I have set up a jig in the garage to build track panels.
There are slots for the ties which are 15" 2x2. Each panel takes 30 ties, 2 rails and 120 pan head screws. I have 6 track gauges at 7 5/8". It takes about 45 min to construct a panel.
I have a rail bender that puts a 30' radius curve in the track. The jig can be formed into a curve and the bent rail attached to the ties.
Then I take a straight rail and using the guages, form it to the curved rail for approx. a 40' radius. If I use 2 bent rails together I get approx. 30' radius.
I bend my rails by pulling them through a rail bender set at 30' radius.