repairing office chair whose metalwork is badly worn

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Old 06-12-12, 11:08 AM
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repairing office chair whose metalwork is badly worn

Hi. My gas lift chair has worn where the cylinder's piston arm passes through the lower plate. This allows the piston arm to rattle about. How can I weld some filler into it so that it works again?
The fixing ring for the top of the piston is supposed to be a tight fit into a steel pressing but it has worked loose because of stress. I shouldn't weld the ring to the plate because I'll then be unable to replace the gas cylinder. Also could the cylinder get hot enough to explode if I did?
 

Last edited by woolyhead; 06-12-12 at 11:09 AM. Reason: spelling
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Old 06-12-12, 12:06 PM
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Badly worn office chair

Hi again. There are various websites where you can see the details of how the component parts of an office chair are arranged but they are written with the idea that you can use spare parts to fix the problem. In my case however, the worn parts are not replaceable. The rest of the chair still looks new so it would be a pity to throw it away. There may be companies who refurbish chairs of this sort but I wanted to do it myself if I could. I thought that maybe I could either lay some weld metal around the inside of the ring and re bore the hole to size or maybe make a new ring which is under size so it fits tightly. Regarding the hole in the lower plate I wondered whether I should drill/file it out to a bigger size and weld a washer with the right size hole in its place. There isn't much spare height so the washer could only be slightly thicker than the original plate. What it needs really is a replaceable sleeve. Any advice, please?
 
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Old 06-12-12, 02:45 PM
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Could you post a pic or two of the damaged portion? http://www.doityourself.com/forum/el...-pictures.html

I'm not sure if this is what you are describing but I had an office chair once that the piston would no longer hold the chair up to the right height. I 'fixed' it by cutting some pvc to the correct length and sliding it over the piston. That made the chair more rigid but it stayed at the correct height
 
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Old 06-13-12, 11:48 AM
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office chair reoair

Hi Mrksr. I would do so if I knew how to do it but I don't see an "attachment" anywhere on this screen. How do I do it?
In words than: a clamped, steel ring with a central hole about 1.5 inches dia. is pushed inside a second ring as a tight fit. Due to the forces imposed on the second ring by my backside as I move about, the ring has moved and worn away what was once the minute gap between the two, thus allowing the rocking motion. If they were welded together this rocking motion would stop but unfortunately this would also make future replacement impossible. Also, passing through the inner ring is a nitrogen gas cylinder under high pressure.

The second problem concerns a flat steel plate with a 0.3 inch nominal diameter, axial to which runs a ball race about 1 inch diameter. Passing through the race is a circular steel shaft about 0.3 of an inch in diameter, which tries to alter the angle at which it goes through, because of the rocking described above. The forces involved have worn the o.3 inch hole so that it no longer prevents the rocking. Behind the steel plate there is virtually no spare space between it and the ball race and in front of the plate there is only enough room for a washer plus a circlip which fits into the circular groove provided and near the end of the rod The problem is how to replace the missing metal into the worn hole. If you have any ideas please let me know. Thanks.
 

Last edited by woolyhead; 06-13-12 at 11:49 AM. Reason: spelling
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Old 06-13-12, 11:58 AM
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repair worn office chair

I'm still looking at Ray2047 article ref how to send a picture on this forum. I'll try to make it work.
 
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Old 06-14-12, 04:01 AM
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repairing a badly worn office chair

Hi marksr. Sorry about the spelling error last time. I also omitted the work rod after "0.3 inch nominal diameter". I studied Ray2047's report about posting drawings but so far I can make neither head nor tail of it. I don't seem to have the toolbar he refers to so what he says I can't do. What is the procedure for sending a sketch?
In case you are wondering why the rocking motion causes a lot of noise I should explain that there is a washer near the top, between the cylinder and a bigger, surrounding tube, which acts as a pivot so that any (rocking) motion at the top of the cylinder is magnified by the ratio of the lengths of those parts of the gas cylinder below and those above the washer and it's the resulting increased motion which makes the gas cylinder's piston rod bang against the sides of the worn hole in the plate. I suppose a pristine hole would tend to stop the rocking motion to some extent but it's the wrong way to do so as it might put a lot of stress on the gas cylinder. The best way is to stop it at source, ie the loose fit between the rings. My problem is that these rings are not parts of any repair kit that I've seen so far. Having said that I suppose I could make two good ones. I hadn't thought of that before. Just talking about it triggered the old brain. Any comments?
 

Last edited by woolyhead; 06-14-12 at 04:18 AM. Reason: omission
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Old 06-14-12, 04:30 AM
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You're not alone having difficulty posting pics, while I have done it successfully before, I've also attempted and fail I assume posting a diagram would be similar.

There are many times it's prudent to make your own part - hope it works for you! Let us know how it works.
 
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Old 06-14-12, 09:27 AM
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Oh yes mrksnr, when I started drawing the setup I realized that I don't know sufficient detail of the metalwork around the rings to be able to draw it correctly. I decided to strip it all down again and make a proper note this time. After that I'll try to draw it and than post it to the forum. Regards.
 
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Old 06-18-12, 10:01 AM
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Hi Mrksr. I found that the problem is due to a manufacturing error. The welds that hold the cylinder taper ring to the rest of the chair mechanism has broken. Trying to wriggle the cylinder free with Stilson grips proved impossible as the cylinder is a taper fit into the ring and the ring moves even if the rest of the lift mechanism is clamped in a vice. I had to throw caution to the wind and place two small tack welds where the ring joins the mechanism, so as to anchor it. Luckily the cylinder didn't get too hot and explode. Grips then applied to the cylinder could screw the cylinder round and it came loose,allowing me to weld the ring firmly in place. Job done.
 
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Old 07-08-12, 04:43 AM
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replacing the gas cylinder with components giving a fixed height.

To avoid having to keep on readjusting the office chair height and replace gas cylinders every so often, here is a simple method that will fix the chair's height "forever":well it will eventually wear out but probably not in 20 years.
Follow any of the on-line web videos about releasing the top half of the chair from the bottom half and slip some steel washers over the protruding cylinder arm. Use enough to give the height required, then put back the washers, legs and clip as shown . Job done. My cylinder needed 47 of the heavy duty M4 washers which I bought in a local hardware shop for 2.82 (6p each).
 

Last edited by woolyhead; 07-08-12 at 04:45 AM. Reason: omission
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