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I need some suggestions for maximizing power output

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OiD

Thu Feb 03 2011, 10:20PM

Registered Member #2150 Joined: Tue Jun 02 2009, 08:33PM
Location:
Posts: 29

Hi quicksilver,

I'm currently using a quad MOT stack witch is giving me around 9Kv, it is ballasted with another MOT. I will measure the current draw tomorrow and do some more tests on the MOT stack. I'll try the NST again to do some low power tunning again.

As for the spark gap... it's toast! I'll rebuild it because I'm having trouble with the rotary spark gap.

Do you notice any changes in the streamers from begining to end of a run?

quicksilver

Fri Feb 04 2011, 06:16PM

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

What I did was pay particular attention to the gap's distance.

As for running it for 3 minutes; it was steady. Frankly did not notice a difference in performance over that period (it may even have been a longer period of time but not a full five minutes: I know that for sure).... but I got about 8 inches, no racing sparks, no strike-rail striking & a good field (I could "feel" it in my arm hairs, etc).

I used copper tubing in parallel for the gap. At 1st I roughly inserted a piece of cardboard (miked at a mm) between each to begin at starting point. I used 8 units on 2 pieces of PTFE; bolted at each corner for a consistent pressure. The tubing was divided w/ their attaching screws so that I would gently move them 1mm or so (I have 8 on one SP unit) - 6 on another). They were placed in a box with a fan which ran off of mains voltage so I kept everything simple. My adjustments were substantial.
It was NOT easy to get them all equal. HOWEVER, the spreading of the spark over several contacts DID help cool and allow for a substantial lessening of noise.

Superficially; it sounds like you may have much to high a current running through there. A coil of the type we are talking about is considered to be smallish to small-medium. IF I had it to do once over again I would have opted for a wider-shorter secondary. I believe my wire is a bit thinner than yours but in most aspects it's very close.

OiD

Thu Feb 10 2011, 11:24AM

Registered Member #2150 Joined: Tue Jun 02 2009, 08:33PM
Location:
Posts: 29

Well, I polished the copper tubing and it works again, still not back to 70cm streamers. Just too much power for the little copper spark gap.

I've doubled the tank capacitor to 20nF and there hasnt been much change to the output. I'll just keep on trying!

On another hand does anyone have some suggestions on how to prevent streamers forming under the top load?
I've built a strike ring now and it tends to arc straight to it and in the proces burning the top windings.

Steve Conner

Thu Feb 10 2011, 12:07PM

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

To stop the streamers breaking out from underneath, you need a bigger topload. Or at least a wider, flatter one that shields the top of the secondary better.

Anyway congrats on achieving your 70cm goal

quicksilver

Thu Feb 10 2011, 05:59PM

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

A larger, wider top-load is the proper method. HOWEVER....if you have money invested OR you have a fine balance & replacement puts you in a position of returning (& possible cap replacement) it what you have already, I found I bit of a "cheat". - The disk from the internals of a hard-drive.

I had spent some money on a TC and was getting a few snapping downward; it was expensive to build & I didn't want to have to make larger scale adjustments. I experimented with different grounding, shielding the primary, etc - & one thing that had worked it the past was elevating the top-load a bit from the secondary. In this instance, it didn't work completely but I was getting great performance. I had read that the straight downward shots are apparently not unique when using spherical top-loads (which is what I was using),However; it does present one issue, in that it can provide a 90 degree breakout point on occasions. But I think it looks nice.
I was either reading pupman or the archives and found someone who did this before. They disassembled HDD and placed one of the disks above the secondary & "snap" no more vicious downward strikes.
It does NOT eliminate them totally however....it just keeps them moderated from a straight down shot to a 120 degree angle & seems to stop those strong white ones. - Just a thought.

OiD

Fri Feb 11 2011, 12:10AM

Registered Member #2150 Joined: Tue Jun 02 2009, 08:33PM
Location:
Posts: 29

Steve McConner wrote ...

To stop the streamers breaking out from underneath, you need a bigger topload. Or at least a wider, flatter one that shields the top of the secondary better.

Anyway congrats on achieving your 70cm goal

Thanks for the congrats :)

quicksilver wrote ...

A larger, wider top-load is the proper method. HOWEVER....if you have money invested OR you have a fine balance & replacement puts you in a position of returning (& possible cap replacement) it what you have already, I found I bit of a "cheat". - The disk from the internals of a hard-drive.

I had spent some money on a TC and was getting a few snapping downward; it was expensive to build & I didn't want to have to make larger scale adjustments. I experimented with different grounding, shielding the primary, etc - & one thing that had worked it the past was elevating the top-load a bit from the secondary. In this instance, it didn't work completely but I was getting great performance. I had read that the straight downward shots are apparently not unique when using spherical top-loads (which is what I was using),However; it does present one issue, in that it can provide a 90 degree breakout point on occasions. But I think it looks nice.
I was either reading pupman or the archives and found someone who did this before. They disassembled HDD and placed one of the disks above the secondary & "snap" no more vicious downward strikes.
It does NOT eliminate them totally however....it just keeps them moderated from a straight down shot to a 120 degree angle & seems to stop those strong white ones. - Just a thought.

I gave it a try with a piece of scrap metal and it stoped the formation of streamers from the coil, but as it was sharp the streamers also formed on the piece of metal.

I'll definatly have a try with some hard drive disks, although I don't think they are large enough for my coil.

For now I'll give TC a rest until I find another job and get the MOT stack under oil as the RSG caused arcing from the MOT core to the 230V primary starting some nice little fires.

Thanks again!

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