Mel,
I bought the parts in the very first link You posted....just for the cog rail that the scratch/bash bridge needed to lift it. All those parts are very finely made without any flash. Also used many gears from them also for the bridge. I recommend them.
Take Care!
Frank
The cog rail is sandwiched between the two truss girders (pointed down) that are pulled into the control tower with more gears and two electric motors.
zstripe Mel, I bought the parts in the very first link You posted....just for the cog rail that the scratch/bash bridge needed to lift it. All those parts are very finely made without any flash. Also used many gears from them also for the bridge. I recommend them. Take Care! Frank