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LAN_403

Nah

Thu Apr 21 2011, 11:45PM

Registered Member #3567 Joined: Mon Jan 03 2011, 10:49PM
Location: USA, 1960s
Posts: 260

Ah, make it baklite.

Steve Conner

Fri Apr 22 2011, 07:46AM

Registered Member #30 Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706

I'm sure I remember seeing a copper toilet float ball used as a topload. Soda and beer cans also work for small coils.

I've seen extremely large toroids made out of arrays of discs. Maybe you could use the bottoms of beer cans.

RickR

Fri Apr 22 2011, 03:20PM

Registered Member #93 Joined: Thu Feb 09 2006, 04:11PM
Location: Houston, Texas
Posts: 64

Copper tubing toroid, not a commodity item.

Pros: looks cool, works, you can determine the final size.

Cons: you have to invest some time and (maybe not a lot of) money:
http://4hv.org/e107_plugins/forum/forum_viewtopic.php?27432.0#post_33439.

Look about 2/3 of the way down on the first page of posts.

-Rick

Ash Small

Fri Apr 22 2011, 04:25PM

Registered Member #3414 Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245

Another idea might be to use four 90 degree pipe bends.

They come in different diameters and radiuses (radii?), a bit of careful cutting and welding, with subsequent polishing should produce an acceptable toroid.

I've seen these in cast aluminium, as well as other materials.

EDIT:

and using these would be even easier, 180 degree bends:

quicksilver

Fri Apr 22 2011, 05:28PM

Registered Member #1408 Joined: Fri Mar 21 2008, 03:49PM
Location: Oracle, AZ
Posts: 679

I have tried just what you propose! I weld aluminum and thought of this as an ideal solution.
What happened was that even though I sanded and cleaned up the joints quite well; any imperfection was where I was getting most of my output.
I can see why a spun, turned toroid is valuable. It seems ANY imperfection becomes a consistent breakout point (to a degree of exclusion of the majority of the rest).

Ash Small

Fri Apr 22 2011, 06:12PM

Registered Member #3414 Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245

quicksilver wrote ...

In the same theme, there are many cake or Jello molds,that, buying two of them and bolting (or welding) them together will yield a toroid. In the "Kitchen" section of many stores are various substitutions that may work well. I did find one that was a "half toroid" at WallMart (aluminum), ground the lip off of it and it appeared fairly nice for a small coil.

quicksilver wrote ...

I have tried just what you propose! I weld aluminum and thought of this as an ideal solution.
What happened was that even though I sanded and cleaned up the joints quite well; any imperfection was where I was getting most of my output.
I can see why a spun, turned toroid is valuable. It seems ANY imperfection becomes a consistent breakout point (to a degree of exclusion of the majority of the rest).

At first it seems there is an 'apparent' contradiction between the two above posts.

Are you suggesting that a continuous weld around the outer periphery of the toroid would be ok, but that a weld at only a few points around the periphery will result in breakout from those points only?

If so, maybe this could be overcome by grinding a groove around the periphery, and filling with a bead of weld?

Please clarify.

Steve Conner

Fri Apr 22 2011, 09:19PM

Registered Member #30 Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706

Well, if you're the kind of coiler who likes to watch sparks dance in all directions around a bare toroid, then it has to be nice and smooth. Lumps and bumps will attract the sparks.

But the vast majority of solid-state coils, even DRSSTCs, need a breakout point to get started without blowing something, or to make really long sparks without striking their own electronics and dying. Using a dedicated breakout point makes the toroid shape less critical, you can get away with a small rim or lip. If you like randomly dancing sparks, you can install several points, but the effect isn't quite as nice as an old-school spark-gap coil with a synchronous rotary gap and a smooth spun toroid.

From the old TCML days, I remember seeing toroids made of pipe elbows as suggested above. I believe there is a thing called a "muffler donut" in America at least. It's a toroid made of steel tube, from which you can cut odd-shaped bends when making up custom exhaust headers for engines.

quicksilver

Thu Apr 28 2011, 05:36PM

Registered Member #1408 Joined: Fri Mar 21 2008, 03:49PM
Location: Oracle, AZ
Posts: 679

What may be a seeming contradiction (IMO) in density issues when welding as opposed to mechanically combining two sections. Note, that I noticed this in two examples & realistically that's not a very large sample

No matter how I cleaned up the exterior wall, the interior was uneven in terms to wall density. In a mechanical fitting (a simple bolt through the center, etc) there is a continuous wall thickness.

I should also make clear this was noticed when the circumference was smaller and from a smaller unit overall. This MAY increase sensitivity to non-uniform density. However, in a commercial "turned toroid" the consistency vary only a slight degree. Even with a foil coated tube the thickness would be only 2-3 sheets of foil making the density difference pretty slight.
Obviously only opinion, but I think that the more powerful / larger coils have less sensitivity to this than small units.

Empirically, I had also noticed that in a "quick & dirty" tube coil made with foil, a folded projection also had a tendency to produce a break-out point on a consistent basis; not allowing a more consistent "flow" pattern of sparks from the toroid (again much more so in a lower powered, smaller coil).

Ash Small

Mon May 02 2011, 02:01PM

Registered Member #3414 Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245

@ Quicksilver, That makes sense. Did you use MIG or TIG?

tsgeoman

Mon May 02 2011, 02:42PM

Registered Member #3622 Joined: Sun Jan 16 2011, 05:48PM
Location: Provo, UT
Posts: 5

I found a guy here in Utah that made me these 6x24 foam toroids for $35 each. I will do the wrapped in foil tape method with a plexi glass core.

1304347360 3622 FT113074 Mini Assembly 030

1304347360 3622 FT113074 Mini Assembly 033

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