Idontwanttopedal said:Bruno got a 12095 for sale
The last thing that you want is a magnetic path between the magnets at the gap level. Magnetic spacers, less than 1/2 the magnet height might give a slight advantage as back iron. I think I would use something non-magnetic though and, if not electrically non-conductive, at least insulated. You need to break all possible paths for eddy currents.h0tr0d said:.
What do you guys think about some pieces of metal glued between the magnets? Since the stator applies the forces to the magnets
I have 2 options:
1- Aluminium rods and epoxy; lightweight solution?
2- Mild steel rods and steel filled epoxy; more weight but better magnetic path between magnets?
Miles said:The last thing that you want is a magnetic path between the magnets at the gap level. Magnetic spacers, less than 1/2 the magnet height might give a slight advantage as back iron. I think I would use something non-magnetic though and, if not electrically non-conductive, at least insulated. You need to break all possible paths for eddy currents.
There are two issues:h0tr0d said:I looking at Lebowski's rotors and thought there wouldn't be a problem with something conductive between the magnets...
These will be only slightly electrically conductive but as there's not much advantage to using them as a spacer material anyway.....h0tr0d said:http://www.hobbyking.com/hobbyking/store/__15386__Carbon_Strip_1x3x750mm_5pcs_set_.html?strSearch=carbon%20strip
Would this Carbon Strips be good? I imagine the fibers being parallel to the magnets...
Miles said:There are two issues:
The reason for spacing the magnets apart is that, if the magnets are touching or close, the flux from the edges short circuits and doesn't enter the stator. Using magnetic material to completely fill these gaps is the worst of all cases.
Whilst the fundamental frequency won't generate eddy currents in the rotor, they are generated by the harmonics. This is the reason for the use of segmented poles and insulation between the magnets and back-iron.
They'd be lighter for the same active flux, that's for sure....h0tr0d said:In other words: All motors that have 100% magnet coverage of the back iron (like a hubmotor) could be better if the magnets were a bit apart?
Yes, the upstands act as spacers and to some degree as back-iron.In your inrunner you have the back iron slightly elevated between the magnets for easy mounting and better back iron "efficiency", right?
h0tr0d said:I don't need magnet spacers per se, I need something to connect the 2 rotors. Those carbon strips looked nice for that purpose...
What about putting magnets (halbach'ish array) to unite the 2 rotors? Little gains, big bucks...?
Just for alignment, you mean? Or, structurally?h0tr0d said:don't need magnet spacers per se, I need something to connect the 2 rotors. Those carbon strips looked nice for that purpose..
Honestly, forget it...What about putting magnets (halbach'ish array) to unite the 2 rotors? Little gains, big bucks...?
Miles said:Just for alignment, you mean? Or, structurally?
I was about to suggest thatFarfle said:Take a look at my double wide fat arse outrunner if you want some ideas.
http://www.endless-sphere.com/forums/viewtopic.php?f=30&t=41576&start=75
Farfle said:I would take a mild steel sleeve whose ID is the OD of the existing cans that is the length of the entire twin cans, and use the existing can bolts (obviously longer ones would be needed) to go through both cans