Muller Dynamo

[mondrasek]

What would be good stator dimensions to go with a 20cm Rotor?
Would 30 cm stator plates be enough?

My drive motor and entire system base, and my stator plates are 1/2 in thick plywood and are 1 x 1 foot square.  This was made from what I had at hand since a 1 ft wide strip was left over from a bedding project some time ago.  This size looked about right, if not a bit too big, for my ~18 cm dia. rotor.

Do the shaft and the threaded rods have to be non-magnetic material?
Maybe it doesn't influence the magnets.

All my threaded rods, washers, and nuts are plain steel from a local hardware store.  I had a good chuckle when the older female clerk asked me what I was building.  I smiled politely and answered, "You don't want to know".

These steel items are not ideal.  But they are mounted as far away from the rotor as I could get them and still have the big washers landing on the boards and not hanging over the edges.  I can detect no ill effects from attraction of the rotor magnets to these items but attributed that to the distance.

Down side to the distance is the center of the stator plates are not as ridged as they could be with more central hardware.  But it is still working, so I think that this set up is a bit more forgiving than to required precision levels of laboratory equipment.

I am not sure how much my bearings are becoming magnetized at all and have no idea what long or short term damage such magnetization would cause.  But there are non-magnetic solutions available as already mentioned should they become a problem.

M.

[mondrasek]

@futuristic,

I believe the RomeroUK scope shot you are discussing is from an un-tuned (or poorely) tuned pair of coils.  Here is my breakdown of the wave form:

The long flat sections on each end are simply due to the gap between the rotor magnets.  They occur when the rotor magnets are between coils and not yet influencing the coil where the measurement is being taken.  These flats are therefore NOT desireable if optimizing for power density of the device.  Mine are very small since my magnet spacing is slightly less and my magnets are a bit more powerfull.  But the spacing cannot be too close or you will then decrease the output I think.

As a rotor magnet approaches a coil it pushes voltage high in one direction or another.  As the magnet crosses over that leading group of coil wraps it will enter the "dead" zone at TDC.  So the wave form will be dropping back towards zero.  If the center hole of your coil is large with respect to your rotor magnets you will even get a flat here as well.  But then the magnet begins crossing over the trailing group of coil wraps and will drive the voltage in the opposite direction into a similar rise and then fall sine type wave form.

When you bring a backing magnet towards the back of a coil from far away you can see the wave form change from the RomeroUK wave towards the other:  The center "flip" section straightens out.  After that section straightens out the overall ptp V will begin to grow.

Earlier in these more recent posts (after page 274 for sure) someone said this was because the backing magnet was improving the Q of the coils.  So I believe that explanation deserves more review when trying to understand this phenom.

M.

[poynt99]

Well I was trying to show the waveform type. I just horizontally flipped the bottom hill of the regular magnet motor waveform.
Ok.... if that is your opinion.
But please try to be objective as possible while looking at this image below, and tell me which waveform has more similarities with Romero's...

When I saw your wave form modification, I agreed. Very insightful.

It is quite possibly what Romero has done. The only way to achieve Romero's wave form is to either add or subtract to the coil pair output from another coil pair as I suggested some time back on OUR, or he is combining the outputs of two half-coils from different angular positions.

.99

[xenomorphlabs]

@M

Thanks, i guess in that distance, the steel won't affect the function too much.
Also for a test device it is enough. I just wanna make it spin, minor efficiency issues are irrelevant at the current stage for me.

Concerning the waveform across the coils.
I played with the magnets moving them by hand in different positions and you can clearly see that it narrows the pulse width (or increases the Q).

[chalamadad]

Regarding the addition of biasing magnets - what amount of speed increase are we talking about? I finally observed an increase but that gave me just 10-20 rpm extra per coilpair.