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My first Tesla Coil build.

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LAN_403

Etcetera

Sat May 05 2012, 02:29AM

Registered Member #4672 Joined: Tue May 01 2012, 12:18AM
Location: La Habra, California, USA
Posts: 14

Hey everyone, this is my first post here. I have been lugging a pair of 15kv 60ma NST's around for 20 years and have finally decided to do something with them other than setting up the occasional Jacob's ladder on Halloween.

I'd like to use this thread to firm up my design and solicit feedback. Mostly I don't want to make an expensive mistake...

I really like coils that produce a consistent spark. The output from some coils seems to be somewhat fluid. I really like that effect. Not sure if that is just a well designed coil that is properly tuned, or if there is some specific formula to achieve that. I will gladly give up some spark length to achieve this.

Here is what I'm planning.

I already have the components to build a secondary. Just stuff I've collected over the years.
6" secondary wound on green pvc.
approx 950 turns of 24awg wire
6" x 22" torroid top load

Primary to match with lots of room to tune.

I'm basing my tank cap size on the assumption that a triggered static gap

would require a similar capacitance to a SRSG. If I'm wrong please tell me. To me this seems easier to build than a SRSG and I already have almost all the parts to build one.

Tank Cap CDE 942's 2 strings of 11.

Of course at bare minimum a safety gap, probably a Terry filter.

A (BIG) part of me wants to build it bigger from the get go. I've considered de-potting the NST and removing some shunts. Maybe shoot for 100ma. Then skipping the MMC and going straight to something like this

Should be bullet proof and not that much more cost than building a MMC for the higher current.

Someday it would be fun to build a really big coil. I used to work as an electrician and I have access to a pole pig for free, or very close to free. Lots to learn before making that leap.

That is all for now. I'm itching to start. Comments welcome!

Sigurthr

Sat May 05 2012, 04:20AM

Registered Member #4463 Joined: Wed Apr 18 2012, 08:08AM
Location: MI's Upper Peninsula
Posts: 597

Welcome! I am somewhat new to coiling as well so I can't give you much build avice really, except that SOME of those commercial pulse caps are not meant to run continuously like we need in TCs. Some of them are only designed to pulse maybe once a minute. I've seen pictures of commercial HV caps exploded from TC use. So be careful!

Also, the mechanical engineering side of SGTCs is something to be considered. Think about the base you use and what it will be near. Keep metal away from the TC's vicinity as it can REALLY throw off tuning and cause major problems. I found out the hard way. Pay special attention to the coupling and how you can adjust it (including primary diameter and height) as well, it really helps to have it planned out from the start rather than improvised later on.

Etcetera

Sat May 05 2012, 05:28AM

Registered Member #4672 Joined: Tue May 01 2012, 12:18AM
Location: La Habra, California, USA
Posts: 14

Thanks, I hadn't considered that some of those big pulse caps might be low duty cycle.

Where in the UP? I have family in Ishpeming.

Sigurthr

Sat May 05 2012, 06:05AM

Registered Member #4463 Joined: Wed Apr 18 2012, 08:08AM
Location: MI's Upper Peninsula
Posts: 597

About 170miles east of there, heh. I'm in the greater Sault Ste Marie area.

Etcetera

Thu May 10 2012, 02:31AM

Registered Member #4672 Joined: Tue May 01 2012, 12:18AM
Location: La Habra, California, USA
Posts: 14

I've decided on a MMC cap. Going with the tried and true 942 caps. Playing around with some numbers I've decided to order enough to build a .0461uf mmc at 26kv. That is 52 caps. Found a place with a price break of $3.39 each at 50+ pieces. Worst case I am more than happy with a static gap with a smaller cap and I'll sell the excess on ebay or maybe this site.
Here's the link

If there is a better place to buy them I would love to hear about it.

My memory was faulty and the 6 inch PVC I had stored away was really 8". I can probably get a piece of 6" fiberglass piping from work, but it's not completely smooth. Seems like fiberglass resin might be good as a topcoat for the windings.

Hoping to get most of the construction done this weekend.

Sigurthr

Thu May 10 2012, 06:39AM

Registered Member #4463 Joined: Wed Apr 18 2012, 08:08AM
Location: MI's Upper Peninsula
Posts: 597

Onlinecomponents is where I buy my 942 series caps, you really can't go wrong with them - great prices and top notch caps.

If you can afford it, go for more than 26kV. I'd shoot for around 30kV.

Why did you chose 0.046uF? JavaTC recommends 0.0277uF for a SRSG using a 15/60NST. You need to remember to avoid resonant rise if you don't want to blow up both your MMC and your NST, especially if your MMC isn't rated for at least 1.5x the Vpk of your NST.

Etcetera

Thu May 10 2012, 12:54PM

Registered Member #4672 Joined: Tue May 01 2012, 12:18AM
Location: La Habra, California, USA
Posts: 14

Initially I'm building a .015uf cap for a static gap. Eventually I want to depot the nst and shoot for 100 ma with a rotary gap.

Sulaiman

Thu May 10 2012, 07:02PM

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

As this is your first TC I strongly advise;
- do not remove the NST shunts
- use a 'safety spark gap'
- use this

online calculator
.......... it takes a little time but it's worth the effort.
- use a static spark gap with a good strong airflow across the gap(s)
- use good capacitors for the MMC (the CDE are tried and tested)

As far as possible copy the design of a known good SGTC
(several members here have TC related web pages)

Etcetera

Thu May 10 2012, 10:58PM

Registered Member #4672 Joined: Tue May 01 2012, 12:18AM
Location: La Habra, California, USA
Posts: 14

Thank you very much for the advice. JavaTC has been my primary calculation tool, it's great.

At a minimum I plan on a safety gap, possibly a Terry filter.

Pictures to follow. I'm hoping to have the secondary wound and coated this weekend. Depending on how that goes I'll work on the primary which I plan to make from .25" copper tubing and plexiglass as the former.

One question I have regarding placement of components. Sigurthr mentioned not to have metal in the vicinity of the coil. Does this mean I should not build the rotary gap and transformer into the base of my coil? Ideally I would like to make it self contained with just a control box to supply power from a safe distance.

Thank you everyone again for the advice. Looking forward to making some parts.

Eric

Sulaiman wrote ...

As this is your first TC I strongly advise;
- do not remove the NST shunts
- use a 'safety spark gap'
- use this

Etcetera

Mon May 14 2012, 06:04PM

Registered Member #4672 Joined: Tue May 01 2012, 12:18AM
Location: La Habra, California, USA
Posts: 14

Didn't get as much done on the weekend as I hoped. Spent my free time on Saturday troubleshooting and repairing the VFD for my lathe. Broken solder joint.... Anyways, this morning I started. Secondary is 4 inch ABS pipe. 4.5" OD. I drilled a 45 degree countersink in an end cap and mounted it in my lathe. Used a large Allan wrench as the axle for the wire spool. Set the lathe up for it's slowest speed and drove the motor at about 15 HZ. When ahead and wound it. Took about 15 minutes or so and it came out pretty nice I think. Going to do a bit of research and head to Home Depot for some type of coating, (EDIT: Found some Minwax polycrylic in my garage, did a search and found that at least a couple people are using it. ) Hoping to have it coated today.

Ended up being about 23.125" of winding which calculates out to about 1050 turns. Aspect ratio of 5.14 to 1. I measured the wire with a micrometer at .022 inches diameter. It's double coated 200C 24 gauge wire.

Next is to cut up a piece of plastic to make a primary former.

Moving along!!! Hoping to make sparks this weekend.

Eric

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