[TCML] Strike rail hits and loud bangs

[bartb]

A correction to my statement:
I said "It conducts and also forces a breakdown at the safety gap (bang)."

This is not correct. The main gap won't conduct. The voltage on the cap 
simply over-charges to the breakdown voltage of the safety gap and then 
"bang", the safety gap dumps the cap energy.

Cheers,
Bart

bartb wrote:
> I wanted to explain my theory a little better:
>
> If the primary is hit (racing spark gets near the bottom and arcs to 
> the primary or rail gets hit and arcs to the primary), the voltage at 
> the main gap opposite the charging stationary electrode voltage is 
> higher (the felt potential across the gap is lower) and thus the 
> difference across the gap does not reach breakdown (causing mis-firing 
> with rotary [time dependent for this to occur] or no firing if a 
> static gap). The cap however continues to charge. Once the potential 
> across the gap is high enough to breakdown, there is a very high 
> voltage on the cap. It conducts and also forces a breakdown at the 
> safety gap (bang). So add primary strikes as another cause to this 
> phenomenon.
>
> Take care,
> Bart
>
> bartb wrote:
>> In cases where I've experienced bangs, it appeared the safety gap was 
>> producing the bang. In many cases, this was associated with anomalies 
>> such as  rail to primary flash-overs and racing sparks running down 
>> to the ground at the bottom of the secondary (both of which are tied 
>> to the safety gap and both can also be tied to the main gap via the 
>> primary). In this particular case, I couldn't tell if it was a racing 
>> spark or a primary flash as it was on the back side. But considering 
>> the brightness and reflection, it may have been a racing spark as it 
>> did illuminate the entire back side of the coil. I have sometimes 
>> wondered if these high voltage breakdowns to ground had altered the 
>> gaps ability to fire (causing a mis-firing or two) allowing the cap 
>> to charge higher and as a result a following safety gap breakdown 
>> (thus the flash and bang). From the video however, I could not make 
>> out the bang well enough or play with the video enough to note a 
>> difference in time between flash and bang. This theory would support 
>> higher occurrences of safety gap breakdown with higher coupling and 
>> with mis-tuned coils.
>>
>> Regards,
>> Bart
>>
>> Lau, Gary wrote:
>>> In my experience, loud bangs are the safety gaps firing, due to the 
>>> presence of a too-high cap voltage, so the safety gap discharges the 
>>> bang instead of the main gap.  If the safety gap is firing just 
>>> because of a primary strike, I wouldn't think that it would be 
>>> nearly so loud, as the current is many times smaller than if the gap 
>>> is discharging the primary cap into the tank circuit.  Could it be 
>>> that there was a too-high cap voltage, the safety fired for that 
>>> reason, and the larger than normal bang caused a longer than normal 
>>> secondary spark to strike the strike rail?
>>>
>>> Regards, Gary Lau
>>> MA, USA
>>>
>>>  
>>>> -----Original Message-----
>>>> From: tesla-bounces at pupman.com [mailto:tesla-bounces at pupman.com] On
>>>> Behalf Of David Nelson
>>>> Sent: Thursday, October 02, 2008 10:24 AM
>>>> To: Tesla Coil Mailing List
>>>> Subject: Re: [TCML] Strike rail hits and loud bangs
>>>>
>>>> Is there a chance that the loud bang is a spark between bottom of the
>>>> secondary and the inner turn of the primary? Overcoupling. I had 
>>>> this and I
>>>> removed half a turn from the inside of the primary and re-routed 
>>>> the wiring
>>>> (down and out) to fix the problem. I kind of feel that performance 
>>>> went down
>>>> slightly, but no more loud, annoying and scary bangs.
>>>>
>>>> Dave Nelson
>>>> ----- Original Message -----
>>>> From: "Stephen J. Hobley" <shobley at userfs.com>
>>>> To: "Tesla Coil Mailing List" <tesla at pupman.com>
>>>> Sent: Wednesday, October 01, 2008 11:37 AM
>>>> Subject: [TCML] Strike rail hits and loud bangs
>>>>
>>>>
>>>> We have a fairly simple coil using a 60ma NST. Recently I changed 
>>>> the tap
>>>> point on the primary and by chance hit a really sweet spot.
>>>>
>>>> Usually the Tesla Tuner is pretty accurate and gives good results, 
>>>> but in
>>>> this case it did not indicate that this tap point was a good one.
>>>>
>>>> The streamer length has increased by at least 50% - but we did 
>>>> notice some
>>>> rather worrying "bangs" from the Terry filter spark gap when the 
>>>> strike rail
>>>> is being hit. Is this normal?
>>>>
>>>> Is it possible to tune a Tesla coil into a self-destructive state?
>>>>
>>>> I would take some pictures, but the darned thing scares me to death...
>>>> :-)
>>>>
>>>> Steve
>>>>     
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