N
Nate Nagel
Hah. I must have that "look" because it seems that nobody ever messes
with me. I haven't tried anything blatantly suicidal like walking
through Anacostia though.
nate
with me. I haven't tried anything blatantly suicidal like walking
through Anacostia though.
nate
My office chair hasn't broken in the same way but what happened is the gas cylinder failed and when I took the assembly to pieces I found the ball bearing race had fallen apart. A replacement unit in the UK costs about 8.5 pounds and I reckoned I could make a far better one for no more than that. So I bought the 3/16 inch balls for 1.75 pounds and made a new ball carrier from 1/8 inch aluminium scrap. Then I found the reason why the chair used to rock side to side: the circular hole in the 1.5mm plate welded to the base of the tube that surrounds the gas cylinder and the bearing race and takes all the downward force from my weight had worn into a slot which allowed the piston rod to move sideways. To cure this slot fault I screwed a 3mm thick steel "penny washer" with a circular central hole to the worn plate to act as a new guide for the rod. It should last twice as long as the original plate. I reassembled the whole thing and then found there was insufficient room to fit the thin washer and clip so I filed away a few mm from the rod to let it protrude further. This sorted that. The chair now works 100% and the repair only cost me 2.5 pounds. But I found also that the piston rod did not fit smoothly into its manufacturer's hole but wanted to go through the plate to one side of centre. I had to force it to go through my new plate. The rod is coaxial with the cylinder. My question is this...how can I remove the rod's tendency to go off to one side? In other words why is the gas cylinder not pointing the rod towards the center hole of the plate?
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My office chair is un branded. As described above it began to rock from side to side. I put up with it until the gas cylinder sank down and refused to stay up. When I stripped it down I found that (a) I needed a replacement cylinder. Cost 8.5 pounds online. (b). The bearings had also broken. Cost 8.5 pounds online. The gas cylinder has a piston rod sticking out of one end and this presses down via the bearing set on to a circular plate 2 inches dia, welded to the base of the black tube which is a press fit into the 5 legged base of the chair. This plug-in base has a big hole in its centre through which a small part of the piston rod protrudes and which rod has a groove for taking the clip that holds it all together. CAUSE OF ROCKING....this was due to the circular hole in the 2 inch dia welded plate having worn oval. thus allowing sideways movement of the piston rod. I then noticed that the dia of the manufactured hole in the 2 inch plate was considerably bigger that the dia of the rod. I also saw that where the bearing unit fits the bottom of the rod there is a taper on the rod. not a sharp shoulder. This taper allows the top pressure plate of the bearing unit to slid up the rod a short way until it jams. Presumably this taper-jam arrangement of the bearing plate is done to ensure the plate rotates when the chair rotates and thus prevent the pressure plate from rotating against the rod itself and causing excessive wear. Note that I am not talking about the taper fit at both ends of the support struts, only the actual ball bearing unit. I then made a replacement bearing set. I also fitted another 2 inch dia plate on top of the worn one and which had the correct diameter hole in its CENTRE, anticipating that I would somehow get the piston rod to run coaxially with the rest of the assembly. I final achieved the latter by filing the hole in the plastic guide which is mounted in the top of the black tube. So now you have the complete saga.
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On reflection I think the chair's support mechanism was poorly designed. For one thing the piston rod is only held at its top end in the black cylinder while the lower end has the potential to flop about from side to side in the oversize hole in the welded plate. That might not matter if only the hole in the top support for the gas cylinder in the black cylinder was accurate. But in my chair it wasn't. It made the cylinder point to one side of centre at the welded plate. Another weakness is the ball race is not closed and all sorts of grit and dust can easily get in and spoil the smooth running of the ball race. Enclosed ball races of approx. the right size are available on line for as little as 3.5 pounds. Enough moaning.
Underneath the reply box, there should be a button saying "upload a file" - if you click that, you can add attachments
.Is it an image file? If so, you may be able to resize it using something like this (http://www.picresize.com/).
Here should be the key to my picture of the chair but it seems that the file does not have an extension, whatever that means so I cannot show it. Sorry.
But here is the list of items shown in the picture. 1). Gas cylinder. 2). Plastic sleeve and guide for item 1. 3). 1 9/16 inch dia black tube. 4). Piston rod. 5). Thinned down diameter of item 4. 5a). Groove for spring clip. 6). Manufacturer's thrust and support plate. This supports the weight of the user and upper part of the chair. 7). Weld joining item 6 to item 3. 8). Five legged base unit. 9). The five legs. 10). Manufacturer's original hole. 11). Item 10 worn oval by side thrust from item 4 due to the hole in item 2 not being coaxial with item 3. A). Home made patch plate screwed to item 6.