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Any oppinions on spark gaps

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Sam

Wed Mar 15 2006, 04:01AM

Registered Member #227 Joined: Mon Feb 20 2006, 10:47PM
Location: Cambridge Ontario, Canada!!
Posts: 127

lol! the ballast is smoking because its cutting back I's say about 10 amps or more! its just a 120v to 12v 5 amp supply with the secondary shorted out. I've got more dont worry. as for the Tesla part, I was just using it as some quick fill-in coils, the new coil will have a primary made of 1/4 copper tubing set at 35 deg.(apperently opptimum) and a secondary made of 22 or 24 gauge mag. wire at about 2 feet tall.
The tank cap is res. at 160-ish nF.

as for the spark gap, should it really be a sphere shape? I heard it should be pointed? oh well. What kind of tank cap should I make? I cant really make an MMC but plate caps and bottle caps are a maybe...

Keep the sugestions comming
Sam-0

Part Scavenger

Wed Mar 15 2006, 04:31AM

Registered Member #79 Joined: Thu Feb 09 2006, 11:35AM
Location: Arkansas
Posts: 673

benguy wrote ...

I do think no so much. Lets say it pulls 1000w from any source, 1000w, at 120 thats 8.33 amps yes?
now on 220 thats 4.54 amps correct? same wattage different current eh!

And about the static spark gap, What would I use to blow the gap clean? like a PC fan or somwething?

Woah, buddy. That ain't right. Provided the core doesn't saturate and you estimate current correctly, all ideal, it will pull more (9 something amps, 220V, 2000W) because you doubled the voltage. And if you're using an MOT, that current estimate might be way off. You had the right idea, but wattage is not constant on a MOT.

Oh yeah. The deal with toriods is:
The toroid shape is used because it shields the secondary circuit and tends to propel the streamers outward. The ball tends to concentrate all the energy into one streamer, but makes it a whole lot more likely to strike the primary and secondary.

EDIT=> Oh, reread tells me you were talking about SG's not toroids, sorry. They are rounded because a pointed gap is harder to quench (turn off) and requires a much lower voltage before it fires. Rounded is better.

GimpyJoe

Wed Mar 15 2006, 04:35AM

Registered Member #316 Joined: Mon Mar 13 2006, 01:30PM
Location: Marietta, GA
Posts: 212

Part Scavenger wrote ...

I think he means that instead of having the primaries in parallel he would put them in series and run off a 220v outlet so he can draw more power without tripping the breaker.

Sam

Wed Mar 15 2006, 04:48AM

Registered Member #227 Joined: Mon Feb 20 2006, 10:47PM
Location: Cambridge Ontario, Canada!!
Posts: 127

Right about the 220 thing. and thanks for the info on toroids and spark gaps

Hazmatt_(The Underdog)

Wed Mar 15 2006, 06:50AM

Registered Member #135 Joined: Sat Feb 11 2006, 12:06AM
Location: Anywhere is fine
Posts: 1735

I think you're really going to have a problem with the PVC even if you have a blower pushing air past the terminals. The threaded rod is going to heat up too fast and melt the PVC.

I want to suggest copper pipe pieces but I can't because that would only work for a NST application where the current isn't high enough to cause a meltdown.

I'm thinking metal hardware to fasten the threaded rods like a heatsink with the same thread as the rod, that might dissipate enough heat, and have that mounted inside the PVC. Then have 2 corona nuts or spheres on the rods.
I think if I were in your situation I would make maybe 3 sets of these and parallel them inside a length of pipe and force air through. Either that or I would make a lexan box with the heatsinks and such. I think its a tough one because there is so much current.

Sam

Wed Mar 15 2006, 07:02AM

Registered Member #227 Joined: Mon Feb 20 2006, 10:47PM
Location: Cambridge Ontario, Canada!!
Posts: 127

maybe 2 steel "L" shaped bits with holes in top and bottom, brass bolts through there, inside a big pvc? or something like that? It's really early my brain is shut off right now...

What can I put on the bolts to make them spheres?
I'm stuck there...I guess the sphere should be brass too eh?

Sam

Wed Mar 15 2006, 08:51PM

Registered Member #227 Joined: Mon Feb 20 2006, 10:47PM
Location: Cambridge Ontario, Canada!!
Posts: 127

Yay! I got my new ballast today and for free! along with some magnet wire most likely for the secondary(I got some 22g and some 33g and I have some other wire somewhere in my mess of a shop...)
Here is my new 5amp ballast, its not quite powerfull enough but it keeps my variac from overheating(smkoking

)
I also got about 15 feet of white PVC for $5(canadian) I want to make some different secondaries... What wire and what lenth should I use? The teslamap software is confusing me...

vasil

Wed Mar 15 2006, 09:45PM

Registered Member #229 Joined: Tue Feb 21 2006, 07:33PM
Location: Romania
Posts: 506

For a good quenching just use your bigg brass screws in a good configuration. Ex:

http://www.geocities.com/gemaria_ro/multigap.html

With good MOT ballasting will work. Of couse, for unballasted MOTs, the sucker gap is better, but with the homemade caps you have i dont see you runing high currents (you need more primary cap to load the MOT output)

Sam

Thu Mar 16 2006, 02:13AM

Registered Member #227 Joined: Mon Feb 20 2006, 10:47PM
Location: Cambridge Ontario, Canada!!
Posts: 127

Thanks for the cool spark gap design! I have to try that. As for the last few hours I've been winding the secondary coil for this project.
Secondary specs:
-22 gauge
-about 1200 turns
-32.5 inches tall
-2 inches O.D.

Teslamap says this is not a good hight to width ratio so I may redo this one...

GimpyJoe

Thu Mar 16 2006, 03:01AM

Registered Member #316 Joined: Mon Mar 13 2006, 01:30PM
Location: Marietta, GA
Posts: 212

Yeah, that secondary would work, but the H/D ratio is way off. A better secondary would be about four inches diameter and two feet long.
As you've obviously just found out, hand winding sucks. The best winding method I've found is to make a winding jig with a board and some L brackets. Then have a friend use a variable speed electric drill to spin the form. Tape the wire on one end and have the spool on an axle and supports so it can rotate freely. Now have your friend start spinning the form very very slowly and use your hand to guide ten or twenty turns tightly onto the form. Once this is done you have a good start against which you can "cram" the rest of the wire. Guide the wire with one hand and use the fingernails of the other hand (or you can use a tongue depressor, but it's harder) to cram the wire against the winding as your friend increases the speed of the drill. Once you get the feel for it you can easily get up to full speed. My friend and I wound a 3.5"x18" secondary in less than ten minutes this way. Even with making the rig, you'll still spend much less time winding. Hope this helps.

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