Oxfordshire & West Berks (OWBAG) Meeting Tues 12th July

[ianpenberth]

At The Plough Inn, High Street, Long Wittenham, OX14 4QB, on Tuesday 12th July from 19:30 onwards.

Our room is booked from 19:30 - 21:30. The pub will be open beforehand and serving meals and the usual refreshments. Please contact the pub directly to let them know you're coming if you intend to eat - 01865 407738.

All welcome, whether local or just passing through. Feel free to bring along something you have built or are working on.

[ianpenberth]

Another pleasant get-together last Tuesday with an interesting range of subjects under discussion.

Rob delved back into the past again and showed a part completed model of GWR 4-6-0 No 36, scratchbuilt in brass by David Simmonite.

Robin brought along a Bachmann C Class 0-6-0 which he'd converted using an 'Easichas' kit, finding it not quite so 'easi' as all that. Its Railtec transfers gave rise to positive comments, and a discussion on transfers generally.

Mike demonstrated his method of drilling axial keyways to prevent wheels rotating on axles and, also looking back into a shady past, showed a rather uniquely designed sprung chassis for a GWR mogul which didn't make it into production for Masokits.

Martin described a Railmotor resurrection project he's working on as a diversion from scenic work on Burford.

Gareth, as an experienced modeller just getting going in P4, showed a couple of AJ-fitted wagons and described his continuing tribulations with trying to get them to uncouple reliably. The house was split on whether AJs are a good idea or not, but Gareth has promised to keep trying.

Ian bought along the bogies from a Bachmann single unit railcar (Class 121) - he'd started out on a P4 conversion using Branchlines wheels and found that the 121, and 117s, are not quite the same as the earlier Bachmann DMUs. More to follow.

Next meeting at the same time and place, second Tuesday again, August 9th.

[Chris Pendlenton]

It is indeed trickier to get AJs to uncouple reliably than just to couple. I expended a great deal of effort on trying to shine a light on the issues involved in my article "Winning with Jacksons" in MRJ 223. It is largely about simple key settings and dimensions closely following Alex Jackson's prescriptions though with some enhancements of execution. Too many folk I suspect just approximate and ignore the vital interactions of these settings. I have a fleet of @150 vehicles so fitted and within limitations of curvature, setting errors, handling damage etc they work well .I have yet to hear from the wider world if my article was seen as helpful.

Chris Pendlenton

[bécasse]

One potential (and possibly unnoticed) problem with uncoupling AJCs using electromagnets is that DC current derived from AC using rectifiers still has a wave format and, if an AJ coupling wire is a particular length, this wave format can induce harmonics in it. That is, it will vibrate up and down at high speed, typically a multiple of 100 cps, something that it is not particularly easy to see.

Half a century ago we had one such coupling on Bembridge and it took some days of operation (or rather mis-operation) to realise what the problem was. It is a long while ago now but I think we cured the problem by damping the wire by fastening one of those split round fishing weights on it, well back towards its point of fixation. Obviously using a pure DC source would solve that problem too.

Otherwise we had few problems with AJCs and they were certainly very satisfying to use in front of a substantial audience.

[GarethSmith]

Chris - I can confirm that your MRJ article was/is very helpful. I was pointed towards it in a forum post and was able to buy a copy of that back issue of MRJ. I have only tried a handful of vehicles but found rather unreliable uncoupling. On reviewing I found that some of what I had done was rather out of spec. Of course the significance of what is written in your article and other places is sometimes (often?) only realized after trying something yourself.

I have replaced the simple vertical dropper I was trying with your clip-on loop and that has given much more consistent pull-down of the coupling. A consequence was the need to drop the voltage applied to the DG electromagnets (from Wizard Models) I have used. The 12v I applied is now too strong and about 5v works better.

I also found that some of my coupling hooks had the tail too short. This sometimes caused the coupling to re-engage after the one hook was released from the magnet and lifted again. In essence it was making the coupling more sensitive to mis-alignment. The Turner jig does a good job of producing a coupling hook but I have slightly increased the length of wire folded back on itself in the initial bend and now check the lengths of the nose and tail. For my last batch of hooks I used straight wire - which was produced by hanging one of the guitar strings up with a small bulldog clip on the end and leaving it for some time (in fact some months before I got round to using it). I posted on the forum something about the angles in the hook a while back. This may not have been of any use to anyone else, but I am confident I can reliaby produce a good hook. What I still have to work on is making sure I have the position (including hook orientation) and spinginess (uplift) correct. This latter requires care with the pivoted mount.

Gareth Smith

[zebedeesknees]

Obviously using a pure DC source would solve that problem too.

A battery ?!!!?