A journal following the history, design, construction and operation of Bernard Kempinski's O Scale model railroad depicting the U. S. Military Railroad (USMRR) Aquia-Falmouth line in 1863, and other model railroad projects.
©Bernard Kempinski All text and images, except as noted, on this blog are copyrighted by the author and may not be used without permission.

November 2, 2020

Leaving the Stone Age

Yes, even a cave man like me needs to evolve. For many years I've had learning how to do 3D drafting for 3D printing  on my do list. This past week I finally started to make a more serious attempt to learn 3D drawing, first with Tinkercad and now with Fusion360. While I am still an absolute neophyte in the applications, I was able to make a few decent drawings. 

As I mentioned in my last post, I drew a smoke stack for my locomotive project using Tinkercad. Unfortunately, that drawing did not have enough polygons to make a decent 3D print despite my setting it to maximum steps. 

So, I decided to try drawing the same part in Fusion360. It took me a few hours, but I got a decent drawing that Shapeways says will print.   I have an associate that has a high resolution resin printer that will try to print it for me.

 Emboldened with my newly learned skills, feeble as they are, I tried doing a test drawing of the frame of the locomotive. 

I exported the side frames as a DXF from my drawing in Adobe Illustrator. Then I imported that into Fusion360, copied and offset it the appropriate amount,  and extruded some cross members.

The resulting image looks like this.

Then I uploaded the frame part to Shapeways to get an estimate of the cost to print in metal. I was surprised to learn that the frame would cost about $50 including shipping if printed in steel. I thought the price would be much higher. So now I think I will proceed with finishing the drawing in 3D including adding the cylinder and smoke box saddles, and perhaps the cylinders and hangers. Then trying printing the frame in steel or aluminum. The steel printing process involves a furnace sintering step that results in shrinking. So steel might not be a good choice for this part. The aluminum process uses direct laser melting of aluminum powder, so it is more accurate and doesn't shrink. But it is three times as expensive. 

One advantage of 3D printing is I can add some additional detail to the springs to better capture how they look on the actual locomotive. Also, the frame will be assembled when it is printed. I do not know the tolerances that the 3D printed metal will allow, but most of the dimensions are not critical. I will make the holes undersized and uses reamers to get precise diameters.

I will proceed on the drive rods and valve gear with laser cut nickel-silver or maybe stainless steel.

Meanwhile, the brass tubes and some sheet nickel-silver I ordered arrived. The boiler will be made from a section of 1.125 inch brass. The side walls are 0.064 inches so the inner diameter is just under one inch. The motor will fit nicely inside. The thick walled brass will also add some heft to the loco. 

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