Gas lift office charis

Hi,
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
works.
If this is OT or anyone knows a better group for this question, please let
me know.
Cheers in advance,
Bruce.
Reply to
news.virgin.net
I recall some new chairs being delivered to my office. The top was just pressed onto a tapered spigot. A thump would dismantle such an arrangement - but never tried it.
Reply to
John
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.
nasty business.
Robert
Reply to
RobertL
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.
Reply to
news.virgin.net
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 manner.
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 them.
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 go there.
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 all).
Reply to
Andy Dingley
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).
Reply to
Andy Dingley
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 ?
Reply to
news.virgin.net
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.
Gas lift
Reply to
Andy Dingley
Thanks, I get it now. I'll stuff a bit of wood next to the piston until I can organise a repair - It's a nice chair that works well for my back and I'm reluctant to change.
Reply to
news.virgin.net
In message , Andy Dingley writes
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 reliable Dieseling.
Fortunately, age, discretion and a firearms certificate intervened.
regards
Reply to
Tim Lamb
There was a James Bond film where Q had made a contraption that did that.
It was demonstrated and the throw away line was "That'd bring tears to your eyes"
Reply to
Andy Hall
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.
Reply to
JA
There is a new product to fix an office chair with a failed gas lift cylind= er. It called a Chair Saver kit and can be found at
formatting link
= No tools are required and installs in under a minute. Cost 8-20 times less= than a new cylinder or buying a new ergo chair.
Reply to
grid1010
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.
Brian
Reply to
Brian Gaff
wrote:
r.com. No tools are required and installs in under a minute. Cost 8-20 times less than a new cylinder or buying a new ergo chair.
Fuck off spammer (trad.)
Reply to
Steve Firth

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