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More on Decoupling Magnets - Hints, Tips & Smaller Projects. - Getting You Started. - Your Model Railway Club
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 Posted: Tue Jun 18th, 2019 12:57 pm
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BCDR
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Michael raises an important point - the orientation of the magnet. Discs seem to be vertical, cubes will be vertical or horizontal depending on which way they are laid, bars can be vertical or horizontal, usually horizontal. Cubes would seem to be the most problematic. 

N = Neo = MGOe. apexmagnets.com has some really useful information that will help in optimizing the force (may it always be with you). 

Metal ramps were common from the advent of AWS, modern era has them everywhere, so an over-the-sleepers magnet looks OK with with a bit of weathering or some yellow. 

Nigel



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 Posted: Thu Jun 20th, 2019 08:19 am
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Colin W
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It's time to close off on this topic; thanks to Sol I've now tried his PUMS method which uses a stack of magnets between the sleepers.


The big plus for PUMS in a retro fitting situation is that existing ballast can be extracted and replaced by the magnets with far less visual impact than my flat magnet method (that BTW uncouples just as well with no axle attraction).


I've still some 20 * 10 * 2mm Neos on their way from China for under track installation in all the locations in my Goods Sidings which remain un-ballasted / loosely fixed down. No more "Cans of Worms" will be opened, promise!


Thanks to everyone for helpful input,


Colin

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 Posted: Tue Jun 25th, 2019 11:38 am
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Colin W
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I thought I'd finish by telling how I went with installing Sol's PUMS configuration magnets.

I had on hand 100 small disc Neo magnets, 3mm diameter and ~1mm thick. 12 of these end to end were inserted into a 14mm length of black PVC heat shrink tube (Φ 2.5/1.25) which takes the discs snuggly. A tiny plug of Blutac at each end tamped in to prevent escape, the whole assembly fits between sleepers. Three rows of these as per the prototype work very well. 

Being smaller than the 3mm cubes and I suspect less powerful, I don't get any axle drag of note but 100% success in both push and pull modes thru the uncoupling zone. Pull mode requires a full stop of course but a slow push will uncouple on the fly and the uncoupled rake can be gently pushed forward in delayed uncoupling mode. Most impressive! Thanks again Sol.


Colin

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 Posted: Tue Jun 25th, 2019 12:19 pm
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Colin, they were installed level with sleepers or a bit higher?
Can you get a photo two please?
I replaced sleepers with the row of magnets & I guess your method could also replace sleepers.
I have never seen Kadees uncouple even pushing without stopping and backing up a small bit to allow the hook parts of the knuckles to separate to allow for the delayed setting.



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 Posted: Tue Jun 25th, 2019 04:05 pm
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Hi Colin,

I think the only way it can uncouple on the fly is with axle drag from the magnet. Doesn't do that with brass axles.Then again I use Kadee magnets that seem to have lateral rather than vertical magnetic fields. Although if you stacked the circular magnets that is what you probably have.

Hope you didn't heat shrink the heat shrink.

Nigel




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 Posted: Tue Jun 25th, 2019 09:44 pm
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Colin W
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Sol, Nigel,


good points and questions,
  • The tubes are about 1mm below rail height so about 1.7mm above tops of sleepers. That was the best height I found by trial and error.

  • Disc magnets are stacked then laid sideways so magnetic field is tangential to the track as per PUMS



  • great idea to replace the sleepers now I've got it working, should have thought about that.
  • Heat Shrink was not shrunk, that's going to kill magnets if overdone. Could even be fire risk with Neos. Hence Blutak plugs on ends to hold in place. Laid with fields aligned (all Norths same end), the little magnets had a habit of being repelled out of their tubes by the adjacent field.

  • I'll try video of the uncoupling, so far it's been careful "handomatic" operations as they were tested on loose track in my study. Now they're installed I'll hook up a loco and report back.

  • As mentioned I can't see any obvious drag pulling axles over the uncoupling zone. I had seen it before with other larger magnets but not these small ones


Colin

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 Posted: Tue Jun 25th, 2019 11:09 pm
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That's very nice ballasting, Colin!

Michael



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 Posted: Tue Jun 25th, 2019 11:58 pm
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Colin W
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Thanks, some of my recent work :cool:

Credit must go in part to excellent tips I picked up here about using a paint brush with shortened bristles to spread, level and settle ballast. I extended that to using a tiny paint brush, given the same shortening, to do the fine distribution. Pity my earlier work isn't of quite the same standard!

Colin

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 Posted: Wed Jun 26th, 2019 03:26 am
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BCDR
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Hi Colin,

That looks good. You can always paint the covers with grey, black and off white dots to look like ballast, or even give it a thin coat of ballast.

Nigel



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 Posted: Fri Jun 28th, 2019 12:20 pm
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Colin W
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An early trial with the Magnet tubes, these small magnets operation is sensitive to height, too low and they don't work, too high and they can snag the trip pin by pulling it into direct contact. Get that right and they do work very well as this shows:


Note scenic work in this area is at a very early stage, only ballasting done with any level of completeness




I'm going to have one more try with my larger magnets in line with track (where all this started) but with opposing poles up on the opposite sides of the track as per Headmaster's advice.


Colin






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 Posted: Fri Jun 28th, 2019 01:21 pm
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Very nice little video, and well done on the magnets.  Is consistency good?  

I like the glowing firebox - very neat!

Michael



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 Posted: Wed Jul 3rd, 2019 11:03 pm
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Colin W
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In its final form this shows the magnet insert on my test track:






To sumarise the key features:

  • A solution for Kadee uncoupling if track and ballast have already been laid
  • Three rows of 3mm * 1mm disc magnets assembled in heat shrink tubes, magnets all aligned in same direction. Tube OD 3.5mm - (do not heat shrink, plug the ends with blutak)
  • A support base of 24 * 14 * 0.5mm PS sheet to place the magnets' top edges 0.8mm below rail tops
  • Tube spacing - to mimic removed sleepers
In my testing this works as well as under rail slab magnets and there's no evidence of axle grab.

Assembly tips:

  • Tape the cut PS base to the underside of a piece of track, locate in line and between rails
  • Beneath this, tape two slab magnets 1 under each rail opposite poles up. This will help keep the tube magnets in situ while gluing. Otherwise they have a nasty habit of jumping out onto the adjacent tube, superglue and all!
  • dab tiny specks of CA superglue onto the PS sheet between sleepers and insert magnets one at a time ensuring poles are all in the same direction #. They are drawn to the magnets beneath so fix quickly
# getting the correct alignment is helped by the under-side magnets that set the polarity for the tubes being inserted

To remove existing ballast


I first softened it by applying a concentrated solution from those "bubble blowing" packs. This contains glycerol, detergent and water, I let mine concentrate for a while by evaporation ( not essential) before applying with a dropper. This viscous mix doesn't spread too far beyond the treated area and hangs around for long enough to soften the hard PVA glue. Leave 1 day. The end result is easy to scoop out as a gritty paste.


Colin

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 Posted: Thu Jul 4th, 2019 12:14 am
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Very neat, Colin. I think there are a number of different solutions, and each have their fans.  My magnets under the track caused a bit of axle drag, which I could solve with a bit of weight in the wagon and a small sponge "brake".  But once it was all ballasted on my test track, the drag was greatly reduced and only the weight was needed.  I basically followed the NMRA standards and that seems to work.  I will see when I do the actual track....

Will you be adding sleepers to extend outside the rails?  

Regards

Michael



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 Posted: Thu Jul 4th, 2019 12:23 am
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Colin W
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Thx Michael,


since I'm cutting out existing sleepers after removing the ballast, the outer sections will be left as they are.


I'll use under track magnets for new installations.


Colin





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