All 3 of the above engines were built by Rocky and Randy Rockwell. The one to the right is of course the "Monitor" engine. The 2 green engines are Root and Vandervoort and the Rockwells not only built these engines, but supply the castings as well. The one on the left is a 1/2 scale horizontal engine. There is no published information yet on the vertical engine. They just got this one running, but will have both castings and drawings available for it soon. You can take a look at their website, but as I said, no information there yet on the vertical.
http://home.earthlink.net/~randyarockwell/