Instructables

Step 3: Fabricate door bracket / install pistons

Picture of Fabricate door bracket / install pistons
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Next I had to fabricate a bracket to connect the pistons above the door to the actual door.  I welded up a bracket out of some steel flat bar from Home Depot and attached it to the back of the door with a spacer block. I could have really used some more advanced tools at this point, but I had to work with what I had at the time.  You can fabricate this bracket from sheet metal, steel bar, wood, or whatever you can find.

With the two brackets fabricated and installed, I mounted the two 16" pistons above the door, side by side. Air supplied to the back of the pistons would open the doors, and air supplied to the front of the pistons would close the doors, as seen below. I rigged up the valve temporarily to test everything out.
 
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Dave920403 years ago
I hope y'all realize that the doors on the various ST sets weren't really operated by anything other than by people opening and shutting them. No fancy mechanics, no electricity or pneumatics. The sounds were added in later by the Foley people.
yes, and I bet yer a lot of fun at parties ;)
Markus8903 years ago
Saying about opening in an Emergency, if you use MattPL idea but in reverse and use the Air to hold the doors closed.
That if there's a power/air failure the doors will automatic open.
I spent far too much time thinking about this when it was featured on Fark.com the other day...
but yes.. yer absolutely right.. back from my old Industrial automations day this is how a such a circuit would be wired / piped. standard procedure for a "crush point" would be a closed circuit. as in , the Solenoid engaging the pneumatic cylinder had to be engaged, to engage the tube. loss of control voltage, as in.. turning it off, would send the cylinder to its at rest "open" position.

so.. if you loose power at the house? the holding circuit drops out, and the door opens.

this is standard E-stop stuff, or as we called it in the industry , *slapping the OH SH*T!" button"
CaptainSlug3 years ago
Rather than use pneumatic pressure to close the door, you could simply use an extension spring to pull the doors closed when the air supply is closed off and the cylinders are vented.
Controlling the speed of them closing could be done with flow control valves.

If you want to allow the doors to be forced and held open by hand in the event of a power outage you could use a solenoid valve with a check valve. Setup to allow the now unused ports of the air cylinders to both vent and draw air when power is provided, but only vent (and not draw) air when the power is cut off.
The resulting vacuum in the cylinder will prevent the springs from pulling the doors closed all the way.

If you need a diagram of the above I would be happy to provide one.