I've put my 28mm Steam Tank model online at
https://www.wargaming3d.com/product/steam-tank/I'll be curious to see if it gets any traction there. I don't believe anyone ever bought it from Shapeways, but then even in 15mm it was big enough to be horrendously expensive when printed by them.
The zip file contains two turrets: one is completely solid, for simplicity, while the other is hollow and can have the gun assembled to be free elevated. Both turrets can be rotated at will.
The running gear (tracks) are in two separate components, port and starboard.
The Gatling gun is a separate model, and can be emplaced via a hole in the floor of the model. If you don’t like the idea of having a gaping cavity there, it will have to be patched after assembly. You can put as many Gatlings in there as you can cram in; more than two is probably pushing it.