Howard Johnson Replication Tube Claim

[mikestocks2006]

Hey Mike, good to see you mate

Agree it would help to stabalise it, but also add friction.

Some people will say that the friction could be helping with the effect as it is holding the Rotor back from getting carried away.
My answer to that is that the Air Gap between the Stator/Armature magnet could be reduced with less friction and then maybe allow the Stator/Armature magnet to last longer.

All guess work till we replicate I suppose, but as usual good fun

Cheers

Sean.

Great to see you too working on this
It could very well be a single bearing with single row, and to keep a stable geometric positioning of the aluminum disk edge (about 9 in moment arm load there for about 1.5-2 in support across the bearing inner/outer race ball contact diameter) it would most likely be a hi precision preloaded one.. Preloading does increase precision for the rated load, but also has increased friction too, maybe an acceptable tradeoff. There appears to be very little if any wobble when the disk rotates or is handled initially. They are pricey too Mylows bearing â€"he mentions it’s very precise-- and it also seems to be of sealed type, most likely Viton or EPDM seal and grease packed inside.
To reduce friction, one can do the std routine: remove seal, clean grease, dry…

An alternative would be 2 cheaper open race (looser ones, very light or no preload) bearings that would provide needed stability and support at lower prices etc.

For initial replication purposes however; it maybe best to keep the parts as close as possible to the original, so no additional variables regardless how small are introduced.

Good fun stuf
All the best
Mike

[derricka]

Contrary to what has been suggested, I strongly recommend avoiding the use of flexible magnets.  Many of the commercially available strip and sheet type magnets have alternating poles (NSNSNS) due to being magnetized with electromagnets powered by AC.  These types of plastic magnetic materials vary widely in composition, are usually very weak, demagnetize easily, and some formulations won't re-magnetize. In summary, forget trying to get consistency, or reproducibility, if you use flexible magnet material.

[PaulLowrance]

Contrary to what has been suggested, I strongly recommend avoiding the use of flexible magnets.  Many of the commercially available strip and sheet type magnets have alternating poles (NSNSNS) due to being magnetized with electromagnets powered by AC.

I'm doing a test to see how long it takes a NdFeB PM to remagnetize a flexible PM. That will make the flexible PM all in the same pole. Roughly a week ago my experiment on alnico show that it took ~ 1/2 an hour to remagnetize.

These types of plastic magnetic materials vary widely in composition, are usually very weak, demagnetize easily, and some formulations won't re-magnetize. In summary, forget trying to get consistency, or reproducibility, if you use flexible magnet material.

Yes, which could be the reason why they're working for mylow. Someone emailed me saying that Steorn claims the secret is in "crappy" magnets. My measurements in *long term* magnetic viscosity (another key to Steorn's acclaimed success) have shown that weak magnets have high long term magnetic viscosity on the order of seconds and beyond. Whereas strong magnets have long term magnetic viscosity on the order of centuries; e.g., NdFeB. So it's possible that strong magnets would require rpm's far too low to be useful.

PL

[lostcauses10x]

For these things to do what it does to the stator magnet, a lot of magnetic vibration is going on. It would take a 3d sim to show the whole thing with this stuff. The spacing of the magnets seem to be a major part of the vibration. I suspect the velocity will be linked to this vibration timing and amplitude for the drive of this, if it is real.

Pole position of the stator magnet would be interesting to view. 

[PaulLowrance]

Just checked the flexible PM's. It didn't take very long to magnetize them, but maybe they'll still increase in strength if left on longer. Anyhow, as expected, they're very weak because of they're exceptionally thin as compared to over all front surface area, which makes all PM's weaker. Just cut a bunch of them, then stack to form a normal shaped PM; e.g., 0.5" square by 2" long. It could be comparable in strength to an alnico.

PL