I'm working on expanding my Minecraft Redstone experience and contraptions. Here, I have a 2 blocks high x 3 blocks wide section of a tunnel with a track approaching it that is meant to act as a "blast door" or "flood lock". The minecart arrives at the detector rail, the three pistons in the ceiling and floor retract, and the one in the side pushes the rail out, delayed slightly. Perfect. enter image description here enter image description here

The problem, however, is when the cart moves through the gate and the blocks return to their original location. The yellow block that the rail is resting on gets pushed up, taking the rail up with it (and both sides) immediately. Then, the side piston retracts, taking the yellow wool block sideways, snapping the rail into three pieces. enter image description here

The wiring is fairly simple (which is probably my downfall).

This is the wiring for the "lower" pistions. The redstone torch (next to the detector rail) turns off, retracting the pistons. enter image description here

The wiring for the upper section is equally simple. The redstone goes up and onto the area where the two glass sections are, hitting the repeaters and triggering the pistons. enter image description here

Finally, the wiring for the track piston. Delayed and inverted this is most likely to be the issue. enter image description here

What can I do (is it even possible) to get this to work?

  • very nice design! (I didn't know sticky pistons work for railtracks)
    – Zommuter
    Commented Jan 10, 2012 at 20:59
  • @TobiasKienzler, yes, sideways they do. Try to place a track on top (on the sticky part) or on top of a block on the sticky part and it fails. That's why I had to go for a 3x2 design rather than a 2x3 that poppued the track up from underneath. I expect it could be done with a double-piston setup though.
    – tombull89
    Commented Jan 10, 2012 at 22:40
  • 1
    Not entirely convinced that Wool is the best material for a blast door. Commented Jan 11, 2012 at 21:12
  • @TomO'Connor: It's not, but it's the most aesthetically pleasing. Maybe "blast door" was the wrong word, as it's more likely to be a "flood lock". I could replace it with iron and gold blocks but it doesn't really matter.
    – tombull89
    Commented Jan 11, 2012 at 21:25

3 Answers 3


I've made a video of a working example:

All you need are properly calibrated repeaters (4 ticks each), a "short-cut" for the door pistons and an inverter on one of the system parts.

  • nice work. And quick, too!
    – Zommuter
    Commented Jan 10, 2012 at 21:12
  • 2
    I like to debug things :)
    – Alec Mev
    Commented Jan 10, 2012 at 21:15
  • 1
    that's the spirit :) If only big publishers shared that enthusiasm...
    – Zommuter
    Commented Jan 10, 2012 at 21:21
  • Nicely done. This is why I love gaming.se - I wasn't expecting a video. So, I could replace the level with the minecart detector, and add repeaters to delay the door opening until the cart gets close enough, and do the same thing the other side for a returning minecart. I hope this would work online, although could depend on lag.
    – tombull89
    Commented Jan 10, 2012 at 22:45
  • .. Thats 'all' thats needed!? Sounds like alot to me!
    – James
    Commented Jan 10, 2012 at 23:12

What you need is for the doors the change both before and after the track moves. What you want is a separate track of repeaters to keep the doors open for longer so that the track retracts before the door closes.

  • +1 (the repeater track should be in addition to the original one)
    – Zommuter
    Commented Jan 10, 2012 at 20:56

Adding a second connection to the blocks in addition to the other one but with a delay slightly longer than the railtrack one should do the trick.

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