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Re: [TCML] Spark gap

Henry -

Thanks for the clarification.
You're absolutely correct, in the usual "RQ" gap with air flow parallel to the pipe axis there is very little airflow through the actual "gaps".
Some time ago I built a segmented copper pipe gap that forced 100% of the airflow through the gaps. This consisted of a plywood box about 10" long X 8" high X 7" wide. At one end of the box was mounted a very high-flow muffin-type fan, one designed to maintain a high flow rate against a pretty substantial back-pressure. The copper pipe segments were layed across the open "top" of the box, resting in notches cut in strips of 3/8" thick phenolic material that were screwed to the inner walls of the box. I used pieces of 1" dia brass rod for the "end segments" of the gap, and one end of each rod was drilled and tapped for a 1/4" bolt that secured a big lug on the ends of the primary wiring. By shifting around the location of the brass rods, I could "select" the number of effective gap segments, from 1 to 7 gaps.
This worked very well on my 6" 15KV/120ma NST coil, although the copper pipe segments did tend to oxidize fairly rapidly along the gap line. Rotating the copper pipe segments a fraction of a turn restored performance. 

Regards,
Scott Hanson
----- Original Message ----- From: "hallam" <hallam@xxxxxxx> 
To: <tesla@xxxxxxxxxx>
Sent: Friday, February 22, 2008 2:24 PM
Subject: Re: [TCML] Spark gap



Hi Scott,
I absolutely don't have any data supporting that claim.  It's really just
"received wisdom" :)

One of the problems with the classic RQ gap is that unless it's baffled
correctly, most of the airflow goes through the copper pipes and through the large central gap, with relatively little going through the tight space between the pipes. This is just fine for cooling but not so great for air-blast style 
quenching.  Though of course, cooling does help with quenching.

Henry

Quoting huil888 <huil888@xxxxxxxxxxxx>:


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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