Tomy Plarail compatible train track.  Tight 45 degree curve, just enough to allow a 3-car train to get around a 180 degree (4 printed sections).  Useful for creative layouts that lack space for normal radius corners.  I got the idea from a commercial cross-track that included switches to make the train turn rather than go straight through.  I copied that turn radius.  It works... just.

The model prints and fits very well in PLA.  You may need to scale for other materials.

(Now free.   Get the bundle if you want to buy me a cup of coffee.)