Reboot of my first N Scale railroad and my first layout in 20+ years
There are straight sections and sections that exactly match the Kato 13.75” Radius rails. Remove the Kato rails from the Kato trackbed and insert the rails into the printed bridge ties.
These models include guard rails and spikes compatible with Kato N Scale rail profiles. Kato rails can be threaded through the spikes and will fit snugly holding their shape. You must use curved rails of the same radius with the curved ties. It is too difficult to bend straight rails into the curve while simultaneously threading through the printed-in spikes. Apply Super Glue every few centimeters along the outsides of the rails to permanently fix the rail to the ties.
I printed these models using PLA 1.75mm filament at 200C with 0.4mm nozzle and 0.1mm layer heights. PLA is just soft enough to flex slightly as you insert rails through spikes but rigid enough to hold rails at the proper gauge.
You will almost certainly need to experiment with your printer settings to achieve satisfactory prints.