Self running coil?

[NextGen67]

My cap (120000 uF) is only rated 15 V. So i can not go up to 25 V with this one.

I have found a 33 uF film cap (250 V). Maybe i can try this one.

Skywatcher,

You still have your previous [somewhat working one] intact?

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NextGen67

[skywatcher]

Skywatcher,

You still have your previous [somewhat working one] intact?

--
NextGen67

Yes...

I wonder why the magnet has such a low impact on the inductance. Maybe the permeability of the core is too low.

[NextGen67]

Yes...

I wonder why the magnet has such a low impact on the inductance. Maybe the permeability of the core is too low.

yes, your core material and magnet do not match up.

You did not time exactly how long it 'ran' last time - right?    You may want to give it another try with that [working] one, and time how long it keeps going.  After that, try to clamp your magnet a bit to the coil, so that its movement get strongly restricted [you may need to re-tune the frequency after that a bit], and 'run' it again... sere how long it can run now.... If I'm right [and you re-tuned correctly], your 2nd run should be longer

Also, be sure to have NO metallic objects in near vicinity.

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NextGen67

[mscoffman]

Also the magnet has no visible effects. It reduces the inductance only slightly (about half the value measured without magnet) although it's a very strong neo magnet (N48, 10 mm diameter x 10 mm).

Maybe the ferrite core is not suitable to see the effects. I don't know. But i'm not motivated to make dozens of new coils with other cores to try this out.   

My cap (120000 uF) is only rated 15 V. So i can not go up to 25 V with this one.

@skywatcher

I think, there was a video of the measurement of the toroid coil with
and without the magnet stack right at the surface of the coil. The
measurement were 1040mh [without] and 44mheneries [with]. I would
submit that this nearly 25 times difference represents the action of a high
performance ferrite material possibly traceable to Metglass. I also notice
sometimes the gotoluc diagrams are showing lines like the toroid may
be split by small gaps into halves. That also might make a difference.

So I don't think I would attempt duplicating this experiment until I got
measurements somewhat similar to his or else could invalidate, correct
or explain what was shown with a coil at least somewhat similar to his.
Yours sounds like what I might expect, maybe low, but his values
seem extraordinary. I've heard that metglass material is like this.

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You don't happen to have two of these 120Kuf capacitors do you? 

If so...place them in series...According to theory, equal
values of series capacitors divide their capacitance by
two so you have 60Kuf and they would split the Q charge,
so the working voltage of the two combined would be
doubled to 30Volts.

When I was using them I would check to see, once in a while,
that they were dividing the sum of the DC voltage between
them equally, and not continue if they were not. (due to
unbalanced DC leakage current, and unbalanced delta C)

:S:MarkSCoffman

[skywatcher]

You did not time exactly how long it 'ran' last time - right?    You may want to give it another try with that [working] one, and time how long it keeps going.  After that, try to clamp your magnet a bit to the coil, so that its movement get strongly restricted [you may need to re-tune the frequency after that a bit], and 'run' it again... sere how long it can run now.... If I'm right [and you re-tuned correctly], your 2nd run should be longer  

At the moment, i can not even replicate the 'long' runtime o got last Friday. I don't know exactly how long it was running then, but today it's much less.

Also, be sure to have NO metallic objects in near vicinity.

That's not possible. If you look at Luc's videos, there are also plenty of metallic objects...