Egad, what a CAD

This post is about Computer-Aided Design (CAD) tools for model layout planning. The title actually comes from an obscure, one-act melodrama that is occasionally put on by high schools, more commonly back in, oh, say, the 1970s. Don't ask me how I know that.

I managed to avoid CAD for layout design for a long time. I downloaded a few demo products back in 2003 but after realizing they all had steep learning curves I stuck to graph paper, pencil, erasers, a ruler and a compass.

However, after I completed the high-level layout design and made my first attempt at a detailed staging design I realized that I was going to need CAD to complete this layout. I'd been working at it for about 2 hours when I realized that the approach I was taking simply could not work, and that I'd need to shift the entire track arrangement around. Then it occurred to me that this was likely going to happen many, many times given the nature of what I was trying to fit into the space. A tool that would allow me to shift whole track groups quickly from place-to-place, trying to find the best arrangement, was going to be essential if I was to complete the design in the same decade.

There are several CAD tools available for model railroaders. I'm sure I don't have a comprehensive list but CADrail and 3rd PlanIt seem to be the most popular choices. There is also a free tool from Atlas which apparently is acceptable if you are using their sectional track, and I've heard there is a model railroad version of Xtra CAD somewhere, but it didn't turn up in my quick Google search.

Which is the best? Heck if I know. Like almost everyone else I just picked one, learned it, and since it works I haven't bothered to try another since the learning curve is steep for each tool. I've read a few reviews of the various tools in Model Railroader, but they are careful to avoid making any one tool look better than the others.

So, I picked 3rd PlanIt only because when I tried the demo I was able to locate quickly the templates for the N scale switches I was going to use. Not the most scientific approach, but at least I knew it was going to work for me. I've found it a good tool, but if I had to recommend one now I'd suggest you look at CADrail only because I can't get the 3rd PlanIt people to respond to my emails.

The learning curve is steep even if you are adept at computer use and even have CAD experience, say from home design software. Actually I can't imagine how someone who has limited computer experience could possibly learn this tool on his/her own. Yes, part of the learning has to do with getting used to the concept of working with objects segregated by layers -- only some of which may be visible at a given time -- and part of it has to do with getting used to thinking in three dimensions. But most of the learning has to do with getting used to setting up the track and the connections between the track, including topics like easements, parallel track, and connecting track that doesn't align to the nanometer.

In my case I spent maybe 3 weeks getting the lower deck designed, then did the upper deck over the next 2 weeks, then re-did the lower deck now that I really understood the tool.

And once you are skilled at using the tool you'll find, if you compare notes with another skilled user, that your approach and his/hers are completely different, yet both are effective. This is because the tool has so many options that it's likely no two people use it in exactly the same way.

So, thus far all I've said is that I used 3rd PlanIt to design my layout, I am skilled with the tool, and it took me a long time to learn how to use it. But the real questions are: do I consider it worth the effort, and if so what are the advantages? The answer to the first question is an emphatic yes -- I wished I learned it years ago and saved the time I spent doing smaller layout designs on graph paper. The answer to the second question is that these are, IMHO, the advantages of using a CAD tool:

1. Speed. Once you are adept you can put down the initial version of a track section at least as fast as you can using graph paper. After that is done subsequent adjustments can be done in mere seconds or minutes. You can save literally hours or days with a single redesign effort.
2. Precision of design. On paper, no matter how hard you try to be exact, you can too easily "fudge" the angle of a switch or the radius of a curve, and deceive yourself about the workability of a track arrangement. With CAD what you design is what you get. "Fudging" is only possible if you cheat by, say, forcing two tracks together that don't really fit. If you use the standard connect tools that won't happen.
3. Precision of implementation. CAD allows you to know the exact location, down to 1/32nd of an inch if you like, for a given switch or start of a curve.
4. 3D and overlays. It is a challenge to figure out how elements fit together in a three dimensional space using graph paper. With CAD you can easily select which layers to view, allowing you to see how different elements fit together without distractions from other elements. Futhermore, most CAD programs have 3D views so you can confirm it all works.
5. Precise calculations. Will that siding be long enough? What is the exact slope of this grade? What is the exact radius of this curve? All these and more are quickly answered with CAD, but often can be calculated only approximately, and after a lot of work, with graph paper.
6. Easy printing and sharing of designs. A nice side effect of CAD.

In addition, there are other features of CAD which I haven't used, such as testing out scenic views or actual train operations, which many people find helpful.

The only caution I'd give to someone using CAD is that it really helps if you have experience building from CAD before you decide that your CAD design is "final". This is because CAD's extremely precise calculations can mislead you about how the design will translate to reality. My plans, for example, are calculated to the 16th of an inch. When you start working in your layout room you'll find that real life isn't always like that. Floors aren't always level and walls aren't always plumb (in fact, they usually aren't). The peninsulas you build may not be exactly perpendicular from the wall. You may also find that if you carefully plot two locations of a line from the CAD to your benchwork, that when you extend the line outwards it doesn't seem to correctly line up. In part this is because 1/16th of an inch is really small -- your pen mark may be that wide! You probably will need to check measurements again and again at different locations, and also be prepared to adapt your CAD design slightly based on what you encounter on the benchwork. Once you've done this once or twice you'll take it into account when doing your next CAD design, and leave yourself a little slack room in the design.

So, I used CAD for the iNdoor layout design, and then later for the Garden railroad as well. In future posts I'll describe those designs.