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question about different types of spark gaps

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lokeycmos

Fri Sept 07 2012, 12:17AM

Registered Member #2553 Joined: Fri Dec 18 2009, 01:36PM
Location: St Cloud Minnesota
Posts: 97

i just finished building my own spark gap tesla coil with a richard quick gap. the video is here if your interested:

i want to build another larger one, but i have a question first. could someone please explain the differences between and the pros/cons of synchronous and asynchronous spark gaps? thank you in advance!

Herr Zapp

Fri Sept 07 2012, 03:15AM

Registered Member #480 Joined: Thu Jul 06 2006, 07:08PM
Location: North America
Posts: 644

lc-

Everything you need to know is right here:

See the sections "Rotary Gap Overview" and "Rotary Gap Analysis".

Herr Zapp

HV Enthusiast

Fri Sept 07 2012, 01:14PM

Registered Member #15 Joined: Thu Feb 02 2006, 01:11PM
Location:
Posts: 3068

Practically speaking, a asynchronous gap is much easier to build and also gives a coil a wider range of effects as the break rate can be continuously varied.

Sychronous gaps are more difficult to build because synchronous motors are much more difficult to find - i don't know of any commercial ones even available right off the shelf. You also have to worry about tuning them to your coil and so forth . . .

I would recommend doing an asychronous gap. You can get a nice univeral AC motor from Granger which will fit the bill nicely.

Herr Zapp

Sat Sept 08 2012, 04:18AM

Registered Member #480 Joined: Thu Jul 06 2006, 07:08PM
Location: North America
Posts: 644

EVR -

True, a variable-speed RSG can provide very interesting sound and visual effects not obtainble with a synchronous RSG, but ONLY if the variable-speed RSG is part of a DC or DC resonant-charged primary circuit.

Combining an asynch RSG with a conventional AC-charged TC usually doesn't provide very good results.

Herr Zapp

HV Enthusiast

Mon Sept 10 2012, 01:41PM

Registered Member #15 Joined: Thu Feb 02 2006, 01:11PM
Location:
Posts: 3068

Herr Zapp wrote ...

EVR -

True, a variable-speed RSG can provide very interesting sound and visual effects not obtainble with a synchronous RSG, but ONLY if the variable-speed RSG is part of a DC or DC resonant-charged primary circuit.

Combining an asynch RSG with a conventional AC-charged TC usually doesn't provide very good results.

Herr Zapp

Really?

ARSG spark gaps are used all the time in conventional Tesla coils. I have used them exclusively for all the spark gap coils I have built, and many of the big names in amateur coiling here in the US have used ASRG coils their conventional spark gap and magnifier coils.

Master coil builder Ed Wingate of Rochester, NY uses ARSGs in his giant magnifier system he designed and built. He has also used them with smaller conventional spark gap coils if I am not mistaken.

Terry Blake, another great amateur Tesla coil builder has used ARSGs with his conventional coils as well.
His coil featured here is one of my favorite amateur coils. I believe he used ARSG propellar gaps for all his conventional spark gaps coils and they all worked quite impressively!!!

TeslaDownUnder also uses ARSGs in his conventional coils.

Steve Conner

Mon Sept 10 2012, 03:16PM

Registered Member #30 Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706

The combination of an ARSG with AC charging is indeed very popular. It works fine. There is somewhat of a performance limitation: you have to run the spark gap at 200 electrode presentations per second or faster, to avoid resonance conditions that can overvolt the transformer. This causes a slight hit in efficiency, because 200bps is less efficient for streamer growth than 100 or 120.

Herr Zapp

Tue Sept 11 2012, 07:35AM

Registered Member #480 Joined: Thu Jul 06 2006, 07:08PM
Location: North America
Posts: 644

EVR -

I should have been more specific ......

The problem with the "typical" ASRG that's assembled by a first-time TC builder is that it frequently uses an 1800 RPM induction motor, and only has 4 or 6 flying electrodes.

As Steve C. stated, the resulting low breakrate can (in some cases) allow the tank voltage to ring up to destructively high values, unless a carefully-adjusted safety gap is present.

I believe that a properly timed SRSG can process more power through the tank circuit than any ASRG, all other factors remaining the same.

But as your examples show, an ASRG can produce good results in a system that's been carefully assembled and tuned. Most of the ARSGs that I've seen exhibited rather "ragged" firing characteristics, not the pure. clean tone that a properly set up SRSG can produce.

Herr Zapp

HV Enthusiast

Tue Sept 11 2012, 12:20PM

Registered Member #15 Joined: Thu Feb 02 2006, 01:11PM
Location:
Posts: 3068

Herr Zapp,

I agree with your assessment. Also, i didn't mean to imply that ARSG were better or more efficient than SRSG, but rather they do work and are a popular choice for amateur coilers as they universal motors are readily available as opposed to synchronous motors which can be more challenging to procure and/or modify.

But - yes! Agree with the low break rates. I've had that problem myself initially we these as i didn't run my breakrates high enough.

Herr Zapp

Wed Sept 12 2012, 04:45AM

Registered Member #480 Joined: Thu Jul 06 2006, 07:08PM
Location: North America
Posts: 644

EVR -

If you really want to squeeze the last inch of streamer length out of a rotary gap system, the SRSG with "staggered" electrode angular position adds an interesting twist. The staggered electrode design "adjusts" cap charging time to maximize cap voltage at the instant of firing. I think Finn Hammer at some point built several staggered-gap RSGs, and Richie Burnett has an informative writeup at:

Herr Zapp

Wed Sept 12 2012, 05:06AM

Registered Member #480 Joined: Thu Jul 06 2006, 07:08PM
Location: North America
Posts: 644

Herr Zapp

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