I have a gas lift office chair which started slowly sinking when the
weather turned cold a couple of weeks ago. I've dissassembled it but the gas
lift bit is still connected to the tilt mechanism at the top. I can't see
how to dissassemble it further for access the seals. Is there any way of
repairing these ? I tried pouring oil down the valve at the top to improve
the gas seal but it made no difference. If the cylinder has to be replaced,
I can't see how it detaches from the tilt mechanism - anyone know how this
If this is OT or anyone knows a better group for this question, please let
Cheers in advance,
is it not dangerous to dismantle these gas struts becuase they can be
highly pressureised? I even recall that someone was killed by one
which came a part and fired the steel rod upwards penetrating through
the seat of the chair while he was sitting on it.
I think there is a spring in there, no gas pressure especially since it's
got a leak. I thought it might be possible to replace a seal or use a
lubricant to improve the gas seal of the existing seal. This must be a
common problem with an appropriate bodge.
You can't fix gas lifts. If they've used a standard part, then you
may be able to replace the gas lift cartridge with another one (there
are on-line vendors with catalogues). This is often useful in big
offices with standard chairs (strip the cartridge from the one with
the broken arm, etc.) but usually it's difficult to buy a new
compatible cartridge for less than the price of a new chair. 10-15
years ago was another matter, but now any retail-market stuff just
arrives magically for almost nothing from the Chinese chair-pixies.
You _really_ can't repair gas struts themselves. They're made by roll-
forming the top to lock the seal cartridge in, and that's a one-shot
process. Even the factory couldn't open one up in a re-sealable
Nor do gas struts necessarily fail because the seal has just failed.
They fail primarily because their gas pressure has dropped, and that
can happen slowly too. If you _could_ repressurise them, you might not
even need to replace the seal, in order to get a few more years out of
Opening gas struts is too hazardous to discuss on Usenet, for fear of
legal action by vendors of pressurised gas containers (those with long
memories might remember what I'm talking about!). It's certainly
hazardous though, same as opening up any hydraulic accumulator. Don't
It is possible (as it has been done at least once to my knowledge) to
re-pressurise a strut into working order again by refilling the gas
and not touching the seal at all. Vent it, drill the back (away from
the piston travel) solder in a pipe fitting, refill with high pressure
nitrogen and then crimp seal. Not trivial though.
There are no credible reports for anyone ever being "harpooned" by a
chair. Nor does the physics of it make much sense. Certainly I worked
in a BT office in '86 where all our gas-lifts were modified to screw
locks, after such an "incident". I can't prove the incident ever
actually happened or didn't happen, but they certainly spent lots of
money on chair conversions (A few days afterwards I obviously snuck
my hidden cartridge back in - a geek has standards to maintain, after
PS - If you did do this, remember that they need to be filled with dry
nitrogen not air, oxygen must be excluded and the lubricant grease
must be non-combustible under pressure. The only vaguely credible
explanation for the harpooning stories would be fatso flopping down
heavily onto one, then having it turn into a Diesel pogo stick (as any
airgunner will understand).
You know, I don't think I've been asking the right question - I assumed it
was a gas lift because I heard the term and assumed that was what it was
called beacuse gas goes in and out of it as it goes up and down but I'm
pretty sure this one has a spring in it - you sit on it and pull the lever
and it goes down or get off it, pull the lever and it goes up - I'm not even
sure I know what a gas lift chair is now. Anybody clear up these
'conceptual' errors please ?
They're filled with high pressure gas (few hundred psi) but it's just
trapped in one space, it doesn't "go anywhere". It's trapped in the
bottom of the cylinder, the piston sits on top of it and the gas is
merely compressed in situ beneath the piston.
The effective spring rate will change as the gas compresses, so you
need to allow some ullage space at the bottom of the travel, i.e. the
piston never goes all the way down. A 12" long tube might only allow
6" of useful movement. Some extra-compact designs wrap this extra
space around the sides of the cylinder, so there's a smaller cylinder
tube inside a bigger container tube. These can allow nearlly 11" of
movement from a 12" tube.
Gas is cheap, metal springs are expensive. If you need to support a
couple of hundred pounds on soemthing only an inch in diameter, then
it's cheaper to use a gas spring. A metal spring this small and
capable of supporting it is a high-quality bit of metallurgy and not
cheap. It's especially difficult if you want to make a "chair", where
the adjustment range is nearly comparable to the available height to
fit the mechanism into. Chairs used to use metal springs in past
decades, but these were nearly always high-force low-travel things
used through some sort of lever mechanism.
In message , Andy
As a 17 year old, I spent a significant part of my waking hours trying
to configure a piston latch and ether injection system to produce
Fortunately, age, discretion and a firearms certificate intervened.
So do gas lift chairs require special handling when you want to get rid
of them? I've got one whose gas strut is functioning just fine but the
rest of the chair has fallen apart and so I was just going to throw it
out with the normal household waste.
Its a combination of a right charlie and a chair who thinks that making
posts about things they want to sell as if they have just discovered them is
going to fool anyone. Be the product good or bad, who knows but this form of
marketing is a bit stupid in my view.