Electric Motor Secrets

[Necchi]

Is that not also an issue with lindemann's cross design? Or do you mean at the low rpm of a bike wheel?

"At 10 MPH a 27 inch bicycle wheel would be turning about 125 RPM, a 24 inch one about 140 RPM"
--http://www.fieldlines.com/story/2006/10/16/113432/61

[Jetijs]

Necchi, I see another problem with your design. Lets suppose the rotor is turned so that the stator pole is between two rotor poles. If you apply the power to the coils now, it will try to go both ways as the attraction will be equal to both rotor poles.

[Necchi]

No I don't want a PM motor, I want a lindemann hub motor, or at least to rule out the possibility. I'm currently looking into non permanent ceramics as the material for the rotor in my drawing.

[Beshires1]

Yes, thats it "armature" , I was experiencing confusion (the results of a brain fart). I said that your design would have little or no torque thinking about it having a iron armature. Now throwing that aside, if you plan on a PM hub motor that would work. Of Course it would not be as efficient, as the Iron armature attraction motor(It would consume a lot more battery), But it would give you a lot more torque, and higher speeds on the flats. But you might gain some battery coasting down hills. But only if it is brushless.

[Necchi]

(I think this is the term you were looking for in your last post btw - Armature (electrical engineering - Wikipedia, the free encyclopedia)).

On second thought I guess this is wrong since the whole drum is the armature. I've tried again to think of a term and I came up with "armature conduit". So the lindemann cross has 2 armature conduits, and my diagram also has 2 armature conduits. Or you could say magnetic conduit or magneto-conduit.

[Necchi]

Now I think this motor will run but will have very little if any torque. And the larger the spinning drum the more so. Think of it this way, a fairly heavy wheel solidly attached to a axle is easier to stop from spinning by grabbing the outside of the wheel than to stop by grabbing the axle.

I think what you said about torque was wrong. If the mechanical power originates at the gap, then surely the farther towards the rim of the bicycle the better? Both for torque and also to maximize the number of armatures - I should mention my diagram was simplified, in practice I would take a dead PM hub motor and work from there, so there would be more than four of them. (I think this is the term you were looking for in your last post btw - Armature (electrical engineering - Wikipedia, the free encyclopedia)).

What I'm worried about is how easily the magnetic current will follow the half-circle path around the drum.

Also I was going to follow up with a question about lighter weight materials. Remember my goal is to find some way of modifying a bicycle to at least get me up hills without dragging on flats, so I don't think iron is going to cut it. In a normal PM motor as shown at the bottom of this page...

go-hub electric bike conversion kits. USA DISTRIBUTER

...the rotor is just some permanent magnets so the weight isn't so much of a factor. If permanent magnets can be lightweight, I don't see why there shouldn't be some lightweight material that can take the place of soft iron or silicon steel. I'm looking into ferrite ceramics at the moment.

[Beshires1]

Its sorta weird, I know their normally referred to as poles, because they obviously will lack either a North Pole face or South Pole face, I didn't think you would understand me asking "How many Neutrals will your rotor have?" Or "Blobs of iron?" Protruding from the motor shaft. Any who, I figured you would know what I meant by Posts.

[Jetijs]

What do you mean? How many poles? If yes, then my rotor will have just two poles, something like this:



Just the stator core will now have a bit different pole shape, like in pictures above

[Beshires1]

Jetijs,
Sorry, I misdirected my statement threw you. By the way, how many post will your rotor have?

[Jetijs]

Of course you are right about the bearings. What I meant with the efficiency was that I did not know if such a design as Necchi suggested was more efficient than the design I am currently working on. It would be a bigger load on bearings, but also there would be an increased flywheel effect.
As for bearings. As far as I know, the more precise the bearings are, the less backlash they have thus a little more friction. Of course, the smaller the friction the better, but in attraction motor we need the air gaps as small as we can make them, mine was 0.08mm And at those gap sizes, ordinary bearings might not be suitable and precision bearings should be used. This adds a little more drag but you don't really have a choice.

[Beshires1]

If I understand correctly, in this case the rotor will acts as stator and the stator will act like rotor. The rotor will be stationary and the stator will rotate, right? If so, I don't see a reason why this should not work. I don't know about efficiencies and such, but it should work.

Think about electric motor efficiencies like this. Jetis in your design, you want your bearings to rotate freely as possible, Less friction from the bearings translate to a smoother more efficient motor than a motor with the exact same setup windings, rotor size weight etc that has grease packed bearings that operate smoothly but the bearings have to churn threw the grease. The easier the motor can operate the less power consumed to do work. Ideally if you spin the rotating shaft, or drum by hand, It should spin freely for some time, gradually slowing down until it stops. As apposed to spinning by hand and it stops after only a round or two. Also any commutator source that produces sparks in the making or breaking of contacts will not be as efficient as one that doesn't produce sparks. Using a magnetic or reed switch as opposed to a micro switch (Lever) and cam design to time the rotor to the stator. AHH the list of things goes on and on....

[Jetijs]

Is it possible to swap the stator and rotor as in the drawing I've attached?

If I understand correctly, in this case the rotor will acts as stator and the stator will act like rotor. The rotor will be stationary and the stator will rotate, right? If so, I don't see a reason why this should not work. I don't know about efficiencies and such, but it should work.

[Beshires1]

My Bad ... But if the outer is spinning around the stationary inner Coil then commutation will become difficult indeed. The rotor would have to be drum like , and have to support the entire rotor from one set of bearings. One end would have to be left open or have a bearing large enough to allow the stator wires to go through the bearings to the Stator. This could be done via a slot grooved in the stators stationary shaft. Now I think this motor will run but will have very little if any torque. And the larger the spinning drum the more so. Think of it this way, a fairly heavy wheel solidly attached to a axle is easier to stop from spinning by grabbing the outside of the wheel than to stop by grabbing the axle.

[broli]

I think so, But It wouldn't be nearly as efficient. Because of the windings moving around on the rotor, You would have to use some type of commutator to transfer the current from a stationary input to the spinning rotor coils (this usually means an energy lose due to sparking) A stationary coil as on the stator can be pulsed efficiently without these loses.

There are no rotational coils. According to his drawing there's only one stationary coil.

[Beshires1]

Is it possible to swap the stator and rotor as in the drawing I've attached?

I think so, But It wouldn't be nearly as efficient. Because of the windings moving around on the rotor, You would have to use some type of commutator to transfer the current from a stationary input to the spinning rotor coils (this usually means an energy lose due to sparking) A stationary coil as on the stator can be pulsed efficiently without these loses.