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I model in HO, and for the dedicated cab units (like an EMD F7 or Alco FA), I have been using Miniatronics 2-conductor connectors to pass the right and left rail power from all wheels to all DCC decoders.  It helps immensely in reducing stalls on track, because now (in the case of the B&LE A-B-A lash-up) there are 12 wheels on each rail picking up power for the three decoders.  The Miniatronics connector can easily be passed through the doorways of the units without being visible.

However, for the hood units (like SD-9s and GP-7s or these two sample DL-600bs), this jumper looks way too large, and is difficult to keep out of the way.  The recent post on airhoses with magnets got me to thinking that one might be able to hook up a jumper that looks like a real MU cable, albeit without the gladhands, to pass power between units.  In fact, if done with "MU cables" for the right and left rails, it would alleviate the need to track polarity based on the physical direction each loco is pointing.

Anyway... here is the Miniatronics cable applied to the Alco DL600-b models.  It is a little too obvious for my liking, and a pain to stuff the plug up safely under the pilot of the one loco.  Given the installation, these two are captive to one another from here on out.  So a better way is being sought.

Interesting problem

Milt,

Prototype info (in case you or anyone else might not know):

MU hoses do not cross from one side to the other.  Instead, there are duplicate sets on each side, and only one set (actually, one of each hose  -I have mixed left & right before) needs to be connected to work.  MU cables do cross from one side to the other, above the couplers.  Each unit typically has a cable on each end, and three receptacles - two dummy and one live.  One cable must run from live to live, with the other cable secured in the dummy receptacles on one unit.

Also, just to pic a nit, the train line hose crosses in the opposite direction from your wires.  On a VERY few locomotives and cars, I have seen the train line come out on the left side of the coupler, but in 99.99% of the cases it's on the right side.

While I haven't done it (steam locos don't have MU connections!), I might try one of two things:

1. Make up a set of MU "hoses" with plugs on each end.  I'm thinking a small 3 pin header, with pins on each end and wires between.  Cut out a portion of the end plate of each unit to allow a recessed 3 pin receptacle where the MU hoses should go.  Also make up some dummy plugs with MU hose details.  Whenever you couple two locomotives, remove the dummy MU hoses and add the jumper on one side.  Only two wires would be needed, of course, but three would look more prototypical.
2. Use a combination of the train line and MU cables, again fitting into receptacles on the engines.  I don't know if there's a way to make the automatic air hoses pass electricity, but if so that would take care of one half of the circuit.

No a nit - just accuracy

You are right, Ken, and my lack of precision could send someone in the wrong direction.  What I am thinking is an MU hose being the connector.  A hose on the right would connect to the other loco's same-side MU hose - that is, not crossing over like the brake hoses do.  I haven't added brake hoses yet, pending the jumper solution.

My thought was to have altered 2 MU hose receptacles on the ends of the diesels - presumably the outermost hose on either side of the coupler, for ease of access.  Then manually (tweezers) add a short loop of wire, plugging in each end to one loco and the other, giving, I hope, a prototypical look of the sagging MU hose.  Inside the loco, the receptacle would be wired to that side's pick-up (rail) circuit. 

This way head-to-tail or head-to-head loco orientation wouldn't matter.

I think the MU cable would be inordinately difficult to connect, and to scale appropriately, but don't let that stop anyone from dreaming up solutions.

MU hose jumpers

That's why I suggested making a single multiple-wire MU "hose" jumper.  Assuming that there is a socket on each side (yeah, 4 per loco, which is a lot of work) then you'd only have to connect one on either side.  The larger size would make it a little easier to handle the jumper, as would only having one per coupling to make.  The dummy MU hoses were just a suggestion to hide the rather large hole needed to make the jumper work practically.

What about the chains?

I just had a different idea..  Every time I couple two locomotives together, I connect the chains on the handrails.  You could use the chains to carry electricity from one unit to the other.  Put a hook on one side, and solder the chain to the handrails on the other.  Just hang the chain between the units when you couple them.  Depending on the chain, it might not make a perfect connection.  But given that it's just making a backup connection anyway, less than 100% reliability might be acceptable.

The only problem I can see would be that you couldn't hang the chain across the handrails on an uncoupled unit, since it could cause a short.  Perhaps a second, insulated hook could be added for the purpose.

Old MR has one solution

Dear Milt,

Can't recall exactly which MR issue it was (mid/late 90s), but I do recall seeing an article where a modeller cut apart DIL IC sockets, the type with round "machine pin" holes. This gave up-to 2x 4-pin connectors per 8-pin DIL socket.

These were mounted at/around frame level on the pilots, either side of the coupler.

The hoses were lengths of NWSL "superflex" wire, with short pieces of bent brass wire soldered to each end as the "plug-in-pin". (Requires manufacturing of hose-sets by the modeller, but result in a better physical appearance).

Result was a set of relatively fine-appearance hoses,
which worked great in "semi-permenantly-coupled" mode,
(needed tweezers for un/coupling, so could be come tedious if a regular occurance),
has more than enough "flex" to handle typical curves and flexing without breaking, or imparting too much "pushback" force on the locos themselves,
and gave up-to 8 (eight!) "wires" between each loco.

That's potentially
- L Rail
- L Motor
- Headlight +
- Speaker A

Coupler

- Speaker B
- Headlight -
- R Motor
- R Rail

Edit Sept 1992 MR, Page 106 article by Dale Oswald is worth a look...

http://www.pedalpartsplus.com/mm5/graphics/00000001/8%20pin%20socket.jpg

Happy Modelling,
Aim to Improve,
Prof Klyzlr

Chains

Ken, nice idea, but think of all the contact points on those links. There are enough problems just from the track to wheels to contact wipers and that's only 3 spots.

Bernd

IC Sockets

That's what I use. Very easy to hide that wires and it works a charm.

Bernd

IC Sockets II

Found a picture of a Radio Controled 2-6-0 steam engine I did.

Bernd