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2021-01-28, 13:49:09
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Author Topic: Lester J Hendershot Generator  (Read 164630 times)
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I'm still very curious about these open-ended coil schematics I see from these fellows.  At some point I'm going to do some experiments with this type of configuration.  The first one will be with coax cable--one side on each end open, the other conductor connected.  I'll wrap the coax around a core and try some various waveforms induced into it and see what it looks like on the scope.  From the conventional viewpoint, I don't expect to see any current developed, but it would be nice to be wrong, then I'll need some help explaining it.
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Posts: 3543
It's turtles all the way down
Orthofield, you had some interesting points to make on the Hendershot Generator here:


I wonder if you have thought about it anymore since that post back in 1997?

I built a unit back in the mid 1980,s but never was able to get it operational. More recently I learned that Hendershot used beeswax to fix the large inner capacitor to the "basket weave" coils. This led me to think there might be some form of acoustic coupling between the two, with the capacitor acting as an electrostatic ultrasonic transducer.

Although the serpentine coils have been later named basket weave, they don't bear much resemblance to actual basket weave coils of the early radio era where that type of construction was used to lower inter-winding capacitance. My guess is the Hendershot coils serve a different purpose acoustically, and may also explain the large capacitance values used in the device.

I have not seen any of the replicators pursue this line of research, not even have I dusted off the old unit to test this idea, but I might!


"Secrecy, secret societies and secret groups have always been repugnant to a free and open society"......John F Kennedy
Group: partzmans Private Group
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Posts: 201
Hi Ion,

Wow, I haven't looked at that in a long time! I don't see too much that I would disagree with, except the assertion that all you need is a resonance and nonreciprocal linkage, and then you have OU. I doubt that to be true. It may be a requirement, but it's not sufficient. After that, the thing I'm less sure about would be the magnetic- ion interaction. I'm not so certain it would give enough C variation to get serious power. But maybe...

As far as thinking about it more, I didn't pay too much more attention to the Hendershot device after that, but went on the hunt for efficient, relatively low frequency, passive, nonreciprocal networks that maybe could be used in an OU device. I went more over to the Hall/Corbino side rather than the vibrating transducer side.

But looking through my papers on this stuff, I note that most of these transducers have a piezoelectric like terfenol, so it makes sense that sound is involved.  I know of one magnetostrictive project with a nonreciprocal element that actually used beeswax (an excellent acoustic conductor.) Also, hey, maybe the clapper actually vibrated the 'basket weave' coil through the base, to add a little extra oomph :-)
I wonder just how easy it is to affect the C of an electrolytic capacitor? Taking one and measuring the C with or without a big fat magnet aligned with the axis would be a place to start.

I'll have to look at the coil again, because there are some cross coil configs with interesting properties (E parallel B EM waves at right angles to the intersection)-- but that's pretty exotic.
I just pulled up the 125 honeycomb coils in the patent database, will look to see if there is anything interesting there...

Group: partzmans Private Group
Full Member

Posts: 201
Hi Ion,

Hmm, it doesn't make any sense to me now that he would use the basket weave coil to reduce parasitic capacitance, because with that big mass of dielectric nearby there would still be plenty of C.  So why use a basket weave? So I went and looked.

De Forest, attached, shows the use of a Lecher line wrapped around a tube, as a highly Q transmission line stub. He discusses detecting both electromagnetic and electrostatic nodes on the wire, similar to the use of Lecher wire to measure wavelength.

With the dielectric nearby in Hendershot, you have a distinct slow line structure. With two such slow lines, you might be able to create some large delay effect, that, for instance delays CEMF from the clapper until it becomes a positive force to drive the clapper? Would need a big mass of dielectric, and a coil with a large cross section (=high L).

Pure speculation-- but resonance effects have been used in permanent magnet motors (which the clapper basically is) to apply CEMF to the next motor cycle. (patents by Goddard, Macdonald, Rupp, Subieta-Garron).
In this case, the Hendershot machine becomes a permanent magnet motor where CEMF does not impede motor action but supports it.

I note that the iron Cook Coils are long enough that there could be a substantial domain motion delay, with the secondary induction on one coil delayed enough to support the primary on the other coil (or something like that). Tesla also had transformers with a thin layer of metal between the windings to cause a delay, which could reach 90 degrees I think.

The patent from 1925 by Willy shows serpentine coils used as retardation coils, and also right angle coils intended to reduce mutual L and C. It's the only patent in this class besides De Forest that seems relevant. Retardation coils seem to be often discussed in these patents as a way to make voices clearer in radio reception. It was a time of extreme levels of experimentation in radio, with all sorts of weird antennas, including underground ones (Rogers) and miscellaneous even stranger things. In fact, I recall a patent (but can't remember who did it right now) for a 'radiant energy detector' that had a clapper or something like it.

These are more like free associations than research, but maybe there are some clues...There's also a patent class for coil/capacitor combinations, maybe there is something there...


Jr. Member

Posts: 80
I'm just now getting back to my Hendershot build. Does it matter which direction the basket weave coils are wound? Should they be oppositely wound or wound in the same direction?
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