Portals

Well, I'm sure you can find or create the needed CAD file for a 3D-printable tunnel, but there are a few issues: first, a realistic stone portal is a *very* complex shape, challenging the skills of even the best 3D craftsman, so you may be limited to other's efforts, if you can find them, at least until your skills develop; second, most portals, especially in O scale, are much too big to print in one piece, so you'll need to deal with finding/creating/printing multiple pieces that have to be assembled; and third (and bottom line), this is not the type of project I'd suggest to someone just starting out in 3D printing.

However, I do have an alternative to suggest: scrap styrofoam. You *can* buy styrofoam sheets (or better yet, the denser pink/green/blue stuff), but you can also just use a hot wire cutting tool to slice pieces off salvaged styrofoam packing to create your own sheets. That's exactly the material I used to craft a drop-over tunnel for my brother-in-law's holiday layout (both the portals *and* the tunnel structure):

The portal design I cribbed from the pair of commercial double portals I had bought earlier for my own layout, transferring the grout lines to the 'blank using a magic marker, and used the pencil tool on my hot wire cutter to gently engrave the stonework (the surface of the salvaged styrofoam was already realistically grainy). I then painted the entire portal light gray, and manually added accent stone colors before black washing the whole portal. I used a full-sized printout of a picture of the model portal as a guide for marking the grout lines and stone layers:

I also later adjusted the width a bit and used the same design to create single track portals for a friend's layout. Believe me, I'm no artist, but I was pleased with the results both times, and the cost can't be beat!

It probably should be noted that white styrofoam is much weaker than either the color stuff or the commercial portals, but if all you're going to do is glue the portals in place, even the weaker salvaged stuff will do just fine! Good luck, in any event . . .

I was about to make the same suggestion as @Steve Tyler. I have been using scraps of insulation foam to make walls and a stone arch bridge. Next up will be a tunnel portal following a prototype of a VERY old bridge which was more of a tunnel. If I want it to look like the real thing, I will need to do it myself and I am not about to explore the world of 3-D printing. I find working with the foam to be relaxing and do it in between wiring or other non-thrilling duties. You can find a few YouTube videos on it. Below is my bridge but I do not have the railing on it yet. I needed a curved one which isn't typical, and I also needed it to be short in height. Here it is just placed on the layout, but the river and other scenery are not complete yet. The second pic is a wall that will go along a cut, again the scenery is not started in this area. I made a brick wall as well but no pic.

Mikki

Hi don't forget there must be a reason why the person is selling off his or her used 3d printer, I would not take the risk, there are also people on the forum that would  print this for you for a cost! check on the forum to find someone typically will let you know how much they will charge!

Alan

Wow.  Thanks for the responses and the pics.  You are all so far ahead of me and this gives me something to look forward to being able to accomplish one day. Great job on your work.  I’m currently in the process of making a hill/mtn out of spray foam.  It’s infancy stage.  I am wanting to put rice terraces that have a semblance to the Banaue Rice Terraces on the mountain sides.  After I get it all painted and contoured, I’ll decide whether I want the fields flooded or not. Perhaps flooded on one side and ready for harvest on the other??   My vision is coming into focus and I’ve definitely found something to occupy my spare time (and $) in retirement. I’ll post some of my progress along the way.  Thanks again! No 3D printer for me for now!

I also endorse the use of foam for tunnel portals. Here is a picture of one of my portals done with blue foam.

I printed this from a design I found on the Internet, it's a pretty good looking portal.  I embellished the sign with my own info, and I can see this design is easily expanded for say two tracks.