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IamSmooth

Thu Nov 09 2006, 03:59PM

Registered Member #190 Joined: Fri Feb 17 2006, 12:00AM
Location:
Posts: 1567

Has anyone here actually tried to spin a toroid in a machine shop on their own? I figure one would have to make a positive and negative mold with a router and then use a machine to spin and press a sheet of aluminum. (I am guessing on this).

If anyone has tried this how were your results?

Steve Conner

Thu Nov 09 2006, 04:11PM

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

I just bought mine from John Freau. His website gives pictures of the process he uses to make them:

Avalanche

Thu Nov 09 2006, 04:17PM

Registered Member #103 Joined: Thu Feb 09 2006, 08:16PM
Location: Derby, UK
Posts: 845

I've tried to spin some aluminium just to see if it could work for a small toroid, but it was hopeless. I thought i'd better stop before I wrecked the lathe. In the end I just turned up a solid one from some thick plate, but that wasn't really a toroid.

I can't understand how it can work so accurately!

IamSmooth

Thu Nov 09 2006, 05:27PM

Registered Member #190 Joined: Fri Feb 17 2006, 12:00AM
Location:
Posts: 1567

I've seen some metal shops use a combination of spinning discs with the object on a rotating axis. I like doing things myself, but this seems to require some dedicated machine shop equipment to do it right.

Marko

Thu Nov 09 2006, 07:20PM

Registered Member #89 Joined: Thu Feb 09 2006, 02:40PM
Location: Zadar, Croatia
Posts: 3145

I *could* try casting a small toroid or sphere out of solid aluminium but that would be too much work. It's simpler to tape a plastic object with some alu tape ant it still looks nice...

Terry Fritz

Thu Nov 09 2006, 11:26PM

Registered Member #393 Joined: Tue Apr 18 2006, 12:30AM
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Posts: 297

Hi,

I have some of John's videos where he is making toroids. It looks really hard!!! He has a lot of special fixtures and stuff and then he "fights and wrestles" the metal to shape. It looks like it could be fairly dangerous too... Before trying, you would definitely want to get John's tapes on this!!!

You may want to consider the bleeding edge "PIRANHA - New Top Load Configuration" thread... I am very happy with that!!!

The spheres I used might be a little too big since mine easily hold in 300kV!!! But the terminal capacitance is nice and high. I have had no problems at all with it. Those old corrugated aluminum toroids are going to the trash now!!

The new one can tune and hold off as needed for all my coils

Cheers,

Terry

HV Enthusiast

Fri Nov 10 2006, 01:06PM

Registered Member #15 Joined: Thu Feb 02 2006, 01:11PM
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Posts: 3068

Spinning aluminum is a difficult skill and basically an artform. It requires a huge initial investment in equipment, fixtures, tooling, etc... and the learning curve is steep - probably take several years to perfect the technique.

IamSmooth

Fri Nov 10 2006, 01:13PM

Registered Member #190 Joined: Fri Feb 17 2006, 12:00AM
Location:
Posts: 1567

I've looked into the cost of lathes and I've perused through various metal spinning links. You are right about the skill level and investment cost. I can only guess that those who spin the toroids already had the equipment for other reasons.

Tesladownunder

Sat Nov 11 2006, 12:45PM

Registered Member #10 Joined: Thu Feb 02 2006, 09:45AM
Location: Bunbury, Australia
Posts: 1424

Terry Fritz wrote ...

...You may want to consider the bleeding edge "PIRANHA - New Top Load Configuration" thread... I am very happy with that!!!
...

Terry, have you considered other sphere numbers other than 4? Strikes me that 3 is easier and perhaps 8 (octopseudotoroid) is neater. Depends if you have the balls or not

Peter

Terry Fritz

Sat Nov 11 2006, 08:29PM

Registered Member #393 Joined: Tue Apr 18 2006, 12:30AM
Location:
Posts: 297

Hi,

Terry, have you considered other sphere numbers other than 4?

I sort of feel now that 8 inch in diameter might be a bit too big. They stand off very high voltage and it is hard to get normal breakout at typical voltages and power levels. Maybe 6 inch would be a better choice for the "next wild guess"

In my case, I always use breakout points anyway, so not big deal.

I think three balls might work but the capacitance will not be as great. 6 balls might give almost "toroid like" field distribution. The balls can also be moved inward and outward to change tuning and the fields. The more they stick out, perhaps the more likely they are to breakout. I think one would have to sort of decide how "big" you want it and fill that space with a "nice number" of balls. I don't have any "rules" there...

Of course, one could start with three and simply add more if needed. Only the center mount and number of rods would change which could be made very flexible with some thought.

I think I will use ball terminals from now on. I am going to throw away the old corrugated aluminum ones. They are "better" than expensive spun terminals since they are so highly resistant to damage and trivial to repair in any case. I never use the $400 big spun terminal since I don't want to scratch it (I had better sell it before it becomes obsolete

). The tuning and excellent capacitance and voltage standoff of the ball terminals make them an obvious choice.

On the bad side. They are very new and things like best ball size, number of balls to use, etc. is pretty much a pure guess. Calculating the capacitance is also unknown other than they are sort of close to a toroid of the same dimension (I really have not checked that actually...) But there ability to "tune" sort of makes up for that.

So far I love the ball terminal!!

Cheers,

Terry

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