I’m a great fan of Kadee and I’ve used under track permanent Kadee uncoupler magnets for a long time, they work really well and allow a frieght yard to be worked as realistically as you can get on a model rarilroad.
I’m putting them in my new HO layout and proving them as I go so I know they are in the right place for working my railtroad. (By the way, I router out the space throught the cork and into the 3/4" ply so they are flat and the right height under the track.)
OK… finally the question! I want to put a permanent Kadee magnet under a very slightly curved section of track. (It’s a tight plan with little room.) I know that Kadee say that uncouplers must be on a straight track but I’m sure there must be a a little lee way in the design. Does anyone know at what radius Kadee will not uncouple? (No matter how small.)
the LDSIG and the NMRA are speaking about problemless (un)coupling if you apply a 1;5 ratio for your radius; 5 times as large as the length of your longest car.
With a few pieces of flextrack you can do some experimenting. Please do not forget to share the outcome.
I tried on 22 to 30 inch radius curves and gave up on putting the magnets between the rails at these radii because they do not work with modern equipment.
Please post the results, it is great information to have.
The LDSIG rule of thumb states that a 5 times longest car length is the minimum radius for successful coupling with body mounted couplers. It further states that to automatically couple at a 3X minimum radius, wider than normal coupler swing is required. The details are at http://www.macrodyn.com/ldsig/wiki/index.php?title=Curve_radius_rule-of-thumb. Uncoupling is not addressed. I do not know of any methodical testing that when into the rule of thumb; I believe it was generated based on observations of LDSIG members on their home layouts. Some of the issues are discussed more thoroughly in the January 2009 issue of Model Railroad Hobbyist - a free online magazine.
Most folks trying to uncouple magnetically on curves have found more success moving the magnet towards the outside of the curve. I believe the idea is to center the magnet under the trip pin locations on the curve. In thinking about the issue, it also seems the couplers cannot be at the limits of their horizontal swing. Nor can the radius be tight enough to “jam” the knuckles together; there must be enough play or slack for the knuckles to move. For these reasons, I suspect the full size Kadees will uncouple on a smaller radius than the scale knuckle size.
I would be very interested in reading your testing results, as would the LDSIG.
My rule is to maintain a straight length of track for a full car-length on either side of the magnet, where a “car length” is the longest car or engine that you expect to uncouple there. If you are using truck-mounted couplers, like those on some longer passenger cars, for example, you can cheat a lot, because the trucks will line up with the track.
You may get the cars to uncouple on a curve with careful placement of the magnet (or use of stronger magnets), but being able to couple on a curve, that’s the trick.
Try the under track type as you can adjust the position till you get it to work, you just have to make the pit bigger than usual so it has some sideways play.
A few months ago, MR had an article on using small tubular permanent magnets inserted into holes in the roadbed. Might this idea be able to be adapted to a curved secton, maybe even with a couple small magnets mounted to the outside of the curve? Relatively invisible and more easily adaptable to a specific situation?
A club that I once belonged to mounted a Kadee under-track magnet under the middle of a #6 double slip switch. Uncoupling was the same no matter which of the routes had been selected.
For a continuous curve, I either reposition the magnet slightly to the outside of the curve or use the miniature supermagnets just outside the tie line.