Imprecise couplings (Iain Rice design)

[John CutlerParticipant]

I have been experimenting with different auto-couplings.

I thought I had concluded that AJs were the way to go and have fitted a few.

However, I realise they require too much precision in the making and are easily distorted.

They were not designed with wonky track in mind either.

I tried enlarging the AJ hook as per Graham Allen’s video on YouTube; that helped performance considerably but not enough to compensate for the AJ downsides (for me).

Winterley couplings were tempting (no uncouplers needed!) but are a bit chunky and the hook ends are impossible to fit to many of my locos.

So I find myself following Iain Rice’s logic (AJs were too unforgiving for him too) and planning to fit his Imprecise design (with some slight deviations) to my stock.

 

Has anyone used these?

 

Iain advocates using phosphor bronze wire for the hooks and loops.

Does anyone know why?

PB does not blacken with gun blue and black marker (Sharpie) ink quickly wears off; that can be seen in Iain’s photo of a wagon in his Cameo Layouts book and confirmed by me experimentally.

I will probably use nickel silver for the loops and steel guitar wire for the hooks, which resemble AJ hooks.

 

Any advice welcome (but not recommending other couplings please!).

 

[Paul TomlinsonParticipant]

John, not advice, but a comment on Iain’s choice of Phosphor Bronze. It is often used to construct pickups – it can be formed to hold a shape, but retains it’s springiness, so in this context shouldn’t deform during repeated coupling/uncoupling operations. I haven’t tried to form steel guitar wire, but I anticipate it might resist being formed into sharp angles. That’s not to say, however, that it isn’t worth a try – there’s very little to lose. Good luck.

[Paul WillisParticipant]

On Paul Tomlinson said

I haven’t tried to form steel guitar wire, but I anticipate it might resist being formed into sharp angles. That’s not to say, however, that it isn’t worth a try – there’s very little to lose. Good luck.

Hi Paul,

Steel guitar wire generally works well formed into sharp angles.  When used for AJ couplings, the first bend is a 180 degree one back on the wire, if I remember correctly.

On occasion I’ve known that bend break, but generally it works.

Best,

Paul

[John CutlerParticipant]

Steel AJs are fairly easy to form with jigs but getting the angles right and fitting can be difficult.

I have been experimenting with Vincent de Bode’s version of the AJ, his AAJ, for some time (see MRJ123). He successfully uses 8 thou steel guitar string instead of 11 thou for the standard AJ. The advantages are that it needs a shorter shank and is marginally less visible. I have only suffered one breakage and that was on a 180 degree bend. Murphy’s Law says it is on the Hornby Adams Radial which is a real pig to fit an AJ hook onto! Vincent experimented with phosphor bronze wire but was unhappy with it. If you are thinking of adopting AJs, I recommend checking out MRJ123.

I will probably persevere with 8 thou steel wire for the Imprecise coupling hook and am still puzzled why Iain Rice chose phosphor-bronze. I wonder if it had anything to do with magnets? PB might be easier to form but conversely it will deform more easily!

 

[John CutlerParticipant]

After fitting the Adams Radial with a loop and experimenting with 3 wagons, I am unconvinced of the overall advantage of the Imprecise coupling.

To sum up:

The advantages are:

1.       Much less precision required than the AJ and so easier and quicker to make and fit.

2.       Being made of wire, less visually obtrusive than couplings with etched hooks such as the Sprat & Winkle or the latest version of Martin Goodall’s Burford coupling.

3.       Cheap to make like the AJ, all parts being hand-made of wire.

4.       More robust in use than the AJ; some distortion does not make them unusable.

5.       If you are used to AJs, the similarities mean you probably already have the jigs to help make the hooks. Indeed I discovered that some wagons with unmodified AJ hooks coupled and uncoupled OK to Imprecise loops.

The disadvantages are:

1.       Having loops as well as hooks means the Imprecise is more visible than the AJ.

2.       Having hooks and loops at both ends of wagons means that to uncouple, both hooks must be depressed more or less simultaneously. This means droppers should preferably be forward of the buffer beams and maybe a longer uncoupling magnet i.e. lengthwise along the track, will be more efficient than a compact one.

3.       Manual uncoupling is a real pain if hooks and loops are at both ends of wagons. The hooks and loops entwine inextricably so a derailment becomes a major disaster! Anyone of advanced years who toyed with Hornby O gauge clockwork trains will know what I mean…. Whereas wagons with AJs can be angled down at one end and just be lifted up off the track. (This was a major advantage of the Peco Simplex/HD coupling over Tri-ang’s tension lock).

4.       I had trouble getting the delayed uncoupling feature to work. I confess that I had more trouble fitting the extra bit of wire to the hook and even more getting it in the right place (a home-made jig is recommended)! From my resulting limited test, I doubt that delayed uncoupling will work reliably if the train is moving and the usual compact magnet is used; I suspect the train might have to stop over the uncoupler first to ensure both hooks disengage. (Note the delay feature only applies to propelled trains, as it does for any other couplings). My sole successfully soldered sample duly fell off in later testing (under duress), due no doubt to my lousy workmanship.

5.       Fitting movable hooks on small tank engines is impossible in many cases. The obvious solution is to fit loops only to both ends of such locos but that requires all wagons having hooks at both ends. In contrast it is possible to fit (short-shafted) fixed AJ hooks to locos without affecting operation.

 

A possible solution to some of the issues above (1-3) is to fit the loops and hooks at opposite ends of wagons only, so they become handed couplings, like Dinghams. But this has repercussions:

1.       Any loco that engages in shunting must have a movable hook fitted at one end. In the case of my Hornby Adams Radial or Dapol B4 this is just impossible without building a new chassis. Tender locos are mostly easy (fitted to the tender) but there will be a tendency for them all to face one way!

2.       The delayed uncoupling feature will only work in one direction.

 

Annoyingly the Hornby Adams Radial is currently my most reliable slow-runner and negotiator of my bumpy yard track. I am extremely reluctant to moth-ball or re-chassis it for the sake of the couplings. So I will look at other couplings first.

 

I have tried out AJs, AAJs (Vincent de Bode’s variation -see MRJ123), AAJs with a wider hook, Winterleys (fantastic operation-wise but bulky at the hook end) and now the Imprecise. If I were to adopt the Imprecise, I would end up with handed stock. If I adopted the Dingham, that is also handed but the uncoupling delay feature is likely to be much more reliable than I could manage or make with the Imprecise. A disadvantage of the Dingham is that it apparently does not like curves of less than 48”. A variation is available, the Flippem (from PreGrouping Railways), which copes with much tighter radii and that will be the subject of my next trial.

 

Who knows? I may end up reverting to the Imprecise (so a sophisticated pivoted hook for the Adams Radial? Or restrict it to passenger duties?) or AJs.

I also have some B&Bs to test……

More trials……and more tribulation!

 

[John CutlerParticipant]

It occurs to me that not many members have access to Iain Rice’s Cameo Layouts book or have seen/noticed these couplings on Hepton Wharf. I cannot reproduce Ian’s drawings due to copyright but here is an explanatory diagram (I am afraid it is not up to Ian’s draughtsmanship standards).

I actually tested a variation on this coupling using Vincent de Bode’s ideas. Unfortunately I dismantled the test couplings from their host wagons and loco before realising that photos might have been useful. Sorry about that.

Anyway here is a comparison diagram of the variation.

I hope this might help anyone looking to experiment.

 

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