Something I discussed with Tito the other day..

Has anyone tried winding a normal coil on a core, then winding a bifi on top of the first winding? Im under the assumption that the bifi might be connected in series and the 2 ends left are connected together also, to make a shorted bifi.

That might be what Romero had done, Remember the solder joints on the coils windings.

A shorted bifi is an LC that will resonate.  More turns on the bifi, the lower the resonant freq/rpms of the rotor, as the more turns, the higher the inductance and capacitance, lower freq.

The regular coil under the bifi is the pickup coil.


As long as this has gone on, it may be worth a try.  ;]

Mags

Quote from: crazycut06 on February 08, 2012, 06:40:59 PM

Hi Khwartz,

Cogging torque
From Wikipedia, the free encyclopedia
Cogging torque of electrical motors is the torque due to the interaction between the permanent magnets of the rotor and the stator slots of a Permanent Magnet (PM) machine. It is also known as detent or 'no-current' torque. This torque is position dependent and its periodicity per revolution depends on the number of magnetic poles and the number of teeth on the stator. Cogging torque is an undesirable component for the operation of such a motor. It is especially prominent at lower speeds, with the symptom of jerkiness. Cogging torque results in torque as well as speed ripple; however, at high speed the motor moment of inertia filters out the effect of cogging torque.


Hope this helps... Good day 

Hi Crazycut!  I knew this phenomenon but didn't know this idea of "teeth" english, I didn't relate too. So Very Thanks for having clear-up to me   

Quote from: konehead on February 09, 2012, 01:43:00 AM
hi Crazycut
forget about solid iron cores against neodimium magnets its jsut too slow to change polarity and theywill get hot and have extreme latching... for cores, sommething low-hysterisis, like metglas, or special amorphous blacksand that lets the magnets glide by instead of latching up like iron does is good for cores- ferrite is OK tppp thats whay romero used - at least it is very fast to swtihc polarity type of stuff...you can always go with aircores too, in your coils and replace the core with another coil inside of it (a "pikcup coil" I call them) then also more secondary/p[ikcup wrap winds around the primary too. and behind it too if you want....with aircores you should short the coils at their sinewave peaks into caps.
As far as I know, the regauging/backing magnets behind the core isnt going to work with aircores since you need a core in there for the bakcing magnets to do something to. However someone said if you have a thick flat ferrous steel washer behind the cores, "maybe" aircores would work but I dont know.
Bill Muller told me if using cores, make the core the same width as the magnet is...this makes sense to me....
For the length of a coil, whatever the field-strength of the rotor \streches out to, and it becomes so weak it seems senseless to make core any longer than that, make the coil that long... same wiht cores I would guess...anyways this is all my opinions on coil/ core subject not absolute fact or anything...

the core should be the same

Hi Konehead,
    Thanks for the info, i'll will try it someothertime, Maybe an iron core is not good with same size of magnets, but with metglass or amorphus blacksand much better,
I've tried a long coil 2"in lenght, the voltage is high but amperage is low, then i re-wound the same wire to a shorter bobbin 1" in lenght, the voltage decreased half in voltage but amperage almost doubled, so its best for coil to be a pancake type, so it receives most of the magnetic flux.

Hi Khwartz,
    Im glad that helps...

Quote from: Magluvin on February 09, 2012, 02:11:07 AM
Something I discussed with Tito the other day..

Has anyone tried winding a normal coil on a core, then winding a bifi on top of the first winding? Im under the assumption that the bifi might be connected in series and the 2 ends left are connected together also, to make a shorted bifi.

That might be what Romero had done, Remember the solder joints on the coils windings.

A shorted bifi is an LC that will resonate.  More turns on the bifi, the lower the resonant freq/rpms of the rotor, as the more turns, the higher the inductance and capacitance, lower freq.

The regular coil under the bifi is the pickup coil.


As long as this has gone on, it may be worth a try.  ;]

Mags

Hi Mags,
     Are the coils you are reffering to is a multifillar winds, not only bifillar, where romero uses litz wire 7 strands? would it be a shorted coil alltogether?