How do I retrofit a TORTOISE™ to a turnout that is already installed?
Since the TORTOISE™ requires a clearance hole for its actuating wire through your layout subroadbed and whatever roadbed material (cork, homasote, etc.), this can be difficult and somewhat dangerous to attempt once a turnout is firmly mounted to the roadbed surface. One slip of a power drill coming up from underneath and you have destroyed an expensive turnout. Here is one method we have found to be reliable and safe.
Start by drilling a small hole DOWN from the top through the throwbar hole. Your drill bit will need to be long enough to penetrate your roadbed and support materials. You can find small diameter long drill bits at industrial supply houses like McMaster-Carr. http://www.mcmaster.com/# Try to keep the small pilot hole perfectly vertical. Then get a drill stop (a collar for larger bits) that will fit a 5/16" bit ( http://www.mcmaster.com/#drill-bit-stop-collars/=ajsnh0 ) and see if you can locate a brad-point 5/16" bit. Brad point bits cut relatively flat bottom holes but do have a small center point which will follow an existing pilot hole. These should also be available from McMaster-Carr :
Now, tighten the collar on the bit so that the exposed bit length INCLUDING THE POINT is just under your total thickness of roadbed and support materials. You want the point of the bit to NOT QUITE penetrate the total. Do a couple test holes to make sure your setup is correct. Then drill up from the underside following your pilot hole and make sure to keep your drill bit as perfectly vertical as possible. Check the drill stop collar often to make sure the set screw(s) remains tight.
Now for the tough part..... removing the final little bit of homasote or cork. We recommend getting a handful of 5/16" OD brass tubes from K & S Engineering (www.KSMetals.com). Leave them long but file or use a saw to fabricate a handful of "teeth" on one end. Take a flat file or sanding board and "sharpen" the toothed end a bit with a slight bevel. Then insert the tool up the hole and rotate back and forth to cut through the final bit of homasote. There are steel hollow gasket cutters available that might do this as well. Again, check McMaster-Carr.
Good Luck, take it slow and careful and all will be good.
You can also place your hole to the outside of the track by boring a new hole through the throwbar extension. You will run less risk of destroying the turnout that way, but the method outlined above should be safe.