Hendershot Replications

[mlurye]

I built my coils.
Selfresonance for both 64 turn coils ~1.2MHz.
Now I'm playing with capacitor. Can not use standard caps. As I found insulation for cap is very important!!!!!

[mlurye]

Resonance circuit should be tuned precise 3-4Hz off and it doesn't work.

[morpher44]

well done...

I built my coils.
Selfresonance for both 64 turn coils ~1.2MHz.
Now I'm playing with capacitor. Can not use standard caps. As I found insulation for cap is very important!!!!!

@mlurye

How did you measure self resonance? Do you have a Q-meter?

-moprher44

[mlurye]

@mlurye

How did you measure self resonance? Do you have a Q-meter?

-moprher44

No. I'm using function generator and neon bulb.

[mlurye]

Some interesting facts:
1. Electromagnet resonates at ~50Hz
2. Transformer resonates at ~50kHz
3. Receiving coil and capacitor resonates at ~500kHz

Does anybody see anything interesting in this numbers?

[NOMDI]

Capacitors

I built my coils.
Selfresonance for both 64 turn coils ~1.2MHz.
Now I'm playing with capacitor. Can not use standard caps. As I found insulation for cap is very important!!!!!

Hi,

Did you try polypropylene motor capacitors ?

They seem to have good insulation and are not too expensive...

[mlurye]

Hi,

Did you try polypropylene motor capacitors ?

They seem to have good insulation and are not too expensive...

Got 50 (20uF 240V) for 20$.

[NOMDI]

Capacitors

Very good price !

For the LC cells i've found 500V 1% 3.9 nF MICA caps specially made for oscillators circuits. Two in parallel may worth a try...

[mlurye]

Very good price !

For the LC cells i've found 500V 1% 3.9 nF MICA caps specially made for oscillators circuits. Two in parallel may worth a try...

NOMDI, do you have Hendershot coil to play with?

[NOMDI]

NOMDI, do you have Hendershot coil to play with?

Oh I'm very in late compares to you or MORPHER44 ...My first tank is on the way... Hard to make, really. And I'm also struggling with the buzzer (by the way I cant believe the DC 6 Ohms value is good : means high current and big wire, which I i've seen nowhere, including on CRUSTYs pictures...). Only had success with relays and magnet experiments, with very high voltage peaks an bright neon... But I keep working on this fascinating project

[mlurye]

You are correct, it is pain in a$$ to build. But it's a lot of fun to play with. I'm planning to use 110V door bell double coil (first I need to get one ).
And 7n8F cap I do believe should be handmade. There is something special about it (Moray used one and 2 in Testatica).

[morpher44]

6 ohm buzzer

And I'm also struggling with the buzzer (by the way I cant believe the DC 6 Ohms value is good : means high current and big wire, which I i've seen nowhere, including on CRUSTYs pictures...).

This week I decided to attempt to wrap my own solenoids.
I realized ... in terms of reverse engineering ... that if you know
the ohms of a coil and its wire gauge, you can derive the wire length
(ball park), and from that you can derive the number of turns.

So if the Hendershot buzzer was 6 ohms, 24 AWG (copper enam.),
this works out to be about 233.7 feet (or 117 feet per bobbin).

So I measured out 117 feet, and just wrapped that on to one
steel bolt. Then another 117 feet ... wrapped that the other
direction.

In the Ed Skilling document there are some photos of the
magnet, solenoids, etc. You can actually measure the sizes
of them on the photos and then extrapolate to actual size
using the light-bulb dimensions or the 5 15/16 coil diameter
to help with that conversion.

When I do so, those solenoids are about 2 inch x 7/8 inch each.
I decided to have a length of 1 inch ... since that length
influences how strong your magnetic field will be.

[NOMDI]

You are correct, it is pain in a$$ to build. But it's a lot of fun to play with. I'm planning to use 110V door bell double coil (first I need to get one ).
And 7n8F cap I do believe should be handmade. There is something special about it (Moray used one and 2 in Testatica).

I tried many "door bells", "PHONE BELLS" "fire bells", etc... with many different voltages (AC/DC, with or without included magnet...).
I've noticed that high voltage bells always have high resistance (it seems obvious I know).
The only bell made for 110V I found has unfortunately a single coil... I measured 1370 Ohms and 1.15 H and the wire is very very thin... Too thin I guess. I heard that "antique" 110V railway station bells are made with two coils and I try to find one on EBAY...

Concerning the 7.8 nF capacitor, i made some experiments with home made, using garbage bag polyethylene film (not easy to make, too). I had some results but I wonder if the only important thing would be the difference between the two tanks capacitors. This is not a new idea, I know... but I can't find out what action the coils could have on capacitors. This is beyond my knowledge and imagination. If somebody knows....

[NOMDI]

This week I decided to attempt to wrap my own solenoids.
I realized ... in terms of reverse engineering ... that if you know
the ohms of a coil and its wire gauge, you can derive the wire length
(ball park), and from that you can derive the number of turns.

So if the Hendershot buzzer was 6 ohms, 24 AWG (copper enam.),
this works out to be about 233.7 feet (or 117 feet per bobbin).

So I measured out 117 feet, and just wrapped that on to one
steel bolt. Then another 117 feet ... wrapped that the other
direction.

In the Ed Skilling document there are some photos of the
magnet, solenoids, etc. You can actually measure the sizes
of them on the photos and then extrapolate to actual size
using the light-bulb dimensions or the 5 15/16 coil diameter
to help with that conversion.

When I do so, those solenoids are about 2 inch x 7/8 inch each.
I decided to have a length of 1 inch ... since that length
influences how strong your magnetic field will be.

Hi MORPHER 44 ! This helps me very much ! I'm going to test it ASAP. Thanks a lot !

[morpher44]

the cap

And 7n8F cap I do believe should be handmade. There is something special about it (Moray used one and 2 in Testatica).

@mlurye

Here are some brief notes on what might be special about it...

1. The cap needs to be variable ... and is in the nF range ... not picoFarad.
You can buy 365 pF variable capacitors ... no problem. But variable
caps in the nanoFarad range are not "off-the-shelf".

2. It needs to be variable because "tuning" is difficult --
or so the story goes.
One possibility is that both tuned circuits on either side of the circuit must
be brought into synchronization or must be brought to a point where
an adequate beat frequency can be established between them.
Buying "fixed" value capacitors (with a 5% tolerance), for example,
would be a crap shoot. Further, it is unlikely that your inductances
on the coils will exactly match in value.

3. In terms of "unknown characteristics" ... there may be a feedback path
between the coils and the collectors. In my coilpacitor experiment,
I can easily demonstrate that a coil wrapped around a copper pipe,
when given a source of high-voltage AC will create a very large
charge in the copper cylinder -- not unlike a van de Graff generator.
So, if it is important that the capacitor cylinder be placed
INSIDE the coils ... for this effect ... than again hand-made is
the only alternative at this point.
Another possibility is that when paraffin is poured between the
coils and the capacitor, that this enhances the coupling effect.
I am torn whether or not this is so. It seems to me that
the paraffin was used ONLY to "lock it all down" ... i.e. to
improve the stability of the coils and capacitors... holding them
at their values. I think that because you would probably have to
"tune" everything first ... and then poor in the wax to seal it all.
This is what old-time radio guys used to do when building
radio gear from scratch.
The downside to this is that temperature changes will
bring everything out of tune. Having it sealed in wax would
make it difficult to re-tune.

4. Hendershot built his cap using foil from another cap that he
dismantled. He would remove the dielectric oil and harvest the
foil only. I'm thinking he did this because that foil is
probably very "thin" and also very ideal in terms of resistance.
Household aluminum foil, which is what I'm attempting to use
is probably no good because the resistance is HIGH.
I do see a very damped oscillation after each spike to the coil.
I'm speculating that is because my foil my be no good.

So yes the hand made capacitor is a challenge.

I did attempt to cut open a $7 AC capacitor and poor out the
oil and harvest the foil. This is not easy. The foil is very delicate.