Cheap office chairs really aren't built to last.
Here's what usually goes wrong:
- The arm rests are screwed into the plywood base of the seat. Any sort of load on the arm rests tends to split the whole side off the seat. Not good when you have kids about - they love to swing on these things which really hastens their demise.
- The gas-lift stops working. These are not really repairable, although they can sometimes be replaced if you can find the right part.
- The back adjustment works using a clutch-like mechanism. The clutch is made of thin steel plates which are welded to the base of the chair. These plates can snap off, and once they've all gone the back of the chair is completely floppy. In our chair, all of the plates have snapped of just before the weld with the base. Unfortunately, the mechanism is not replacable.
Rather than chucking it out, I tried to think of something I could do with the parts, most of which were still OK. The result looks something like this, and we'll come to what exactly it does later:
The conversion is pretty simple, though obviously it depends a bit on the chair and how its made. The first step is to remove the seat post and mechanism. On my chair, the seat post is a light steel tube which is press-fitted into the plastic caster base. Once you remove a locking bolt the post can be removed with a few belts of a mallet.
The seat and back are just bolted on to the main mechanism. Once these are removed you can check them for usability. To mount onto the caster base you want whichever one has the flattest back. On my chair this was the back rather than the seat, though this may vary between chairs.
To fix the seat/back onto the base, juggle the spacing until its right and then drill some holes through the caster base. I just used some large-gague self-tappers to hold the seat in position. If its curved you might need to add some spacers between the base and the seat (eg. using washers or cutting short lengths of tubing).
I thought this would be fun for the kids to play with, and indeed it was for a short while. Since then, I've found several other uses.
- Moving potplants, or other heavy objects. Once you've lifted it on its pretty stable, though you may have to hold your load in place top stop it falling off.
- Moving furniture. For items that are large but not too heavy (eg. sofas), you can lift one end onto the device, and then carry the other end yourself.
- A foot-rest. My wife claims that this is the best foot-rest she has ever had, which given her initial skepticism is saying something. An added benefit is that she keeps it under her desk, so I don't have to find somewhere else to store it.
- A cat throne. (suggested by Kathryn) Providing your cat somewhere to sit may stop it trying to sit in inconvenient places. If you're lucky, it may even scratch here rather than destroying the sofa.
Its pretty easy to get raw materials for these things. If you can't scavenge some broken chairs from a workplace, you can usually find them in kerb-side junk collections.