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In answer to your question! My preferred height for Kadee couplers on my UK 4mm scale models is 14 mm.

Thanks for this. Most of this thread has talked about using Kadees as a general purpose resource where 9.9 mm puts the coupler below a three-link hook, rather than as a representation of a real UK coupler, so here is a link in case people come back in the months to come:

http://www.rmweb.co.uk/community/index.php?/topic/68619-body-mount-or-bogie-mount-for-kadee-couplings/

Ah-ha! Pacific231's last post above has taken me to the NMRA web site, where I found their specifications for the heights of couplers: http://www.nmra.org/standards/sandrp/pdf/S-2_2010.07.pdf

I think they are showing scale heights for US prototypes. For 00 scale (but admittedly, not 00 gauge), they specify a height of 11.50 mm, as opposed to 9.93 mm for HO. Remarkably (given models use the same coupler), they give a larger tolerance on the height: +/- 0.5 mm instead of 0.4 mm. This could point to many of the doubts which people have found and resolved on this thread.

A nice result of today's network problem is I done all my 28 Kadee conversions (56 pairs). I am testing them merely in pairs over a Kadee uncoupler, I think the complete set of permutations is now untestable (2^55?). But my wheels have varied a lot ...

... I think this all reflects the greater influence of the NMRA. If you're a manufacturer selling into the US market and don't follow their standards you probably won't be in business for long.

I would like to think this is so. Here are some of my wagon wheels: Bachmann (left), then Markits, Hornby, Dapol:

The Bachmann ones have nearly cylindrical not conical treads (a bit like old Hornby Dublo wheels), the Hornby ones are commendably thin but eccentric on their axles, and the Dapol ones look good to me, if a bit broad. (I think I have caught all the Bachmann and Hornby ones, they are now either Gibson or Markits).

On a Kadee leaflet supplied with the NEM couplers it states the 9.9mm centre height is subject to a tolerance of +/-0.4mm ... the Hornby ones would use up at least half of this just turning round; and the Bachmann ones are more likely to be slopped sideways. Do Bachmann use a better profile on models for their home market?

My preferred method (#146) is to glue the box to the wagon then use the nylon screw to secure the lid after tapping a hole in the chassis.

 

This requires the wagon to be dismantled unless you are willing to drill and tap the hole through the steel weight. I replace the steel weight with lead flashing achieve my target weight anyway so it's all become part of a standard routine.

If you dismantle the wagon you can trim the steel weight at each end, I think this is easier than drilling it. I have just done a couple of wagons like the one below ... these are #146 couplers, assembled the night before (and left to dry out), fixed up with an M2 bolt and nut, adjusted and tried out, and finally cemented to stop the boxes turning. I have discovered if I cut the right amount off the moulded-on mounts for the original NEM pockets, the standard #242 box fits without having to trim it down. I did try putting washers below the M2 nuts but there wasn't quite enough room to have the bolt long enough to fill the nut and get the body moulding back on.

Some contributors to this discussion have asked how many UK modellers use Kadee couplers and I asked Kadee how many they sell in the UK. The answer to the question remains an unknown, but their response does give me a fresh idea, which goes back to the title of the thread ...

I asked:

"I have started an interesting discussion at www.rmweb.co.uk entitled "Preferred height for Kadee couplers on UK 4mm scale models", there have been over sixty messages so far. The contributors agree the best height is the HO height (25/64"), and there is a lot of constructive input about how to modify UK ready to run models to fit Kadees. There is one nagging question: "what proportion of UK modellers use Kadee couplers?" If (for example) you could tell me how many couplers you sell in the UK each year, I could offer this to the forum and we could try some arithmetic, for example suppose a total of 50 wagons and locos per average user, then estimate the number of users. I believe all Kadee installations on UK models are done by modellers themselves, there is no ready to run equipment already fitted. Regards etc"

And Kadee replied:
"Very interesting and informative discussion you started. We have to deal with the coupler height difference between HO scale (25/64" 9.9 mm ) and OO scale (29/64" 12 mm) especially using the NEM coupler pockets.

We have no way of measuring the market share for the UK or anywhere else. Even if we could we'd keep that info to ourselves as proprietary info. As far as our sales lines up it goes about like this, USA/Canada is the largest of course, the UK and Australia are about even, mainland Europe next, then the rest of the world has the last share of our sales.

We do find that most of the modelers we help from the UK with coupler conversions are individuals and not shops or clubs.

We do sell to certain manufactures that use our couplers on their models. ExactRail, Intermoutain, BLMA, Tangent, MTH, (some) Broadway Limited, and various others (smaller)".

- - - 

I had not read about the 29/64” / 12 mm height for 00, but I get the feeling most 00 modellers who use Kadees as general-purpose couplers (meaning as a resource, not within a fixed rake) try to put them at the HO height of 25/64” / 9.9 mm. I think I have learnt at least four reasons for this in this thread: to fit below UK buffer beams; to work with NEM pockets; to use delayed uncoupling; to use the HO standard. I wonder ... should we ask Kadee to set their recommended height for 00 to match their standard for HO?

As I paste in this text, I am wondering, by ‘00’ do they mean ‘American 00’, but I think this is worth sharing.

 

I find the NEM sockets on Dapol locos droop so much it makes them useless for use with kadee 18,19 or 20 as its not possible to get the height set correctly. On a couple of locos I've glued the socket in place but that make the left/right springing of the socket inoperable but it hasn't affected the performance of the coupler.

 

If I'm reading this thread correctly, are you removing the Dapol NEM socket and replacing it with a kadee box?

No. I just plugged in a #18 or #19. Maybe I have been lucky or you have been unlucky. My two wagons and two locos are new or nearly new, so I will find out soon enough if they do sag.

The NEM sockets I have removed have been mostly Bachmann ones, but other contributors have suggested removing them all. This does get rid of one third of this marriage of convenience of US coupler, Euro mount and UK stock. The NEM sockets on my two Roco 4-wheel coaches (German prototypes) are engineered differently to all the UK models I have, and have a moulded support bar below the pocket. This would stop any sag, and makes me think of a length of piano wire to lift sagging pockets. I haven't tried this yet. 

I want to keep an open mind on using these pockets with Kadees. The "inboard" ones on locos like the Dapol Western, and the rigid ones on bogies on the Bachmann 2-EPB are useful and and (to my mind) an integral part of the model and I wouldn't want to try a conversion to remove them. The thread has shown that only some pockets are downright "wrong", e.g. the Bachmann wagons early on from post number 1, and there are solutions for these with lowered pockets and without them. I have one wagon with its Bachmann pockets held rigid and at the right height by Peco track pins, this seems to work (the Kadee has its own pivot of course) but the pocket is usually on a flexible mount and I am reluctant to recommend it. I think you must take each model on a case by case basis.

I take it your quoted work-rate is for known jobs - on one or two locos I have encountered, it took most of an evening to do one end!

Thinking about it, I am probably managing nearer two vehicles per evening not per hour. Dapol locos and wagons with NEM pockets have been straightforward to set up, and without these my average would be a lot slower. Tonight I shall assemble some 146s into their boxes, and do something/anything else while they set :-).

Trust me, RTR manufacturers OO wheels aren't a patch on HO. "Good enough" just doesn't cut it, it's only recently Hornby have supplied something round with their stock. It's true that aftermarket wheels are alot better but we're talking about quick "out of the box and onto the layout" modifications here, right...?

All the locos I have converted have the manufacturer's wheels, and about half of the rolling stock too. The manufacturer's wheels I have kept have worked with Kadees; the converted ones are the remains of a foray into EM gauge rather than problems with the originals. So for me, I do mean 'good enough'; but I realise this is not universal.

I am describing what has worked for me. I ran three locos and four wagons on a club layout last night and they worked. I am hopeful I have found the level of precision of alignment I need to get the performance I want, but I want many months of use and lots of delayed uncoupling to be confident of this. Nothing I have written has meant to imply a particularly quick conversion. Some vehicles are easier than others, some have needed two or three goes, but practice (especially when it goes wrong) helps a lot. I am averaging about two vehicles per hour.

Logically the sideways play ought to be a problem but like John I could not point a finger at it. I suspect most modern 00 wheels are as good as the wheels on the HO models the Kadees are designed to work with, and this means "good enough". One way to find out would be to set up a vehicle with some old fashioned coarse Tri-ang wheels and see what happens ... but these wheels won't go through modern pointwork and maybe hit the sleepers too. Perhaps a good practice would be to require a wheel back to back of 14.5 mm for 00, and replace wheels which won't meet this standard.

When my Kadees fail to couple it seems to be because the wheels on the loose wagons are too free running, and they just trundle away!

1. If you are going to improve a model by fitting better wheels, cast buffers etc., make sure you do it BEFORE fitting the couplers ...

 

2. I still come across the odd new situation even after all this time and r-t-r models sometimes get altered between batches, so always measure before you cut, even if you think you have done the same job before.

Wheel diameters and buffers are important. I didn't mention wheels because I thought it would confuse the issue with facts ... I was lucky in that I had converted a lot of this stock to EM, and then regauged it to 00, and I knew I didn't want to change the wheels again. Sometimes scale wheels are a little larger than the originals, e.g. Limby 121 Bubblecar and this could play havoc if you decide to rewheel and/or reset the bogie mounts. There is an unwritten rule, "don't make too many permanent changes", I am thinking especially of the huge moulded-on Lima couplings, where there may be a temptation to saw the whole thing off when you really want to keep part of it as a mount for the Kadee. I have a Mainline J72 I converted to scale 3-links many years ago and I removed all traces of the original coupler mounts. I am now stuck with the 3-links. It may be prudent to run some vehicles with a "converter wagon" until you know what you want to improve. Do the couplings last.

I am not sure where this thread can go now, but perhaps it is worth posting a few of shots of fairly ancient and modern implementations of the real thing, a BR Mk1 (retracting buffers) and a class 170 DMU (no buffers). My feeling is, buffers will always make us compromise; any idea of a commercial 4mm scale coupler is a non-starter; and actually, the Kadee looks quite neat.

I have now fitted Kadee couplings to 21 vehicles (42 couplings), which probably means I should get out more, but I offer my conclusions so far:

1. The most difficult part of the conversion is wading through the Kadee marketing speak. When you have a whisker coupler you will know it is just like their earlier models but with a built-in hair spring, but it is hard to work this out from the literature .. sometimes it seems to only make sense when you know what it is talking about ...

2. If there is a NEM 362 socket in the right place and the vehicle has buffers then I use a #18. If the socket is too far back, e.g. some locos with fairings, then a #19. (I guess a #17 would suit something like a Freightliner chassis with no buffers).

3. Most NEM socket housings seem to be a bit too tall internally, I put a scrap of 0.015" styrene shaved down to fit below the coupler. This stops it drooping in the socket. I have a Roco HO coach with a built-in phosphor-bronze spring in its sockets, which does this properly, but this coach is a one-off for me.

4. If the NEM socket is at the wrong height then get rid of it and put a #146 or possibly a #149, trim down the gear box to fit. You can bend the metal coupler shanks a bit to trim the height of the knuckle.

5. If a loco has screwed-on tension lock couplers, drill out the shank of a #20 and screw it in the place of the original coupler (same as post no. 8). This installation omits the pivot usually present on the shank or the NEM socket and relies on the pivot behind the coupler head ... this seems ok for a loco, I have doubts whether it is suitable for a two similarly equipped vehicles coupled together (Hornby J94):

6. If the model has Hornby-Dublo type couplings screwed onto a bogie chassis from above (e.g. the HD Co-Bo!) then use an M3 nut and bolt with a #5 (or better a slightly longer shank), this will be the right height.

7. It is a lot better to use a height gauge than a chosen 'good wagon'. I could not find a Kadee gauge to buy so I made one from a #5 coupling, an M3 screw and a lock nut:

8. If you can slip a 0.030" thick steel rule above the rails below the trip pin, its height is pretty close to 1/32".

Having cleared my back log, I think if I stock up on some #146, #18 and a few #20 this will cover most installations.

John,

 

That is exactly what I did when adding Kadee's to my Lima 6-wheel tankers, as you can see below.  For these, I've simply used the standard box that comes with the coupler. I have used the #252 on other wagons where, as you've said, space is at a premium.

You can also trim down the #242 box which comes with the #146 and similar 'Whisker' couplers. I assembled the coupler and glued up the box, and the next evening cut about 1.5 mm off the back edge of it. This let me line up the inner face of the coupler knuckle with the front of the buffers, and the coupler box is nicely recessed behind the buffer beam. This is another Bachmann wagon, I used a cut-off disc in a mini drill to remove the mount for the NEM362 socket but keep the body retaining screw. This installation puts the coupler shank pivot in about the same location as the flexible mounting of the original socket. (Ignore the use of an overset #149 coupler, this is just a personal experiment).

Exactly why or how did UK manufacturers decide to fit NEM boxes to RTR stock anyway...?

I will hazard a guess (always a bit reckless in these forums!) that the RTR manufacturers wanted to give purchasers of locomotives the opportunity to fit scale couplings (usually screw couplings) and brake pipes/hoses instead of tension locks, for example on the 'front' of a loco or on both ends of a model in a display case. The pocket lets people install a standardised working coupling (though not remove it) without the use of tool.

... you run the risk of compromising the auto and delayed coupling and uncoupling which is afterall why most 00 modellers will accept the incorrect looks of the coupler on UK stock

Well ... I chose mine because they look so much neater than a tension lock coupler, and a brief personal foray into scale three-link ones told me I needed something automatic. As a bonus, the closer coupling between wagons is better too. I always rather liked the coupling used by Hornby Dublo, but I believe the designer or patent holder wanted royalties from users and so it faded away. If not I would have happily gone for HD. I've not used the Kadee delayed uncoupling feature yet (no layout ...), but I do think it is nice to have it there.

Just to chuck in my two' penneth (after discussing Kadee's earlier), I've never quite understood why ...

The whole point of starting this thread was to try to find out what standard the majority use; and the resulting discussion has revealed a reasonable 'best practice', all from the point of view of interoperability and ease of use.

There is no need to create new standards where a useful one already exists; and here we already have the same standard for NEM pockets for 1:87 and 1:64. Surely, it is only sensible for 1:76 to use the same.

Nothing wrong with train station - its like a bus station, but with trains in it. It stopped being a railway station when the railway stopped being a common carrier. Fighting it is like saying font (typeface not baptismal) should be fount.

Everything wrong with Kaydee though, but at least it's only in my posts in this thread. Sorry. It might be subconscious; the wife of a friend who models US railways is Kay.

EDIT: It occurs to me now, this is probably why I couldn't find much on 'Kadees' on the forums :-)

I suspect I asked the wrong question in post number 1; but the replies all point to a Best Practice for 00, this being to adopt the standard for HO for NEM 362 coupler pockets; and (somewhat unrelated to this, but in a similar vein) to follow Kadee’s instructions for HO for their couplers.

I started on the wrong footing because I happened to buy some Bachmann wagons which had the coupler pockets higher than the location standardised for HO. Perhaps Bachmann had already made a few thousand offset hook and bar couplers; or perhaps they made a mistake on this wagon chassis moulding and had to compensate for it ... but I doubt they were trying to define a standard for NEM pockets for 00. Their later models are ‘correct’.

I do like the idea of the pocket as the basis for using Kaydee couplers because it lets you shim a coupler up or down or swap out a broken coupler. Or, you could replace a whole pocket/coupler assembly, without making a permanent alteration to the stock. For one of my Bachmann wagons I have cut down the hook of a Kaydee no. 6 coupler (metal, no offset), crushed it sideways and expoxied it into the NEM socket. This is then at the spec. height of 25/64 in. Maybe it will fail too soon (the pocket is a flexible plastic, the glue may pull out), I will wait and see. Incidentally I wouldn’t recommend the no. 6 for a standard install any UK stock with buffers, it is too short and the housing is too long.

For my one and only Bachmann coach (a BR Mk1) I have drilled through the shank of a Kaydee no. 20 and used a small screw to fix it to the underside of the coupler pocket. This keeps the original close coupling mechanism. It works for a one-coach train, it might be too weak for a long train.

EDIT: removed misleading description of fitting a coupling to a Hornby J94

I ran out of couplers at 5.30, just as the local model shop closed, probably a good thing for the time being ...

I ordered up a blue 'Western Venturer' from Dapol's online shop. The package arrived yesterday, but inside was a maroon 'Western Sultan' in a box for a blue 'Venturer'. Swapped box lids I guess. I phoned Dapol and the lady there told me "we have one blue one left in stock, I will post it out to you. Please could you send the maroon one back to our Freepost address". It seemed so nice to meet such a feeling of trust. The blue one was arrived today, just before I made it to the Post Office with the maroon one. This is surely the best "customer service" (without a name) you could imagine (the lady was in Accounts) ... Dapol full marks for service as well as this incredible model. And, if you are reading this thread pondering whether to actually buy one (as I was), do it soon.

I looked at some of my more recent purchases this evening. These models all have their NEM 362 coupler sockets at the height specified by NEM 362:

• Dapol / Model Rail Sentinel
• Dapol cement wagon
• Hornby R6561 horse box
• Bachmann 37-980W Conflat

All four models also have the sockets at the specified offset behind the buffer heads. Plugging in a Kaydee no.18 immediately puts the coupler at or very near to the Kaydee height (25/64 in), and with vehicles reasonably close coupled but far enough apart to just about go round a no.2 reverse curve.

I am glad I went for the NEM/Kaydee standard (the HO standard) last time, if not very permanently - I wasn't sure what the manufacturers were trying to do. I have six wagons (all early NEM-fitted Bachmann) which would benefit from me re-working their coupler installations, I agree the No.5 (which I have used on a pre-NEM wagon) looks the sensible way to go.

I suppose ratification would be NEM 362 being up-issued to cover 00 as well as HO, S and O, but I suspect MOROP/NEM is concerned with Europe, not a scale peculiar to one of its member states. Thank you to everyone, Richard.

I work in engineering where it is sometimes said we love our standards - that's why we have so many of them. Kaydee specify a standard height for their couplers, a centre line 25/64 inch above rail level - say 9.9 or 10mm. This sounds like it should be really simple for everyone (including the main stream manufacturers) to adopt.

Some years ago I converted some RTR wagons to use Kaydees and found that the NEM sockets on most of them (especially Bachmann) were about 1mm too high. I chose to reset the coupler pockets to give the "proper" 9.9mm, and pop in a Kaydee no. 18 or 19:

I want to convert some more models. It is easy to undo the modifications on coupler pockets and set them to a different height ... but once I start cementing Kaydee no.5 couplers onto underframes they will be stuck forever. It would be easier to accept the "too high" setting of 11mm, and just tweak the trip pins as needed to work with uncouplers. After all, I don't "need" interoperability with other people's models, and I could set up a converter wagon to take along on club nights.

My doubt is this. Now, meaning in mid-2013, are the UK 4mm scale modellers who use Kaydees setting them at the Kaydee height of 9.9 mm or what I might call "Bachmann UK height" around 11mm, or some other preferred height? I would feel happier if I knew I was going with the majority.

Here is a second photo to finish the thread off. The 'white' is Holts primer - this seems to dry matt if you just dust it on, but with a slight sheen after a heavier coat. I have never had a white engine before, but it seems to suit! I now have some aerosols of U-Pol 'Acid no.8' and Halfords grey primer no. 473116, but these will have to wait for a future model. Halfords range of primers was a bit overwhelming, but I am guessing this one will be suitable for most materials. Thanks again for all the ideas, Richard.

Has the paint got a use by date on it? Phoenix Precision aerosol etch primers, which I use with no problems, are time sensitive, I'm not sure about the tinned stuff.

 

If I'm not mistaken that's an A1 Models kit, which should be fairly new, so dirty brass shouldn't really be a problem.

The paint is 'jarred' rather than 'tinned' so to speak, there is a use by date but it is around 5 years from now. I am sure the problem is grime or grease, and it is my fault. It is indeed an A1 Models kit (their p/n A18), but put together with sloping bonnet sides and grill onto a different body/chassis ... and I fiddled around a lot while I worked out what I wanted it to look like. It is a good kit for a beginner. I will post another pic when I finish it.

Well, my second attempt with the PQ32/31 was sort of less unsuccessful than the first. This evening (30 hours on), the primer easily rubbed off the top and one side of the bonnet (just like a lottery scratchcard), but held firm elsewhere. I can only conclude I have a modelling hygiene problem. Patience ended, I cleaned the bare areas, again, and applied three coats of the Holts acrylic primer all over.

If we have an 'innovations' competition this year, I know what my suggestion will be ... for manufacturers of etched brass kits to put a base primer on the 'outside' face of the parts! Somehow I suspect small/medium batch production using an industrial metal cleaner or shot blasting, a larger volume mix and a controlled spray application has a better chance of success than me.

I

That primer is only supposed to be used as a single thin coat to allow a normal coat of primer to stik in the normal way on top of it!
Trying to apply a second coat will only soften and release the initial layer as you have found out

Wally, this is an important point and I can only plead ignorance, the instructions mention 'top coats' but there is no mention of using conventional primer nor your single-coat rule. I saw it soften, but imagined it would set again.

I had splodged some primer onto an unprepared bare brass fret last weekend, this stuck well ... indeed I cannot scrape it off. This tells me the mix was good, but second application and possibly the surface preparation was wrong. I had cleaned the surface with only PQ-17. I have now cleaned the model with white vinegar, then a glass fibre brush, then PQ-17, then the fibre brush again. Wet and dry seemed a bit harsh. Working in daylight I can see the PQ-17 evaporates quickly but leaves a residue on the surface. Hence the second working with the fibre brush. I have today made a fresh mix, this time about 55% primer / 45% thinner in an attempt to make it more brushable, 'painted' it onto the model and left it to harden. Tomorrow will tell.

Meanwhile ... the Holts acrylic white primer stuck well on a flat surface but rubs off easily on sharp edges. It will be my second coat (tomorrow), unless someone steers me towards a different route! I will look out for the other products everyone has suggested.

Miss Prism: as Mike suggests, the thinner and paint are from Phoenix Precision.

Ian: I have some Holts acrylic primer, I will try this on some scrap brass. I like the idea of an OHP pen.

On the bright side, I have stripped the model very easily.