Mixing 3D Printing With Scratch Building

I’ve been trying to learn CAD for a while now with a couple purposes in mind, first as a way to create drawings of what I’m trying to create to make it easier to convey. As an example of this drawing of a Thrall side beam.

The other would be to use 3D printed parts, or printed tools and jigs to simplify construction. In the example of the thrall side beam I’ve used a scribing tool with some success but it’s still time consuming and easy to make a very visible mistake as this contour is very distinctive. I figured I could go two ways with this, 1) print the piece directly and use it as if I’d cut it or were using a Details Associate or similar piece 2) print a jig to simplify cutting the piece.

Idea one in this case is the simplest so I started with that. Once I got the wheels on my first scratch built flat car it was clear to me just how much weight was needed. Fortunately for that one I had already planned on a load but what if I wanted to run one empty? I need a way to put on some pounds. I’m willing to sacrifice underbody details for the weight, I just need to put it somewhere. I happen to have a collection of steel plates that were salvaged from various lost causes in the past and while they’ll be a little underweight by NMRA standards they should still track a lot better empty.

The solution was to nibble a bit out of the the inside frames as shown on top in the diagram also with the space for the coupler box, bottom shows the profile of an outer frame.

The picture on the left is how the outer beams came off the printer (it’s hard to see  but trust me they are both there), and the right after I’ve removed the brim. The brim is used to give the print a bit more purchase on the print bed so it doesn’t get knocked out of place during printing. Trust me it’s a good idea (nothing like 5 hours into a larger print and having it all lost because one of the pieces came lose).

Here is a comparison of a beam I’ve cut and a printed one. Obviously the printed one has a bit of a stair step look on the angles which could be sanded down, and also obviously I’m not very good with an xacto blade.

The printed version is not without it’s faults either with some cavities that will likely have to be filled in, which for the record is much easier to see in person than to photograph. There are also layer lines, it’ll be interesting to see how noticeable  they are on a finished and painted model. I might also use some filler to smooth it out.

The inner beams I specifically left an area for the weight which is demonstrated on the right. In the left top beam some of the support material is left in place. because of the orientation of the print the center section needed to be supported while printing which just adds a little more cleanup to the part.

So far I’m pretty happy with how these parts came out, it will be interesting to see how they play with the rest of the build.