The way caboose ground throws are designed to be installed is sitting on top of the head blocks, with the pin going down throw a hole in the throw bar. Here's a 208S ground throw mounted the way caboose industries intended on wood ties on the older section of my layout.
|Caboose 208S mounted as designed.|
Atlas turnouts don't have long head block ties, so some form of extension is needed. While I was experimenting with that, I came up with what I think is a better approach to get both extended head blocks and less conspicuous ground throws.
|Inconspicuous ground throw on Atlas O turnout.|
The red paint on the ground throw handle indicates the turnout is reversed. The opposite side is painted green for normal. It's a nice idea I got from a friend that helps orient visitors.
Inconspicuous is achieved by mounting the ground throw at roadbed level instead of tie level. Since I used homabed, I notch out the beveled edge by the throw bar and fill in a wood block to match the roadbed height. The pin sticking down from the ground throw is cut off, and I drill and tap a small hole in the end to accept a small screw. The throw bar on the turnout gets shortened a little - pretty much just clip off the part on the end - so it ends up almost flush with the ends of the ties when you push it so the opposite point hits the opposite stock rail.
|Modified ground throw ready to install.|
Then attach the ground throw to the throw bar, center the points, center the ground throw handle, and mark where to drill holes to screw down the ground throw.
|Center everything to locate holes.|
And here it is in working order.
|Working but ugly.|
At this point you could stop, but it's not pretty. Once I'm sure it's lined up and working correctly, I add the head blocks. Since the ground throw is at roadbed level, they need to go around the ground throw. I clip out a pair of ties from some Atlas flex track leaving the bit of plastic that joins them in place for the time being, and cut off the other end at the tie plates. Here's a pic of it at that stage sitting where it needs to go, but as you can see it doesn't fit down over the ground throw. Yet.
|Test fitting head blocks.|
Using a burr in a dremel tool, a razor saw, an xacto knife, a mill file, and a rat tail file I remove everything that seems to get in the way of a fit. The plastic bit joining the two ties keeps you honest about alignment at this stage. Here's a shot of it sitting in place after I made it fit.
Here's a shot of what the bottom looks like. The notches get around the "hips" of the ground throw, and the cross groove in the middle clears the tops of the #2 wood screws I mounted the ground throw with. Since my wood block ended up just a smidgen above the roadbed level (oops) I filed the entire bottom a little.
|Bottom view of trimmed head blocks.|
The final step is to cut off the other end of the ties at the tie plates. I used CA to glue them to the ends of the switch ties and the roadbed. Being VERY careful not to get any one something that's supposed to move! It would be nice if the ties were just a bit longer, but you can't get a longer molded plastic Atlas tie without mangling a switch - something I'm not willing to do. And I think the fact that the head blocks are the same material and surface texture makes them blend in better than using wood or raw styrene shapes. Here it is glued up.
|Head blocks glued on.|
All that's left to do is use some putty around the edges to keep ballast and glue from getting in where they might cause trouble.
The ground throw sticks up above rail height only about 1/8 inch, so it can be pretty close to the track with no concern about pilots or whatever hitting it. Looks better at that height too.