My track plan called for a double crossover. I am using a Shinohara Code 100 double crossover I had from a previous layout. The actual installation of the crossover was not difficult but controlling the turnout was proving to be a small challenge. The challenge being faced was that I did not want to use 4 tortoise switch machines to throw this single set of turnouts. Ideally one turnout would have been the best solution, however, the final setup used two switch machines.
Two Tortoise switch machines were used with very little modification. The only change was the addition of a second throwbar to the drive mechanism of the switch machine. This additional throwbar was manufactured from a piece of 1/4" wide brass stock.
The challenge of using only two switch machines was to build the necessary linkage to activate the other two sets of turnouts on double crossover (for a total of 4 turnouts).
This secondary set of linkage was fabricated from 3/8" wide x 1/16" thick brass stock, 1/2" wide x .025" thick brass stock, .039" diameter piano wire (what I use for standard installation of Toroise switch machines), 4 #2-56 screws, 1 #4 x1/2" screw, 1"x 2"x2 3/4", 2 1/4"x2 1/4"x 1/4" luan plywood, an 1/8 tall standoff, and one #4 washer.
The 3/8" brass stock was cut to about an inch in length. Three holes were drill in this link. The outer two holes were drilled and tapped for #2-56 screws. the center hole was drill slightly larger than the diameter of the standoff (the standoff acts a sleeve bearing). The washer and the #4 screw act as the pivot point holding the standoff in place and the washer keeps the link from falling off the mount. The wire up to the turnout is connected via a 2-56 screw to the lower hole in the link. The upper hole connects the link to newly fabricated throwbar on the Tortoise switch machine.
The fulcrum point is constructed from the 1/2" wide brass stock. It is attached directly to the 1"x2" mount at the same level as the fulcrum point on the Tortoise with 2 #2-56 screws.
The secondary set of linkage uses the same template, for mounting, as the Tortoise switch machine. This greatly sped up installation of the completed unit. There are two sets of Secondary linkages for the double crossover, but they are both identical.
UPDATE: I did find a problem with my design when I went to wire the double crossover. The Shinohara switch that I used has metal throwbars and because of this I was getting shorts every time I tried to power up the switch block. What turned out to be the problem is the linkage was conducting electricity. I replaced the linkage between the secondary linkage and the tortoise switch machine with an insulated throwbar made from Popsicle sticks. This eliminated the shorts in the switch.
I have also been asked how I mount my turnouts. I use the template that comes on the instructions with the switch machine. I cut out the template and mounted it to a scrap piece of 1/4" luan plywood. I then drilled a 5/16" hole and 4 smaller 1/16" holes. I glue a 5/16" dowel into the larger hole. This dowel fits into the hole I drill below the switch machine, making a perfect alignment every time. I use the small holes as drilling guide into the underside of the railroad, for the mounting screws used to hold the tortoise in place.
Also I have seen many people having a problem with the original wire that comes with the tortoise. I don't even bother with it because it is not stiff enough. I use .039 piano wire on all my Tortoises. I also don't try to stick the larger wire in the hole in the Tortoise. I simply use the screw to hold the wire. I bend the wire such that wraps around the screw and is not reliant on the hole in the actuating mechanism (see below).
I have installed 25 tortoises so far with another 15 or so to be installed. It takes about ten minutes to install and wire the turnouts for use. Now I just need to buy the other 15 tortoises.