Building a Diesel Shay Pt 1

 Two years ago, April 2018, I started to build a diesel Shay based on several photos of the prototype built by Canadian Forest Products in the 1950's.  They apparently took a two truck Shay steam engine and removed the boiler, replacing it with diesel power and a homemade cab.  I thought I could replicate this using an HO scale Roundhouse Shay locomotive and a diesel body kit from Mount Blue.  It looked good on paper.  When I got the body built it looked more S scale than 1:48 and my Roundhouse Shay had serious operation issues.  The project got shelved.

Now two years later I'm finally getting around to laying track for my layout and have a new purpose for that Shay.  I also have better tools in the way of a 3D printer.  To develop my track laying skills I practiced on my test track in the shop.  My test track had expanded into a shunting puzzle (click here) and I decided I wanted dedicated boxcars and a switching loco for the game.  The old diesel Shay would be perfect for this and with no "turn-around" the Shay's "good side" would always be showing. I got out the Mount Blue body and thought I could improve it by simply replacing the cab.  I went on-line and found a 1:32 scale EMD SW1500 diesel on Thingiverse (click here).  I downloaded the STL file and resized it in TinkerCAD to 1:48 scale.  When I added the cab to the Mount Blue body I was less than thrilled.

I then decided to use parts of the SW1500 to make the rest of my custom built Shay body, ditching the Mount Blue body completely.  I quickly realized that simply shrinking down the 1:32 parts wouldn't give me the detail and quality I wanted and ended up designing most of the parts from scratch based on parts and details from the SW1500.  This redesign process taught me a lot about my printer and I finally have settings that give highly detailed parts (at least for a filament printer).   Part of this was accomplished by exaggerating details (gaps between doors, hinges, latches) so they would print better.  I also changed the orientation of some parts on the printer tray (the hoods standing on end for example) so they would print up cleaner.  Another thing was using "raft style build plate adhesion" and adjusting the "raft air gap" to 0.08mm so the raft would break away cleanly and easily from the part.  The pictures below are screen shots of my diesel Shay body design done using TinkerCAD.

To help with the printing I broke up the design into 25 parts and printed them out separately.  In the photo below you can see the headlight buckets and brackets are still attached to the "printing raft".  It uses a lot of filament and the printing time goes through the roof but the end results are worth it.  It took about three days to print up these parts but part of that was spent reprinting the same parts several times to get better quality through refines in detail or re-positioning.

While doing this I got power to my test track and tried running the Roundhouse Shay.  The gears bind and it walks like a drunk donkey.  I have a NWSL gear kit for this thing (no longer in production) so I installed that but in the end I decided the loco just has too many basic design issues and will never run as nicely as I would want.  The gear installation is pictured below.  I have a Bachmann On30 Shay that runs smoothly at all speeds and considered using that but it's one of my favorite locos.  I mean.... the wheels are too big.  Yeah, that's it.  I also have a Bachmann HO three truck Shay that I converted to two trucks for a Gilpin Shay kit from Boulder Valley Models (also no longer in production).  This would be perfect except I also don't want to give up my Gilpin Shay so I'll spend some time on eBay bidding on another Bachmann HO Shay.

More updates as progress is made on this project.