Having spent the majority of my N scale modeling time in the American arena I have not kept up-to-date with the British N gauge modeling scene. However I’ve recently become involved with the Poole and District Model Railway Society in England who focus on British N gauge modeling and I now have the opportunity to find out what’s been going on.

The Rapido coupling has been an industry standard for more than 30 years in both N scale and N gauge and in this post I wanted to share with you some of the things that can be done to make your older British rolling stock with Rapido couplers look comparable to the new NEM coupled stock.

The majority of American N scale modelers and manufacturers have moved away from the Rapido coupling in favour of knuckle couplings from companies like Micro-Trains, formally Kadee.   British N gauge modelers and manufacturers are now also moving away from the Rapido and using NEM couplers from companies like Dapol and Graham Farish.

The classic Repido pictured below is a very simple but extremely functional coupler.  It allows trains to navigate very tight corners whilst remaining strong and reliable.

Because Arnold-Rapido, the inventors, allowed the design to be freely copied by other manufacturers it soon became the standard for the scale.  As shown above there are many variants to the design but the fundamental parts are all the same. Up until recently Rapido was the industry standard but now technology has moved on and manufacturers have started to introduce new coupling designs which look like the real thing in size and shape.  Initially the new design of couplers still used the Rapido socket and often new rolling stock would come with Rapido couplings installed with the new design coupling in the box to be installed if required.  Now a lot of manufactures only have their new style of couplers fixed to the rolling stock.  With new British stock even the socket has been updated to the new NEM standard socket although the actual Rapido coupling is still in use.

The biggest immediate difference between Rapido and NEM coupled stock is the gap between them.  Below is a photo of some British N gauge coaches made by Graham Farish,  the red GUV or mail express system coaches behind have the traditional Rapido couplers and the Pullman coaches in the front have the new NEM couplers.

There has to be some gap between the coaches to alow them to navigate corners without becoming buffer locked.  This is when the buffers on the corners of the coach touch each other and prevent the body of the coach from swinging.  With full size trains this is not an issue as the buffers are sprung allowing the buffer to compress and the coach corridor connections to touch.

My first solution is to use my fixed link couplings, pictured below. These fit into the standard Rapido socket on two coaches permanently coupling them together.

By using a shorter fixed link the gap between the coaches is reduced, as shown below.  This is ideal for connecting locomotives together, particularly if they share a DCC decoder as with my E7 DCC conversion, but it is not so good for lots of coaches.

For short trains with three coaches or less this would work well but for longer trains with, say ten coaches, it would be very hard to transport them if they were all coupled together.

My second solution is to 3D print a shorter Rapido coupling. The standard Rapido coupling has a shank length of 3.5mm as shown below.

So I re-drew the Rapido in a range of lengths decreasing by 1/2mm at a time.

Because I wanted these to be cost-effective they have been designed to be printed in the Black Strong And Flexible material offered by Shapeways.  This has three main advantages over the Frosted Ultra Detail material in that it doesn’t need cleaning on arrival, it is already black so they are ready to use right out of the packet and it’s cheaper.  The BS&F material does have a rough finish but this just helps to make them look a bit more realistic.

The first test prints have arrived from Shapeways and have already been successfully tested with Graham Farish coaches.  Although I ordered the full range of sizes all the coaches we tested worked best with the smallest coupler which has a shank length of only 1.5mm. Using a pair of these couplers, one in each coach, it reduced the gap between the coaches by 4mm which in N gauge is a lot.  Below are the same Graham Farish GOV coaches as pictured before but the pair on the left have the new 3D printed Rapido couplers installed.

The difference was considerable but a test on a corner was required to check for buffer lock.  We used one of the tightest corners on the club’s N gauge layout for the test and as you can see below it was successful.

Below is a close up on the original Rapido couplings.

And below is a close up on the new 3D printed short Rapido couplings.  You can see that the buffers don’t actually meet.

We also tested the short couplings on some Graham Farish Suburban coaches with equal success.  Again the short couplings are between the left hand pair.

And a close up of the 3D printed ones.

The 3D printed couplings still need to go through a few more tests and I have also made a few tiny improvements to the design to help with the fit into the Graham Farash coaches.  Once complete I will make them available to buy, and I will also offer them for sale in packs of 20 direct from this site.

One of the tests currently going on is looking to see which length 3D printed couplers work best with an N Gauge HST set, but that will have to wait for another post.

Over the years I have acquired several Y6B mallet 2-8-8-2 steam locomotives made by Rowa.  First produced in 1969 these are beautiful models and run like sewing machines, even by todays standards.  My only issue with them is the motor which, in my opinion, is underpowered for such a large locomotive.  My solution to this is to run two together at the front of a long train, as the railroads often did.  The problem with this is the front coupling is a dummy knuckle coupler and is purely cosmetic.  In this post I wanted to share with you how I overcame this.

These mallet locomotives where first manufactured by MRC/Rowa, then Charmertz/Bemo and finally by Con-Cor/Rivarossi.  They were also released by Con-Cor/Rivarossi as 2-8-8-0 EL-5. Despite minor improvements over the years the main model has stayed the same, here is one sat on the turntable at the roundhouse on Bob Norris layout Somewhere west.

Micro-Trains do offer a conversion kit for this locomotive, No 1048, but all this is is a pair of body mount couplers and you need to cut your own hole in the pilot which can go very wrong.

The pilot on the front, as well as having the coupling, also carries the headlight.  The whole assembly, as shown below, is made up from eight parts which includes the main body, handrails, dummy knuckle coupler, front cylinders and headlight, two plastic valve gear bars, clear plastic light corridor and a metal nut used to bolt it onto the locomotive.  The dummy knuckle coupler is not shown (it was missing on this particular locomotive).

To remove the pilot you will need to first remove the front set pilot wheels.  With the locomotive upside down remove the plastic plug holding in the front wheel set, this usually has a whisker of plastic running passed the wheel set to give it some springiness, again on this particular model it is missing.

The wheel set then simply lifts out.

The newly exsposed screw holds the pilot in place.

Once removed the whole assembly will slide off.

The assembly then comes apart very easily into the seven different parts.  Although I have found out that the very early versions had this assembly glued together and are very reluctant to come apart.

Once I had all the parts separated I set about drawing a 3D model of the main pilot section.  My original intention was to make a replacement part that had a socket to receive a Micro-trains Z scale bodymount coupling.  With the 3D model complete and successfully uploaded to Shapeways I ordered one and as usual within about eight days it arrived on my doorstep.  With this first test print it quickly became apparent that I had incorrectly measured the original because as you can see from the image below the steps are smaller than the original on the left. But this is the reason why I test print everything.

Although the steps were the wrong size I was still able to experiment with the pilot to see how the Z scale coupler fitted.  Although it did fit well I do find the Z scale couplings really tricky to put together and I felt that it looked too small on such a big locomotive.  You may have also noticed that the cow catcher bars run in a different direction, this is because I used the same 3D model parts I have already drawn for my Atlas 2-8-2 replacement pilots.

So taking all that into account it was back to the drawing board, or at least the laptop.  I first fixed the issue with the steps and I also refined a few other details.  Because I wasn’t keen on the Z scale coupling I created a new version with a pocket to accept the N scale Micro-trains body mount coupling and added horizontal cow catcher bars.

The test prints this time came out fantastic, shown below are the two pilots either side of the original. Z Scale coupling on the left and N scale coupling on the right.

To reassemble the pilot, first the handrails need to be secured.  The front two pegs clip into the new pilot and the rear tabs fit under the walkways as shown below.

Then the cylinders fit onto the main body and the plastic light strip is inserted into the rear of the headlight.

The last part to add was the actual coupling.  This slides in from the front and is secured by a screw.  The standard screw which comes with the body mount couplers is too long and would protrude up through the pilot if left as it is, so I cut it short with a pair of side snips. Please use safety goggles if you are going to do this as the ends fly all over the place.  I left about 2mm (0.078″) of the screw protruding from the coupling, the coupling will need to be installed before the screw is fitted.

Next came the actual test fit onto the locomotive and as you can see below it went well.

The final test was a coupler height check and for this the locomotive is put onto the track and coupled to a Mocro-trains height gauge.

This same set of checks were also carried out for the pilot with the Z scale coupling and again, as shown below, it all lined up.

So using the N scale pilot, my preferred coupling, here are two Rowa Y6Bs coupled together.

Now I know that the 3D printed pilots work all that is required is a coat of pain.  I used a simple matt black acrylic paint and the finished locomotive looks like this.

Normally when I show a new product I also share with you where you can get it but this week I need to do one more final test before I am happy to release the Rowa Y6B replacement pilots, and that is a full running test on a layout with curves and inclines.  This is to check that the Micro-trains bodymount coupler does not interfere with the leading set of wheels as they are very close.  So in a future post I will have some more pictures, maybe some video and I will let you know where you can purchase your own.