I had done a rather extensive fabrication of a turntable in O-scale. Using some Diamond Scale parts and a Bowser deck detail kit.
Here is a link to another post I did on another forum. I should give you an idea as to how complex the project can be. http://ogaugerr.infopop.cc/eve/forums/a/tpc/f/3681097934/m/6381056754?r=6381056754#6381056754
Pictures posted on my website.
http://www.mikedian.net/trains/Model%20Train%20Pics/Model%20Train%20Pictures/Fort%20Pitt%20Hi-Railers/Turntable/index.html
Here is a link to another post I did on another forum. I should give you an idea as to how complex the project can be. http://ogaugerr.infopop.cc/eve/forums/a/tpc/f/3681097934/m/6381056754?r=6381056754#6381056754
Pictures posted on my website.
http://www.mikedian.net/trains/Model%20Train%20Pics/Model%20Train%20Pictures/Fort%20Pitt%20Hi-Railers/Turntable/index.html