@StevefromPA posted:You've got good advice above! I've done the 27 to 31, 31 to 42,and 42 to 72.
To answer your question regarding the switches could be a rather lengthy explanation as you have to take into account the switch placement post-change to 042, straight track removal, etc... However, it appears you have a loop with an inner passing that uses o31 switches? In that case, you shouldn't have to change the curve radius of your inner passing but the location of the switches to enter the inner passing may change due to track geometry.
Also, before you decide to go o42, if you are ever thinking of going to o54, o60, o63, 072, etc... you might want to hold off on the o42- I would have in retrospect. Basically, to make a circle using full o54, o60, o72 or o36 half curves requires 16 pieces. Thus, on my layout I have an o72 and three o60s in each corner of the outer loop(used to have 072- 2 o60- 1 half o36 but that o36 was just too tight)
Just wanted to give you a heads up. If you have more questions, just ask.
Thank you for your advice I appreciate you taking the time to look at my issue!
