Refined Bullfrogs

It might not have been apparent, but that first Bullfrog posting showed pictures of a proof of concept installation. Now that I am installing them on the actual layout, here is an update on some of the refinements I’ve made.

The two shown above are the switches for the two spurs off the siding on the south section. The top (nearer) one is the second, and slightly improved version. Here are the improvements made:

  • The switch stand is thrown by an accurately drilled plate, rather than relying on bending the end of the push rod in a pig tail. The pig tail proved to be too difficult to adjust, and when it was made out of threaded rod, it didn’t allow the end of the switch stand lever to glide through the hole easily. I’m calling this plate the “push rod extension” and it is tapped to engage the threaded rod on one end, and drilled to allow the switch stand lever to rotate at the other end.
  • The switch stand lever is supported by a heavier tube, which also serves as a bearing. This keeps it from flexing as much and thereby finding other ways to accommodate the movement of the push rod, rather than rotating. Notice in the bottom installation, I didn’t do this, and had to add a collar to the switch stand lever to force the rotation; you can see it is trying to bend.
  • I’ve beefed up the Bullfrog itself with a chunk of 3/4″ plywood. This gives me a positive place to anchor the end of the choke cable, and also takes the strain off the Bullfrog itself.

I found the switch stand rotation is surprisingly sensitive to the length of the extension to the push rod. The best thing to do was to center the Bullfrog, and mark the extension plate at the hole in the Bullfrog and at the switch stand lever. Even then, there is a lot of adjusting to be done by screwing the extension up and down the threaded rod; I was glad to be working with the module upright, rather than trying to do it Michelangelo-style.

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