Compact yard throat

I just finished my new O27 yard throat, which is unusually compact. I thought I would try to describe it here for anyone who can use the idea. The yard is along one side of the room and the yard lead is across the adjoining side; so the throat fits into the corner between them, and a train entering the yard changes direction by 90 degrees. The throat uses only 28 inches in O27 and has the unusual property of not getting any longer as you add yard tracks.

As you face the corner, the lead is on the right and the yard on the left. The lead becomes a ladder track, with a left-hand switch every 11.5 inches. This requires a 2.661-inch straight track between switches. Each ladder-track switch leads eventually to 4 yard tracks. The last ladder-track switch is replaced by a simple 45-degree left turn.

Each ladder-track switch connects directly to another left-hand switch. Each of these intermediate switches has a .498-inch straight section on its non-diverging outlet, followed by a 30-degree left turn. On the diverging outlet, there is a .131-inch straight section, then a 15-degree right turn. (These straight sections are so short that I simply cut the turns long by the small amount needed.)

After that, each track goes into a final switch, which is a left-hand switch cut down to a 30-degree diverging turn and a 7.817-inch straight. The diverging outlet goes to a 15-degree right turn and the non-diverging to a 15-degree left turn. (The diverging outlet is 1.08 inches shorter than the non-diverging, so the yard-track lengths differ by that much.) The yard tracks are 2.875-inches apart on centers, which is my standard spacing.

Of course, this design can be made in a mirror image, with right-hand switches. It should also be possible to scale it up for O31. I will have to leave the housings off the Lionel switch machines of the final switches.