I originally wrote about this several years ago but since the topic has come up again on a forum I’m going to take a little look back at my thoughts on couplings.
There are 2 schools of thought on the issue of coupling trains together. Something that looks like the real thing, or something that can work automatically. The downsides of these are that the real thing type can be fiddly (and the closer you get to dead scale the more fiddly it gets) and the often bemoaned ‘hand of god’ that seems to be wheeled out as a regular complaint by some forum go-ers. The automatic type doesn’t look like the real thing (unless you are doing some sort of buckeye type prototype) and many of them require fixed magnets and an odd ‘shuffle’ to be performed by the driver to uncouple. How this shuffle looks any better than the hand of god I don’t really know and to my mind its better to credit your viewer with the ability to suspend their disbelief for a moment while you uncouple a vehicle than for said vehicle to look wrong all of the time!
Problem is with New Street I don’t have much choice. Loco’s will need to be changed and all that overhead along with a shopping centre means that a manual hook isn’t going be in any way practical! So automatic it will have to be and as only certain rakes will need to be uncoupled some sort of DCC on board solution seemed the obvious answer
Proof of concept. The coupling of choice being the Dingham coupling which will couple to a Smiths hook (not automatically mind you), By fitting these to coaches that have gangways they can be hidden as much as possible and there’s no requirement for a weird coupling on the loco. As supplied the Dingham has a steel dropper that when passing over a magnet is pulled down to raise the loop. By fitting a magnet instead and using an opposing magnet the loop can be raised from inside the vehicle.
By salvaging an electro-magnet from a cheap relay and wiring it to a DCC decoder this process can be simply automated. with no power the loop sits in its normal position.
But when power is supplied via a decoder function the loop is raised and coupling/uncoupling can be done. It’s all quite simple really!
Hi Jim,
Brilliant! I might have a bash at that. Where might I get those cheap relays please?
Cheers,
Tim
Hi Tim
I used one of these, http://www.maplin.co.uk/p/5a-12v-dc-dpdt-interface-relay-n31aw
Jim, you mention about the loco having to shuffle so as to uncouple. This is just like the real thing! As a diesel traction trainee on a well known railway in North Yorkshire, I often get to go in between and uncouple the loco. If the driver is good, then you sometimes get away with slackening the screw coupler. Otherwise, it is a case of putting the vac bag onto the loco dummy, so the loco can move, then climbing out while the driver squeezes the buffers. So – a shuffle!!
The only problem is that at my age I am too old for all of this climbing in and out nonsense…..
All the best,
Eddie
New street had a distinctive technique which I’ve not seen elsewhere (I’ve not looked though). The buffers seemed to have been compressed already in stopping so they just uncoupled the loco. Certainly no in – out – in for the shunters as you describe (perhaps the timescales involved didn’t allow it?)
The coupling up was something I’ve not seen modelled either. Locos would tend to stop short, probably about 10 feet or so, then creep up to the train.
The automatic coupling shuffle more often than not involves shuffling the whole train back and forth over an electro magnet until the couplings release. Again nothing like the squeeze you describe. Unless you were able to actually brake the train I’m not sure you could do it in 4mm scale could you?