Making your own DCC plugs and connectors

With a lot of DCC installations, particularly on older locomotives, the wires and plugs need to be modified in order to make them fit.  This often creates weak wire joints, especially in areas where the wires can move, so I wanted to find a way to protect these areas.

Recently I have been installing single DCC decoders in multiple locomotive consists; below is a set of Con-Cor Alco PA/PB units.


Both the PA (Cab units) are powered and the PB (Cabless booster) is a dummy.  Inside the PB I have installed a Digitrax sound decoder with the wires running through the corridor connections to the two motors, similar to the Con-Cor EMD E7 DCC installation from my previous post.

I decided to add connectors into the system so I could separate the units if required, which also made it easier to trace any faults such as short circuits whilst testing the units.  Below is an image of the wire harness before it was fitted into the PB unit.  The bit in the middle is a socket for the DCC decoder with a homemade plug fitted into it which joins all the wires together for DC operation and testing.

PA Wire Harnes

Although the wires are soldered to the pins, they are still delicate and given the limited number of strands, individually the wires could easily be broken off.  To prevent this from happening, after I had tested the harness I painted the soldered connections and wire ends with a PVA glue. I used a cheap PVA designed for school projects from a local art shop. The PVA went on well and as it went tacky it held in all the pockets between the wires.

PVA Socket

I also added a second coat a few hours later to ensure I had good coverage.  Once dried it went clear and held all the wires in place, plus it gave them a coating to prevent any shorting.  I also did the same thing with the plug ends.

PVA Plug

Once everything is assembled the PA units can be separated from the PB unit by simply pulling the plug without risking damage to the soldered wires at their weakest point.

Con-Co PA-PB with Sound

Another advantage of this is a second PB dummy unit (or possibly a powered unit) could be added into the consist as long as it had the same wires and plugs running through it.

Here is as short video of the D&RGW Prospector pulling into Solent Summit station.

Sadly the sound decoder speaker is not as loud as the noise from the older Con-Cor motors which drowned it out, but that is a challenge for another post.

Cost-effective DCC installs for consisted locomotives

With Digital Command Control becoming ever more popular more clubs and home layouts are switching to it, but it can be quite costly to convert all your locomotives to DCC, so I’ve been looking at ways to make this cheaper.

A lot of US outline trains run with several powered units forming one consist and using one DCC decoder for the whole consist is my plan.   A good example of this is the set of powered EMD E7 units below.


These models, made by Con-Cor, will always be run as a set and although the middle unit is a dummy locomotive the other two would normally both require a DCC decoder.  This is because there’s no electrical connection between the three units and, despite both being good runners, the two powered units run at different speeds.   This is a problem because one locomotive will always be pushing or pulling harder than the other.

Below is a video of the two powered units (without their shells) on a DC test track.

Clearly you can see that the nearest locomotive runs much faster than the other.  This is because the motor in the nearest locomotive has a much lower starting voltage.  If both locomotives had their own DDC decoder fitted they could be speed matched.  This is done by adjusting the DCC configuration variables using a DDC controller or a system plugged into a computer.  Doing this effectively alters the starting voltage of one or both of the locomotives to make them run at the same speed.  The drawback of this is that you would still need two decoders, an understanding of how to do this, and, if the train is run on a DC layout, the problem would still be there as the CV settings do not have any affect under DC control.

An alternative is to increase the starting voltage of the faster locomotive motor.  An easy way to do this is to add some resistance into the electrical circuit, but this can cause other problems as resisters do this by turning the unwanted power into heat.

A better way is to add a diode into one of the motor feeds.  A diode works by only allowing DC power to flow in one direction whilst causing about a 1.5 volt drop.  Of course this would mean the motor could only run in one direction so a second diode will also need to be used at the same location but positioned in the other direction.  This meas that the power going to the motor will always pass through a diode irrelevant of the direction of the locomotive but with a reduced voltage.

Depending on the speed difference you have between the two locomotives, you may need to use more diodes to give a bigger voltage drop.  For this particular pair of locomotives three diodes, giving a voltage drop of 4.5v, were required in order to make the two motors run at the same speeds.  There is room between the main chassis and the shell so I constructed the diode circuit to fit in this space using 6 diodes; three for each direction.

Diodes E7 Chassis E7 Chassis With Diodes

E7 Chassis Ready For Shell

With the diode circuit fitted into one of the motor feeds you can see the difference in this video, also on a DC test track.

Now the two power units run at the same speed I can use one DCC decoder to power both motors.  It is important to select a decoder that has a maximum current capacity that is more than the combined current draw of the two motors.  This can easy be checked with an amp meter.  With the shell removed from your locomotive, connect a DC controller to your locomotive, passing one of the motor feeds through the amp meter.  Then using your fingers, prevent the motor from turning and turn on the controller.  The motor will try to turn but will stall as you have it clamped in your fingers, and the amp meter will measure the maximum current drawn by the motor.  Do this with both motors and add the values together.  If the combined value is less that the maximum current capacity of your chosen decoder then it will be ok.

As there’s lots of space inside the dummy unit the DCC decoder is installed in there.  I used a Digitrax decoder and ran the wires through the corridor connections.  This causes a small problem in that the three locomotives are now permanently fixed together by wires; should they come uncoupled it could put too much strain on the wires and cause damage.  To solve this the couplings have been replaced with 3D printed permanent couplings.

Fixed Coupling 1

These have the same ends as Rapido-style couplings and are a direct replacement using the same spring.  A flexible corridor connection was also made using black foam and corrugated card.

E7 Coupling 1 E7 Coupling 2

The chassis for the dummy unit is actually a different make, Life-Like, but this is a bonus because it has power pickup on the trucks.  All three units have power pickups that can now be connected together which greatly improves the performance of the combined locomotives.  So this three unit EMD E7 set is now DCC converted using only one DCC decoder.  Here they are pulling ‘The City Of Los Angeles’ on the GAMRG’s layout at the 2014 NMRA winter meet in Benson, UK.

Hopefully this will save you money on upgrading your locomotives to DCC, which can become incredibly costly given some size layouts and train collections. I’ve been experimenting in a similar way with a sound decoder; if I make any notable progress I’ll post it here.

Benson Winter Meet 2014 – NMRA (BR)

On the weekend I was at the National Model Railroad Association (British Region)’s winter meet and model railroad exhibition in Benson, Oxfordshire, UK and I wanted to share some of the layouts with you.

This is the first exhibition on the calendar for the NMRA (BR) and it was also my first visit. The show is a one day show only, but after talking to several of the regulars it appears to be a very popular show and this year was no exception despite the bad weather and flooding we have been having over the last week.

I wasn’t just visiting the exhibition, I was there with my club, the Gosport American Model Railroad Group, and we had brought part of our modular layout, Solent Summit, along for the day.  So, in between running trains and chatting to the public, I had some time to look around a few of the other layouts and stalls.

NMRA (BR) Benson 2014 Overall

The hall in Benson was a nice size and was filled with layouts and stalls and although there was also more upstairs I didn’t make it that far as I had trains to run!

Here are some of the layouts that were at the exhibition;

Red Hook Bay 1

This is a beautifully detailed HO layout based in Maine, USA in a fictitious setting.

Red Hook Bay 2

Everywhere you look there is fantastic detail and even though I have seen it before I keep spotting new things such as the crab nets on the dock.

Red Hook Bay 3

The layout consists of a small station and yard with a train ferry entrance.

Red Hook Bay 4

For me, the best parts of this layout are the buildings and scenery.

Red Hook Bay 5 Red Hook Bay 6

In particular I loved the lighthouse and the detailing of the action around it around it.

Red Hook Bay 8

Sankei 1

This is a Z sale layout by Peter McConnell. The layout is a city scene  set in Japan with an electrified two-track main line running round to a storage yard at the rear.  In the front there’s a station and yard scene. A branch line runs out from the station to the yard which is not electrified.

Sankei 4

The station has three platforms, the nearest two being an island platform on the main line.

Sankei 2

Leaving the station the main line and branch run parallel around to the yard.

Sankei 3

I’ve never worked in Z scale so I am often impressed by the level of detail, as I was with this one. The trains ran very smoothly and at a good scale speed.

Sankei 5

Black Diamonds

This N scale layout is a modular layout that can be assembled in a variety of ways, from my understanding this was only a small part of the overall layout.  All the modules here have been laid with Atlas code 55 track.  The layout is in a dog bone configuration with a double track main line and a yard at each end.  The layout is setup for running long trains through large open spaces.

Black Diamonds 3 Black Diamonds 5 Black Diamonds 6 Black Diamonds 7 Black Diamonds 8 Black Diamonds 11

Dawes Creek 1

Dave Dawes’s Dawes Creek is an N scale layout set in Australia.  It has a beautifully modeled station scene with a small yard.  Both ends of the main line run around to the rear where there is a staging yard.

Dawes Creek 2 Dawes Creek 3 Dawes Creek 5 Dawes Creek 7

For me the highlight of this layout were the locomotives an rolling stock, in particular loco no. B64 which has the look of an double ended American F unit.  All the locomotive shells are resin casts by Aust-N-Rail and they are fitted onto American prototype chassis.

Dawes Creek 9

Dawes Creek 8   Dawes Creek 4

Dave has more about his layout on his website

Kathy Millatt

Kathy is the Atlantic director of the NMRA and she had brought along part of her modular On3 (O scale narrow gauge 3 foot) layout to do scenery demonstrations throughout the day.

Kathy Millett 3

I was particularly impressed with the track work on the dual gauge section: this was all hand built.

Kathy Millett 2 Kathy Millett 1

N scale in Switzerland

This great little N scale layout, which I forgot to get the name of, is set in the Swiss mountains covered in snow.  There are three loops running around the layout and a scene on the high line of a train wreck due to an avalanche.

N scale in Switzerland 1 N scale in Switzerland 2

Solent Summit

So at last we come to the layout my club brought.  Solent Summit is an N scale modular layout based on a oNe track system; this means all the modules conform to the same set of standards such as the main line must be 4″ from the front.  Therefore the modules all work together in a variety of configurations. At this meet in Benson we brought fourteen modules, which is about a third of the modules we currently have finished. The overall layout took the form of an oval and we will pick it up in the yard;

Benson 2014 1 Start Yard

This yard has six through lines exiting onto a single main line around the bend.

Benson 2014 1 Yard Exit

After rounding the bend the line approaches tunnel 41.

Benson 2014 2 First Bend Benson 2014 3 Tunnel 41

Emerging from tunnel 41 the line rounds the bend next to Ted’s Farm.

Benson 2014 4 tunnel 41 Exit Benson 2014 5 Teds Farm

After passing Ted’s farm the line enters Solent Summit.  Here the main line carries on through the middle, with a station line on the inside and a passing line on the outside.

Benson 2014 6 Enter Solent Summit

In the middle of Solent Summit there is a second, shorter passing loop.

Benson 2014 7 Enter Solent Summit Benson 2014 9 At Solent Summit Benson 2014 9 Logs At Solent Summit Benson 2014 9 Solent Summit

Leaving Solent Summit, the line returns to a single main line and runs past the coal mine.

Benson 2014 10 Leaving Solent Summit Benson 2014 11 Leaving Solent Summit Benson 2014 12 Leaving Solent Summit

The coal mine has three lines, the near side track is the main line which runs through a tunnel.

Benson 2014 14 Entering Coal Mine Benson 2014 13 Entering Coal Mine

Emerging from the tunnel the line crosses Hells Glen on a steel trestle and enters another tunnel.

Benson 2014 18 Hells Glen Trestle

Benson 2014 19 Hells Glen Trestle

Benson 2014 16 Hells Glen Trestle Benson 2014 17 Hells Glen Trestle

Emerging from the second tunnel the line passes the power station where the main line is again the near side track.  The two lines going into the power station are also the first two lines going into the coal mine. They run behind Hells Glen out of sight.

Benson 2014 20 Power Station Benson 2014 21 Power Station Leaving the power station the line rounds the bend and returns to the yard.

Benson 2014 22 Leaving Power Station

So that’s a taster of the Benson NMRA (BR) winter meet. There’s a lot to see at this show, and plenty of stalls, so it’s definitely one for my calendar next year, and I hope to see some more new faces there.

Completing the DD35 Set

Happy New Year!

With all the New Year festivities I haven’t gotten round to painting the new log cars, so for this post I will show you the new DD35 dummy unit which was made available just before Christmas.

When I set out to design and make the DD35 I always intended to have two, as with EMD’s original concept, top and tailed by a GP35 or something similar.  However, as is often the case with model railroading, having all the locos powered in a 4 loco lash-up is overkill, not to mention expensive.  So my second DD35 is to be a dummy unit.

The shell for the powered DD35 was designed to fit over the Bachmann DD40AX chassis so I wanted to design a printable chassis that could be used with the same shell.  This chassis would also incorporate the fuel tank, which was separate on the powered unit, giving it rigidity.

DD35 Chassis 1

It would have been easy to draw a large flat plate  which would have made it incredibly strong, but also very expensive due to the large amount of material it would need to print it. The challenge was to design the chassis so that it is strong but also economical on material as I intended to print it in the FUD material along with a shell and trucks.

DD35 Chassis 2

I decided to draw the trucks in the style used on the DD35 rather than copying the DD40AX.  Although this would mean the trucks would look different from the ones on my powered unit I decided it would be worth it because it would be easy to change the truck sides on the powered unit at a later stage.  I originally intended to use Micro Trains plastic wheels with this unit but on reflection I decided to go with Fox Vally 36″ metal wheels; this was because I wanted to add plenty of weight to the unit to withstand locomotives pulling at one end and pushing at the other and figured that metal wheels would run a lot better with this.

DD35 Truck 1

As with Bachmann’s DD40AX the steps and couplings are part of the truck, totally non prototypical, but as that was the power chassis I have used, the dummy would have to be the same to look right.  The coupler will be a Micro Trains body mount coupler and a pocket will be provided along with a pilot hole for the screw.  The bolster pin will also be printed and is based on a typical freight car pin.

DD35 chassis 3

With the chassis and trucks ready it was time to order the print.  The chassis came out very well and was very strong, and incorporating the fuel tank definitely added to the strength.

EMD DD35 Chassis Kit

The shell which was printed with the chassis is exactly the same as a powered unit. Here you can see it after I had cut out the handrails.

EMD DD35 Dummy Kit

All the parts fitted together perfectly. Next it was time to paint them.

EMD DD35 Dummy

The painting was done by Bob Norris and went very well, the only issue he had was with the trucks.  Due to the FUD material being a bit thin around the neck, which supports the coupling, the end of the truck with the ladders drooped.

DD35 Truck 2

This was remedied by installing a strip of metal under the neck of the truck thereby strengthening it.

DD35 Truck 3

This has now also been corrected in the 3D model by adding a lot more material in that area, removing the need for a metal plate.  With the correction made it was time for testing and the unit ran very well. After a lap of the layout the FW wheels freed up and spun freely. I think there was still some wax residue it the wheel pocket.

Here is the painted DD35 dummy unit. DD35 Dummy

And again with the powered unit, the dummy still needs to be weathered.

DD35s 1

And with a cab unit.

DD35s 2

And finally in a 4 loco lash-up headed by a U50.

DD35s and U50

These units will be going to the NMRA model show this weekend at Benson, in the UK, working hard pulling trains on the GAMRG club layout. If you’re in the area drop in and come and have a chat.