Never mind, I found the thread where I asked the question the first time. The recommendations vary from .035" to .039" music wire or piano wire or whatever you want to call it.
If you go with a larger diameter wire, make sure you check that it will fit in the hole in the Tortoise as well as the hole in the turnout. And do this before you mount the Tortoise; you don’t want to find out that it doesn’t fit after the wire is cut and bent.
.039 is pushing it, .042 definitely won;t fit in the Tortoise hole withotu drilling it out.
One questiosnw hat is being used and what turnouts are being used - I used .039 with my servos through TWO layers of 2" foam, plus 1/4" plwood plus the thickness of cork roadbed and had no issues with Atlas turnouts either moving the points or holding the points in position. Over 4" of length between the servo and the throwbar. Servo vs Tortoise should make no difference - the servo mounts I used worked on the same principle as the Tortoise, one end was fastened to the moving part, then the wire went through a small hole as a fulcrum, and then through the hole in the layout up to the throwbar. 3/4" ply plus homasote, I can’t imagine anything more than .035 would ever be needed, except maybe Pecos with the springs still in them, or short (small frog number) all-rail type turnouts. If the points don’t move freely, especialyl with Atlas turnouts, make sure there is no ballast or glue around the throwbar - they take almost no force to move.
The distance from the top of the Tortoise to the top of the throw bar is 1 5/8" (3/4" plywood, 1/2" Homasote, 1/4" cork approx. and 1/8" to the top of the throw bar.
I’ve already ordered the .039" wire so we will go with it. I realize that we will have to drill out the fulcrum hole.
Some of the used Tortoises that I got on eBay already had heavier wire in them, but the wire was too short.[sigh]
Randy, I was getting ready to challenge you since I was the one who replied about using 0.039 and 0.042 wire. But, then I thought it best to check my wire before replying. Glad I did. When I posted my earlier reply, I spoke from memory…always a bad thing.
I just went down to my layout to check. I use 0.032 (not 0.042) and more recently I bought 0.039 wire. Both of those sizes fit without any modification. My bad. I changed my earlier reply to reflect this correction.
The Tortoise comes with a 0.025 wire, and I often wonder if that isn’t strong enough. The reason that I first bought 0.032 wire years ago was because my LHS guys recommeded it, and I simply followed their recommendation. My more recent purchase of 0.039 wire was done because at the time 0.032 wire was not available from my source.
I think with free moving points, like Atlas, the included wire should be plenty stiff enough. What the give you isn’t long enough for much for that your basic plywood with cork roadbed construction, but also the shorter the wire the less thick it needs to be to get the job done.
I should go check my stock to see if I have .039 or .032 - now that I think about it, I may have used .032 myself. I have a couple of different sizez - one turnout ended up too close to a cross barace even for the tiny servo, so I had to fashion a different type of linkage so I used some brass tube to bring the wire up to tie level then bent it along parallel to the rails to reach the throwbar (a few ties distance). Funny thing is it took no funky linkage under the table - it was all one long piece of wire! The side to side motion of the servo ALSO imparted a rotational aspect to it, which I notriced when operating a conventional turnout where I hadn’t cut the wire off to length and stuck blue flags using painter’s tape so i wouldn;t poke an eye on the exposed lenth of wire - in addition to tilting side to side and pushing the throbar, the flag spun. So it worked out that while the wire went side to side coming off the servo, it was constrained in the brass tube (going through the foam unprotected it would have worn the hole wider), and then with the wire bent over parallel to the rail, the twist became a side to side motion with was able to move the points.