Not quite correct. If you Google "123D Design" you will find lots of sites at which you can download it. However, it is being withdrawn so be quick. Whilst SketchUp is good for buildings, I find that 123D Design is much better for locos and rolling stock.My understanding is that 123d has been discontinued. I have been using SketchUp Make (the free version) as well as TinkerCAD. Tinker is easier but SU has more features, especially with the add-ons ...
AndrewAlan B: Your stand looks very impressive! Do you print only your own design, or can you print someone else's designs?
how large can your printer printAndrew
All of the models on the stand are my own designs, I can and do print for other people mostly because I have a printer capable of large prints. I have a couple of prints I have worked on in a collaborative way with friends which are still in the pipeline .
Alan