This post is about my largest print project to date.

Back in February of this year I started telling you about my designs for an N Scale 3D printed Union Pacific excursion train water tender; you can read that first post here.  The design for the 2007 to present day configuration of these tenders was very successful and below is a photo of a pair of N Scale tenders running behind a UP Challenger class locomotive.

Then, at this year’s National Model Railroad Association (British Regions) Annual Convention, I introduced my HO version of this tender.  Below you can see it running with a Brass UP 844.

Then in November’s post about the Poole & District Model Railway Society’s 2014 Exhibition I told you I’d ordered my largest 3D printed object to date from Shapeways, and here it is: an O Scale tender, 1:48.

This is currently my largest 3D printed item, and I’ve had two of them printed.  Both Jim Adams and Joe Jordan.

As usual the project starts with a 3D model, as shown above.  For the O scale tender I was able to take the HO model and rework it.  I could have used the HO model as it was but this would mean the material would have been twice as thick as it needed to be and although that would have made it very strong it also would have made it very expensive.  Shapeways, and other 3D printing bureaus, charge by material volume to produce prints.

This model will also be different to the HO and N Scale kits I have produced because I will not be supplying a chassis or any trucks with the kit. This is because these are available from Lionel as spare parts for their Union Pacific Water Tenders: you can find the parts here.

Here are the Lionel chassis assembled with truck and couplers.

Using these chassis has two great advantages, the first being that they are cheaper to buy than to have 3D printed, and secondly, they are very heavy and strong.  This is important because in O scale the load which is put on to the couplings and chassis is immense compared to HO and N scale trains.  These metal chassis will take all the strain.

The trucks still need to be removed and disassembled so they can be sprayed silver to match the UP tender in its Armor livery.

The other detail parts which I will be using on the O scale tenders, as seen below, are cut levers, cut lever support brackets, and brake wheels on stands.  On my N & HO scale tenders these are part of the 3D printed body.  (Cut levers are used in the US on the ends of most rolling stock.  It is a lever which allows railroad workers to manually release the couplings between the cars and cutting the train, without going between the cars).

Having the cut levers and their supporting brackets as separately applied details for this model was very useful. If the cut levers had been 3D printed it would mean that the print would be too long for the printer, it really was that close.  As they are now separate parts the reduction in length at each end was just enough and the model now fits.

The handrails on top of the tender can also be printed in situ as they are twice as thick as the HO ones and consequently a lot stronger; if the HO handrails are printed in situ there is a good chance that they will be broken in the cleaning and shipping process.

Below you can see all the parts as they are delivered from Shapeways.

Detail parts such as the ladders, tool boxes, flag plates and headlights are still printed as separately applied parts.  This helps with painting and finishing the model.

These tender kits have been printed in the Shapeways Frosted Detail material.  This has a layer thickness of 32 microns and although it is not quite as sharp as the Frosted Ultra Detail at 29 microns in O scale none of the detail is distorted or missing.

The main test for the shells was to make sure they fitted onto the Lionel chassis, and they dropped right on. The tool boxes on top of the tenders in the images below have already been cleaned ready for painting which is why they are opaque.

The next step is to clean up the main bodies ready for painting. This was a bit more tricky than normal as these are somewhat bigger than my normal 3D printed objects. To give you an idea of just how big they are in O Scale, below is a picture of the N Scale tender with the HO one…

…and then again with the O Scale one behind.

With the second O Scale tender in the mix the scale of these starts to become clear.

Cleaning the O Scale tenders is going to need a much bigger container!

In a later post I will share with you the finishing process and photos of the completed tenders with all their detail parts applied ready to make their way to their new owner.