John Cutler
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!