Magnetic couplers in Z

kevsmith May 24, 2020

  1. kevsmith

    kevsmith TrainBoard Member

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    So the onset of the pandemic threw everything into a spin. All of the shows that I was to take the layouts to were binned. We managed to get the Macclesfield debut of Hakuho away before the lockdown but all the subsequent shows including the big Spring ones fell like dominos. With no deadlines to get layouts ready and working from home I took the opportunity to have a break from Z and finish off some long delayed gauge 1 projects for a change. Now they are finished and written up for the magazines it was time to start on some long delayed Z projects.


    One of the biggest obstacles in modelling British prototypes in Z is couplers. In real life U.K rail vehicles are quite a bit smaller than the rest of the world and we have the added complication of buffers and screw couplings rather than buckeyes.


    Marklin couplers work well but are huge and it is impossible to get the close coupling that is needed visually. MTL couplers are well known and reliable but the closeness of the trucks to the end of the vehicles means there is no room at all for a coupler box. I had a play with Rokuhan couplers with inconclusive results and on the LMS coach rake resorted to pin and link. Reasonably efficient but a nightmare to couple and uncouple.


    So the British Rail coaches went on the back burner while I had a ponder. Meanwhile Max, a fellow British modeller in Z was starting to make noises about magnetic couplers as used in 'T' apparently. So I took the plunge and ordered a load of 2mm Neodymium magnets to have a play


    My word, they are strong! The packet contained all sorts of warnings about how brittle they are and also how poisonous if you swallow one but the first thing was how to get then apart from the backing card as they just kept getting attracted back towards the rest.


    The rake I wanted to get sorted first was the British Rail Mk IIf air conditioned set painted in the Intercity executive dark grey, white and red. These are 3D printed in FUD by Shapeways to Ivan Industries design. The chassis are printed in SBF for strength but don't have all the underframe details. MTL 904s are used attached with 10BA cheesehead screws and I have a stack of Fox 36" wheels to fit to increase rollability


    All of the locos have Marklin Couplers so the first thing was to decide if I was going to convert one chassis to magnetics but instead decided to do a 'Translator' vehicle. British express trains often had luggage/mail vans at the head end so a BG (Brake gangway) I had already completed was taken apart and one Marklin bogie removed. This was replaced by a non coupler fitted version

    [​IMG]

    A piece of 2mm brass strip was pivoted off the underside of the underframe with a 14BA cheese head crew just in front of the bogie. This was bent down at 90 degrees just past the bufferheads. The magnet was attached with thick superglue. So far so good as an intensive turn on the test track, with 47 676 'Northamptonshire' which is one of my 'jerkier' Marklin powered class 47s, did not reveal any issues. The test track has a couple of evil reverse curves, far tighter than any on the show layouts, as my thoughts are that if they go round that, they'll go around anything

    [​IMG]

    Next I fitted a pair to a TSO ( A standard open coach) with the same at either end making sure that the magnets were fitted with opposite polarities end to end. Buffering the BG up to it and a quick run round the track and to my surprise it worked. Uncoupling really only required one vehicle to be lifted to slide the magnets apart to break the attraction. Propelling the TSO worked equally well which was an unexpected bonus. So I fitted two more vehicles and coupled up and off they went. It was only when I got up to five coaches that a problem emerged as I had a series of derailments. Was I pushing it too far? Closer inspection revealed that because not all the holes in the underframe had drilled in the same place I was getting contact with either the buffers or ends by being too greedy to get the closest spacing possible between the coaches. A longer coupler and problem solved.

    [​IMG]


    So I'm thinking it can't be this easy, can it?


    Finished up tonight running a rake of six around Republic Steel with both the 47 and one of the Class 86 AC electrics. No random uncouplings, no derailments even through the reverse curves of the passing loops and quite quick to do.


    [​IMG]

    Tomorrow I'm going to have a go at either, the Atlas editions 'Golden Arrow' Streamlined Merchant Navy. A Southern railway (ours not yours!) 4-6-2, motorised with a Marklin Bavarian Pacific chassis and/or Ivan's 3D printed version of the same loco on the same chassis and the rake of matching Atlas Pullmans


    Kev
     
  2. kevsmith

    kevsmith TrainBoard Member

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    First video....



    Kev
     
  3. rray

    rray Staff Member

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    Looks like they work pretty good Kev. Thanks for sharing.
     
  4. JoeS

    JoeS TrainBoard Member

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    I have to say it does make them couple tighter and no slinky effect either.
     
    Kurt Moose likes this.
  5. DB_Z

    DB_Z TrainBoard Member

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    Hi Kev,

    I tried this approach to couple up a scratchbuilt EMU. However, what I found was that if I didn't uncouple the coaches for some time, the bond between the magnets seemed to get stronger and stronger. In the end, as I tried to uncouple the unit, both magnets would remain stuck together and one would just rip off its mounting (despite having been superglued). Have you experienced this problem?

    I am going to have a go with just a metal bar on one coach and one magnet on the other; maybe that will work better.

    Carim
     
    bostonjim likes this.
  6. kevsmith

    kevsmith TrainBoard Member

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    Not had a problem like that yet. In real terms they will only be coupled together for a few hours a day at a show. The rest of the time they will be in the stockboxes serpertaed by the dividers and foam inserts. I'll keep a watch for it happening though.

    The silver boxes with red tray originally came full of barbeque tools from the loco supermarket

    Seen filled with the stock for the japanese layout

    [​IMG]

    The 3D printed 'Spamcan'

    [​IMG]

    Slabs of nickel silver added to the tender to give it some weight. Brass weights being added to the inside of the bodyshell for the same reason. Drawbar at fron ot tender and magnetic coupler at the rear.

    I've made the Pullman couplers too short and the corridor connections are fouling but the loco to coach connection is fine
    [​IMG]

    The coaches behind are the start of the Blue/grey Mk II rake

    Kev
     
  7. ubiminor

    ubiminor TrainBoard Member

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    Hi Kevin,
    magnetic couplers are very interesting and in fact many have tried them. The first I recall were the Lego train sets in the early 70's. here is how they looked.
    [​IMG]
    Many use the idea that the magnetic field is on the same line as the pulling force between wagons.
    So the higher the traction force is the stronger (and bulkier) the magnet must be.
    The advent of Neodymium magnets has of course made possible to have tiny magnets with high force
    Nevertheless, to account for slopes, extra friction, variable length of trains, one has to use a larger magnet than desirable.

    I have invented a system that allows me to use the tiniest magnets ever.
    I use the magnetic field to initiate coupling, however coupling itself relies on mechanical interlocking.
    This development came after many prototypes. In fact I am on version 3.2.
    This version uses cylindrical magnets of 1.5 mm (or 1mm) of diameter and 0.5 mm of height, with N-S poles on their flat faces.

    The magnets are framed into a bracket made of 0.3 mm brass sheet, cut and folded to present 2 prongs on one side and a stem terminating with an eye on the opposites side.

    The eye is used to secure the bracket to an eye nail (made with a 0.4 mm brass wire) that is then inserted in the buffer plate of a car.
    11.png
    The couplers are made so that they can stack vertically one over the other, so that prongs and stem interlock.
    12.png

    here is a picture of one of such couplers on a FS flatcar.
    13.jpg
    and another picture of one, blackened, on a FS D343 class

    14.jpg
    and here a couple of videos showing how it works.


    I have also made a decoupling mechanism


    More info on the couplers and instructions on how to make them are on this page at my web site.
     
    Last edited: Jun 13, 2020
  8. bostonjim

    bostonjim TrainBoard Member

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    Very impressive. Low-key looking. Thanks for sharing it. Jim
     
  9. CNE1899

    CNE1899 TrainBoard Member

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    As an Industrial Designer, I have to say this is a very well thought out concept! Love how it uncouples as well.
     
    bostonjim likes this.
  10. Reptilian Feline

    Reptilian Feline TrainBoard Member

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    Is there a way to uncouple on the layout without touching the train? If I remember correctly, there was some kind of coupler for N where you put a device on the track that would lift up and uncouple. Is there something similar that can be made for these magnetic ones? Something simple DIY?
     
  11. LWR21

    LWR21 TrainBoard Member

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    Rokuhan has a magnetic uncoupling track, for use with MTL's couplers.
     
  12. ubiminor

    ubiminor TrainBoard Member

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    For my couplers, the uncoupling device is rather simple.
    When two couplers are engaged, they stack on each other horizontally, parallel to the track while, the magnetic field is oriented vertically, orthogonal to the track.
    The uncoupling device is just a solenoid under the track, that once energised, pulls the magnets down . This makes the two couplers swing downwards and hence disengage from each other.
     
    Last edited: Jul 28, 2020
    Reptilian Feline likes this.
  13. Reptilian Feline

    Reptilian Feline TrainBoard Member

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    ubiminor, that sounds perfect!
     

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