I use XTrkCAD, and am very happy with it for the small layouts I like to experiment with. It has an extensive N scale Unitrack library, other sectional track products, as well as facilities for designing with flex and hand-laid trackage. The price is certainly right ($free), which keeps more budget available for other RR acquisitions. There is an interface to export to JMRI Panel Pro too, but I have not tried that yet. I have found the development team receptive to thoughtful suggestions for improvements and additional features.
Hemi has some good points about the yard; the turntable will not allow running around consists of the length needed to haul 4 meter long trains, supported by your yard, up the helix. If not planning on running trains of nearly that length, I would provide a set of crossovers roughly midway along the length of the yard, to effectively double the yard tracks (at half the length each,) while providing run-around capabilities to boot. Failing that (and perhaps in any case), since the switching lead currently would extend back down the helix, backing up long cuts of cars to push them onto different yard tracks would be very problematic. I would add a separate, level switch lead track around the outside of the helix, and avoid the uphill backing/pushing moves with long cuts.
Shapeways does have a GF6C (rides on a SD40-2 mechanism)... https://www.shapeways.com/product/A...-railway-gf6c?optionId=4114048&li=marketplace
I like the revision. One caution: long wheelbase/6-axle units may not like that return loop if they are body-mount coupler-equipped, or at least not with short shank couplers. Might require longer shank couplers to navigate the loop. I assume the 30 is 30cm radius, which is just under 12" radius. A big articulated steamer will not like that, but SD40-2s or big Alco/MLW Centuries will probably be fine. A coal train or cars shorter than 70 scale ft long will probably navigate that loop fine, too as long as the train isn't too long. This will allow a continuous run option for those days you just want to see trains run with minimum fuss.
The loop is only for engines! Exclusively DASH, SD's and ALCO's. I'll try it out and determine the possible radius. The loop is only for turning the engines.
Do you not have room to turn that last corner on the upper level before the turning loop? At least that next wall is vertical, and the back of the loop would be above the back of the main level. I'm just concerned about reaching the lower level tracks all the way back in the corner under that turning loop... Or maybe you could bring the main level tracks out from that corner in broader (longer radius) curves, so they don't get buried under the turning loop.
