Roll Your Own under track Kadee uncoupler

[Zorcan]

Having decided that Kadee couplings were the optimal way to provide the operating flexibility I wanted on my layout, it only remained to determine the best way to provide the uncoupling function.

 

Kadee make 2 devices:

 

Part code 83 - this sits above the sleepers and between the rails and supports both instant and delayed uncoupling operation. It is, however, visually non-prototypical and each unit costs about £6.50.

 

Part  code KD308 - this sits entirely under the track and comes in at only £4.70 or so.

 

As I needed 30 or more uncouplers for my layout, the cost of either  was discouraging.

 

I have devised and successfully installed an alternative device that sits entirely under the track (and so is 100% invisible), and provides very reliable operation. At less than 2.5 mm depth, it is easily accommodated inside the ballast layer - i.e. the cork (or in my case closed-cell foam) track bed that many modellers use to reduce noise and help model the ballast bed.

 

It even works on curves - I have used them successfully down to 1000mm radius.

 

These devices are simple and quite quick to make and come in at less than £2 per head.

 

The attached document is a guide as to how to make and install them.

Uncoupler Guide.pdf

[jamest]

Hi,

 

Speaking as someone who is very committed to Kadees (most of my stock and engines are converted) - and someone who has used both the 'on-track' and 'under-track' off the shelf versions - your design looks very interesting.

 

Can I ask how you determine north and south? Or is it just important to have opposing poles each side of the track? So establish which sides repel and arrange accordingly.

 

Cheers,

James

[ejstubbs]

It doesn't matter which is north and which is south so long as you have opposite poles on either side of the track, so that the magnetic field (which runs N-S) is at right angles to the track.  It's the same with the Kadee between-the-rails uncouplers: it doesn't matter which way round you fit them (in fact it would likely be a complete PITA if it did matter).

 

A number of different approaches to using neodymium magnets for uncoupling Kadees have been described on RMWeb and other online forums.  These include using small bar magnets to replace sleepers, and using rod magnets buried between the sleepers to achieve a similar effect to Zorcan's approach.  Google should turn up most of them.  I don't think I've seen other folks use the tinplate sheet before, though.

 

One intriguing approach that I must try sometime soon was described in the Camel Quay layout thread: if you put a magnet on only one side of the track, the uncoupling apparently only functions in one direction - useful for run-rounds and the like.

Edited November 26, 2017 by ejstubbs

[Harlequin]

If there's a moderator listening, can I suggest this topic is not really relevant to "Layout & Track Design"? Perhaps it could be moved?

[RailwaysInMyDNA]

Hi Guys,

 

I'm currently looking into what magnetic uncouplers are available for Kadee fitted stock.  Does anyone know for certain if they can effect sound fitted locos, ie low fitted speakers?  This may not be an issue as I'm only planning to use one in a siding that shouldn't have a loco pass over it, but I thought I'd ask the question.

 

I'm a little puzzled by the instant and delayed operation at this early stage in my investigation but need to see how big a range of products are out there before deciding on one.

[Dunsignalling]

If there's a moderator listening, can I suggest this topic is not really relevant to "Layout & Track Design"? Perhaps it could be moved?

I would have thought that planning how and where uncoupling will take place is a subject wholly relevant to Layout Design. 

 

John

[Dunsignalling]

Having decided that Kadee couplings were the optimal way to provide the operating flexibility I wanted on my layout, it only remained to determine the best way to provide the uncoupling function.

 

Kadee make 2 devices:

 

Part code 83 - this sits above the sleepers and between the rails and supports both instant and delayed uncoupling operation. It is, however, visually non-prototypical and each unit costs about £6.50.

 

Part  code KD308 - this sits entirely under the track and comes in at only £4.70 or so.

 

As I needed 30 or more uncouplers for my layout, the cost of either  was discouraging.

 

I have devised and successfully installed an alternative device that sits entirely under the track (and so is 100% invisible), and provides very reliable operation. At less than 2.5 mm depth, it is easily accommodated inside the ballast layer - i.e. the cork (or in my case closed-cell foam) track bed that many modellers use to reduce noise and help model the ballast bed.

 

It even works on curves - I have used them successfully down to 1000mm radius.

 

These devices are simple and quite quick to make and come in at less than £2 per head.

 

The attached document is a guide as to how to make and install them.

With the benefit of having been advised by those who found out the hard way, I'd recommend using electro-magnets in running lines. The Kadee item is #309. They aren't cheap but, unless you have a large layout, you shouldn't need many. 

 

If a train slows down and then regains speed when passing over a permanent magnet,  the Kadees go slack and can part.  

 

Also, in a terminus, it pays to use them where you release the loco from incoming trains. With a permanent magnet, if you then propel the stock down to the stop-blocks, it's quite easy to leave the last coach or two behind when departing.   

 

John

Edited December 4, 2017 by Dunsignalling

[Harlequin]

I would have thought that planning how and where uncoupling will take place is a subject wholly relevant to Layout Design. 

 

John

If the topic were about placement I'd agree. But it's more about how to make and install the uncouplers rather than where to place them.

[Zorcan]

With the benefit of having been advised by those who found out the hard way, I'd recommend using electro-magnets in running lines. The Kadee item is #309. They aren't cheap but, unless you have a large layout, you shouldn't need many. 

 

If a train slows down and then regains speed when passing over a permanent magnet,  the Kadees go slack and can part.  

 

Also, in a terminus, it pays to use them where you release the loco from incoming trains. With a permanent magnet, if you then propel the stock down to the stop-blocks, it's quite easy to leave the last coach or two behind when departing.   

 

John

 

Hi John- I had exactly this happening in my initial devices where the magnets were sitting under the running rails. I have not been able to replicate this problem with the published design. It IS true that if the train is not moving smoothly then couplings can part.

[Butler Henderson]

My solution to stopping trains parting is to fit the undertrack kadee to a hinge with it being lifted or lowered by a servo - somewhat cheaper than the electromagnetic 309 and takes up less space. Obviously not necessarily relevant with the diy version of the magnet described here, but I use the Bachmann Ezmate magnets for such purposes as they are usefully slightly narrower than Kadees 308.

[Mike Todd]

Congratulations to Zorcan for devising and writing an excellent procedure for uncoupling Kadees, I have had total success with my similar attempt. Firstly, the mentioned suppliers for both the magnets and the tinplate delivered within 24 hours, I chose to excavate from below existing track (Peco OO code 70) through the sundeala and cork as tracklaying and ballasting were complete. My uncoupler is fitted towards the end of a goods siding where only trucks will be placed. I used plasticard instead of Daler board. Testing has been totally successful with both local and delayed uncoupling, a few trucks move very slightly under the influence of the strong magnets but dc locos are not affected and all is well on a 6 foot radius curve. The end result : inexpensive positive operation without ugly visible plates, no electrics, no unwanted uncoupling whilst slow shunting.