Despite what I wrote in my previous post , I decide to add a ‘rolling’ chassis to my model of ‘Edith’, to help me assess the overall appearance of this little engine. Printing and assembling some of the very small parts created some new challenges.

Our heating system failed last week, just as the weather turned colder. I had not noticed before how sensitive my 3d printer is to the temperature in my work room. For the first time, I experienced a fractured filament as it wound off the reel. I then had continuing trouble with several prints, until I found that the bed levelling needed to be re-set. Something had upset it more than usual.

On the plus side, I did get some of the cleanest rivets I have ever printed, with virtually no whiskers of filament between the individual items – possibly because the extruded filament was solidifying more rapidly than usual.

As usual, I broke the overall design down into sections that were optimised for printing by having a flat surface to lie on the printer bed.  I made the exploded diagram below, to show all the individual parts that I printed. In some cases, I printed several small items together, such as the cylinders and wheels

‘Edith’ broken down into Printable Parts

It really brought it home to me, just how small the engine ‘Edith’ was, when I started to print some of these parts:

3D-printed Smokebox for Edith

As I started to assemble these parts together, I realised once again the challenges that 2mm FS modellers have to meet and overcome – apart from good eyesight, they also need to pay far more attention to tolerances, which can seem very tight indeed.  For the first time, I became aware of the limitations imposed by the 0.4 mm extruder nozzle diameter, when I was creating the smallest parts, such as the inclined cylinder blocks.

I also had difficulty when mounting the rather tiny chimney onto the smokebos.  Although I thought I had left sufficient tolerance for the spigot on the base of the chimney to fit into the socket on the top of the smokebox, the ‘quantisation’, imposed by the extruded filament got in the way!  In this case, it was easy enough to ream out the hole in the smokebox a little but it was a reminder that I was working close to the limits of my printer.

Once again, I found the gel-type superglue to be very good for attaching tiny parts such as the cylinders. I used a cocktail stick to spread a thin film of glue on the mating surfaces and then held the parts together, using fine tweezers, for a few seconds until the joint hardened sufficiently to keep the parts in place.  I read somewhere that superglue doesn’t work with PLA but that’s not my experience.

Eventually, everything came together and the newly assembled model looked as below:

Two views of my 3D-printed ‘Edith’

Over on my Broad Gauge blog, I have been writing about the early GWR broad-gauge engines that were often regarded as ‘freaks’ , although some of them were simply far too under-powered to handle the tasks expected of them. All things are relative and what might be regarded as too small in one context can seem very different, when compared with engines designed for a different purpose.

Many narrow gauge engines, like ‘Edith’, were very small indeed, in comparison with main-line engines, but well suited to the task of moving agricultural produce around a large farming estate. The profound difference is apparent when I bring the models of ‘Edith’ and ‘Aeolus’ together for a joint portrait:

My models of ‘Edith’ and ‘Aeolus’ together

In term of boiler size, there is less difference between these engines than might appear to be the case at first glance. The boiler of ‘Edith’ is stated as having 2’ 8” inside diameter and length 7’ 6” (including internal firebox), whereas that of ‘Aeolus’ was 3’ 6” diameter and 8’ 2” length. The very considerable difference in appearance is largely down to the higher pitch of the ‘Aeolus’ boiler, needed to clear the driving axle of the large diameter wheels.

One of my objectives in building ‘Edith’ was to provide alternative motive power on my my narrow-gauge system around North Leigh . Since Buscot was not many miles South from the area covered by my layout, it seems reasonable that similar engines could have been used on both systems!

To turn my model ‘Edith’ into a working locomotive, I plan to adapt it to take a similar type of chassis to that currently under ‘Jeanette’.

Peco ‘Jeanette’, with ‘Edith’

The two engines have quite different appearances but the use of a common chassis seems feasible, with some modifications to the body of ‘Edith’. These modifications will be the subject of a future post.