Homopolar Generators (N-Machine) by Bruce de Palma

[scotty1]

Isn't that MAGNETOSTRICTION?
I was going to make the Tesla double wheel design....I thought i could ues 2 brake drums from an old car...I still have them but never made the machine...
You see that Tesla spoke of a spoked wheel that must consist of many sets of closed circuits....I have one of those too....in fact...if you look at Ed Leedskalnin's magnet wheel...you can see that it can be made as a spoked wheel of symetrical closed circuits.....which I think is interesting....scince Ed wrote in his notes "when you start the magnets in an orbit, then they will never stop, until the orbit is broken."
Ed also wrote..."Imagine a wheel with many coils around the wheel turning, then you would be making all kinds of light.....do not make the machine...I already have application for Patent in the Patent office."
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If anyone ever found that Patent application...you would have the machine you are looking for...
Scotty

[PulsedPower]

Seems we have healthy discussion going here and some good points cropping up

@Gearhead

The magnetic field may dislodge electrons that are collected or moved by the centrifugal force of the disk conductor.

The effect is exactly the same with linear motion. One of physics books doesn't go into much detail but mentions that the hall effect is responsible for part of the behavior.

It makes things easier to forget this rotation stuff, the effect is purely related to linear velocity rather than angular velocity, to calculate the output of a homopolar generator I just work out the average velocity of the disk between my current pickup points and plug that into the equation e=Bvl using the radial distance between the pickup points as the conductor length. If you write this out as an equation and simplify it it gives the familar e=Bwr^2 where w = angular velocity (can't get the greek lower case Omega so w will have to do)

The space shuttle flying perpendicular to the earths magnetic field would generate considerable voltage but it would never be apparent to the people on the shuttle as they would all have the same induced voltage meaning no net potential difference, if the space shuttle was flying though a conductive atmosphere then current would flow because of relative velocity ditterence between the forward conductor (shuttle) and return conductor (atmosphere), this is an MHD generator run backward. Also even if the space shuttle and the tether wire were traveling in the same direction the field lines may bend to create a differing speed relative to the field, drum type homopolar generators use this technique.

i think the disk is moving relative to the magnetic field.
i dont think this effect can occur any other way.

It can:  if the magnetic field is not moving relative to the rotor then it is moving relative to the return conductor and the voltage will be generated in that instead but you will not know this because if you put a meter across the return conductor it will only read the voltage drop due to resistance the induced voltage will not show because the meter and the test leads are moving at the same speed with respect to the rotor and attached magnet. The return conductor is not any special device any wire connected to the current pickup point will be cut by the same magnetic field as the rotor, that was why I suggested to draw both the magnetic circuit as well as the electrical circuit. In a contra rotating homopolar generator the return conductor is a second rotor spinning in the opposite direction usually at the same speed, as the relative velocity between the conductors is doubled so is the output voltage and it is taken off the rims of the two rotors

As for the iron filings not being disturbed by a rotating magnet,  the field is uniform in the plane of rotation, iron filings line up along lines of  flux, for a circulary uniform field these do not change with rotation try it with a bar magnet and watch the filings shift as the field is not uniform in the plane of rotation. 

A bit more reading later, the speed that the source of the magnetic field is travelling should make no difference,it is only the relative speed of the conductors though which that field passes which is important for making a voltage so in effect SmOkey2's assertion that the field is stationary is partially correct in that it doesn't need to have a sense of speed provided it is uniform. This idea is similar to Gearheads Interial frame of reference.  Unfortunately that blows the idea that making the magnets travel with the rotor will make the machine over unity as if the field has no sense of speed then no torque can appear on the magnet no matter whether it is stationary, rotating, provided by the earth sun or anything else the speed is only a function of the relative motion of two conductors meaning that any torque will be between these conductors. This is how I believed homopolar generators to work, torque on the magnet was never a part of the engineering design but torque and forces on the conductors was.

An interesting  point touched on in one of my physics books is that if you calculate the rate of change of flux enclosed between any 2 arbitrary forward and return conductors it will give the same voltage as if that rate of change of flux were happening in an equivalent induction loop so even though the flux is not changing in value the conductor had moved on to a new bit of flux and that counts as a change.

@scotty If you look back about 10 posts I mentioned very similar points about self excited homopolar generators, they have been built and self excite  very well, even an air cored field can go over 2T,  A design I had a play with went to 8T though you only get a fraction of a second at this field strength because the current required to sustain it  (500kA in my design) slows the rotor very rapidly not to mention heating up the field coil.

[sm0ky2]

@ Pulsedpower


The point im trying to stress here, which is exactly what Tesla explained in the patent mentioned above ---

is that the magnetic field is not moving at all !!!

you can spin the magnet all day long, the (uniform) field stays stationary. if your field is truly uniform, and rotating parallel to the flux meridian, a bar magnet placed in the field does not move.


the induction caused by the return circuit is from the (moving) electromagnetic -field generated on the charged disk. This can be avoided via the angle at which your return circuit crosses the field-lines of the EMF. [ im not sure how/if that could be achieved w/ a spiral-cut disk]

the back torque caused by the magnet is not a fuction of the current drawn. it is a function of the voltage induced, which is proportional to the rotational speed, and is often attributed with other losses, such as that of friction, inertia, ect. - the point about moving the magnets with the disk is that, even though the mass increases (as do inertial losses) the drag from the stationary magnet drops out of the equation, making the disk easier to turn, (less losses from back torque). this is irrelevant to the current drawn off the disk, and does not effect the output power in any way.
what IS effected is the INPUT power- the energy required to rotate the disk through the magnetic field.
thus making the generator more efficient.

[PulsedPower]

@ smOkey2

is that the magnetic field is not moving at all !!!

you can spin the magnet all day long, the (uniform) field stays stationary. if your field is truly uniform, and rotating parallel to the flux meridian, a bar magnet placed in the field does not move.

My problem is with the concept of stationary, the word stationary means locked to a particular frame of reference, The point I was tying to make was the field wasn't stationary just that with no field gradient then the concept of movement means nothing.

Imagine driving in a place with no features and perfectly even lighting, even if you were moving it wouldn't be apparent to your eyes. A uniform field has no features, my point about the bar magnet but I wasn't clear enough was to rotate the bar magnet lengthwise so that there is a nonuniformity in the field, then rotation would be aparent.

he back torque caused by the magnet is not a fuction of the current drawn. it is a function of the voltage induced, which is proportional to the rotational speed, and is often attributed with other losses, such as that of friction, inertia, ect. - the point about moving the magnets with the disk is that, even though the mass increases (as do inertial losses) the drag from the stationary magnet drops out of the equation, making the disk easier to turn, (less losses from back torque). this is irrelevant to the current drawn off the disk, and does not effect the output power in any way.

The magnet has never been a significant source of drag on a homopolar generator, as long as the field is uniform there will be no eddy currents set up in the rotor, Eddy current drag is the only form of drag that I  know of associated with the magnet. I have said all along that the drag (torque reaction) on these machines never appears on the magnet if the field is uniform. There is no way of avoiding the torque reaction between the forward (moving) and return (stationary) conductor as it is a product of the current flowing in them, if you reduce the torque by some means then the available voltage from the system will reduce accordingly. While homopolar generators are thoeretically quite efficient in practice, friction from the current pickups (liquid metal is the best) and magnet losses reduce their efficiency.

There is no way of avoiding the return conductor as that is needed to have a circuit, a spiral on the rotor will not make any difference to power input at any given field strength becuase the vector sum of the radial component of the current flowing in the rotor ( what causes the torque reaction) is the same for both a spiral and a spoke.

AFAIK Tesla never demonstated a generator which was over unity and never proved such claims, OTOH there have been many well instrumented Homopolar generators (all using stationary field coils) which have not displayed over unity, A patent means nothing, it is just a legal instrument to give the patent holder a right to sue anyone who uses similar ideas, the inventor can claim anything that appears plausible, it is checked by patent clerks not people skilled in the respective art.

[Koen1]

I must agree with PulsedPower on this one.
Although the homopolar generator may seem to be an extraordinary device
in the classical view as it may, depending on your interpretation, seem that no
"flux lines" are "cut" as the magnet may be rotated along with the conductor,
in a more realistic and modern view it is clear that there is actually nothing
odd going on. I don't see people getting all hyped up about the Hall-effect,
and that is actually almost the exact same effect, but instead of moving
a conductor through a magnetic field it depends on moving an electrical
charge through a magnetic field. Same resultant "induced" currents at same
angles to the direction of motion and the mag.field.

@PulsedPower: nicely said.