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First tesla coil thread - Dual Mot

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LAN_403

Kizmo

Sun Dec 15 2013, 08:07PM

Registered Member #599 Joined: Thu Mar 22 2007, 07:40PM
Location: Northern Finland, Rovaniemi
Posts: 624

Hey that looks great! What was your power input? You may gain some spark by doing more careful tuning.

Also, bigger toroid would help too, these spark gappers seem to love large top loads :)

MrFlatox

Sun Dec 15 2013, 10:10PM

Registered Member #9349 Joined: Mon Jan 07 2013, 08:50AM
Location: France
Posts: 102

Thank you ! When it runs, it draws about 16A @240V. As my breaker is rated for 16A, I only do short tests because otherwise it will trip off.

As for the tuning, it's rather hard, because I could not see any difference in the output when tapping from 4 turns to 3.25 turns. I could definitely add another toroid on the actual one or make a bigger one as long as it does not move my tapping point outside of my short primary coil (4.75turns max).

Hydron

Mon Dec 16 2013, 08:11AM

Registered Member #30656 Joined: Tue Jul 30 2013, 02:40AM
Location: UK
Posts: 208

Hey congratulations on getting it going in the end, looks good!

And yeah, as I found with my DRSSTC the noise level is extreme. While it is impressive, it would be much easier if it were quieter, especially this time of year (doesn't get dark till nearly 9pm at the moment here in New Zealand, so keeping neighbours happy is hard).

MrFlatox

Tue Dec 17 2013, 09:53AM

Registered Member #9349 Joined: Mon Jan 07 2013, 08:50AM
Location: France
Posts: 102

Thanks

ah ! I don't have this problem at this time since it's dark at 5pm, and freezing cold. Neighbours stay inside, but even then, they will clearly hear it !

Another thing I saw, is that sometimes, the RF field poduced by the tesla coil cuts my internet connection if the coil is too close of the ADSL buried cable

Still, definitely worth it !

MrFlatox

Sun Dec 22 2013, 11:42AM

Registered Member #9349 Joined: Mon Jan 07 2013, 08:50AM
Location: France
Posts: 102

Hi,

I did some more tests, and noticed that without breakout point, most of the sparks the coil produces directly hit the ground rail around the primary. I know that this rail is there for this very reason, but I would like streamers to fly everywhere rather than to the bottom. Is there any way to achieve this ? Maybe add more spacing between the toroid and secondary winding end ?

I also added a little more capacitance to the topload (a stainless steel salad bowl), and after tuning the coil, it performs a little bit better.

Here is a few long exposure pictures, as you can see, most streamers are hitting the ground rail.

Thanks, have a nice day.

Kizmo

Sun Dec 22 2013, 01:36PM

Registered Member #599 Joined: Thu Mar 22 2007, 07:40PM
Location: Northern Finland, Rovaniemi
Posts: 624

I have found out that the toroid outer diameter should be quite a lot larger than the diameter of your base and strike rail. Then you wont get that many strike rail hits.

Here the outer diameter of my toroid was roughly 2x the diameter of the base. It worked really well up to 4x secondary length spark.

MrFlatox

Tue Dec 31 2013, 04:53PM

Registered Member #9349 Joined: Mon Jan 07 2013, 08:50AM
Location: France
Posts: 102

Hi !

I solved the issue stated above where the streamers mainly hit my ground rail. I added another toroid with a much smoother finish, which also make the streamers more beefy.

However, my two standing electrodes in the rotary spark gap cannot handle the heat, and they start to melt quickly. They are made of stainless steel, and this might not be the best material for this purpose ! see for yourself :

Even if the electrodes are attached to a large heatsink, they cannot evacuate the heat, and get red hot after less than a 30 seconds run, whereas the heatsink stay cool. I was wondering how copper electrodes would behave in this case. Copper will conduct away heat much better than SS, despite having a lower melting point. I will try those.

Here is a video of the coil with its new toroid, and the spark gap melting :

Happy new year ealier btw !

H. Love

Thu Jan 02 2014, 01:58AM

Registered Member #13419 Joined: Thu Apr 11 2013, 01:35AM
Location:
Posts: 7

Nice stuff! I would recommend using tungsten for the spark gap electrodes, however, due to its high melting point. Tungsten is a bit more expensive though.

redruM69

Thu Jan 02 2014, 06:15AM

Registered Member #31557 Joined: Tue Aug 06 2013, 02:38AM
Location:
Posts: 58

I have a bunch of extra 1/8" tungsten. I can spare a couple if you want. PM me.

MrFlatox

Thu Jan 02 2014, 10:05AM

Registered Member #9349 Joined: Mon Jan 07 2013, 08:50AM
Location: France
Posts: 102

Thank you,

@ redruM69 : Are those electrodes the ones you used for your rotating electrodes and safety gap ? I don't know how they behave, but I would think that 1/8" (or 3.5 mm) is rather thin for static electrodes.

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