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Permission to use this article from Model Trains International issue nos. 23 and 24 1999 has been given by Chris Ellis for which I thank him most profusely.


Magnetic Couplings for British 4mm

Chris Ellis explains a simple and effective way to do it, using Kadee products.

This is an article from Chris Ellis of Model Trains International explaining a simple and effective way to fit Kadee couplers to British Outline stock.

Mainline J72 with hopper, both fitted with Kadee No 18 couplers give closer spacing than tension-locks.

If you are a collector who does not actually run models on a layout, or the sort of operator who runs long trains round display layouts for the sheer fun of it, the actual couplings on your models won't matter much. No need to read further into this article! However, if like me you like to simulate real railway operation as far as possible in miniature, then the ability to shunt and make up trains, coupling and uncoupling wagons at will, preferably without having to prod them or fiddle via 'the big hand in the sky', is something to strive for. In fact the less you have to touch the models on the track the better it is, for many derailments arise from clumsy handling. With British models the tension-lock coupler is the most commonly used in 4mm scale and it comes on most models. Vehicles so fitted will generally couple together when pushed together, but to uncouple you either stop over a sprung ramp - when the couplings will separate - or you need to uncouple by hand, possibly using various devices (hook lifters) that can be made up.
So far so good, but you cannot fly shunt or push wagons along sidings uncoupled using tension-locks. You need a ramp at every uncoupling point, which is a bit limiting if you wish to simulate real shunting. Keith and Dale Edwards, the American inventors of Kadee solved the problem over 35 years ago with their knuckle coupler which did a good job of resembling the real thing (the American auto coupler) while at the same time separating if the vehicle stopped over a magnet in the track, and then could be pushed and released where required in a siding or at a loading bank. This is almost the norm for operating in America, but is still not known to everyone in Britain in my experience. Certainly at every show I attend someone does a double-take when Kadees are used and asks how it is done, assuming some electronic magic or wiring rather than a simple magnet set between the running rails.
For British modellers, the Alex Jackson and Sprat & Winkle (and other) British-devised magnetic coupler systems have been around for years, but they involve a certain amount of craftwork and skill to fit so are not widely used, and not all that widely known in my experience among 'average' modellers. The Kadee always scored in that it came assembled and in various styles of draft box that fitted American HO models and can usually be fitted in moments to American style freight cars and locomotives which mostly have compatible housings for them these days in any case. Recently Kadee-style look alikes have appeared such as McHenry/EZmate, Intermountain, etc. See MTI- 11 for our last update on these American magnetics.

It gets easier!
About ten years ago Kadee introduced a range of magnetic couplers (Nos. 17-20) for the European HO market to fit the NEM 362 standard coupler mount that had been taken up by all European HO makers in the 1970s and 1980s. This coupler has the 'swallow tail' shank just like the various European made couplers that fit the NEM 362 pocket, the idea being that modellers can fit any type of coupler of choice to their models, and from 1989-90 that included the Kadee for magnetic operation.

Fitting the Kadee No 18 coupler to a screw-mount bogie, in this case the Replica BG full brake.

Twenty years ago I spent a lot of time seeing if Kadee couplers would fit to British or European models for OO/HO operation - see Model Trains March 1980 for my report on this. It was long before the Kadee 17-20 couplers were available, and the Kadee couplers then were all intended for American models though they did have some that they said would fit European models. My findings back in 1980 were not good. In particular fitting Kadees to British 4mrn models was very much a hit or miss affair - mostly miss! This was largely because all the British makers had different ways of fitting their tension-lock couplers and it was difficult to get a flat mount for the Kadee draft box at the correct operating height. Sometimes when you hacked off the tension-lock coupler you ended up with a big hole or some other nasty mess unfriendly to draft boxes. Unless you were persistent or determined, I concluded, fitting Kadees to British models was at best a hassle and mostly a time-consuming nightmare. It was no better with the Peco Magni-Simplex coupler (still available) a British magnetic which operates in similar style to Kadee (but is bigger and non-compatible). Though that fits Peco's own Wonderful Wagons perfectly it was as difficult as Kadees to fit to others. Fitting magnetics to locomotives was even more difficult.

Close view of Mainline chassis, wheels omitted, to show exactly how the Kadee No 18 couplers are secured using the original screws and screw sockets.

Though I've always been an avid modeller of the British scene, I've long put off building a British layout since it has always been so much more satisfying operating American or German models using the magnetic couplers and doing realistic switching/ shunting. However, a fairly brief letter from a reader in Railway Modeller last year made me start investigating the magnetic coupler scene for British models in the light of what is currently available. This letter noted that the Kadee European coupler could be fitted to Bachmann wagons by drilling a hole in the shank and using the screw that holds the tension-lock in place to secure the Kadee coupler in the same hole. Maybe others have been doing this for years and I haven't noticed, but it was a new notion to me and I duly got together some Kadee European couplers and a few Bachmann, Mainline, and Replica wagons (BMR for short, all from the same designs and moulds) and had a go.

It's very easy!
Well, the good news is that it is very easy, almost instant in fact. Quite by luck, and certainly not by design, the screw mount for the BMR type tension-lock (the sort with the spring in it) provides the correct operating height for the Kadee coupler. If you use the most common coupler, the No 18, you also get a perfect coupling distance between wagons, just closer than the distance given by the tension-locks themselves. You need a Minidrill to drill out a securing hole in the coupler shank, quickly done-by holding the swallow tails in pliers in the left hand, and using your right hand to direct the Minidrill right through the No 18 engraved on the shank - a perfect aiming mark (obviously use the opposite hands if you are left-handed).

Modification needed for the Kadee No 18 coupler. (A) Drill (1.5mm diameter) through the '18' engraved here on the shank. (B) Cut off shanks where space is restricted behind mounting, as on some locomotives. Same procedure applied if modifying No 19 or No 20 couplers.

A 1.5mm drill is required. It takes only seconds to drill each hole and you can drill out a batch of coupler shanks at a time. Then unscrew the tension-lock coupler and screw the Kadee No 18 into its place. You get the correct operating height and don't even need a height gauge for this - it's right every time. With long or short wheelbase stock there is sufficient spring in the coupler head to get round the tightest radius Setrack curves, and small radius Setrack or Hornby points with no problems at all. I carried out extensive tests and found no hiccups in the system.

Here is a view of the Kadee No 18 coupler drilled through the engraved '18' on the shank and ready to fit to any of the standard Bachmann/Mainline/Replica wagons as described. The same procedure is used on the No 19 or 20 couplers.

Obviously it is only this easy with the BMR wagon designs since Hornby, Dapol, and others have other sorts of coupler mount without this easy screw fixing. But there are enough BMR wagons to keep you going and if you only need sufficient stock for an Inglenook, Timesaver, or branch line layout the BMR ranges offer plenty of choice and old second-hand Mainline wagons at shows can often be found for as little as £2.50 or less. You can ditch the old tension-locks or give them away, but if you want to sell second-hand later you might want to remove the Kadee and put the tension-lock back. For this reason I left the outer spigots in place on my wagons, but if desired they could be cut off since only the centre screw hole is needed to hold the Kadee coupler rigidly in place.

Underside of Hornby Bulleid tender with the Kadee No 18 replacing the tension-lock in the same screw mount. Similar fitting is on the front bogie.

Some might jib at the cost, but at today's prices a pair of couplers will add about £1.40 (UK) [1999..ukms] to the cost of the wagon, but in my view this is more than worthwhile for the enhanced operational pleasure given. If any wagons (or coaches) operate in rakes (as on a MGR coal train or B-set) you only need the Kadees on the outer positions and the tension-locks can be retained elsewhere.

Mention of coaches needs elaboration. The early Mainline coaches, plus some of the Replica coaches (such as their scale length BG) have the tension-lock couplers fitted to the bogies by screw, and on these you can fix the No 18 Kadee coupler in the same way. Easy again. But later coaches, such as most of Bachmann's have a 'production economy' whereby the coupler is moulded integral with the bogie. You can saw this off, but you do not often get a convenient fixing position. For example, having fitted the Kadee coupler to a Hornby Bulleid Pacific you might fancy a set of Bachmann Bulleid coaches for it to pull. But saw off the fixed coupler from the Bulleid bogie and you just have an empty void above with no easy way of fitting the Kadee, as with my 1979-80 experience. So you don't win every time, but there are enough 'easy' fitting BMR models for the inconvenient ones to be avoided. I'll cover some of the non-standard fitments for British wagons in a later article, since there are non-BMR models which still take the screw-fitted Kadee.

However, I will just mention the Bachmann 'Blue Riband' wagons here. These are the ones with the built-in NEM coupler mount (see review in MTI-19) which is pointless since it is set at the wrong operating height for any coupler with the 'swallow tail' shank. Again, by accident rather than design, I found that the Kadee No 17 coupler shank will glue to the underside of the coupler box using contact adhesive, and by a happy chance it once again comes out at the correct operating height. For tests I glued one set of couplers only, and on a second wagon I reinforced the glue with a track pin driven through the shank and the box above it. So far neither has pulled out despite extensive shunting tests. The Bachmann VGA wagon does have the NEM coupler box at the correct height and on this model you can just slip the No 18 coupler inside in the way intended.

The Bachmann 'Blue Riband' wagons are fitted for magnetics by using the Kadee No 17 contact - glued below the NEM coupler mount. The mount itself is set too high for its intended purpose.

You need slow running.
You will be delighted at the way the magnetic couplers work - just as good as with American models, and sometimes better in fact! You need to set the Kadee magnet in the track with its top flush with the rail top, but the instructions come with the magnets and coupler packs anyway. With the tension-lock couplers removed there is a big visual improvement, too, and the wagons look more 'scale like'. Some may object that the Kadee couplers are unprototypical, too, but they are much less conspicuous that tension-locks and in the case of BR coaching stock they are close to prototype anyway.

Dapol or Hornby Terrier and J94 are 'best buy' performers for shunting with magnetic couplers. Here is a Kadee-fitted Terrier with the Replica BG.

A key necessity with good magnetic coupler operation and shunting is a slow reliably running locomotive and this is where some limitations may creep in. In a recent letter to Railroad Model Craftsman, the design director for Life-Like's Proto 2000 series says they aim to achieve a steady low speed of three scale miles per hour which is what they consider absolutely essential for efficient switching/shunting in HO. In my experience Bachmann USA get even slower than this with their GE 44 and 70 ton switchers. Finding any British 4mm model that matches this is difficult. I tested all the small shunting engines available that I could lay hands on to find out which would run at slow steady speed without faltering, stalling on dead frogs, or failing to respond to the controls. Essential is the steady speed with magnetic coupling, since if the loco judders or hesitates the chances are that the couplers will re-engage and spoil the shunting move. Rubber traction tyres have a bad effect here. Likewise stalling on a dead frog (all too common with many British outline models) is a no-no, as is 'sticking' - failing to restart when you stop the loco and put it into reverse.

Only two of the models I tested fully meet all conditions - slow running, non-stalling, and fully responsive - and these are the Hornby J94 and Terrier, or their earlier Dapol versions. If you have live frog points the Pug also qualifies and only its very short wheelbase causes it to stall at slow speed on dead frogs. Even with these models (I tested four of each) some run slightly smoother than others, though all those I have run well enough, even the least good. You may find other models you have that match up to the standards. I have a very early Mainline J72 of the first release (1976) which runs superbly, and though noisy runs nearly as well as my J94s and Terriers, but no other J72s I've seen (save my second model from this period which I converted to a HO 573) run as well as mine. If you can commend any other ready-to-run shunting engine (I did not quite test them all, no 04 for example) please tell us about it.

Fitting to the Mainline or Bachmann J72 is easy - no need to trim the shank - but not all J72s will run well enough for slow shunting.

The other virtue of the Hornby J94, Terrier, and Pug is that the couplers are held in by screws just like the BMR wagon couplers, so the No 18 coupler once again is just screwed in position in place of the tension-lock coupler fitted to the loco. However, because the chassis intrudes you need to chop the swallow tail shanks off (with a craft knife) before screwing the couplers in place. If you have got very sharp curves on your layout, I suggest you fit the No 19 coupler (which has a longer shank) on the rear of the J94 since the locating hole is set well in and there is less 'play' possible if the No 18 coupler is fitted. With gentler curves the No 18 is fine, however.

Fitting the No 18 coupler to the Dapol/Hornby Terrier/J94/Pug requires the shank to be trimmed short as shown in diagram on opposite page.

If you want to fit magnetic couplers to larger locos it is no problem if the tension-locks are screwed in place. For example the Hornby Bulleid Pacific and Bachmann 93XX are easy to convert. I'll return to this subject again, later, in particular to show how stock with awkward fixings (ie, not the BMR design) can be dealt with. One virtue of the BMR design is that the axles are non-magnetic, an absolute necessity when using Kadees, again by accident rather than design. Because of their pin-point nature, too, you can simulate actual British style shunting whereby the loco is braked to leave the wagon rolling on down the siding to bang (gently) up against the other wagons already there, just as I remember from watching goods yard operation in steam days. Great fun and not at all possible if you stay with tension-locks.

Typical example of a larger loco fitted with the Kadee No 18 coupler. This is a much detailed Hornby Bulleid Light Pacific which has suitable screw-mounts for 'instant' magnetic conversion.

Other Makes of Wagon
[The above text shows…ukms] how the Bachmann/Mainline/Replica (BMR in short) wagon underframes for 00 (or EM converted, etc) could be modified easily to take the Kadee No 18 magnetic coupler adapted to fit by drilling out a hole in its shank. All very easy and you could leave it at that if you are happy with the choice of BMR wagons, which has been considerable over the years.

Kadee magnetics can be fitted to 00, EM, or P4/S4 if the fitting is easy. These EM wagons on EM track use Bachmann chassis so the fitting is the same as described here.

Easiest models to fit with Kadee No 18s are the Bachmann/Mainline/Replica rolling stock such as this salt wagon. Closer coupling is a bonus - closer than tension-locks permit.

However, we are all perverse enough to have other favourite wagons or consider certain models to be desirable, and they may well be outside the BMR range. For example you may well want a Lowmac or two, as nicely provided by Hornby from the ex- Dapol, moulds. The most numerous good standard wagons rivalling the BMR ranges are, of course, the old Airfix or Dapol wagons and their modem reincarnations as Hornby models. The ADH type for short. The ADH models have a very different coupler fitting, a boxy housing into which the tension-lock coupler plugs. It is easy enough to remove the tension-lock coupler - just give it a tug! Experimenting with fitting the No 18 coupler to these I found that the easiest way of doing it was to cut 3mrn off the end of the shank, smearing the inside of the coupler box with contact adhesive, putting more contact adhesive on the remains of the 'swallow tail' shank, jamming it into the coupler box and leaving it to set. It isn't anything like as easy and positive as screw-fixing the coupler shank to a BMR wagon, but it works and brings the coupler to correct operating height. The only essential, of course, is to ensure the glued coupler sets exactly horizontal. If it droops it will not be at correct operating height. If necessary prop it with scrap wood blocks while it sets and keep checking. Essentially the end of the shank just jams up against the pin inside the coupler box on these ADH wagons. Crude, but it works. I have fitted the GWR Toad, LMS brake van, Lowmacs, and various attractive 20 ton wagons with magnetic couplers this way, with total success, though the extra hassle involved means I have only done this where there is not a BMR equivalent. In some cases you may find it better to use a No 19 coupler on a longer vehicle, but it's a matter of judgement depending on the model.

Basic bodging for the Airfix/Dapol/Hornby coupler mount. The Kadee shank is cut short and the stump is glued inside the mount. This is the latest Hornby Lowmac model. Putting a pin through the joint is optional, but has not been done here and experience shows it unnecessary.

When we get to Lima it is a sadder story Aside from the coarse wheels, which need replacing if you prefer shallow flanges (or use Code 75 track), removal of the plug-in tension-lock coupler leaves a nasty hole. One answer here is to avoid using Lima wagons as far as possible, but certain models are worth having, including the CCT. You have no alternative but to bodge it, and this I did by cementing a lmm thick strip of scrap hardwood over each plug hole, then glued a No 19 coupler to this, again ensuring it stays perfectly horizontal while the glue sets.

Bodging supreme is going on here! The very nice Lima CCT fitted with Kadee No 19 couplers, and finer wheels. Left: How it is done. A lmm thick strip of hardwood (with edges painted black or dark grey) is glued over the original coupler 'plug hole' and the No 19 coupler is glued to that.

This, again, gives correct operating height. Bodging is needed for nearly all models not covered by the BMR arid ADH ranges, and even much of the BMR and ADH bogie stock needs bodging where the coupler is moulded integral with the bogie. Same applies to Lima and older Hornby (non-ADH) bogie stock. You just have to cut off the integral tension lock coupler, leaving as much stump as possible, then glue a No 19 Kadee coupler above or below the stump as best you can. But unless you have special 'wants' you can do as I have done by ignoring non-'user friendly' models as far as possible. I will say that using contact adhesive for securing the couplers has not caused problems. None of mine have pulled off so far, and if they did I'd simply glue them back in place. In one or two cases I have driven a track pin through the coupler shank and into the underframe to reinforce the join, but where I have not done that I have not experienced pulled off couplers, so I have given up bothering.

With all the other odd ranges bodging is very much essential. Few of the old pre-ADH Hornby wagons are worth worrying about, lacking the scale precision most of us look for, but there are some good ones such as modem tankers and the LBSC/SR brake van (not currently listed) and most of these have the tension-lock coupler riveted in place. When you pull out the rivet you are left with a block and hole just like the BMR wagons, but the hole is too wide to take the Bachmann-screw (sold as a spare pack if you need more) so you either need to fill it with model putty and screw in, or do as I did which was to fill the hole with glue and just stick the screw into it, leaving it to set. On the Ratio GWR 4-wheel coach underframe (and probably others by Ratio) you need to pack out behind the buffer beam with a scrap wood block that falls 2mm below the buffer beam edge. Then glue (or glue/pin) a No 18 or No 19 coupler to the wood.

The Hornby LBSC/SR brake van with No 18 coupler fitted, using a screw in the original rivet hole for the tension-lock coupler.

Some models lend themselves to happier bodging. John Flann kindly passed to me an old Dublo Mica A, with a perfect body but a battered chassis with the coarse old Dublo wheels. Checking it out I found the body would fit the BMR standard 1 OR underframe so it was a simple job to get a spare underframe and glue the Mica A body to it. Detail changes are needed to the brake gear, but once the body is on the BMR underframe the magnetic coupler problem solves itself Clearly there must be more ancient wagon bodies around that will fit modern under-frames in the same way.

It's a doddle really.
All the foregoing are 'worst case' situations which you can ignore altogether unless you are someone like me who actually wants a SR brake van or a BR CCT running with magnetic couplings. None of the bodges I did was very difficult. They were just not as convenient as the simple process of screwing a No 18 Kadee coupler to the BMR chassis. Similarly, the loco situation is simplified by reason that only the Hornby (or old Dapol) Terrier or J94 is worth worrying about as a loco with a performance good enough for shunting British 4mm wagons with magnetic couplers. The others you can forget, though the Bachmann 08 when it arrives may be good enough to join the select list of 'good enough' locos - if it is as good as Bachmann say it is.

Uncoupling over the magnet set in the track. Stopping the loco and backing up a touch takes the tension off the couplers and they spring apart and separate - a 'hands off' procedure.

For those not familiar with magnetic coupling using Kadee it is worth saying that you need to set the top of the magnet flush with the rail top. The Kadee leaflet says that with Code 100 track you just glue the magnet to the sleeper top. That may once have been true, but on Code 100 track sold in Britain (of any make) you need to carve down the sleeper tops sufficiently to let the magnet sit level with the rail top. If you glue it to the sleeper top it will be too high and some locos may bottom on it, and some couplers may hit it. An alternative with Code 100 track is to cut out the sleepers completely between the rails where the magnet is to go, then pack it up with card or balsa sheet to set it flush with the rail top. With Code 75 (Peco Fine) or Code 83 track you need to cut out the sleepers between the rail and, again, use card to pack it up to rail top height. When you are satisfied, glue the lot in position.

It is essential to know that all coupling must be done on straight track (you may get away with very gentle curves) because the coupler is displaced sideways on a curve so the faces won't match up. Also the uncoupling magnet must be in a straight stretch to operate correctly, though you can push wagons in the 'delay' mode round very sharp curves, including the sharpest Setrack, plus Setrack points. So far I have found no limitations using British wagons and locos with magnetic couplers and in many ways they work better than Continental models with magnetic couplers, largely due to the shortness of most wagons, the good flexibility of the Kadee sprung knuckle, and the sprung head. The Kadee leaflet gives all operating information, of course, but you need to check the springs regularly. If you lose the transverse spring from the head it has to be replaced (using tweezers in daylight preferably) as without it the knuckle just flops to one side. Conversely if this happens inexplicably, check it out as will certainly mean the spring has fallen out. A heavy shunt can cause this, but with magnetic couplers and good running locos you should get a new dimension in operating British RTR models - nice slow running and gently nudged coupling, all 'hands off' of course. In fact if you are like everyone else I've met who has tried it, once you are into Kadee magnetics you won't even think of reverting to cruder existing methods of coupling. Switching all my British 4mm models to Kadee means that all layout activities (British, Continental, USA) are now 100 per cent Kadee. My British HO was converted to Kadee in the early 1990s but that all had to be bodged except for the locos. Now I have a jam jar full of unwanted tension-lock couplers to get rid of!

Just in case anyone finds it hard to believe that only the Hornby Terrier and J94 can be unreservedly commended as suited to use with magnetic coupling, let me emphasise that I'm only considering locomotives suitable for shunting. Like me you might find others nearly as good, such as my old Mainline J72. Quite a lot of bigger British outline locos (with more wheels) have good slow running performance (such as Bachmann 93XX, Hornby 'Castle', 'County' 4-6-0, etc) and these are also easy enough for fitting the Kadee coupler. The old Hornby Bulleid Pacific is another easy one. However, these are not locos you would normally use for shunting.

All the text and photographs in this article are copyright Chris Ellis and may not be reproduced without permission.

And finally, a comment from the UK Model Shops Directory Modeller -
Yes what he says does work, as I have used this very same article to convert my own stock.
Adrian Hall 2001

This page last updated on
8 April, 2014


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