here is the report
This progress report is mostly to give evidence that I am still working on this project. When I started this more than a year ago I had two goals (aside from having a Shay). The first goal is to create a great running Shay. The second goal has been to create an easy to assemble shay that, when assembled with off the bed parts, meets the first goal. It has been the second goal that has been more work than the first (although goal #1 has not been easy either).
Originally I was going to print only some of the parts and supplement them with brass PSC parts, however as I go along my desire now is to use all my own designs and to try and print most parts. When it comes to just static detail parts the process of making and 3D printing stuff is pretty easy, design, print, examine, fix things I don’t like, print, examine, and repeat until I get a part I like. When it comes to printing parts like the trucks and the engine (by engine I am referring to the cylinders, not the electrical motor) it gets way more involved.
The trucks were the first parts I designed, however I have redesigned those as well (more on that later). I thought the engine was going to be easy because all I wanted to do was to print the cylinder castings and use all PSC (originally Kemtron) parts for the crankshaft, valve gear, and piston crossheads and connecting rods. As you can see in my last post I actually did build a modified PSC crankshaft and I did print the cylinder castings, all of which I assembled, however it was too much of a finicky process to build. Also, when it came time to use the PSC valve gear it just got to be too much monkeying around to assemble it all. I had built PSC Shay engines before but too much time has passed, and I forgot just how much it takes to get them together, running, running well, and then painting with out messing it all up. I wanted an engine that assembled as designed with no tuning so I could paint the parts before assembly. I decided to go back to a blank sheet and start all over with my own design.
A major change to my cylinder castings (actually a print) is that I decided not to split the cylinders in half like PSC does, instead my print is solid, and like the prototype I made separate journal main caps that attach with 1mm screws. Making the journal caps separate allows for the crank shaft to be bottom loaded all assembled, just like an automotive engine. Because my journal main caps screw on I can paint the engine without the crankshaft installed, paint the crank shaft, then put the two together. For the main rods and the eccentric rods I decided to make them snap in, like Bachmann, which requires some special resin that will flex and not shatter. I used the same special resin to print valve gear parts, all of which are pinned together with blackened pins.
Once I started going down the road of using all my own designs I also had to go and make the crankshaft so it could be printed. The crankshaft is a special issue because it has printed journals for the main rods but used brass rod for the main rod journals. To assemble the crankshaft I had to come up with a jig that will allow the crankshaft to be clocked and spaced while the glue dried. For gluing I am using thin ACC, and to make the ACC bite into the brass I spline the ends of the brass shafts. It gets a little hairy gluing the crankshaft together because there is not a lot of time to put the parts together and get them on the jig. I am going to seek out a different glue that will hold as good but be slower setting. It may sound like a glued and printed crank shaft is not strong, but I have tested one and it held up well.
I have printed dozens of valve gear parts, all tested and redesigned for better assembly. I am really happy with how the valve gear is turning out and how close I have been able to keep it to scale.
What has been really hard is that I make myself stop if I reach an assembly step that is hard or requires some tweaking, then I try and think of ways to make it better, then go back and redesign the parts, reprint the parts, then start all over and reassemble. I have built the engine over and over so many times I see it in my sleep…for real.
Now just when I thought I was done and the engine assembly was going well two things made me have to go back again, almost to the beginning and do a new design, one was a gear change and the other was ball bearings. That’s right, ball bearings baby! As if there was divine intervention, I was walking down the aisle at my local hobby shop and a package of tiny ball bearings caught my eyes, then a quick search online for small ball bearings and all things changed.
I purchased two sizes of ball bearings, 1mm ID and 1.5mm ID. The small bearings I used on the spur gear chain, crankshaft, and truck line shafts. The larger bearings I used on the wheel sets and on the larger gears in the gearbox. All in all there are now 29 sets of ball bearings in this locomotive, and at $0.50 they are totally worth it.
Along with the bearings I also found one other significant item that totally transformed the gearbox and made a major improvement in the drive line, however I have to keep a this change a secret until this project is finished.
Ok, enough typing, lets see some photos.
the photo above shows just how small the 1mm bearings are.
above are the 1mm bearings installed in the crankshaft case. there are two 1mm screws to hold each main cap in place, the screws are angled to miss the bearings.
above you can see 1mm bearings being used on the line shafts and 1.5mm bearings on the axles.
above are some of the valve gear parts printed out of a resin that has some more flex to it, normal resin will just shatter when I try to snap the parts together. I bought HO scale valve gear rivets to assemble the valve gear but trying to peen over the rivets also caused damage. I found some small pins that were blackened and they work out really nice, a small drop of thin ACC placed on the back where the pin protrudes is enough to wick in and hole the pin in place. you can see the pile of test printed valve gear parts and a tin of test engines.
above is the assembled engine (no valve gear or main rods) with all the bearings and the new gear drive (along with the secret part), it is super smooth. only two 2.4mm screws are required to mount the engine to the frame. I have designed it so the motor stays with the locomotive and is mounted up in the boiler, this allows the engine to be painted in pieces and then assembled, totally opposite from brass.
the last images are just for motivation. I have taken a beat down on this and I just needed to see that it will actually look like something, all the parts are just set in place. This process has been sort of like the scene in "Cool Hand Luke" when Paul Newman was getting knocked down over and over, but he just kept having to get back up.
I hope that very soon I will have a running locomotive to show. Thanks for reading along.
