John Armstrong. Track Planning for Realistic Operation (2nd ed. 1979) Every time I look into this book, I notice something that I’ve either forgotten, or didn’t pay enough attention to previously. And it’s always good to refresh one’s understanding of Armstrong’s concepts. This time, I reconsidered curvature and “squares,” Armstrong’s brilliant insight that since layout design is constrained mostly by curves, a square within which one can fit a quarter circle of minimum or design radius is a basic measurement.
I have decided that my 12'6" x 12'6" space (actually slightly larger, but it’s best to design for a slightly smaller space) will allow 5x5 squares with a design radius of 26". A skewed U design with stacked loops would produce a nice long run, but entails duck-unders to the centres of the loops. Round-the-wall plus peninsula would be a walk-in design, but would still entail a duck-under to permit access to the track along the base of the peninsula where it meets the wall. A swing-away or drop-leaf entrance section would also be required. No matter what, a smallish square space like this one means severe compromise with one or another desideratum. Oh well. Anyhow, Armstrong’s book was a pleasure to look through. I even re-read a couple of chapters. *** (2005)
Track Planning, 1st edition
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