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Uncoupling with rare earth magnets

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Uncoupling with rare earth magnets
Posted by BigDaddy on Sunday, December 11, 2016 10:12 AM

I don't like the look of the Kadee above track magnet and didn't plan far enough in advance to use their below track electromagnet.

I've looked at a couple Youtube videos and bought a stack of cylindrical rare earth magnets.  The look too small to do anything, but I wiped together a little test track on foam and 3 magnets on each side do, in fact, work.

So here's my question for you guys using these:  Is their an optimum number of magnets or to state it another way what is a practical length of track to install the magnets?  It strikes me the 3 or less pairs might require exact positioning for uncoupling.  Maybe there is a reason that the KD 321 is that long?

Henry

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Posted by BroadwayLion on Sunday, December 11, 2016 11:39 AM

LION has looked at such magnets. Kadee magnets have their N and S poles along the edges, not at the ends. This pulls the pins to the sides, opening the coupler.

LION has some rare earth magnets salvaged from Hard Disk Drives, very poerful, but the N and S poles are at the ends... You can mount them under the tracks, but they have to be crosswise... Just remove a few ties, and put the couplers under the tracks. INSULATE THEM from the rails!

It will work, but... it does not give you a lot of wigle room, you must stop and revers in exactly the right place. LION mounted a lamp on a pole where the magnet is so that from across the room he can stop the train correctly.

Modern locomotives are so smooth that simply stopping on the magnet will not necessairaly open the knuckles. LION invented the "Cutting Key" (Idea stolen from transit couplers). In this case it is a push button, a reversing switch. A brief touch of the button jogs the engine just enough to effect the uncoupling, but is imperceptible to gawking geese.

 

ROAR

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Posted by CentralGulf on Sunday, December 11, 2016 1:09 PM

Lion, what about mounting the rare earth magnets in parallel, poles to the sides. Does that work? I imagine it would take a well thought out mounting, as the magnets would tend to repell each other.

CG

 

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Posted by peahrens on Sunday, December 11, 2016 1:42 PM

I've recently installed some 1/8" diameter by 3/8" long cylinder magnets from K&J Magnetics on my HO layout.  They are Grade 42, #D26, 36 cents each. 

http://www.kjmagnetics.com/proddetail.asp?prod=D26

I used these based on some earlier threads I had read.  I had tried a couple of Kadee flat plate under track types but decided to tear them out.  I installed the cylinders vertically, in 3 pairs, just inside each rail, between the ties, by drilling a 1/8" hole and pushing the cylinders into the cork/plywood roadbed so the tops were just below the ties.  After reading old threads and looking at magnetic fields on Google, I was still confused on orientation, so I put the cylinders along one rail with N side up and the opposite cylinders with S side up.  I thought that might just pull both coupler hoses to the same side but indeed it pulls them to opposite sides.  I suppose, since the field is perpendicular to the rails and the two coupler hoses start at an angle toward the nearest rail, that the field just pulls the hose to try to align it with the crosswise field??

I can't report on the specifics of the OPs question as I haven't experimented with it much at all.  I'm thinking it may be ok to add a longer uncoupling spot with more pairs of magnets if desired, say 4-5 pair instead of 3 pair.  I don't think it would make too strong a field as the couplers seem to respond mainly to the nearest 1-2 magnet pairs. 

I did notice that I can get some undesired mainline uncouplings if slack occurs as the train is travelling past the uncouplers.  This can occur because of some slight bucking / slackening of the train, very dependent on the speed and cars involved.  Perhaps a slightly weaker magnet could be used that would still uncouple but better minimize undesired "slight slack" uncoupling.  Or recessing the existing magnets slightly.  Some more experimenting is called for.  One good thing is that if it does not work well, it will be easy simply to remove the magnets from the 1/8" holes. 

UPDATE: I just played with this a bit.  I've concluded that I should try a 4th pair of magnets to give much more flexibility in positioning the cars to be uncoupled.  Getting the train positioned so the uncoupling occurs is not too difficult with the 3 magnet pairs.  But when the loco is pulled forward and then backed, to push the uncoupled cars backward to a desired spot, the uncoupler at the loco string may not open sufficiently to not re-engage.  This can occur if the standing car's uncoupler is not near the middle of the 3 magnet pairs, but rather near the loco end of the setup.  When this is the case, the backing loco string's coupler may not open soon enough or far enough to preclude re-engagement before contacting the standing car's coupler.  So I believe the 4 pair will work better than 3 pair regarding the need for spotting precision.  Of course, that will add 72 cents to each setup. 

Paul

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Posted by garya on Monday, December 12, 2016 11:28 AM

My friend likes the rare earth magnets, and he uses them for uncoupling on his switching layout.  He drilled holes between the ties and dropped them in with some epoxy.  I'll ask how many he used, but I think just one pair. 

One has to be dead on to get uncoupling to work.  It is also possible to get random uncoupling if there is slack in a cut of cars, too.  The final issue he's had is using Athearn wheelsets--the steel axles are attracted to the magnets, so if a car is spotted near the magnets, it will get pulled right over the uncoupler.

Gary
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Posted by wvg_ca on Tuesday, December 13, 2016 7:25 AM

I use the 1/8 x 3/8 rare earth magnets as well, two mounted vertically on each side just inside the rails, and flush with the top of the ties .. works well, and the price is right  ..

I use craft beads with a ordinary pin inside for a marker, on my first layout I painted the facing side of the rail yellow as a marker instead

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Posted by Geared Steam on Tuesday, December 13, 2016 9:24 PM

LaughThey can work a little too good sometimes, experiment to find your best performance. 

"The true sign of intelligence is not knowledge but imagination."-Albert Einstein

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Posted by BigDaddy on Thursday, December 15, 2016 5:56 PM

wvg_ca
I use the 1/8 x 3/8 rare earth magnets as well, two mounted vertically on each side just inside the rails, and flush with the top of the ties .. works well, and the price is right  ..

I use craft beads with a ordinary pin inside for a marker, on my first layout I painted the facing side of the rail yellow as a marker instead

Some people use scenic details - discarded tires, ties, mile posts to mark uncoupling locations.

Geared Steam Funny picture

I think I oriented all the magnets with the same polarity on both sides of the track.  Maybe I should repeat the experiment before I get out the glue.  I can't say whether Kadee magnets have their N/S orientation at the sides, but if they do, what are the ends? 

It seems to me that the coupler glad hand ought to be attracted to the nearest magnet, whether North or South.  Alternating adjacent magnets on the same side of the rail may not provide the same degree of magnetic putl.   I am not certain of that though.  But as a function of OCD I would never alternate them.

Henry

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Posted by hobo9941 on Thursday, December 15, 2016 11:00 PM

Just curious. Would magnets just on one side be enough to pull one knuckle open and uncouple the cars?

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Posted by Alantrains on Friday, December 16, 2016 4:39 AM

No not relyably.

 

Alan Jones in Sunny Queensland (Oz)

 

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Posted by CentralGulf on Friday, December 16, 2016 10:28 AM

BigDaddy

  I can't say whether Kadee magnets have their N/S orientation at the sides, but if they do, what are the ends? 

Kadee says the poles are on the sides, which makes sense for uncoupling. The ends' magnetic orientation and strength would vary from one corner to the other, swapping orientation in the middle of the end.

CG

 

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Posted by BigDaddy on Saturday, September 09, 2017 3:22 AM

Graymater's other thread made me think or resurrecting this thread. 

I'm doing scenicing and only have a couple cars on the layout, but I have a problem.   Instead of the couplers being pulled to opposite sides of the track, they both are pulled to the same side and they don't uncouple. 

As far as I can tell, the couplers move freely from side to side and the magnets are visually the same height.  Haven't tried very many cars to see if this is just a sampling error or it's going to be an unreliable system.  There was no mention of this problem on youtube, and I did not see it on the little test track I made.

 

Henry

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Posted by mikeGTW on Monday, September 11, 2017 11:49 AM
I have a question on the magnets seems all use the 1/8 x 3/8 size it has a .86lb pull will the 1/10 x 3/8 .59lb pull or the 1/16 x 3/8 .19 lb pull work just as well All we are trying to effect is a kadee coupler My reason is I have qite a few of the kadee magnets and I've been ballesting my tracks so far used 25lb need more and I don't like the look of the flat magnets any thoughts on these ?
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Posted by Old Fat Robert on Monday, September 11, 2017 12:18 PM

My track is 90% code 70 (HO) and I am testing some 1/8 x 1/4 RE magnets on both the layout and my seperate programming track. Placed at the inside edge of the rail even with the top of the ties. Same polarity at the top. Absolutely amazed at how well this works. Looking forward to installing them on the layout.

Old Fat Robert

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Posted by RR_Mel on Monday, September 11, 2017 1:08 PM

I went with the ⅛” x ⅜” Neodymium Magnets, three N up next to one rail and three S up next to the opposite rail.  I drill ⅛” holes between the ties and a drop of CA on the magnet then press the magnet just below the ties, enough that I can cover the magnets with ballast.
 
You have to mark the uncoupling spot as it is only ¾” long, I use power/telephone poles to mark the uncoupling spots.
 
I’ve never had any non planned uncoupling.
 
I have had several problems like Geared Steam, a loose coupler pocket or coupler cover and you will have a ready to reinstall coupler.  “Tain’t funny McGee!”
 
I mount my steam DCC speakers to the floor the tenders and if you don’t attach the rare Earth uncoupling magnets securely they will ding an unprotected speaker as it derails the tender.  That “Tain’t funny either McGee!”
 
 
 
Mel
 
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Posted by BATMAN on Monday, September 11, 2017 1:27 PM

For years I have been pulling the little magnets off our Sonicare toothbrush heads when the brushes are worn out. These are very strong little magnets. Two work well, four work really well. 

Brent

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Posted by BigDaddy on Monday, September 11, 2017 2:11 PM

mikeGTW
will the 1/10 x 3/8 .59lb pull or the 1/16 x 3/8 .19 lb pull work just as well

I don't have enough pull with the 1/8"; at least on one side.

 

Henry

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Posted by mikeGTW on Monday, September 11, 2017 2:22 PM
Henry are you sure they are mounted north on one side and south on the other ? Those 1/8 inch can pick up almost a pound you would think they will be able to pull a kadee coupler I ordered some of all three sizes and will see which ones will work best I just went down and counted and there are at least 40 magnets to replace prob more
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Posted by BigDaddy on Monday, September 11, 2017 5:55 PM

No they are probably mounted N - N  Reason being, I could see why the the coupler trip pin, which points to one side or the other, depending on which car it's on, would be selectively attracted to N or S. 

IdeaIdeaHowever if the connected couplers start to move even a tiny bit, they have to continue to the side.  Now I get it. 

 

Henry

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Posted by SeeYou190 on Monday, September 11, 2017 7:35 PM

My only experiment wih rare earth magnets was to glue them to the inside of the ballast of Kato Unitrack. I was trying to make a fully hidden uncoupling ramp.

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All attempts failed completely.

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-Kevin

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Happily modeling the STRATTON & GILLETTE RAILROAD located in a world of plausible nonsense set in August, 1954.

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Posted by mikeGTW on Thursday, September 14, 2017 10:37 AM
Got my magnets today the 1/16 x 3/8 kinda work so not using them the 1/10 x 3/8 work great need to order some more now so I can use either the 1/10 or 1/8 size the 1/10 size are cheaper Messing with the magnets now I see i can build another coaling tower just have to move one switch Too bad I can't use the Cheyanne 650 ton tower its too big I have an old model power kit that will fit If anyone wants the Cheyanne kit for postage let me know

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