Magnets, motion and measurement

[Floor]

a section of toothed belt and a .gear

Very nice improvisation

            thanks

[DreamThinkBuild]

Hi Floor and Norman6538,

Been following your detailed work. I whipped up a quick sketch of a mechanism for moving the shields. The idea is to make a push slider which the trolley hits when it gets almost near the end. This of course would have to depend on the strength of the magnets and actuation distance needed. Thinner magnets could maybe help. I do not have enough hands on experience with your model so I do not know where the magnet starts to switch from shielding to repulsion( the most likely sticky spot). Maybe this will inspire another idea if it's not feasible.

Instead of the push slider another idea is using a compliant mechanism like the "Airplane" which creates a snap action toggle.

https://www.compliantmechanisms.byu.edu/flexlinks

[norman6538]

Thanks  Dreamthinkbuild. Nice drawing.  My problem now is I cannot
get the magnets to balance well and the closer or stronger magnets
I use the worse that is. I realize that not all magnets are identical in
power.

Norman

[Floor]

@ all readers

The sliding fixtures used must be rigid before you can get good results. 

Flexing of the magnets from their positions can mess things up quicker than just about any thing else.  Powerful neo magnets require high precision / very strong fixtures.
                                           Use of ceramic magnets recommended.

There is a ratio between the surface area magnets and their flux density.  Yes
                                           Use of ceramic magnets recommended.

Small and yet powerful magnets (neos) are very difficult to align precisely enough to get good results. 

A larger surface area of the magnets makes a workable alignment easier, because it allows for more margin of error in alignment.
                    example
A miss alignment of 1/16 inch off,  out of a 1 inch by 1 inch surface area, is off by 1/16. 
A miss alignment of 1/16 inch off, out of a 2 inch by 2 inch surface area, is like being off by 1/32 if the magnet were instead, a 1 inch by 1 inch surface area.                                                                   

A miss alignment by 1/32 inch might be well within a tolerable / workable limit when using 1 and 7/8 inch  by 5/8 inch surface area ceramic magnets.

If instead, one were using 1/2 inch by 3/8 inch, n48 magnets, the precision in alignment might need
to be within one thousandths of an inch !

Also, the alignment precision needed, is somewhat dependent upon which magnet configuration /
method / device you are using.

https://overunity.com/16954/magnets-motion-and-measurement/dlattach/attach/169684/

        regards
                floor

[Floor]

more

A misalignment of 1/32 inch when using a 1 and 7/8" by 5/8 inch
ceramic magnet, in some circumstances might result in a only a few
grams of force imbalance  The same amount of misalignment,  when
using 1/2 inch by 3/8 inch n48 magnets can easily result in a force imbalance
of HUNDREDS of grams.

This is due to BOTH, the greater strength of the the neos and the ratio of magnet's strength to
the width of the magnet's face.

          floor