# Safely de-pressurizing an air spring



## hman (Apr 22, 2014)

Actually, more like shop-*UN*made tooling ... but this is my best guess for where to post it ...


I've often used various odd parts of old office chairs (which I get at Goodwill for a very few bucks).  For instance, the base "spiders" make dandy Lazy Susan "bearings."  I've also kept a few of the lift cylinders, hoping I could find a way to "harvest" the nicely polished rods, etc.  But I've been paranoid about cutting into them, given the pressures involved!:nono:

Today I figured out how to do it safely!  The breakthrough came when I thought about how well polished the rod has to be, in order to maintain the pressure seal against the internal gaskets.

I started by grinding a tiny groove in the rod with a Dremel disk. It doesn't need to be deep, and probably doesn't need to be as long as I made mine (~1/4").  The groove is visible in the photo, just outside the cylinder.




Next, I put  couple of washers around the release button at the other end.  Normal air springs don't have this, so the washers aren't needed.  I just needed to end up with a flat surface when the button was depressed, as it doesn't retract completely.




Finally, I put the air spring into a suitable (ie, long enough) gluing clamp.  Before tightening the clamp and compressing the air spring, I made sure that the groove was facing down toward the table.  I also placed a rag atop the air spring, so that any oil or whatever wouldn't fly around.  I then slowly tightened the clamp.  The first 1/8" or so compressed the release button.  Then after about an inch, I started to hear a slight hiss.  




I left the assembly alone until the hissing stopped, then closed the clamp a bit further to be sure of the last of the pressure.

Once that was done, I took the deflated air spring to the lathe, sliced the ends off the cylinder, and completed the deconstruction.  The "harvest" was not just a nice piece of very straight, hard, and highly polished shafting, but also some heavy walled tubing (the outer cylinder) and a piece of thinner tubing that was inside the assembly.


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## 12bolts (Apr 22, 2014)

I just put a small cut in the cylinder wall with a hacksaw. When it starts to hiss just stop cutting and let it go. When it stops hissing complete the cut.


Cheers Phil


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## Rbeckett (Apr 22, 2014)

I use a small drill and work slowly to avoid a broken bit and allow the pressure to bleed the oil out too.  Just make sure you have your safety glasses on your face and not on top of your head and go slow and you wont get a big gush of oil or gas when the drill breaks through the tube and into the oil.  My little 8 speed mini drill press works perfectly and the oil keeps the table and machine lubed so that corrosion stays away!!!!  2 Birds with one stone, I like that!!!

Bob


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## hman (Apr 22, 2014)

12bolts said:


> I just put a small cut in the cylinder wall with a hacksaw. When it starts to hiss just stop cutting and let it go. When it stops hissing complete the cut.





Rbeckett said:


> I use a small drill and work slowly to avoid a broken bit and allow the pressure to bleed the oil out too.  Just make sure you have your safety glasses on your face and not on top of your head and go slow and you wont get a big gush of oil or gas when the drill breaks through the tube and into the oil.



I'd considered both of these methods, but thought they had several disadvantages - 
(1) You're working on the upper surface of the cylinder, so any pressure/oil/crud being released will be directed toward YOU.  Safety glasses are of course vital, and a shield on the drill bit might be of help ... but who wants the rest of their face (or shirt) covered with oil?
(2) The break-through point will always be a surprise, and if you happen to be cutting or drilling a bit too fast at that instant, you can get more than you bargained for.
(3) Once you've broken through, there's no stopping the outflow.  With the groove-and-compression method, you can always back off the clamp, or even knock the air spring out from between the clamp pads.
(4) As I discovered with the chair lift, there's all kinds of "hardware" at both ends of the cylinder.  If you drill or saw at the wrong spot, you might get into an area where the pressure won't release ... restart.

Maybe I'm just being paranoid, but I do like to approach the unknown with a lot of caution.:bitingnails:


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## David S (Apr 22, 2014)

John I commend you for putting safety first.  You didn't really know what the stored energy was, or what else was in there, so you proceeded with an abundance of caution.  You could control the release of energy and no one got hurt.  And as you say could back off if needed.  I like your process and also all the goodies you got from the salvage.

David


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