that that is actually discussed earlier in this thread, what i am suggesting is, that using a manifactured coil, that is easy to obtain from junk devices, you wouldnt have to worry about winding one yourself, and could easily pull the tech specs on the particular coil for reference when calculating your results.

then just tie the inner lead to a pick-up on or near the shaft and another to an outer ring or possible a secondary (insulated) shaft ring. turning it so the coils are alligned with the direction of rotation, and placing a ring/circular magnet over one of both ends then rotating this all together should achieve the desired higher voltage/medium current that we are attempting to obtain.

an afterthought:.....


if the coil has a ferromagnetic inner core, you want to put a magnet on top AND bottom so the entire core is under influence, that way the rotating magnetic field will be "stationary". (no back EMF) which is a primary requirement of these devices.

Hi I am new to this forum but I couldn't resist the topic as homopolar generators have been an interest from way back. I have never understood how they came to be associated with over unity energy. The university of Texas http://www.utexas.edu/research/cem/homopolar%20generators.html has done lots of research on these devices in the field of pulsed power and none of their papers to my knowledge have mentioned any anomalous energy output not to say that there couldn't be any. I will try to explain what a homopolar machine is for people who dont know. Basically it relies on the magnetic thoery that when magnetic flux penetrates a conductor moving perpendicular to the lines of flux a voltage proportional to the length of the conductor and perpendicular to the direction of travel appears. This does not have to be a disk, the disk is just a mechanical contrivance to recycle the conductor or save on magnets. MHD devices use exactly the same principle except that they are linear motion using an expendable conductor. Rail guns are very similar as well.

One of the previous posts showed a spiral conductor as a possible means of increasing the voltage output, AFAIK this wont work, the conductor length perpendicular to the direction of travel (wheel outer brush contact radius - wheel inner brush radius) is the same with either a spiral or a disk so there is no increase in voltage. Before flaming me, remember vectors and the point "conductor length perpendicular to the direction or travel" This also invalidates the other proposed methods of increasing the voltage with long wires and the like I wish it were otherwise. Check out the Kollmorgan servodisc motors for an ingenious way around this, though they are not over unity by any stretch of the imagination.

The common methods of increasing a homopolar machines output voltage are increasing the rotor radius, increasing the field strength and increasing the rotor speed. Using these methods I designed a unit which would output 1Kv not a practical generator just a pulse power machine with a pulse duration of < 1 sec.

Anybody who thinks that a homopolar is a low torque machine is mistaken, with a 4T field one of the UNI's discharged a 140lb rotor running at 27000 rpm in around 1ms The torque reaction that a homopolar machine can exert is considerable, that is why many homoploar machines are built with 2 contra rotating rotors so all the torque reaction is cancelled in the unit body. Unlike an inductive generator the magnet does not see any torque reaction the reaction is between the rotor and the return conductor which happens to be the other rotor in a contra rotating setup.

The main technical issues with homopolar machines is that they are low voltage high current machines, the current pickup speeds are very high and the magetic circuit has a large air gap resulting in very large excitation power with non superconducting field coils.

Liquid metal pickup is one way to achieve current pickup, MHD forces and the mess factor are problems with this.

Permanent magnets are viable for small machines but eddy current losses with solid discs can be appreciable is the excition field if not uniform .

Hope this answers a few questions about these machines

Maybe this point hasn't been made here in this thread yet - but

If you attach the magnets to the shaft so they spin WITH the disk,
there IS NO BACK EMF.

theres nothing to push against, the magnetic source is spinning with the disk.

but the field, being circular, remains stationary.

What is so unusual about the homo polar generator is that it defies logic that it takes torque even with the magnet spinning with the conducting disk .  Intuitively it seems impossible that the magnet can resist rotation when it is just spinning in space with the disk.  Faraday was unable to prove if the magnetic field rotated with the magnet or not although it appears that it does not.