Don't know what it's called...

[corytran]

I'm thinking of this robotic part but I have no idea what it is called...

You've probably seen this part so many times on doors and stuff that opens and closes...

It's a cylinder tube with a shaft inside of it and the shaft goes in and out....

I need this part to build a box that opens and closes...does neone know what this part is called, where i can get it and how it is powered?

[bulkhead]

Electric linear actuators? http://servocity.com/html/12v_linear_actuators.html

[ed1380]

hydraulic or air powered?

[corytran]

Yes! That's what i am looking for...but OMG they are SOOO EXPENSIVE!!

[Admin]

The thing thats on doors is called a pneumatic spring, and they are fairly cheap ($10-$20).
(assuming you didn't mean a linear actuator)

[corytran]

where can i get this "pneumatic spring" thingy?

and how is it powered?

[Steve Joblin]

I assume you are thinking about this device?  http://img.underbid.com/Theidealplace/383137343435.jpg   If so, any hardware store or home center sells them.   They aren't powered at all... there is a spring inside the unit that stretches when you open the screen door.  when you let go of the door, the spring contracts and closes the door.  there is a pocket of air in the tube that prevents the door from being slammed shut, but the unit has little hole letting the air out slowly, so evententually the door closes.

[Admin]

where can i get this "pneumatic spring" thingy?

and how is it powered?

Well its not powered, its not an actuator - just passive. Its just like what you have on the trunk of your car/van . . . its that spring that makes that hissing sound and holds the hood open.

Go to mcmaster.com and type in 'gas spring' in the top left search box. A new page will come up, with not only parts but also some theory and equations to help you select which one you want. It even demonstrates exactly how its used for opening/closing the lid of a box (by coincidence is what you are working on, no?)!

[krich]

A neighbor of mine uses screen door pneumatic springs in his Halloween animatronics displays.  If you remove the "adjustment screw" and screw in a brass fitting, you can hook that up to an air compressor and electronic valve (sprinkler valves work great).  Activate the valve and the air moves the actuator.  Turn off the valve and the system bleeds air at a slow enough pace to drop the actuator back into position.

This makes a very cheap, but not very precise actuator.  Good enough for what he's doing and he can get replacement parts at any hardware store.

I bet you could find instructions on how to do this on the internet.

[bukowski]

A good way to do it if you want it electrically controlled would be a simple linear solenoid. Rig the box lid to a spring and attach the latch to a solenoid. They cost about 9-13 bucks on mcmaster.com.