Say if you want to run long trains, as in 40 or more cars and are not stupid putting light cars up near the front of the train. Without any grade what is the smallest circle of track that will not make cars tip inside of the curve and derail?
I have run 30 car trains on 042 curves but I would expect that to run 40 car trains you have a pretty good size layout. If so I would max it out with the largest radius possible. On my latest layout the outside main is 081.
All my curves and switches to move from one mainline to the other are 072. Seems to work great for long trains.
I have a straight section of track that goes down at a 2% grade and into a 42" diameter, 90 degree turn to the left. The trains can roll real fast down the grade and into that curve, but I have yet to have a derailment due to the speed.
I run 031 & 042 curves and have found that 031 limits you as to size of the frieght or passenger cars in length as well as how many you can run on one train. 042 works better even with some of the engines that are being made today, unless the instruction sheet calls for a much larger curve.
Other things that can cause derailments are going too fast, or stopping too fast with a long train.
Lee F.