Common return wiring

[Eric]

I'm building a small layout (1.2 x 0.6m) with my two sons (7 & 9) consisting of a single track run round with passing loop; a small yard with a headshunt and a couple of sidings; and a branch up an incline to a seperate station with a couple of sidings. I've acquired a job lot of centre off double throw switches which I'm planning on using for track feeds, splitting the layout up into several isolated sections which I can then wire up to two seperate controllers (once I have aquired a second controller!) using common return wiring so that we can control any particular section of track from either controler at a flick of a switch. I also plan on fitting SEEP point motors controled using probe & stud, using their built in switches to power the frogs. Because of the size of the layout, we are unlikely to ever want to have more than two engines in motion at any one time, but having the option of two on the go will hopefully help with brotherly harmony!

Does this sound do-able, are there any pitfalls I should look out for?

I've never tried anything like this before, and I must admit that I do not really fully understand how common return actually works (I know that each controller needs to have its own transformer and that you need to designate one rail as the common return.) With this project, I am wedded to the idea of DC rather than getting into DCC because I see it as having more scope for learning about circuits for the boys. There is plenty of time to explore DCC at a later date.

Anyway any warnings about pitfalls greatfully recieved!
Cheers Eric (& Oskar & Ruben)


 

[JulienW]

Certainly having two controllers on one layout is possible, as I have done this with Latham's Brewery, though this is not wired on a common return which makes life complicated when it comes to stringing to the control panel!

Essentially you will need to decide which rail is to be the common return.  For each section one rail will be common, the other rail will be wired the center contact of the switch with the other two contact being fed from the output of the two controllers so that each section can be driven by either of the 2 controllers according to the position of the switch.  Also, each of te controllers needs a separate transformer, but some (Gaugemaster for example) sell transformers with two separate coils and it is possible to wire a system with one controller per coil.

One note of caution though is that depending on your track layout you may not be able to get away with only gapping the one rail all the ime (I recall that passing loops are a problem) as not doing this correctly means that you will get electrical shorts.  It is also worth having a common return feed to each section (ie. two wires) rather han just the one (switched feed) and rely on the common rail to do the job.

Finally, a bit of psychology.  Whilst using the twin controller system you suggest will allow your boys to have a moving train each, they can still argue over which sections of track are switched to 'their' controller! Whilst there have not been arguments (or worse) between operators there have been problems on Latham's with some movements needing a section switched to the other controller.  This is often because someone has forgotten to switch it back, but perhaps a 7 and 9 year old may not be so understanding...

I know that you have said that you would rather not go down the DCC route yet, but with DCC your boys can have a loco each and even drive it on the same bit of track reguardless of any section switches.  The circuits to feed the AC current are much the same (multiple feeds on both rails, good connections, etc) as those for DC and you can still get shotrs at loops if the rails are not gapped properly.  It might also be easier to start with DCC now, particularly with spreading the cost of chipping locos, rather than do so in a couple of year's time when your collection of locos will need to be done in one hit.  Equally, DCC is more like driving real trains and with the potential for real collisions causing real damage to models they have built (and the subsiquent investigaion by the Parental Railway Inspectorate) may learn that cooperation and comprimise is better than charging on without any heed to the consiquences of their actions.

Alternatively they may find that the mini rail crashes are more fun.  In that case, they can definitely make their own 'battle trains'!

[B.Meldon]

Common return wiring is the same basic concept as used in virtually all electrical circuitry. It will remove the need for just under half the wires but very careful planning is required when it comes to isolating sections and trailing points. That is points with a power source on the left or right hand switched tracks.
The

[JulienW]

I would also suggest that the section switches have a centre off position.

Brian Meldon

Absolutely, as not doing so will mean that you can not isolate any of the sections...

[Eric]

Thanks for all this. The switches that I have are definitely centre off ones. I'll post some photos of work in progress in the layouts section in the next few days.
The battle trains concept raised a smile - but one for a later day methinks....
Cheers
Eric