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Re: [TCML] Climbing Arcs

Hi Tony,

Some suggestions:
1. Use a wide "V" to more rapidly spread the arc. The higher the current the wider the end gap should be 
2. Use inductive ballasting for best performance
3. Use smooth rails to avoid incandescent "hot spots" that will cause the arc roots to temporarily hang in one spot. I'd recommend using 3/4" hard copper pipe or non-magnetic stainless steel tubing. Periodically remove any oxide buildup. I suspect the oxidation of the galvanizing may a major part of the problem you're seeing. 4. Enclose on 4 sides to reduce disruption by air currents. Leave top AND bottom portion open to permit vertical air flow. Be sure to leave plenty of clearance on either side of the gap, especially for a higher current ladder. 5. For grins, try connecting a small (500 - 1000 pF) HV doorknob cap across the gap to make for "snappier" performance at start and at long arc lengths. 

Good luck,

Bert

Sfxneon@xxxxxxx wrote:

Hi Ken,
You're right, the arc climbs because it's hotter and less dense than the surrounding air. I've had no problem making the small NST powered ones work, but at higher currents the middle of the arc tends to rise faster than the ends. It grows in length but hardly ever makes it to the top of the rails, even when set close. It seems to get stuck along the way and doesn't want to climb smoothly. Does anyone know if the smoothness of the rail's surface or the zinc coating would have anything to do with it? Thanks, Tony G
In a message dated 5/27/2008 8:47:52 A.M. Central Daylight Time, kwillison2@xxxxxxx writes: 

I never built a really large one. I have however observed that any  air
movement across the ladder will disrupt the arc. Conducted some  experiments
tilting the electrodes from vertical it would not work beyond 30  degrees.
The curve of the arc remained vertical while the electrodes were  tilted. I
surmised that heat causes the arc to rise and heat raises  vertically so
won't work when it passes about 30  degrees.
Ken

-----Original Message-----
From:  tesla-bounces@xxxxxxxxxx [mailto:tesla-bounces@xxxxxxxxxx] On Behalf
Of  Sfxneon@xxxxxxx
Sent: Tuesday, May 27, 2008 12:10 AM
To:  tesla@xxxxxxxxxx
Subject: [TCML] Climbing Arcs

Hi All,

I have a  spare 12.5 kVA/20 kV bombarding transformer and sliding choke   with
which I'm building a large Jacob's ladder using 3/4" x 10' EMT conduit. It works reasonably well, but the arc tends to rise up the rails too slowly and the middle of the arc outruns the ends, resulting in a restart before it reaches the top. I've adjusted the angle of the rails from near parallel to about 18" apart at the top, without much success. 

Does anyone know how to tweak the performance of a big climbing  arc so that

it will climb to the top of the rails more often? I'm  guessing that
increasing the air convection around the arc would help it to climb, so will inclosing it in a tall clear tube or box make a difference? Does the material that the rails are made of have any effect? How about the ballasting of the transformer, as far as inductive or resistive, etc? 
Thanks,

Tony Greer
**************Get trade secrets for amazing burgers. Watch "Cooking with Tyler Florence" on AOL Food. (http://food.aol.com/tyler-florence?video=4&?NCID=aolfod00030000000002) 
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