View Single Post
 
Old 11-22-2018, 09:22 PM
gyula gyula is offline
Silver Member
 
Join Date: Apr 2007
Posts: 820
Hi Paul,

Just noticed your latest answer while I was preparing an answer so I include what I wrote, it may be relevant.

Yes, in your previous video your vertical setup can freely rotate for quite a long time (like the toy does), even though there is a little friction at the bottom of your rotor shaft where the tip of the shaft touches the knife surface.

From your latest video ( https://www.youtube.com/watch?v=nW0H0D41uM4 ) it does not appear to me that "There is currently physical contact but barely." My impression is that there is a small 1 mm or slightly less air gap on both sides of the floating rotor versus the stator surfaces. Watching your video, there are moments when the floating rotor is displaced by your pushing shaft i.e. length wise towards the left or the right side stator Alu cases.

You could build a simple test setup using much smaller magnets and no Alu enclosure for the magnets at all, to see that a thus floating rotor is able to spin freely at all (like it does in the toy setup), see a drawing attached. If the floating rotor can spin for a relatively long time, then insert an Alu sheet of certain thickness into both air gaps to see whether spinning slows down or not. You may need to increase air gaps to accomodate for the thickness of the Alu (or copper) plates.
Similarly, you can place Alu sheets as if they were side walls, close to the floating spinning rotor to see any decelaration.
Either 4 cube or 4 cylinder magnets you happen to have could be used for such tests. Alu plate thickness counts too.

You write that you consider using 316 stainless steel instead of the Alu frame : unfortunately eddy currents can also be induced in them, they conduct current like Alu or copper.

For the holding structure you may consider hard plastic,like polyamide or similar material or even wood planks, boards etc: no any metal content which would conduct current.

Gyula
Attached Images
File Type: jpg principle test.jpg (16.6 KB, 6 views)
__________________
 
Reply With Quote