Pictures speak a thousand words, so:
Down:
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In the down position the platforms form a flat walkable surface, and in the up position the form something like urian's stairs: each row of platforms is 1 block higher than the previous row. The 'drawbridge' makes a 45° angle with the ground. So in the up position the platforms can be climbed up from one side, but not the other. The 'drawbridge' makes a 45° angle with the ground.
There are 2 ways of making this:
1: The easiest: like in the previous pictures, each pulley is placed right above the corresponding platform's up position, and the amount of rope is added to how much the corresponding platform must be lowered to reach the down position. Each pulley is connected with gearboxes and axles to a mech power source offcourse, with a lever or something controlling up or down by stopping/starting a gearbox. Quite simple.
In my pictures i made it so that each pulley recieves mechanical power or is cut from it at the same time by adding extra gearboxes at the right places, so that the movement of the platforms is smoothly. This complicates things but is not necessairy.
2:
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The pulleys are all placed at the same height. When the drawbridge needs to go up, the pulleys recieve mechanical power and each pulley is then successivly disabled (paused) by redstone current each time with the correct delay so that the next pulley to be disabled can lift its platform 1 block higher than the previous pulley. Since the pulleys have to be right next to eachother and they have to recieve their current at a different time, this is as said rather difficult to make and requires alot of redstone and place. As you can see in the pictures i only wired half of my test drawbridge to go up because i was tired of it when that part was finally finished.
Picture of the wirering:
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Also, this was made before 1.7 and turntables so it might me possible to make this more compact but i'm not going to try it because well imo the first method is way better anyway. But it's something to keep in mind if you do want to try this.
So, opinions?
