This is very cool. An automatic door is always nice. There is a question of safety that comes to mind as yoguy121 brought up. What if the door were to get stuck? What if you lost power or worse, there was a fire. If you don't mind some suggestions, this may save your life or your child's.

The "return action" of the Star Trek Turbo-Lift doors didn't really have a sound to them (until much later in the series that is). So, perhaps the "return spring" method of closing isn't such a bad idea.

The thing I find dangerous is that you didn't incorporate any kind of "Manual Override" in your design. Since you're using compressed air as the actual power for the door pneumatics you wouldn't need electrical power in an emergency. Just a bypass valve in one of your access panels or add a new panel or two. One for both sides of the door, because you never know what side you're going to be on when power goes out and you need to get in (or out) of the room.

Also, if you're thinking that a battery backup will suffice to answer these issues, you're just begging for problems. Battery powered UPSs are notorious for having the battery go bad from non-use. Yes I said NON-use. Plus the power that compressor takes at start-up will just pop the weak little breaker on the UPS leaving you still stuck on one side or the other. So I wouldn't bet my life or my kids life on a $50 UPS you got at Best Buy.

This is a mechanical device and it should have a manual bypass. Seems to me that this is a no-brainer and all that's needed is a couple 1/4turn ball valves and a couple anti-reversing valves installed.

A "Neat Door" is not worth dying over because you cheaped out. In my opinion, there is never a "Good day to die".

This is very cool though. There are still other things that you could do to it. Like add an RFID system or Thumb-print scanner or freak out your friends with an Ocular or Handprint Scanner to open the door! How about Voice operated command system or just a simple contact pad (like in the grocery stores) or a short range motion detector to activate it.

Also, there is a "single ram" method to open both doors that goes hand-in-hand with the "spring return" closure, using a thin cable and a couple small pulley-type wheels. Super simple design uses only 1 air line to the ram! This would decrease the cost and complexity of the build by a factor of 4 (don't ask, it just sounds good). So, you could have done either 2 doors with the parts you now have or just saved youself from buying the second ram, the extra hosing and fittings and the time it took to install all that extra stuff.

If you're interested, PM me and I'll send you a drawing of the modification.

These are just some things to think about.

Good job with the instructable. I liked it and so did a bunch of other people!