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What To Do With All My NST's

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KeeDx3

Mon Jul 31 2017, 12:23AM

Registered Member #61435 Joined: Thu Jan 19 2017, 06:46AM
Location:
Posts: 25

Well, I guess it pays to befriend a neon guy.

I bought these Franceformer NST's for $5 each: 17x 12/30 and 3x 10,500/30. Any suggestions on what to do with them? I have a feeling I'll be selling a bunch of them, but I am also wondering what kinds of cool projects I could build. I'm basically a beginner - I have a 15/60 Jacob's Ladder, a little 7500v HV pendulum, and I've started on a 12/30 SGTC (with plans to build a larger once I gain confidence after this build). What other intermediate/beginner projects am I overlooking?

12/30 isn't a lot of power, but I guess I could parallel a bunch of them. How many NST's will a 15-20A circuit handle, anyway?

NHqI1Xi

Sulaiman

Mon Jul 31 2017, 04:01AM

Registered Member #162 Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3140

What a haul !

first approximation: (120V x 20A) / (12kV x 30mA) = 2400W / 360W = 6.67 NSTs

KeeDx3

Mon Jul 31 2017, 04:55AM

Registered Member #61435 Joined: Thu Jan 19 2017, 06:46AM
Location:
Posts: 25

Sulaiman wrote ...

What a haul !

first approximation: (120V x 20A) / (12kV x 30mA) = 2400W / 360W = 6.67 NSTs

Thank you! Definitely going to keep that information in my back pocket.

He said he's going to keep my number because his brother has "a few" 15/30's that he'd also be willing to get rid of. Of course he said the same thing about a "few" 12/30's, so I'm excited to see what he comes up with. I also gave him an extra $40 and he was so appreciative that he cut me a few dozen feet of GTO wire.

He drove about 30 minutes to deliver them to me, with his wife and kids in the car. He said they were headed to Sam's Club (big "buy bulk & save" warehouse store in the US). I guess he was planning on doing some grocery shopping with the money from the NST's, and I like to think I helped make their life a little better this week. All in all, a win/win!

Oh and I misspoke. I paid $10 each for them - but I still feel like I got a really good deal.

RogerInOhio

Mon Jul 31 2017, 04:57PM

Registered Member #1034 Joined: Sat Sept 29 2007, 12:50PM
Location: Chillicothe, Ohio
Posts: 154

If these are the old type I'd say they are worth their weight in gold. The new ones have ground fault protection that makes them useless for Teslacoils without modification.

For a beginer one of these would be perfect for constructing there first coil unless they go the solid state rout.

KeeDx3

Tue Aug 01 2017, 04:46AM

Registered Member #61435 Joined: Thu Jan 19 2017, 06:46AM
Location:
Posts: 25

RogerInOhio wrote ...

If these are the old type I'd say they are worth their weight in gold. The new ones have ground fault protection that makes them useless for Teslacoils without modification.

Yeah, I lucked out. These are all the old style without the GFI.

My neon guy actually called me today asking to see pics/videos of what I am doing with them. Thinks it's pretty neat. He said he's also checking around for some 15Kv's, so I'm keeping my fingers crossed on that one. I might also get some free sticks of neon out of the deal. Pretty excited over here! It's amazing the generosity you'll come across when you visit people and show interest. I think the extra money on top of the $10/ea he was asking didn't hurt either. He seemed like he needed the money and I was excited to be getting a good deal on a bunch of NST's. Everyone is happy.

Sulaiman

Tue Aug 01 2017, 07:55AM

Registered Member #162 Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3140

IF you have enough time and similar NSTs in reasonable condition it may be worthwhile to sell complete classic spark gap tesla coil kits.

It would be an easy way for newly interested hobbyists to start

A 'Museum Quality' coil would of course sell for more,
a 'new-age' / 'steam-punk' / 'head-shop' (or whatever is in fashion) version for even more,
but starting with used NSTs I would offer them as part of an affordable starter kit
- and carry less liabilities.

and you should be able to make quite a little profit.
(cheap NSTs and bulk-buy discounts/economies)

Inspect (cracked tar etc.) and Test the NSTs,
make SGTC Version 1 quickly, don't try to perfect everything before jumping in,
it is very unlikely that your first sgtc will be optimum unless you copy a published design exactly
DO FIT SAFETY SPARK GAPS and never run without them - NSTs are valuable you know !.
for this power NST there are lots of prototypes to copy,
winding coils is easy, copper and capacitors are not cheap so some optimisation may be required,
spark gaps are CRITICAL to performance, experiment here,
then make a Version 2, it may be selable, but Ver.3 will be better :)

Check eBay / the market for current prices and potential demand - I believe there is more than enough demand.

If due to hobby tinkering you discover that the commercial Ver.3 can be optimised or enhanced further, then you could make kits available for that too. (safety spark gap / Terry Filter), (Mylar / Polypropylene) and especially Spark Gaps.

I would like to see some youths taking up classic Tesla Coiling to keep it alive.
A 'brave' minimal system of

NST - Spark Gap - Capacitor - Coil - Coil - Topload,

six components, is all that is required.
(but don't forget to add the safety spark gap, or better, a Terry Filter or similar, plus safety for sentient beings)

(make a spare kit for your kind donor)

KeeDx3

Tue Aug 01 2017, 08:26AM

Registered Member #61435 Joined: Thu Jan 19 2017, 06:46AM
Location:
Posts: 25

Great ideas, Sulaiman. I definitely want to 'pay it forward', as it were. I'm actually selling two NST's to a coworker (for the same price I bought them) since he made an off-the-wall comment about wanting to build a Jacob's Ladder with his daughter - but didn't know quite where to begin. So I'm hooking him up with two 12/30's and a few feet of GTO wire (and some free advice to get started safely). Feels good getting others involved.

All the NST's are in good physical condition if not a bit weathered. Some light rust around the bases/feet. They should clean up nice and would probably look perfect if painted.

You mentioned cracked tar â€” I've seen this in many of my own NST's, especially the older ones. Is this a thing I should fix asap? I suspect the solution to the problem is letting them sit in the sun or running them shorted for a few hours, and then restirring the tar?

Also, good advice on just diving right in to TC ver. 1. I've been at a standstill with my own first coil since I'm such a perfectionist... Even though I planned this coil to be 'quick and dirty' all along. I just need to finalize the MMC array, buy/build the Terry Filter, and the rest is assembly. Of course I also need to remember the specs of my secondary. Slept a few times since I wound it. Pretty sure it's 3.5" and nearly 1,000 turns. Originally slated to use 25' 1/4" copper tube for the primary but that only gets me 7 or 8 turns. Probably need more.

Sulaiman

Tue Aug 01 2017, 08:52AM

Registered Member #162 Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3140

Cracks in the tar allow moisture into the windings leading to failure,
heating the NST GENTLY in an oven until the tar melts, then for another hour, helps to 'heal' the insulation and vapourise out any water.
Often a failed NST has been repaired this way,
I 'repaired' one of mine twice succesfully

and once unsuccesfully

(For sgtc-playing I now have only an OBIT, 5 kV, 23 mA ... still fun)

DO NOT DO THIS IN A SHARED OVEN !

smelly smoke will permeate everywhere.
I've not tried the s/c secondary heating method - it may be more convenient.

25 ft. does sound a little short, try a simulator to check,
a helical primary wound on pvc pipe (with the pipe taller than the coil for added pri-sec insulation) may help save copper.

P.S. the 'dive-right-in' advice is mainly due to my own tendency towards extreme procrastination,
(my wife just calls it laziness)
I like doing theoretical revisions and calculations
- actually very little calculation is required,
(simplified Medhurst and Wheeler approximations are enough, simulators are a little more accurate but not as instructive)
experimental development is what is required
- I'll get round to some next year, or maybe ...

teravolt

Tue Aug 01 2017, 07:39PM

Registered Member #195 Joined: Fri Feb 17 2006, 08:27PM
Location: Berkeley, ca.
Posts: 1111

most nst have 2 secondaries out of phase. If you want to combine there power you can phase and parallel the outputs. As your current grows you can draw the arc out further. If you do this combine transformers of the same voltages. In this way you can deliver more power to your tesla

Sulaiman

Tue Aug 01 2017, 07:51PM

Registered Member #162 Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3140

Last thought (for today) ... spark length is approximately proportional to SQRT(Power)
i.e. to double spark length you need 4 NSTs
to quadruple the spark length, 16 NSTs would be required

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