Not true. Since the adjacent magnets have opposite poles the motion of the rotor will mean both cause either an increasing or decreasing flux in the coil. That is, their effects act to add. That's one of the charms of the design.
I'm wondering if in fact with the 10 inch rotor and the size magnets given, whether it would be better to go with 12 one inch by two inch magnets long side placed radially with a minimum spacing of about half an inch. This increases both the potential flux and the number of coils by 50 percent. It does not increase the amount of copper by 50 per cent, though. Perhaps Flux would like to compare the effectiveness of the two designs. I don't think I'd be happy with the wide spacing one would get using 8 of the magnets on the 10 inch rotor, either. You either make the coils 3+ inches wide to get the most of the magnet - coil interactions or you give up output by going to smaller coils. Simply put, that amount of copper relative to those size magnets seems excessive with 8 magnets on a 10 inch rotor. Or am I missing something? GeoM[ Parent ]
You could indeed improve the set up I gave him. I just gave him something that would adequately manage a 6 ft prop with a common magnet size that works out nice and cheap.
It would perfectly well have gone on 8" discs and been a better compromise, but using 8" discs he would run out of space at the centrer of the stator and if he wants to use a standard trailer hub there would be trouble. I used 8" discs but I had to make a special hub.
Going up to 12 magnets makes the thing capable of managing an 8ft prop and it will need to be really tamed down with lots of series line resistance at 6ft. It seems pointless using 8 more magnets. Eight poles of the 2 x 1 x 1/2 will still be ok, I just happened to use the metric magnets as they are far easier to get here.
Rather than squeeze every bit out of a small design, this was generous enough not to have to worry about making it ideal. It was derived from Hugh's single rotor 8 pole 4 ft machine. I have scaled it up to 5ft with a second disc with no magnets and it would just probably take 6ft with care. Doubling up on the magnets gives it lots in hand for 6ft and there would be no real need to go to great lengths to get a wire size to make the coils touch. Unless it is 12v with normal line resistance it will be well towards stall and may need added resistance. At least the heat is better dissipated in the line rather than a higher resistance stator.
Flux[ Parent ]
This brings up memories of other posts where it was disputed if the power came from the coil legs or from the coil as a whole. This design will cut the "legs" by half. I can easily do a test with a single rotor without gluing the magnets. First with magnets the traditional way, then sideways. The test coil will be the same size either way so I just rotate it 90 degrees also. I may not put that argument to bed but I can post real comparisons. Andy[ Parent ]
http://www.fieldlines.com/story/2007/10/8/161429/170
Looks like DanB did the exact same test. Well, it wouldn't hurt my education to do it also. A little more shop time instead of book time...Andy[ Parent ]
