Model Rail Coach Project (Metropolitan Railway, Chesham Set)

Firstly welcome to this project, for the Instructables competition.

This is a project I dreamed up some 5 years ago now, after reading about 3D printing and what people have done with the technology with in the model railway hobby. I usually shy away from such things tending to stick to good old fashioned scratch building, but I could certainly see some benefits using 3D printing.
For some like myself railway modelling is a challenge, to source, or build things that are not available on the market, this is where 3D printing comes in to it's own.

The story starts some 5 years ago, seeing the 100 year old teak London Underground coaches known as the Chesham set, built around 1898. The coaches have a lot of history, and are some of the oldest preserved coaches, but sadly no-one produces models or kits of these wonderful coaches, which is where I have to get creative.

The aim was to 3D print, in 4mm scale: coach bodies, coach chassis, and wheel sets plus any other small details that were not available to me to build these coaches.

It would certainly prove challenging and difficult at times, as I was still very much learning about the CAD and printing side this technology, and finding where the limits where.

Step 1: Introduction / Research:

I model in 4mm to the foot (1/76th scale) and I model a particular region or place, or anything that takes my fancy, I attended an event in London the Metropolitan Railway 150th anniversary, where steam returned to the London Underground, pulling a set of 4x beautiful teak coaches, built by Ashbury's.
Sadly there are no kit's for these and I certainly wanted a set, so I turned to 3D printing to achieve it.

Research:
Firstly calling on a number of contacts in the railway world for drawings, measurements, and pictures of the coaches I managed to acquire quite a bit of information, which was necessary in order to build a 3D model of each coach.
All four coaches were the same length, same or similar chassis but position of doors, windows and panelling were different on quite a few.
I also visited the Bluebell Railway in Sussex to photograph various areas of the coaches, like the doors, the panelling / mouldings, wheel sets, buffers, and any small details.
Drawings from James R.Snowdon Metropolitan Railway Rolling stock was very helpful.
This then gave me enough to start building a 3D model, and understanding what I could print and what I couldn't.

Step 2: Material and CAD

Firstly as I found later on, researching the material of what you want to print in is quite decisive before actually designing the models.
The coaches needed to be quite high in detail, with small surface details like mouldings, handles, vents ect... Originally I was going to produce most of these through Shapeways, and decided on a standard design, having 1mm thick walls, which pretty much covered most materials and minimum surface detail of 0.2 - 0.3mm.

So the materials I looked at was White strong and flexible which is a laser sintered or SLS for those in the know, and UFD (Ultra frosted detail) for those smaller detailed Items.

Firstly I managed to get a good friend on board who was also interested in the project so we worked together and split the design load between us, using a couple of programs, Google SketchUp for me a CAD program I understand and also Creo Elements/Direct Modeling Express, which would be used to do the bulk work on the coach bodies and detail items.
We firstly designed one body, a wheel set (A bogie), roof vents, and a chassis.
Before we went to far with the project we wanted to ensure that they would print O.K and any changes could be made after we got the samples back.

Step 3: Samples and Adjustments, and a Suprise..

I received the first test print from Shapeways in the materials mentioned on the previous step.

Overall I was pretty satisfied with the first prints, all the detail came through, although the surface was a little rough from what I had read it wasn't too bad when it was actually finished or painted. Of course there are better materials out there to be used which sadly at that moment in time were a bit out of reach in terms of price.

A few changes were made to the bogie design, and also seating inside the coach, which was designed by my friend and partner on the project, these would slide in between the coach partition walls, which also would add strength to the model.

Another 2 coaches were printed, costing approximately £100 each which wasn't too bad, the models were starting to get quite a bit of attention, after doing some writing for a blog on this very project, I got an e-mail from Form Labs who asked if they could use one of my models to print and test their new SLA desktop printer, of course I said yes :) who wouldn't?
This was a completely new material so I was looking forward to seeing how it would come out....

Step 4: Form Labs Test Print and the Final Coach...

A week or two later a box arrived from Form Labs, after inspecting the prints I was very impressed with what I saw, very faint print lines, a much smoother surface finish, all in all much better, so it certainly looked like the way to go, as the quality was much better.

This print will eventually replace the one that had already been printed seen on the previous step.

So the last coach body was to be printed so I started looking around for a printer in the UK to see if I could get them printed in the same/similar material. I found a 3D print place in my local town who actually do work for Formula 1 teams, and they use the SLA type printer.
The company Graphite additive manufacturing company took up one of my models to be printed in a Grey resin.
The finish of the fresh printed model was the next step up from a desktop printer and was simply amazing... then again it should be for the price....

Step 5: Finishing, and the Presentation.

Not so much 3D printing but finishing, all the models were painted at more or less the same time to ensure they were more or less the same, coated in white primer, then a base coach with a weathered teak colour over the top, letting the model dry, and then applying various brass detailing, then transfers, and varnish.

Overall comments from various people have been very positive and impressed with what can be achieve with the technology of 3D printing.

Step 6: Summary.

So people have been quite impressed with what is possible with 3D printing, but sadly they were not impressed with the cost. Looking back on the whole project I probably should of gone down producing 3D print masters and using them to create moulds possibly for resin castings which might be more cost effective when other modellers want a set at a better price.

For me it was worth it, it was a big learning curve, learning what I can and can't do, but due to the cost I think it is probably best 3D printing is used for small detail items, and one offs.

I have since been producing small coach prototypes and using 3D Hubs and Form 1+ printers to test prints of the coaches again one offs, but a bit more affordable at about £20.

Its been good fun, learning and building, and using this technology, I am sure it will have some future in my hobby. But for now maybe not quite yet.