[TCML] LTR/STR and spark length

[bartb]

Hi Neal,

Just thought I'd share my little coil with you since it's similar (4" x 
20" these days) and uses a supply voltage about 10.6kV at 200mA 
(modified 12/60 NST), so similar to your power supply. I'm also running 
a static gap on this coil. Early on and in the pics below I have had 
some primary strikes but hardly get those any longer. In the pics (at 
the link below), the coil ran with a rather tight coupling. Some months 
later after these pics, I ended up catching the bottom of the secondary 
on fire (bottom turns shorted). When I realized the glowing red spots, I 
decided to just continue and let disaster happen (which did). I ended up 
removing about 1/2" of winding which also lowered coupling. The coil 
these days is painted red, but nothing else has changed other than a 
slightly looser coupling. No more problems with the sec bottom turns. 
This coil has also ran very long runs (which I did mainly to verify 
coupling was good for it's duration and I was curious as to how 
everything would do over a long duration). I was happily surprised.

Well, I just wanted to show why I think your coil could probably do 
better than it is now. BTW, the MMC is 18.8nF, so I also am running STR 
with this setup. Other than maybe the gap and toroid, our coils are 
probably not that different. Also, on this coil, I typically run about 
90 to 100 volt input via a variac to keep sparks out of harms way.

http://www.classictesla.com/photos/ba45/ba45.html

Take care,
Bart

bartb wrote:
> Hi Neal,
>
> With a 9/180 supply, you should be doing much better than 18" sparks. 
> I have to assume spark gap losses are a large reason why you are not. 
> I don't know any details of your static gap but I have to assume it's 
> running an extremely high bps as the gap is set narrow to due the 9kV 
> output.
>
> The sphere should have done better than the small toroid you 
> described. But, a larger toroid in the 5" x 20" range would double the 
> top capacitance beyond that of the sphere and also add a couple more 
> turns on the primary and do even better. It would be nice if you could 
> upgrade the cap bank to 70 or 80nF and run LTR. You might want to 
> start heading towards an SRSG upgrade if you can get a cap size up 
> there. Both cap and rsg upgrades can get expensive and I know it's 
> easier said than done.
>
> The larger secondary looks real nice! This should be a nice coil but 
> it will require all new components and all the same upgrades.
>
> Take care,
> Bart
>
> Neal Namowicz wrote:
>> First, I'd like to thank Gary Lau on the previous advice you gave me 
>> re: resonance and capacitance. If you'll recall, I started out with a 
>> 2nf cap bank, bumped it up to 4, and then after I was told that was 
>> significantly str I managed to bump it up to 25 nf. (I had more caps 
>> laying around than I realized). Here's my question- how much is one's 
>> potential spark length limited by the height of the secondary? Here's 
>> basically what I have; 4" x 18" secondary, flat spiral primary using 
>> .25" cu tube, and I changed to a 9kv, 180ma power supply. I've tried 
>> various toploads, and I've found that I'm still partial to the sphere 
>> shape. I tried a dryer duct toroid that ended up being just slightly 
>> wider than the secondary is high, and had good arcs breaking out all 
>> over at 18"+ . Then I went back to a 10" sphere with a 12" brass rod 
>> stuck into a hole in the sphere. I'm getting easy 18 to 20" streamers 
>> off the top. Given that I'd like to stick to my quenched single 
>> static gap (for now, at least), can I expect to get any better, or is 
>> it time to "upgrade" to a bigger secondary? A long time ago I started 
>> a bigger coil, but didn't get any farther than winding the secondary 
>> (8"x48", wound with 18 ga). Thanks everyone, for your help and input.
>>
>> Neal.
>> _______________________________________________
>> Tesla mailing list
>> Tesla at www.pupman.com
>> http://www.pupman.com/mailman/listinfo/tesla
>>
>>
>>   
>
> _______________________________________________
> Tesla mailing list
> Tesla at www.pupman.com
> http://www.pupman.com/mailman/listinfo/tesla
>
>