Load Chapter 48, go right and climb up the wall infront of you to where the patrouling light is.
Wait until the light goes to the right and then turn the crank as far as you can until the light comes back.
You want to put the contraption the crank moves, right above you, so the lower arm of it is right below you, keep in mind to evade the light while you do this.
After you managed to get it in the right position, go back to where you came from and dive into the small space of water before the wall.
Follow the way to the right and get to the surface where you should be able to access the platform with the machine for the achievement on it, if you put the crank in the right positon.