In “Track Planing for Realistic Operation” John Armstrong mentions a loop track arangement for “drive-thru” loading of coal or ore at a mine. So what is the smallest loop I can make in N scale to represent a set up like this? There would not be any need for long passenger cars, just a locomotive and hoppers. Any Ideas?
As I recall, in the 1970’s, the Clinchfield model RR by Kalmbach had an in and out coal mine to power plant arrangement. One train had empty hoppers, and the other had full hoppers…well, you get the idea. In the hidden area between the mine and the power plant, the trains went up or down a helix of less than 11 inch radius. You may want to double check on that, but I don’t think you’ll need a big radius for what you want to do.
Since coal hoppers are small they can take tight turns–the main limitation would be the locomotive you’re using. Obviously if you’re modeling modern diesels or big articulated steam you’ll need a wider loop.
But you can always do without a tight curve by having such a setup in the middle of an oval of track with a view block (a tall hill or scenic divider)–powerplant on one side, coal mine on the other, with a straight or relatively straight chunk of track between the two.