best way to secure coil / Tesla Coils / Forums

Forums

4hv.org :: Forums :: Tesla Coils

« Previous topic | Next topic »

best way to secure coil

1 2 next

Move Thread

LAN_403

lokeycmos

Fri Oct 21 2011, 06:42PM

Registered Member #2553 Joined: Fri Dec 18 2009, 01:36PM
Location: St Cloud Minnesota
Posts: 97

i have my secondary wound with 24g wire. 3.5"x22". what is the best way to secure the ends of the coil? i read NOT to drill holes and feed inside the tube. i have the whole coil taped up with painter tape and afraid that it will uncoil and make a mess if i take the tape off.

Dr. Dark Current

Fri Oct 21 2011, 06:56PM

Registered Member #152 Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384

At first coat the secondary with enamel to fix it in place. Then, I have never had problems with feeding the wire through the secondary form - however you must not let it stick away from the former. On my secondaries I drill 2 small holes next to each other, wrap the wire through them a few times and fix with super glue. Then I glue a "wire washer" (? dont know the right word) to the coil form and drill a hole for a screw.

lokeycmos

Fri Oct 21 2011, 07:12PM

Registered Member #2553 Joined: Fri Dec 18 2009, 01:36PM
Location: St Cloud Minnesota
Posts: 97

oh ok. i thought that if you drill holes for the ends it creates extra corona. another Q i have is where do you feed the bottom lead to earth ground so it doesnt arc to the primary or any other parts underneath the coil?

Dr. Dark Current

Fri Oct 21 2011, 07:31PM

Registered Member #152 Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384

If there is space below the coil assembly, just feed the wire through whatever the coils sit on. If the coils are on ground (or table) level, I just put the wire under the primary former (make a small window for it). Of course the distance to primary must take into account voltages present on the primary so it doesn't arc over, also the distance to primary should be increased when the grounding impedance is higher (eg. long ground wire + ground rod).

Note: in the previous I assumed that the primary is on a former. In any case, you can use a HV rated wire for the secondary ground, this should eliminate arc overs.

lokeycmos

Fri Oct 21 2011, 07:56PM

Registered Member #2553 Joined: Fri Dec 18 2009, 01:36PM
Location: St Cloud Minnesota
Posts: 97

TY. i have some clear lacquer and some clear acrylic varnish. which do you think i should use:?

genious 7

Sat Oct 22 2011, 12:24AM

Registered Member #2887 Joined: Sat May 29 2010, 11:10PM
Location: Panama City, Panama
Posts: 107

The drilling hole issue starts when the streamers have the length of the secondary. If the wires pass through the inside, a streamer may develop on the inside of the coil former instead of upwards, which limits your maximum streamer length. A member had that problem recently, I'll try to find the thread. If you know your streamers (or ground arcs) are not going to reach the secondary length, the advice is not as important, although still useful.

M.A.D.

Sat Oct 22 2011, 07:51AM

Registered Member #4052 Joined: Thu Aug 11 2011, 04:43AM
Location: IN ,USA
Posts: 69

On my first sgtc I feed both ends of the secondary inside the tube because it was easy and I thought that it would never make arcs that long anyway.However it did arc all the way down the tube, leaving a deep carbonized scar. The sad part is that I was only ever able to get arcs on the outside of the coil about half as long.

This coil had many other problems though, (seriously untuned, my asynchonous rotory gap was erratic at best, my homemade mason jar caps sucked, and it was extremely over coupled) so it might be fine if your coil is well built.

however, I will never put the leads on the inside again, because even after I had removed all the carbon, filled the tube with wax, and moved the wires to the outside it still continued to arc on the inside and eventualy destroyed the coil.

The remains of this coil are now archived in the ''what not to do'' section.

Dr. Dark Current

Sat Oct 22 2011, 10:54AM

Registered Member #152 Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384

I've never had issues with the wire passing on the inside of the form, but then I only built SSTCs and VTTCs which had sparks slightly longer than the secondary winding. However this might be an issue on pulsed coils such as SGTC or DRSSTC, but I never experimented with those.

Herr Zapp

Sat Oct 22 2011, 06:05PM

Registered Member #480 Joined: Thu Jul 06 2006, 07:08PM
Location: North America
Posts: 644

lokey -

Securing the ends of your secondary winding through holes in the coilform is perfectly acceptable as long as you provide one or more "sealed" insulating baffles inside the secondary. Install the baffle 2-3" below the top of the coilform, and make sure that it is absolutely hermetically sealed using silicone sealant (preferebly electronic grade, which does not liberate acetic acid during curing).

The real concern here is "surface tracking". A small coil that generates 10" air streamers will easily arc along the surface of an insulator (like the inside of a PVC coilform) 2X that distance. As a well-tuned coil can generate streamers considerably longer than secondary coil, adding a baffle (or two) is cheap insurance against a destroyed secondary. Once surface tracking takes place and burns a carbonized path into the surface of the coilform, it's very difficult to fix.

Herr Zapp

lokeycmos

Sat Oct 22 2011, 06:44PM

Registered Member #2553 Joined: Fri Dec 18 2009, 01:36PM
Location: St Cloud Minnesota
Posts: 97

i got my coil wound. i didnt drill any holes. i attached a pic. im still kinda confused as to where to run the ground wire. should i run it directly through the PVC base straight down the middle and keep it isolated from the power source and other components that will be mounted on the very bottom base?

1 2 next

Moderator(s): Chris Russell, Noelle, Alex, Tesladownunder, Dave Marshall, Dave Billington, Bjørn, Steve Conner, Wolfram, Kizmo, Mads Barnkob