Homopolar Generators (N-Machine) by Bruce de Palma

[keithturtle]

OK, then I just came up with about 6 square feet of some 0.062" copper sheet.   I hope to fashion some 11 inch disks to spin in some ferrite magnet fields. 

Maybe after 4 years I can finally get something built.

Progress notes; got three ~12 inch disks with 1 1/4" copper plumbing caps as center pick-up hubs made.  Also cut out some 15" disks and plan on 2" caps for them.

For the cylinder model I have a section of 6" diameter copper pipe that can handle about 12 linear inches of internal field magnets.   Got more bearings on the way.

Errata, the DC motor (it's 1/2 HP) will only spin 1750 rpm max, so I gotta get a bigger drive pulley.  I can get upwards of 6000 rpm out of an old Shopsmith lathe motor, and will set up with that to start.

Nothing is done, assembled or tested yet, but I am making [comparatively] great progress on the hardware and equipment side of this project.  I've done some practice "hard-solder" brazing of the copper scraps; I intend to add a stiffening perimeter strip to the edge of the disks to keep them true, and to pick off power radially without creating Z-axis lateral flex.  The idea is to keep things from wobbling, as I'm convinced the tight spins in the field magnet's corners, near proximity, have much more potential than field effect at a distance (Howard Johnson stuff).  I am optimistic.

No pics or data yet.

More later

Turtle, plodding along

[tim123]

Hi Keith
  why more than one disk? Are you going to join them together?

I was wondering whether the copper would be hard enough to spin at a high speed? I would imagine that the outside of a 12" disk at 3000 RPM would have a lot of force on it... I guess the rims should help...

I was thinking about the magnets - and was wondering if perhaps a pair of pancake-type coils either side of the disk - but run as an induction heater - i.e. Hi Freq AC tuned circuit - might be good. The coils could be made of 4 or 6mm copper tube... Just a thought. It might make a more uniform field. It might not.

Regards, Tim

[keithturtle]

  why more than one disk? Are you going to join them together?

Yes.   With two identical 12" disks with a large copper plumbing cap [hub] soldered to the center of each, I can add an array of magnets in the middle with polarity facing each disk differently; the rims will allow a band of Cu to attach the disks and complete the circuit, pick off power at each hub.

There must be no electrical contact in the common shaft.  I still have details to work out, but since I haven't even made any power off a single disk, I have no frame of reference for the dual disk design.   I'm just now getting the arbors and perches set up so I can begin spinning next week.

I was thinking about the magnets - and was wondering if perhaps a pair of pancake-type coils either side of the disk - but run as an induction heater - i.e. Hi Freq AC tuned circuit - might be good. The coils could be made of 4 or 6mm copper tube... Just a thought. It might make a more uniform field.

So, copper tube conducts the field current, creating a field without steel backing?   Will that truly be a uniform field?  Why tube over solid conductor? I don't know, but I have some 6 gauge solid wire I can coil into a pancake to try.  Tube I have is at least 10mm dia.

Turtle, slow

[TinselKoala]

You might get some ideas from US Patent 5,587,618

[keithturtle]

Good stuff there, TK, I have not yet read this one, thanks

Turtle