Cars not uncoupling at crest of the hump

[bbussey]

If you bury these in the roadbed next to the track ties on either side, you'll accomplish your desired results.  They can go end-to-end to make longer magnets and traverse uneven terrain.  You may have to experiment with how deep to bury them, and you have to have the proper orientation so they attract and not repel the trip pins.  But at least you can install with having to rip track up, or have unsightly surface magnets between the rails.  The 1/8" is the thickness.

1" x 1/4" x 1/8":  https://www.kjmagnetics.com/proddetail.asp?prod=BX042
2" x 1/4" x 1/8":  https://www.kjmagnetics.com/proddetail.asp?prod=BY042

If these are too strong for your liking, they make then in 1/16" thickness and in narrower width.  For more strength, get wider than 1/4".  I wouldn't go more than 1/4" wide and 1/8" thick, because then you have to be concerned about the magnets attracting other foreign objects.  As it is, you would have to bury the magnets well into the roadbed so that they cannot move.

When I started using these, I placed them under the track 1/8" down.  But they have to be perfectly centered under the rails or the trip pins pull to one side.  I discovered during the process that I could bury the magnets next to the ties on either side and get the desired results without the need of perfect centering.

As noted up-thread, steel-wheeled cars do not like them, instant application of emergency brakes and/or derailment.  Cars with steel weights also are affected and will stop and hover over, but they won't prevent an engine from pulling them.

[videobruce]

How about the metal wheels of locos ??

[peteski]

How about the metal wheels of locos ??

Metal wheels on locos and today's rolling stock are made from non-magnetic materials.  Usually plated brass or nickel silver. Same with the axles. Either plastic or non-magnetic.  The days of Atlas boxcar axles being attracted to the uncoupling magnets are long gone (unless you still use those cars).  But some cars still use steel weights which will be attracted by strong magnets.  Locos, no so much as the chassis is made from a non-magnetic alloy.

[mark.hinds]

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When I started using these, I placed them under the track 1/8" down.  But they have to be perfectly centered under the rails or the trip pins pull to one side.  I discovered during the process that I could bury the magnets next to the ties on either side and get the desired results without the need of perfect centering.

(text removed)

That is very interesting, because in my experience, getting the MT under-track magnets perfectly centered has always been tricky.  Perhaps because my uncoupler design is from the 80s, it never occurred to me to try 2 of the small modern magnets on either side of the track.  Thanks for posting this. 

[peteski]

That is very interesting, because in my experience, getting the MT under-track magnets perfectly centered has always been tricky.  Perhaps because my uncoupler design is from the 80s, it never occurred to me to try 2 of the small modern magnets on either side of the track.  Thanks for posting this. 

That is because the under-magnet uncoupler has the poles (on its edges) aligned with the track.  The center of the magnet is neutral (or very weak).  So each pole at the edge of that magnet attracts one of the trip pins, causing them to swing to the outside.  If not lined up at the track center line, this will not happen.

If the strong (and independent)  magnets are placed outside of the track the alignment is not that critical since the trip pins will just swing out to meet the magnetic field on t he outside of the track. 

[mark.hinds]

Metal wheels on locos and today's rolling stock are made from non-magnetic materials.  Usually plated brass or nickel silver. Same with the axles. Either plastic or non-magnetic.  The days of Atlas boxcar axles being attracted to the uncoupling magnets are long gone (unless you still use those cars).  But some cars still use steel weights which will be attracted by strong magnets.  Locos, no so much as the chassis is made from a non-magnetic alloy.

Not true for my Atlas PS-1 box cars, and various other non-MT boxcars I purchased for my 50s-era layout.  To avoid the strong reaction to my MT under-track magnets, I have had to replace the wheel sets with plastic equivalents from MT.  Are you saying that more recent releases have recognized this issue?  (Not that it will do me much good, as I already purchased pretty much everything I will need for my prototype). 

EDITED, after reading Peteski's post more carefully; sorry about that...)
MH

[mark.hinds]

That is because the under-magnet uncoupler has the poles (on its edges) aligned with the track.  The center of the magnet is neutral (or very weak).  So each pole at the edge of that magnet attracts one of the trip pins, causing them to swing to the outside.  If not lined up at the track center line, this will not happen.

If the strong (and independent)  magnets are placed outside of the track the alignment is not that critical since the trip pins will just swing out to meet the magnetic field on t he outside of the track.

The problem (at least with the single MT under-track permanent magnet) is not that the pins won't swing, but that they can both swing to the same side if the magnet is not perfectly aligned (and I do mean perfectly).  If they both swing to the same side, the cars will not uncouple typically. 

MH

[peteski]

The problem (at least with the single MT under-track permanent magnet) is not that the pins won't swing, but that they can both swing to the same side if the magnet is not perfectly aligned (and I do mean perfectly).  If they both swing to the same side, the cars will not uncouple typically. 

MH

That is exactly what happens. I didn't go into that much detail.  Because the center of the magnet is neutral, both pins will be attracted to the same pole.

[bbussey]

Not true for my Atlas PS-1 box cars, and various other non-MT boxcars I purchased for my 50s-era layout.  To avoid the strong reaction to my MT under-track magnets, I have had to replace the wheel sets with plastic equivalents from MT.  Are you saying that more recent releases have recognized this issue?  (Not that it will do me much good, as I already purchased pretty much everything I will need for my prototype). 

The current-tooling Atlas PS-1 boxcars (and the TOFCs I believe) have come equipped with steel wheels since they debuted.  I just swap them out.  With the PS-1, I swap in BLMA/Atlas ASF A-3 trucks since the bulk of the prototype ran on them, and then save the Barber S-2A trucks for upgrades to other rolling stock — which serves the additional benefit of lowering the ride height — but not before swapping in ESM or FVM wheels (the S-2A trucks with new wheels tremendously improve the appearance of the MTL 3-dome tank for example).    I much prefer metal wheels over plastic wheels, so that wouldn't be an option for me.

[nkalanaga]

My ESM 33" wheels apparently have magnetic axles.  The wheels aren't, but a strong magnet will hold the end of the axle.  I doubt that it would be a problem for magnetic uncoupling, though, as they're very weakly magnetic.  Not like solid steel.  Given the strength of the magnets, I wonder if it's the nickel plating?

[bbussey]

Interesting. I use the K&J magnets for motive power changeovers in New Haven, as well as switching on the station bypass line which primarily is used by freight consists. I can report that ESM axles are not affected, or rather, not affected to the point where it impedes operation. Cars don’t even slow down when pushed to roll freely over the magnets. Just the couplers wiggle.

[NtheBasement]

If the magnets are strong enough they also attract OEM car weights.  I have this issue with my Atlas coal hoppers over a Rapido Railcrew uncoupler when the coupler is "off" and the magnet swings parallel to the track.  If I lower the magnet to avoid it then uncoupling isn't so reliable.  Unfortunately the weights are permanently glued.

[peteski]

My ESM 33" wheels apparently have magnetic axles.  The wheels aren't, but a strong magnet will hold the end of the axle.  I doubt that it would be a problem for magnetic uncoupling, though, as they're very weakly magnetic.  Not like solid steel.  Given the strength of the magnets, I wonder if it's the nickel plating?

I suspect that they are stainless steel.  Some alloys are *SLIGHTLY* ferromagnetic. If you have any Kato axles, they will probably have the same properties.  I haven't tested at other brands, but I suspect that other brand axles which have steel look to them are also stainless steel. Nothing to worry about with uncoupling magnets.

[videobruce]

If the magnets are strong enough they also attract OEM car weights.  I have this issue with my Atlas coal hoppers over a Rapido Railcrew uncoupler when the coupler is "off" and the magnet swings parallel to the track.  If I lower the magnet to avoid it then uncoupling isn't so reliable.  Unfortunately the weights are permanently glued.

Interesting point, I never thought about car weights. No one else mentioned this.

[peteski]

Interesting point, I never thought about car weights. No one else mentioned this.

But I have - yesterday. 
https://www.therailwire.net/forum/index.php?topic=54457.msg747680#msg747680