In the absence of evidence to the contrary, possibly...

When I replied to this message there was no text, just a title.  I assume a fluke of timing...

Kadee has you covered

Dear Bill,

Kadee has the 308 permanent magnet uncoupler for exactly this situation.

http://kadee.com/htmbord/page308.htm

Magnets follow the inverse-square law, so even a small increase in distance between the magnet and "the thing you are trying to magnet onto" results in a significant drop in effective magnetic force/flux. This is one reason why the 308s are supplied with an steel "Intensifier plate".

Happy Modelling,
Aim to Improve,
Prof Klyzlr

Uncoupling Magnet

See if this Kadee sheet answers your question: http://www.kadee.com/html/309ins.pdf

[EDIT] The quick fingered prof beat me to it!

Hardware Store

Just go to your local Hardware store and look for magnets, usually $2 or so for a pair. You put the pair together next to each other with the middle lined up along the center of the track and you have your uncoupling magnet. Much cheaper than the Kadee ones and more powerful, in fact a few of mine are too strong, the cars always uncouple even when you don't want them to! Some experimentation is in order to get the right distance below the track, and to complicate things, ballasting will reduce the strength. (its a function of the density of the material that the magnet has to work through)

If you want to make them so that they are controllable, mount them on a hinge or a sliding arrangement so that they drop out of the way and pull into place for uncoupling.

Brent

handling "slack action" over permanent uncouplers

Dear Brent, Bill,

Believe the issues of handling "slack action" and the resulting inadvertent uncoupling over permanent magnets was discussed a little while ago...

https://forum.mrhmag.com/post/fine-tuning-couplers-how-do-i-cure-inadvertent-uncoupling-12187317

Happy Modelling,
Aim to Improve,
Prof Klyzlr

PS anyone else having issues with Kadee's site
(front page loads fine, all product-specific pages load "blank white"), on IE8 / WinXP?

Yeah Mike I had a minor issue

Yeah Mike I had a minor issue with my learning curve and this posting system, lol.  Its a good thing I took a few seconds before I got back in and actually put in my post as I don't see a censor button on my blog editor. lol..

Kadee Website

It's working fine for me using Firefox on WinXP.  Maybe something temporary.

-Jack

(front page loads fine, all product-specific pages load "blank white"), on IE8 / WinXP?< < <

Same as you describe. I am using WinXP.

Jerome

OKC

Under the track magnets

There are 4 ways (well, probably more than that) of handling the "where to hide/disguise the uncoupling magnet" issue:

1. Hide a magnet between the rails by embedding it in a road or in dirt that is level with the rail tops.
2. Use the Kadee 308 under the track uncoupling magnet (or other powerful magnets). Be aware that this monster magnet is powerful enough that if you are using wheel sets with steel axles under your cars, the magnet will act on them and you are likely to get false uncouplings. Often, it's more efficient to use the "delayed uncoupling" feature of the Kadee magne-matic system with a single magnet in the throat of a staging area (uncouple over the magnet then push the uncoupled cars to their spot) than to place a non-delayed magnet at every car spot. Unfortunately, the surging of steel-axeld cars over these magnets will result in a number of false uncouplings. If you replace all your steel axle wheel sets with non-ferrous sets this problem will disappear. If your cars have a lot of steel or iron weights, mounted low in them, they may also exhibit this problem albeit to a much lesser extent (magnetic field strength drops off as the square or is it the cube of the distance from the magnet).
3. Use an under the track electromagnet. Same benefits as a 308 under the track magnet but no false uncouplings when the magent is turned off. These are a lot more work to install, you'll needed to cut a hole through the roadbed under the track. I'd recommend using a push button switch to activate the magnet (or an electronic timer that will give you a few seconds of magnet action should you be in a place where both hands are required for another purpose while uncoupling). It's nearly inevitable that a toggle switch will be inadvertently be left in the "on" position potentially causing the magnet to overheat (especially with a DC power supply). Because a lot of heat is generated I'd be reluctant to use these with pink foam scenery surrounding them -- the pink foam will prevent the heat from escaping making a potential fire hazard.
4. Use some kind of mechanical mechanism to raise and lower a permanent magnet into position under the track. Raise it to uncouple, lower it to run without any magnet attracting steel car parts issues.  However, using cars without ferrous parts (just about all cars produced these days) renders these last two technologies obsolete.

A final thought. If your industries are so far away from an aisle their car spots can't be reached without contortions or use of a small gantry crane, uncoupling is only one of your problems. How do you plan to:

• rescue derailed equipment?
• clean the track?
• work on that area?

If your industries/car spots are reachable from an aisle, have you considered using uncoupling picks instead of magnets? Uncoupling picks let you uncouple anywhere needed instead of at a few pre-selected locations, plus bamboo skewers are a lot less expensive than magnets and don't require any special installation.

FWIW

Charlie