Big Boy locomotive

This one is more to do with 3D printing, but it is still an impressive model

Brian

What's better is that the stl files are (if I remember correctly) free. Impressive work, though!

Did see a real 3-1/2" gauge Big Boy locomotive at Montreal last summer, running. Now, that was impressive! Keith Wood of the Montreal club had done work on it for someone, and was testing it out.

Here's a pic of Keith giving it a run on a rainy, damp day:

I tried a few files, and each one I tried seemed to have a few errors. I tried the main driving wheels, axles and cylinders. Tried to open them in SolidWorks and a modeller of my own writing. The same errors showed up in both modellers - so I think it was a file error rather than a reader error. Or the same incorrect assumptions were made in each modeller (though for the life of me, I can't find any assumptions in my STL import routine).

Fantastic project though.

Regards,

Richard

Hi Richard,

Out of curiosity I tried opening a few parts in Rhino 3D version 1.0 and they look ok to me. I checked the Rhino documentation and it says "STL files contain polygon mesh objects. Polygon mesh objects are imported into Rhino as polygon mesh objects. They are not converted to NURBS."

Ed.

And, that is correct - STL files are simple, low level meshes.

I do have an Android App on the app store that reads and analyzes and displays STL files - it will find mesh errors, or try polygon reduction tactics, etc, maybe I should forget going into the workshop, and try these files in it? (smile)

JohnS.

Ed,

I was opening the files as a mesh in my own 3D modeller. My modeller can open both binary and Ascii STL files, but once the data for each facet has been extracted it is treated in the same way. Each facet has three corner points, defined in 3D one after the other in the file, a normal can be defined at each corner. My modeller creates two lines, then defines a flat surface between those lines - the modeller is aimed at creating 3D finite element models which use flat surfaces to join nodes. Anyway, the procedures are pretty simple and hard to get wrong if the co-ordinates of the corner points are defined correctly in the STL file.

I also tried importing the models ways into SolidWorks - as a mesh and as a standard solid where SolidWorks converts the solid into its native entity type. I get the same shape after importing the files as with my modeller. To take an example: For some reason the facets defining the inboard face of the counterbalance weight on the driving wheel are coplanar with the facets defining the outer face, leading to a hollow on the inboard face where the counterbalance weight should be. The other two models I mentioned have similar types of problems.

Regards,

Richard.