The N gauge project is firmly analogue DC. This is because the core of the stock has been sitting in a drawer for nearly 15 years and none of the four locos concerned are "plug and play" DCC ready . Indeed the Farish 04 isn't DCC Ready at all and would be a real pig to convert. (I understand current production of the model will take a decoder)

Electrical wiring was long one of my blind spots. The wiring of Tramlink (Kent) consisted of a few bits of bell-wire and an on/off switch. Points were dead-frog. The Boxfile marked a huge step forward: live-frog points with - gasp - point motors . But it was and is extremely small. The club project launched me into a supporting -player involvement in DCC which bore fruit in Blacklade, which has a fairly sophisticated DCC and lighting installation for what is a small terminus to fiddle yard layout.

So Mercia Wagon Repair is the first time I've attempted conventional analogue DC wiring on any real scale. There will be six live-frog points - the Boxfile has just three. There will be six electrical sections and two isolating sections - the Boxfile is in practice one section. There probably won't be any signals - the real thing wouldn't have any - but there might be a little lighting.

Tramlink (Kent)'s boards were built of 2" x 1" timber and 4mm ply. This precludes the use of stall-motor point motors like Cobalts and Tortoises. There simply isn't the frame depth to accomodate them. So point motors are by necessity solenoids - Peco and SEEP types.

There will be no control panel as such , just local switches along the front edge of the two boards . I have learned my lesson about operating positions: if the layout is operated from the front, the switches had better be at the front, conveniently to hand. There is no reason at all to operate from the back with the backscene in the way. This is essentially a shunting layout intended for interesting operation at home. It is portable enough - the whole thing will box up as a unit 3' x 11" x 12"  - so theoretically it could be exhibited . But the last two and a half years have altered the dynamics of the hobby considerably. The exhibition circuit is currently a shadow of what it was three years ago, the next 18 months may be somewhat restrictive, and it is getting difficult to see things going back more or less to where we were in February 2020 in the foreseeable future. In this climate , building a new layout principally for exhibition starts to feel like an act of denial. Put another way - this year I reckon there will be just 3 events within 30 miles of me involving layouts from outside the organising club.

Mercia Wagon Repair is therefore going to be an extremely conventional analogue DC layout. Control gear is borrowed from the Boxfile : a Gaugemaster 100M controller and this:   Hanging By a Thread  .  The inter-board connector with its DIN plugs is also borrowed from the Boxfile.  DIN sockets had already been bought for the intended re-wiring of Tramlink (Kent) and can therefore finally be used. (Tramlink was run from a little Gaugemaster Combi , which also has a 16V AC output, so in theory the four input wires from the Black Box could be connected to that. I haven't seen any need to do so yet as the Gaugemaster 100M is a reliable unit, but it might be worth experimenting with its use on the Boxfile since the Combi takes up less space and might not need the use of an extension block to reach the wall socket)

Only one problem there - taking the high current power to the point motors from an external CDU means a comparatively long length of wire to reach the point motors. This is especially the case with the satellite board, where the current would have to traverse a long DIN connector lead as well. As I had bought a new CDU without really thinking why I needed it, I decided to use it after all on the second, satellite board (the left-hand board) and avoid the issue. 

This means that I need three circuits : 12V DC track power from the controller, 16V AC high current pulse from the external CDU to the point motors on the right-hand board, and 16V AC low current continuous to power the CDU on the left-hand board and, potentially, any other accessories requiring a 16V AC supply. That could include a regulated power supply delivering 12V DC to lighting LEDs

The DIN plug from the output side of the Black Box is 6 pin, and the inter-board  DIN connector cable is 5 pin, So far, so good: the necessary number of connections are available. However you will have noticed that the external CDU was wired up with only 2 circuits (12V DC + 16V AC to/from the CDU). The first step was therefore to open up the Black Box, and add two by-pass wires from the input connector blocks of the CDU (ie the 16V AC continuous input) which were soldered to the two spare wires in the output DIN cable. While I was about it, I found out what went to each connection on the matching 6 pin DIN socket I was about to install on the layout. The equivalent socket on the Boxfile is sealed inside a building, so I had no idea what came out of each pin.

Dropper wires are 7/0.2 wire in red and brown - the electrical trader at Ally Pally didn't have any off-cut packs in black. Every piece of rail has a feed , and longer lengths of rail have two. I find soldering droppers below the rail much more difficult in N than in 4mm, and the sleepers are much more vulnerable to melting. Longer runs are in 16/0.2 or even 24/0.2 wire left over from Blacklade in order to minimise voltage drop

Here we are at an early stage of proceedings. Some bits of the wiring and connectors from Tramlink are still in place: the tag strips from the old wiring were re-used.

A hole at the back to take the DIN socket for the interboard connector is visible on the right hand board.

There are to be 3 electrical sections on each board . No section can bridge the board joint because there aren't enough connections on the connecting cable (Also DIN sockets are relatively tough and 28-way D sockets aren't and are rated for a surprisingly limited number of connections. Anyway, I had the DIN sockets and cables already.)

The usual rule "black to the back" applies to the 12V DC traction supply, though brown is the new black. All the section switching is on the brown side, so red is common throughout. Switches for the sections and point motors are mounted at the front of the boards , a small group of switches on each board. The brown patch on the right hand board reflects the fact that I left the low platform of Tramlink in place, and two layers of 4mm ply is too thick to get the switches through. So I had to chop it out with a chisel and a 16mm wood drill from below

This will show the issue. The front siding - mainline departure siding - is laid along the inner edge of the old platform . At the time this was taken the cork to ramp it to this level was still to go in. The gradient is about 1 in 75 and does not seem to cause any issues. The dots are breakthroughs from the wood drill and mark the location of the switches. The rest of the old platform surface will be covered by ballast and sceney in duie course. The complications of re-using existing boards....

And here we have two shots of the undersides of the boards , largely wired. So far I've laid the "mainline" side of the layout (loop and front siding) amounting to 4 points, 3 electrical sections and the basic electrical architecture. That amounts to about 2/3rds of the wiring.

This is the right hand board, as it currently is. One point still to go in, and also the dropper wires for the works siding fan (the 3rd section on this board). The plethora of dropper wires does eat up tag strip connections. Blue and yellow are high current 16V AC for the point motors - the heavy 24/0.2 wire used for the long runs of the AC common is obvious. The back of the layout is at the bottom. (The 16V AC low current circuit is grey/purple)

Point motors are a mix of SEEP and Peco. I already had two SEEP motors but thought I would need motors with switching for the frogs. In fact Peco code 55 short radius points have no frog switching and rely on the blades. But the medium and large radius Code 55 points are unifrog, and need a switch in live frog mode.... I bought 5 Peco point motors (nearly all "new second-hand") and five switches, but only 3 Peco motors and one switch will be used, because I don't like chopping big holes in my baseboard.

And here we have the left-hand board,  in the heat of battle.

The second point motor - a SEEP - is still to go in. The small hole it requires is visible below the packet of solder, and the ruddy great crater left by installing a Peco motor is visible to the right. The heavier 16/0.2 wire used to reach the satellite tag strips will be obvious . Using heavier wire here should minimise voltage drop : there is another 18" of interboard connector and internal wiring on the other board so this is actually quite a long run. The CDU is bottom centre and the AC common is just starting to be wired. There is an isolating section  to hold a loco at the far end of each board.

As I said - a lot of wiring for a little layout