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Pattern for a small oscillating steam engine

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PatJ:
Here is a pattern I made for a small oscillating steam engine a few years ago.

The original pattern was modeled in 3D, and printed in plastic on a 3D printer.

The pattern was then filled with Dap multipurpose spackling compound, and painted with Krylon spraypaint (because I had some on the shelf, most pattern makers use another product, the name of which eludes me at the moment, getting old, shellac perhaps?).
The filler added some curvature to the surfaces, and helped get some draft angle to make pattern release from the sand easier.

The sand used was petrobond.

The pattern was coated with paste wax (wipe it clean, don't leave wax residue on it) to allow it to release cleanly from the petrobond.

This was one of my first casting efforts, and I had a little gassing, but overall, it was a good learning effort.

PatJ:
I did not have much draft angle on the sides, but the pattern pulled ok after I put screws in the bottom, and tapped it in all directions to get a little clearance around the pattern, and to help break the sand from the pattern.

Just before pulling the pattern from the sand, I sort of walk it around in the tiny clearance beteen the sand and the pattern to sort of firm up the sides of the mold.

Here are the rusults.

Like I said, one of my first attempts at casting, so anything at all would have been ok with me.

PatJ:
This is a bar stock version of the same engine.

I stuck my hand in there to give a sense of scale.

b.lindsey:
Very nice Pat. Did you make one from the casting as well? I have know about the use of 3D printing for patterns for some time now, but yours are the first I recall actually seeing. Looks like they turned out quite well too.

Bill

PatJ:
Bill-

I have been in the learning curve since 2009, trying to learn machining, engine design and assembly, and more recently setting up a foundry and learning how to use it.

My tiny little brain has been through extreme confusion on many fronts about model making, how is it best done, how do I want to do it, etc.
Luckily my brain is so small that it does not have enough critical mass to self-explode, or else it would have already.
(Less is more as they say).

A good description of my efforts would be a blind man stumbling through a mine field that is littered with boulders.
You get the idea.

So no, I never built the engine from castings because once I learned 3D modeling, I wanted to take an entirely new approach to modeling, which is to create 3D models from scratch, with the design taylored for making patterns and then castings.

I had to toss everything about bar stock construction that I had learned over a two year period and "think outside the bar" to coin a phrase.

So my attempts now are for engines with cast passages, etc.
I don't like to drill passages, and I really only want minimal machining and finishing after the castings are made.

I have yet to complete a cast engine, but I have one in the works, and NAMES is approaching fast, so we shall see if the weather and the modeling gods will smile on me or cast me into the gates of foundry hell (foundry work can go either way).

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