3D Printed O Scale Critter Challenge

Here's a Model Rail Radio challenge! Design an O scale critter that utilizes the Atlas (6 wheel) or AHM (4 wheel) O scale Plymouth switchers from the 1970s for a donor mechanism.

These switchers are still readily available on e-bay and at O scale train shows. These locos are not held in high esteem because they are not accurate scale models. However, as a mechanism for a homebrew critter, they're just fine! You should not pay more than US$25 or so for one on e-bay.

Your model can be freelance or prototype (just not a Plymouth, where's the imagination in that!). You can use a single mechanism or two or more mechanisms, subject to the contest rules.

Speaking of the rules, here they are:

The model must be in 1/48, 7mm (1/43.5), 1/45 (European O scale) or 17/64" scale. Please work directly in your chosen variant of O scale and not in real feet and inches (I don't want to have to do the conversions).

The model must fit one of the aforementioned mechanisms. It can sit on the mechanism, fit over it, surround it, or extend beyond it. It can reuse any parts of the donor locomotive. It can incorporate commercial detail castings. However, the 3D printed parts must be the focus of the conversion. It must be capable of running as a viable model locomotive.

You can do the design in any 3D software that produces a .stl file.

The final .stl file must pass Shapeways rules/tests for printing in White, Strong and Flexible plastic. Upload your file, check it and fix it before submitting.

Your design must cost US$100 or less to print in the aforementioned plastic.

Come up with a narrative describing your creation. 1/2 page to no more than 2 pages. Amusing or fanciful stories are OK.

You'll need to send several views of your creation generated by your software as .jpg files. It would be good if one of these files shows its dimensions.

Send the .stl file so that it can be checked, and printed if you win!

All entries should be submitted to terry at the name of the show (all one word) dot com by May 1st, 2015.

And the prizes are:

The two best designs will be printed at Shapeways and sent to their creators. This could be extended to more entrants at the judges' option.

MRR swag for finalists and honorable mentions.

Your design remains your property and you may be able to sell copies of your design on Shapeways; win, lose or draw!

Helpful Hints:

Diesel, gas/mechanical, electric, trolley (freight motor?) and even steam designs (geared loco, steam dummy) are all possible.

Here is a link to an article in O Scale Trains (page 10) about converting the Atlas switcher that you can use for inspiration.

You can include new side frames for the mechanism in your design provided you do not go over the US$100 limit to have it printed.

You can 3D print lots of detail on your model or you can keep it spartan allowing the modeler to add detail castings. Give us the logic for your choice in your write-up.

You don't have to show how you would mount scale couplers. Keeping the original non-scale couplers is OK.

Hollow out everything that you can to keep the cost down. Experience shows that 2 mm wall thickness is strong enough in WSF plastic.

Upload and check your design for printability at Shapeways often. This will allow you to catch printability problems early when they are easier to correct.

Don't work in real feet and inches then scale it down to O scale. The resulting model is unlikely to pass Shapeways printability tests.