I think I have finally found the magnet combinations that I find most reliable. I have experimented with many different magnets… all are from K&J Magnets and all are N42 neodymium magnets.
The easiest to install in existing track work is the B422. It is1/4”x1/8”x1/8” $.27ea and I use 10 per uncoupler or $2.70/uncoupler. The magnets are installed in between the ties of SHS flex, mounted on .005 steel with 3/8” wide styrene to keep them separated. They are flush with the top of the ties so hiding the magnets should be no problem at all.
The reaction of the B422 is very good and delayed uncoupling being equally good, maybe just the slightest pull on steel wheels and no pull on Flyer link couplers (a plus for me). Five magnets per side gives you about 1 3/8” worth of target area and even with my Flyer 0-8-0 operating on DC, I found this to be quite adequate.
Another useful magnet size is the BX024. It is 1”x1/8”x1/4” $1.23 ea. or $2.46/uncoupler. Because it is 1/4” thick, it fits pretty well under the ties on track that is on some sort of roadbed. It the picture I squeezed it under AM flex on 3/16” cork roadbed. The space in between the magnets is 3/8”. I have it on a strip of .005 sheet stock for ease of installation. This is a very strong magnet yet is has no effect of steel wheels or Flyer link couplers.
I would be remiss if I didn’t mention a link that Ed L sent to another thread:
You will find some very good ideas on dual magnet uncoupling. The model RR is H0 and appears in Great Model Railroads 2015
I also googled “dual magnet uncoupling” and found many additional links and uTube videos.
This has been a fun adventure,
in still snowing, Maine