>usually decreases with time due to heat buildup, but for a rotary gap,
>>>>the timing of electrode alignment and the current available to charge
>>>>the cap is the limit for voltage. It is possible to run very high bps,
>>>>but the balance between current and capacitance must be met. If either
>>>>is not designed well for the bps ran, sparks can diminish, but if done
>>>>right, spark lengths can be very good. I personally like a 300 to 340
>>>>bps myself when I run my variable rsg. If I were to change capacitance
>>>>or transformer for the same coil, there would be a different bps range
>>>>where the coil runs best.
>>>>
>>>>Take care,
>>>>Bart
>>>>
>>>>
>>>>
>>>>Tesla list wrote:
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>>Original poster: List moderator <mod1@xxxxxxxxxx>
>>>>>
>>>>>
>>>>>
>>>>>---------- Forwarded message ----------
>>>>>Date: Fri, 01 Jun 2007 05:54:39 -0400
>>>>>From: Scott Bogard <teslas-intern@xxxxxxxxxxx>
>>>>>To: tesla@xxxxxxxxxx
>>>>>Subject: larger than resonant
>>>>>
>>>>>Hey everybody,
>>>>> Can somebody explain to me the advantage to using a "resonant" or
>>>>>"larger than resonant" tank capacitance? I seen coils get huge sparks
>>>>>
>>>>>
>>>>>
>>>>>
>>>>using
>>>>
>>>>
>>>>
>>>>
>>>>>LTR and also very small tank capacitors, so what is the point? Thanks.
>>>>>Scott Bogard.
>>>>>
>>>>>_________________________________________________________________
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>>>>>
>>>>>
>>>>
>>>>
>>>>
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>>
>>
>
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