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Re: [TCML] Spark gap

Hi Gary,
Wow, I've been full of questioning things lately (must have been that cool lunar eclipse the other night).
Regarding multi-segment quenching. I'm not sure that just because the arc is divided into individual segments that it aids gap quenching. The current in the series is the same on all segments and identical to a single section of the same firing voltage at an identical total gap distance. The only difference is that the arc between a multi-segment gap is shorter. I'm not so sure that "shorter" equates to easier arc quenching? I'm curious what physics would enable better quenching in this scenario as opposed to the obvious.
The main difference I see in a multi-segment gap is regulation. As long as Vp stays consistent, I and R will remain consistent given a consistent load. Without multi-sections, there is a higher probability that Vp will change due to thermal regulation and current will be affected as well as the change in R. If regulation on a non-multi-section gap can be controlled the same, then I see no difference between the two. Obviously it's more difficult and "why" multi-sectional gaps were born into existence. But I don't see quenching as part of this due to the individual shorter segmented arcs, but rather stable regulation. 

Just thinking here.

Take care,
Bart

Lau, Gary wrote:

I'm similarly skeptical about a propeller gap's quenching.  The only thing that I can see superior quenching-wise is that the air flow over the gap may be better than in a cylinder gap.  But if that was all you need for superior quenching, then an air-blast gap should be the best solution of all.

I would think that a mult-segment cylinder gap is the best at actual quenching, due to the fact that being divided into multiple small arcs, they would be easier to cool and extinguish.  But I also believe that multi-segment gaps exhibit higher losses (each gap represents a fixed voltage drop, and the more gaps in series, the greater the total gap voltage drop, and loss).

The benefit of a propeller gap comes about in that it's a rotary gap.  If it's a sync gap, it's superior because the bangs can be engineered to be consistent in size and timing, rather than the chaotic mode inherent in static gaps.  If it's an async gap, it may be better than a static gap if the power supply is larger than what can be effectively handled with a static gap.

Regards, Gary Lau
MA, USA


-----Original Message-----
From: tesla-bounces@xxxxxxxxxx [mailto:tesla-bounces@xxxxxxxxxx] On
Behalf Of huil888
Sent: Friday, February 22, 2008 1:34 AM
To: Tesla Coil Mailing List
Subject: Re: [TCML] Spark gap

Henry -

This sounds plausible, but do you have any actual data (scope waveforms,
etc) that would support the claim of better quenching  from a  "propeller
gap" vs a conventional static spark gap?

The data would have to be generated from a test setup where the only
variable was the substitution of the two different types of gaps.

If you have data, could you share it with the List?

Regards,
Scott Hanson


----- Original Message -----
From: "Henry Hallam" <hallam@xxxxxxx>
To: "Tesla Coil Mailing List" <tesla@xxxxxxxxxx>
Sent: Thursday, February 21, 2008 9:42 PM
Subject: Re: [TCML] Spark gap



Among other things, the propeller gap is better at quenching (shutting off
the spark), especially at high power.

Henry


Rich Schmuke wrote:

I am going to ask a simple question but please give a simple answer. I am
not a EE just a builder. I was asking about a rotor gap the other day and
it
was suggested I try a propeller gap for my 200ma coil. Well I have a
motor
from a 8" hard drive now and am going to build a mount as soon as it is
warm
enough to get to my shed. My question is why is a propeller at 3600 RPM
better than a RQ copper tube gap?  60 cycle RQ  vs a 3600RPM it's the
same
break rate I think.


Rich

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