Brian Kirby uncoupling - problems

[checkrail]

Hi again

 

Well, I received my brass axles from Proto:87 in the US and fitted them.  Not a panacea, but they immediately reduced the incidence of involuntary uncoupling by about 40-50%.  Another 5 or 10% turned out to be due to my having over-shortened the Bachmann couplings, so that a small number ended up with the loop very slightly behind the line of the buffer faces - soon fettled. That still left a significant problem, which I've been addressing by seemingly endless tweaking and twiddling on a case-by-case basis as it occurs.

 

Some are amenable to adjustment, e.g. where the coupling loop has ended up at the wrong height or the coupling has sagged a bit. But the remaining instances still seem to be down to the 'skitteriness' of the wagons, being very light and free-running.  The application of some friction to the axles by means of phosphor-bronze strips glued to the wagon floor has proved far easier to fine tune than my previous attempts with foam sponge or springy steel wire, but there's a very fine hair-trigger point between too much interference, where one's rolling stock becomes 'sliding stock', and a return to unwanted uncoupling. (The wagons would benefit from a little weight, but those I'm using as guinea pigs will eventually end up in a fixed train of passing coal empties with 3 link couplings. Future general goods stock conversions will have a bit of weight added.)

 

There's still a hard core of inexplicable (to me, anyway!) spontaneous uncoupling, when couplers seem perfectly adjusted, both hooks are engaged, and wagons are steady, non-jittery runners. It seems random - not always the same vehicles, not always the same magnets. I can shunt the yard successfully in a session in which every single wagon will be hauled over every single magnet at least once without a problem, then just when I think I've cracked it a train will spontaneously part in the middle again as it passes over a pair of magnets.

 

I did try putting the staple at the top of the dropper rather than the bottom, as a proxy for burying the magnets deeper.  It made no difference to the effectiveness of uncoupling at all; unfortunately it made no difference to the involuntary uncoupling either.

 

But I'm 90% of the way there and after the next fortnight away I'll continue doggedly snagging.  When it's working it's immensely satisfying and absorbing to do everything - driving, coupling, uncoupling and point switching - all with one hand from my Prodigy DCC handset.

 

This is my summer of couplings; if I haven't cracked it by September I'll look at electro-magnets.

 

Have a good summer everyone.

John.  

[dasatcopthorne]

Hi again

 

Well, I received my brass axles from Proto:87 in the US and fitted them.  Not a panacea, but they immediately reduced the incidence of involuntary uncoupling by about 40-50%.  Another 5 or 10% turned out to be due to my having over-shortened the Bachmann couplings, so that a small number ended up with the loop very slightly behind the line of the buffer faces - soon fettled. That still left a significant problem, which I've been addressing by seemingly endless tweaking and twiddling on a case-by-case basis as it occurs.

 

Some are amenable to adjustment, e.g. where the coupling loop has ended up at the wrong height or the coupling has sagged a bit. But the remaining instances still seem to be down to the 'skitteriness' of the wagons, being very light and free-running.  The application of some friction to the axles by means of phosphor-bronze strips glued to the wagon floor has proved far easier to fine tune than my previous attempts with foam sponge or springy steel wire, but there's a very fine hair-trigger point between too much interference, where one's rolling stock becomes 'sliding stock', and a return to unwanted uncoupling. (The wagons would benefit from a little weight, but those I'm using as guinea pigs will eventually end up in a fixed train of passing coal empties with 3 link couplings. Future general goods stock conversions will have a bit of weight added.)

 

There's still a hard core of inexplicable (to me, anyway!) spontaneous uncoupling, when couplers seem perfectly adjusted, both hooks are engaged, and wagons are steady, non-jittery runners. It seems random - not always the same vehicles, not always the same magnets. I can shunt the yard successfully in a session in which every single wagon will be hauled over every single magnet at least once without a problem, then just when I think I've cracked it a train will spontaneously part in the middle again as it passes over a pair of magnets.

 

I did try putting the staple at the top of the dropper rather than the bottom, as a proxy for burying the magnets deeper.  It made no difference to the effectiveness of uncoupling at all; unfortunately it made no difference to the involuntary uncoupling either.

 

But I'm 90% of the way there and after the next fortnight away I'll continue doggedly snagging.  When it's working it's immensely satisfying and absorbing to do everything - driving, coupling, uncoupling and point switching - all with one hand from my Prodigy DCC handset.

 

This is my summer of couplings; if I haven't cracked it by September I'll look at electro-magnets.

 

Have a good summer everyone.

John.  

 

John.

 

The instances of most unwanted uncoupling on Falcon Road seems to be down to the following:

 

Although two couplings seem to be engaged the little 'return' part of the hooks haven't caught under the lip on the rear face of the loop. Thus there is nothing stopping the hook from rising.

 

This seems to be usually caused if the coupling is not level, being lower at the rear (fixing point). Therefore the hook is slightly pointing upwards and is unable to engage its 'return' under the lip on the opposite loop.

 

I used to 'tweek' my coulings by bending up or down but now any tweeking is done by filing or packing. making sure the whole is level when at the required hight.

 

Best of luck

 

Dave

[philsandy]

John,

Make sure that the loops of the couplings are level in both planes, as above, as Dave has described, and when you look at a wagon end on, that the bar of the loop is parallel with the track / wagon axle.

 

I had a couple of wagons coming uncoupled even though they are all set exactly at the same height.

When I looked at one wagon end on, the coupling bar was not parallel with the axle, about 1mm out. I just slightly twisted it to straighten it up and that solved the problem. 

 

I have also found that some Bachmann couplings to be a slack fit in the "dove tail" part of the coupling and they gradually move and then are at a lower height. I cured this by placing  a very small piece of PTFE tape in the dove tail on the wagon base, and then pushed the coupling into position, giving it a tighter fit in the dove tail. 

[dasatcopthorne]

John,

Make sure that the loops of the couplings are level in both planes, as above, as Dave has described, and when you look at a wagon end on, that the bar of the loop is parallel with the track / wagon axle.

 

I had a couple of wagons coming uncoupled even though they are all set exactly at the same height.

When I looked at one wagon end on, the coupling bar was not parallel with the axle, about 1mm out. I just slightly twisted it to straighten it up and that solved the problem. 

 

I have also found that some Bachmann couplings to be a slack fit in the "dove tail" part of the coupling and they gradually move and then are at a lower height. I cured this by placing  a very small piece of PTFE tape in the dove tail on the wagon base, and then pushed the coupling into position, giving it a tighter fit in the dove tail. 

 

Hi Philsandy.

 

Yas and all that as well.

 

Forgot to mention the leveling on the loop part.

 

Well done.

 

Best think I ever did was the set up a 'master' coupling on an old one plank wagon from which everything else is measured.

 

Dave

[checkrail]

Well, September's here and I think I've finally cracked it (touch wood).  Even better, I haven't had to resort to the nuclear option of electro-magnets.  I wanted to keep the simplicity of Brian's original concept, and with 20 uncoupling points on the layout I certainly didn't relish the wiring (or the expense) involved.

 

I spent a lot of time ironing out any problems due to coupling misalignment as many of you had suggested, but there remained a considerable number of cases where wagons ran forward to the magnets faster than the speed of the train, causing unwanted uncoupling.  I tried replacing the axles with brass ones and the steel weights with lead sheet, but with only limited effect. On some wagons with Alan Gibson wheels I reckon that the wheel tyres and the staple itself were the only remaining ferrous items, yet still the troublesome trucks jumped forward to the magnet and uncoupled.

 

I then tried neodymium magnets, but found that even the strongest (N52) 3mm dia x 10mm rod wouldn't attract the staples unless level with the sleeper tops (I would have wanted them buried under the ballast).  And when they were adjusted so as to attract the staples they made no difference to the unwanted uncoupling.

 

Next experiment was to try burying the Screwfix cupboard door magnets deeper (in the fiddle yard to avoid digging up the ballasted track yet again!).  I chiselled out a rectangular slot in the four-foot, right through the 12mm MDF baseboard, and screwed an offcut of ply underneath.  Then, using thin packing pieces, tried the magnets at a range of depths.  The lowest at which I could get them to operate the couplings was 10mm down (from top of rail to top of magnet).  But guess what - the unwanted uncoupling still occurred.

 

So the final answer was the first one - adding enough friction to free-running wagons to stop the skitteriness and leaping forward to the magnets.  After messing around with springy wire and pb strip I settled on the use of small squares of plastikard glued vertically to the inside face of the coupling mount and bearing on the central part of the axle to the extent that the wheels would hardly go round.  I then filed the face of these squares with the end of a flat needle file a bit at a time, re-inserting the wheels and trying out on the track at intervals until I had just the right amount of friction but no more.  This was a real hair-trigger procedure - half a dozen gentle strokes of the file made all the difference between non-rolling wheels on the one hand and a reversion to unwanted uncoupling on the other.

 

The other consideration was the number of such treated wagons my locos could pull or, even more importantly, push.  After weeks of trial and error I can now set back an 11 wagon pick-up goods into the yard loop - its maximum capacity - over 4 sets of points and a single slip, at slow speed, and proceed to shunt the yard (involving numerous passages over 12 separate uncoupling points) without unwanted uncoupling.  Result!

 

And it's great to do it all with one hand via my handset with no other switches to pull or buttons to push.

 

Of course, all new wagon acquisitions that will ever be shunted, whether kit built or RTR, will need the same treatment.  It can take a couple of hours of tweaking and testing per vehicle to get it right!

 

John C.

[Jeff Smith]

I'm glad you have resolved your problems. Any sort of steel wheels will be attracted - I ended up standardizing on Hornby wagon wheels refitted to brass axles. These are a bit course scale but ok for O-16.5. Some extremely free-running vehicles are attracted by the Kadee trip pin but I generally add weights to combat this.

[Brian Kirby]

Hi Everyone,

Question for Checkrail: Are you using single magnets or magnets in pairs? If the former, that can incorrectly draw the wagons together into the one magnetic field and make the couplings bunch.

 

I'm no professor of magnetism, but i would have thought the deeper any magnets are placed, would widen their magnetic field of attraction, which might lead to premature uncoupling (and we don't want that at our age)? I settled on using pairs of flat cupboard door magnets (Screwfix), immediately under the track, to localize the field for each coupling (as seen in my avatar tag thingy on the left of this post). As i mentioned before, i have suffered the occasional unplanned uncoupling, but that was nearly always down to the "lock" of the tension-lock coupling being disengaged, through incorrect alignment (deepening the aperture of the hook helps and then the hooks are more "relaxed"). What can happen with any tension-lock, is that they may be both perfectly coupled on straight track, then on a sharp curve the hook on the inside of the curve naturally disengages and the hook is temporarily floating. On regaining straight track, this disengaged hook can bounce or jump up on to the surround of the coupling bar and thus remained disengaged, but then the other correctly aligned hook should still hold the train (indeed many of my locos only have a wire bar coupling anyway). Dips in track near the magnets could possibly cause disengagement, where a following wagon rolls forward and the couplings bunch. 

    There's always the safe option of electro-magnets on main running lines for total security (Board Of Trade, etc.), but plain magnets for sidings for ease of operation (look Ma, no hands). Just to re-cap, i recommended using only Bachmann narrow style (Blue Riband, if they still call them that) couplings, since they have non-ferrous alloy hooks (so they won't attract each other), plus (but less important) straightening the droppers (they're cranked for the centre line of the old ramps), so they are further away from each other when the ferrous staples are wrapped around them (again to avoid attraction through passive magnetization). BTW, all this magnetic uncoupling lark started about fifteen years ago, when i got fed up with the various gruesome looking RTR ramps (sprung or motorized) and bits of plastic tape, etc. The final crunch was when my Bachmann 03 shunter got stuck on top of a Peco ramp with the wheels revolving high and dry! I decided we needed something better than this . . . .

                                            Cheers, Brian.

[checkrail]

Yes, I've been using the Screwfix magnets in pairs, under the sleepers, as per Brian's original recommendation. There is one uncoupling point with just one magnet, in a location where the uncoupling of the loco from its train is the sole requirement.  (Like Brian my locos have wire loops in place of tension-lock couplings). This uncoupler has never given any trouble when the rest of the train is hauled over it.

 

In fact, come to think of it, I've had little if any problem with stock decoupling from the loco, over any magnets, single or in pairs.  The goalpost-shaped wire loops engage very well with the claw on the T/L hook, and the height of the wire loop is easy to adjust against a height gauge - easier in fact than a T/L in a NEM pocket.  I recall that Stu told us how he had his stock 'handed', with hooks on one end only, thus requiring only one magnet per uncoupling point.  If the other end had a wire loop that might be the way to go. But it would mean putting up with T/Ls on at least one end of each tank loco, and given that my pairs of prairies and panniers face different ways (for variety) on at least 2 locos it'd have to be be at the front. Not a look I like.

 

I certainly take the point about the importance of the hook engaging properly with the loop, and deepening the notch of the hooks is worth looking at.  Also coupling behaviour on curves.

 

I like Brian's 03 shunter story!  As he says, we needed something better, and I'm grateful to him for devising it and to all of you for your help.

 

John C.

[Stubby47]

How well do the locos push wagons - does the loco wire loop push on the TL loop, or does the hook reach to the loco buffer beam ?

[Brian Kirby]

I mentioned about "many of my locos have thin wire coupling bars", they tend to be the ones that are more difficult to attach Bachmann couplings to (e.g. Warships and Westerns with front skirts and various kit-built locos). Having said that, even then i only fit a Bachmann coupling to the rear of any steam locos and one end of most other diesels, the other end again has a thin wire bar to improve the frontal appearance, the Bachmann coupling facilitates easier double heading. This works fine on steam locos, since double-heading chimney-to-chimney would rarely be seen and even then frowned upon, i believe it was to do with excessive hammerblow?        BK

[34theletterbetweenB&D]

... This works fine on steam locos, since double-heading chimney-to-chimney would rarely be seen and even then frowned upon, i believe it was to do with excessive hammerblow?    

Now that is a really interesting question. No doubt whatsoever that the railway avoided it, and the few photos I have seen are of emergency situations; such as the only available loco to assist a train stalled on a bank had to couple on the front to assist, and couldn't be turned to avoid smokebox to smokebox.

 

I don't believe hammerblow to be the problem. There was no objection to buffering up two, three, four, 0-6-0Ts to push trains up Lickey, and that puts the coupled wheelbases in as close proximity as they are going to get, whichever way around they are.

 

The one BR steam driver who offered an opinion told me that in many wind conditions the exhaust could swirl around in the gap between the smokeboxes, and obscure sighting between the two crews.

[Brian Kirby]

Good point 34BD, but it might still be hammerblow as well, not so much on plain track, but whilst traversing weak bridges or areas prone to subsidence? Anyway, it was still very rarely seen, so it means i can put wire bars on the front and have more room to put screw couplings and pipes on, no requirement for chimney-to-chimney working on my layout. :-)   BK

[checkrail]

In answer to Stu, the wire loop doesn't inhibit pushing.  This is because, for aesthetic reasons, I have shortened all my Bachmann 32-030 mini tension lock couplings so that the front edge of the loop is only very slightly proud of a line across the buffer faces. When propelling, wagons are still buffering loop against loop, but the real buffers are almost touching (and just about are touching on the inside of curves) giving a much better effect.  However, the loco with its wire loop is actually propelling buffer to buffer as per prototype and the sprung buffers on my Bachmann prairie and pannier tanks do actually come into play and compress on the tighter curves. In propelling mode I do find that the wire loop slides over the T/L loop of the adjoining wagon, but this seems to have no detrimental effect on stability or disengagement. Meanwhile the point of that wagon's T/L hook is just about in contact with the loco buffer beam.  Again, no detrimental effects.

 

I shorten the T/Ls by cutting about 2.5 - 3mm off the NEM pocket and shortening the coupling tails to suit.  I then (after testing against the wagon for mount position and relationship to buffer faces) secure the couplings in the pockets by fusing them together with a couple of swift wipes with the soldering iron (using a redundant bit of course!), though I suppose a drop of cyano would do the trick. 

 

Another aesthetic benefit of the shortening is that when viewed from any angle save track level - from where of course one can see the droppers and staples - the T/L couplings are hardly visible any more, being obscured by the almost-touching buffers. (Just a shame that parts of my layout were specifically designed with rail level viewing in mind!)

 

This all works fine on my visible track, which is from C & L components to 00-SF standards with reasonable radii, but in the fiddle yard I have some Peco curved and 3-way points, whose inside radius is I think about 24"? . I don't normally shunt over these but I've just tried propelling a couple of wagons over a reverse curve formed of such points with a 45xx tank and avoided buffer-locking (just!).

 

John C.

[Jeff Smith]

I remember years ago that some people fitted a thin straight wire across the buffer faces on locos. This allowed various types of hooks to engage and also prevented buffer locking.