Magnetic uncoupling options for Atlas Code 55

[conrail98]

We use little circular magnets in between the rails on a number of layouts around me. In HO, they'll use 2 to 4. I figured when the time came, if I were to use them, I'd probably setup 2. These things are pretty small and there was  a sidebar about them in a layout in GMR 2015. Here's a link to the uncoupling mechanism video of said layout:

It shows it in action but the sidebar has more information on it.

Phil

[shark_jj]

I went out today and bought some rare earth magnets to test them.  I bought some that were 1" by 1" and some that were 1/2" by 1/2".  I first tried the 1" by 1" as that would replicate the two magnets that Brian described.  Didn't uncouple the cars.  I then put the two 1/2" by 1/2" together making a magnet that was 1/2" by 1".  The 1" dimension was placed at 90 degrees to the rail.  This worked exceedingly well.  I don't quite understand why the 1' by 1' didn't work, maybe somebody with a better understanding of magnetics could explain it.  The test also demonstrated two other factors to me.  One Brian is absolutely correct about placing the magnets 1/16" inch below the rails.  These are strong magnets.  I covered the magnets with a strip of 1/16" styrene and it didn't affect their performance whatsoever and leveled out the track.  Second, I had one car which kept uncoupling when I was pulling the cars through the magnet as if I was leaving the siding.  Upon examination I discovered that the gladhand on that car was marginally lower than the other three I was testing.  Looks like I will have to add another test to my car standards to ensure that the gladhands are all at the requisite height. (i.e. not just rail clearance). 

PS:  I really appreciate all the insights that the rest of you have been sharing.

John

[GaryHinshaw]

I don't quite understand why the 1' by 1' didn't work, maybe somebody with a better understanding of magnetics could explain it. 

If you have two 1x1" magnets, see which edge they attract each other on, and place that edge under the rails.  You probably had the poles aligned along the axis of the track.  You may find that they are too strong though.

[nkalanaga]

Wolf:  At the atomic level, all magnets are "many in one".  If you cut a magnet halfway between the N and S poles you get two magnets, each with N and S poles, not a N piece and an S piece.  MT's magnets are made just like Peteski's pictures.  If you place two of them side by side, N to S, you end up with a single double-width magnet, with N and S poles on opposite sides, and a neutral area in between, just like the original magnets.

[peteski]

They are single magnets - it is the North and South poles that attract the uncoupling pins to the corresponding sides.  I was also confused about 2 magnets but Bryan explained that if you put 2 magnets together (so their poles attract) then become a single larger magnet (and act just like the stock MT uncoupling magnets).

[bbussey]

I went out today and bought some rare earth magnets to test them.  I bought some that were 1" by 1" and some that were 1/2" by 1/2".  I first tried the 1" by 1" as that would replicate the two magnets that Brian described.  Didn't uncouple the cars.  I then put the two 1/2" by 1/2" together making a magnet that was 1/2" by 1".  The 1" dimension was placed at 90 degrees to the rail.  This worked exceedingly well.  I don't quite understand why the 1' by 1' didn't work, maybe somebody with a better understanding of magnetics could explain it.  The test also demonstrated two other factors to me.  One Brian is absolutely correct about placing the magnets 1/16" inch below the rails.  These are strong magnets.  I covered the magnets with a strip of 1/16" styrene and it didn't affect their performance whatsoever and leveled out the track.  Second, I had one car which kept uncoupling when I was pulling the cars through the magnet as if I was leaving the siding.  Upon examination I discovered that the gladhand on that car was marginally lower than the other three I was testing.  Looks like I will have to add another test to my car standards to ensure that the gladhands are all at the requisite height. (i.e. not just rail clearance). 

PS:  I really appreciate all the insights that the rest of you have been sharing.

John, you also can lower the magnet away from the track more than 1/16".  I settled on that distance because it is easy to cut a square in the 1/8" cork roadbed, push the magnet down to the bottom and cover it with an .060" thick square of styrene.  But as you mentioned, Earth magnets are powerful and would still affect the couplers if lowered slightly more.

Also, regarding your 1"x1" magnet, it may be that the poles were not on the narrow edges.  They could have been on the large flat surfaces.  That was another issue I encountered with the K&J magnets, making sure I acquired not only the proper dimensions but also the proper pole orientation.  Fortunately, they have the specs for each magnet posted on their website.

[peteski]

I covered the magnets with a strip of 1/16" styrene and it didn't affect their performance whatsoever and leveled out the track. 

Just to make things clear, styrene does not affect magnetic field.  But the distance will (the farther away you are from the magnet, the weaker the field).

As far as determining the pole location, long time ago I bought a piece of "magnetic paper" which clearly shows the magnetic field.  I don't recall where I got mine but it is still available. Unfortunately the one source I found is in UK. http://www.grand-illusions.com/acatalog/Magnetic_Field_Paper.html  But I'm sure with some digging around you could find a local source.   This stuff is really handy for seeing the invisible. 

[GaryHinshaw]

There's always Wooly Willie!



(Apparently there is also Designer Beaver, ages 18+...  )

[nkalanaga]

You used to be able to buy cheap compasses in toy stores.  They weren't much good for navigating, but worked wonders telling which end was which on a magnet.

[glakedylan]

I am reminded of an uncoupling tool that was used back in my HO years (decades ago)
it was a handle with an upside down "U" on one end
on each leg of the upside down "U" there was a magnet
it worked by hand placing the upside down "U" portion between the cars at the place of the couplers
the magnets would do their job and then the tool was simply lifted away
it was 0-5-0 portable, and IIRC correctly, very reliable
one could be easily made, be it from styrene or wood or other plastic

just a thought....fwiw

[nkalanaga]

Gary:  That's the one I was thinking of early.  I remember seeing it advertized, but have never seen it in real life.  I've never used magnetic uncoupling, so haven't thought much about how to do it.  I did buy a KD (pre MT) uncoupling track in my teenage years, and put it into my test track.  It worked, but when the entire layout is only a foot wide, so did manual uncoupling, and hands are cheaper than magnets!

That magnet is around here someplace, but I have no idea where.  We have an HO one on the refrigerator, but it came from a piece of track I found in the vacant lot next door!

[shark_jj]

Brian, I wanted to pick your brain a little further.  I have been experimenting with two flat magnets which are 3/4 by 3/4.  When installed this creates a magnet which is 1.5 inches by 3/4 inches with the 1.5 inch dimension being at 90 degrees to the track.  Cars uncouple fine.  The problem I continue to have is when I go to pull cars from the siding.  The first three cars come out fine at slow speed but the fourth car uncouples as it cross the magnet.  I have tried different combinations of cars but the problem remains.  I know that you stated you were using 1/2 by 1/2 inch magnets, and I wonder if this reduces the strength of the magnetic field sufficiently to alleviate this problem.  Can you tell me if you have experienced anything similar. 

Two other points of note:  If I add another layer of cork so that the track is now 3/16's above the magnet, the problem is resolved, ie the cars still uncouple when stopped on the magnet but don't uncouple when pulled across it.  This would strongly indicate that the magnet is too strong for what I am trying to achieve.   Second point is that I am using truck mounted micro trains couplers.  I notice that by the time I reach the fourth car in a string, the tension is gone and I am getting some backward and forward movement in the car.  This movement contributes to the cars ability to uncouple. 

I realize that a simple solution would be to lower the magnets into the benchwork, however, this is a retrofit scenario and lifting track and cork to router out holes 3/16 inches deep would be a pain in the $#@.  If I know that you are not encountering the same problem, then, I will move away from my local supplier and try the KJ Magnetics that you recommended.

Appreciate any info that you can provide.

[djconway]

Shark_jj you have hit on the biggest problem with permanent magnets, as soon as there is slack between the cars they open.
There has been lots of discussions around solving the problem:
1 - Eliminate the slack by using a wheel retaining spring on each car (that's the other little spring MT supplies in the build your own couplers)
2 - Hinge the magnet so that you have to swing it up when you want to uncouple -
3 - Electro magnets.

What you describe is known as the slinky effect. [] the curse of N scale since KayDee started making N scale couplers.

[peteski]

3 - Use an electromagnet. 

[djconway]

3 - Use an electromagnet. 

I was editing my note to include