(I didn\'t know where to post this so, I decided that this whas the best place to gues;))
It is vacation so I had some time to draw a sketch of a posible transportation device. I\'m a very bad artist but any ways here it is
in here.
It should also work in the real world. I\'ll explain how it works.
1). You got a cabel track where you can slide an platform unther (when you suspend the platform with rings unther cabel)
2). There is a empty barel. While this barel is empty the platform can slide to a level lower then the current.
3). When you fill the barel put prefent it from lowering, you got a barel that want\'s to go down. If you attach a rope on it, the barel will pull the rope when it falls. This rope can be used to pull the platform back up again. when the platform is back up again you make the barel leak water and so it becomes empty again (see step 2).