I designed a drop down 'swing gate'. I was unable to find working hinges in O scale so ended up with the design below.
After gluing the gate planks together I glued an 1/8 inch spacer to the bottom then some 'stem' wire to the spacer. I drilled holes into the ends of 1/8 inch bass wood, rounded the ends then cut them to length. When I tried gluing the assembly to the platform the wire came off the spacer. what you don't see is an 1/8 in angle I glued over the wire and onto the spacer.
After gluing the gate to the platform I ended up gluing an 1/8 piece further down as a stop so the gate would not drop straight down.
With stop this is as far as the gate will swing down. I still may buy some chain to attach the ends of the gate to the posts.
Some views of the platform