HO mining engine on a Z scale mechanism, 3d printed

I wanted a small powered mining engine, so I started with a Z Scale power unit.  I picked up a Micro-Trains FB unit from modeltrainstuff.com like the one below, and designed a shell to go over it.  

 

$82.39 right now at modeltrainstuff.com

This is the drawing I came up with.  I designed it to just slip over the Micro-Trains mechanism.

I printed it in Shapeways, Frosted Ultra Detail material, which does not photograph well.

For a little more clarity, I threw on a wash of A&I.

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I drilled the shell and installed grab irons.  The material is Acrylic, so it drills very nice.

The mining safety teem just painted the grab irons, and while they were at it, they gave the critter a name.

The rust is REAL rust, using Sophisticated Finishes.  http://www.patina.com/patina.html  Available at most art supply stores.  http://www.dickblick.com/products/instant-iron-and-instant-rust/

Comparing it to a standard gauge loco, it looks pretty good.

Now I need some mining cars to pull.  I am looking for suggestions on the mining cars.  Obviously they will need to scratch built, and I assume some brass involved to get any weight to them.

And it does run.  

Other shapeways prints I have written about.  The lawn mower repair show is the most popular...

http://nvrr49.blogspot.com/2014/10/shapeways-bath-fixtures-and-more-stuff-8.html

http://nvrr49.blogspot.com/2014/04/latest-shapeways-prints-ho-scale.html

http://nvrr49.blogspot.com/2013/09/lawn-mowersmall-engne-repair-shop.html

http://nvrr49.blogspot.com/2013/02/the-rest-of-details-for-my-ho-scale.html

http://nvrr49.blogspot.com/2013/07/fsm-barnstead-lumber-ho-scale.html

http://nvrr49.blogspot.com/2013/01/2013-model-railroad-and-blog-post-goal.html

http://nvrr49.blogspot.com/2013/08/ice-cream-store-made-from-pill-bottle.html

http://nvrr49.blogspot.com/2013/02/blairline-church.html