Has anyone here done this? Turntable-type chair bases seem to be available, though the ones I've seen have all been on US sites, but I wonder about a DIY approach, perhaps incorporating casters set around a perimeter (stronger and more stable than a single spindle?)
IMHO, casters-on-carpet will have too much friction to swivel. And with good casters on hard surface, you'll never know where the chair would go or be.
Try a turntable base, solidly fixed under the chair, remembering that it needs to take the impact load of one of your stoutest friends jumping onto the chair.
I was given a chair, long ago, with a half-eggshell seat on a swivel base. Fine, intil the foam began to fail.
I was thinking of a circular base on the floor, against which an upper base could rotate, with a central locating spindle and casters between the two. Actually, I don't want a free and easy swivel: a bit of resistance would be fine, so possibly the casters could be dispensed with if the adjacent surfaces were smooth enough. Plus, the chair only really needs to swivel when there's no-one in it. It has to be directionally adjustable rather than swingable.
Thanks very much for that link. 71 stone should just about be enough...
The base of the chair is just over 18" x 18" and the feet are very close to the corners. A circular base would have to be around 25" in diameter so I wonder if a 12" ball race would need bolstering with some form of anti-tipping mechanism at the periphery? It could be as simple as wooden blocks fixed to one of the base plates and just fractionally shorter than the gap between the two.
Something I'm not clear on about those large ball races: how exactly would I fix them?
If I have two 30" diameter wooden discs, the upper attached to the chair, the lower resting on the floor, I don't see how I could get access to the fixing holes around the perimeter of the 12" (or whatever) diameter ball race.
Most likely trick I can imagine is that certain rotations of the disks give access to the mounting holes/screws to one through the other. If you fix the bearing to the base disk first and have an equivalent hole drilled in the base ply then you will gain access to the fixing holes to attach the upper bearing to the chair disk.
I was planning to suggest a more DIY approach of having a couple of ply disks with machined circular grooves in their faces and filling the grooves with decent sized steel balls (bearing for the use of) but on reflection, I don't think bare machined ply or MDF would be up to the forces involved and the grooves would soon chew up.
Fred, thanks for that. It was about the only explanation I could come up with too, short of suggesting that the two halves of the ball race might come apart, which seems very unlikely. Various suppliers sell large ball races at prices low enough for a bit of a punt, so I've placed an order for a 12" model and will see what the fixing situation is when it turns up.
That was actually the first method I thought of. I rejected it, not because I was worried about possible wear on the ply/MDF but because I wasn't confident of being able to cut the circular grooves with sufficient accuracy. I'm still slightly concerned about cutting the discs well enough so the exposed edges beneath the bottom of the chair will look OK.
Did you not buy a router when you were trimming a window frame in your garage (or was that someone else)?
They usually come with a radius rod and spike that lets you route out circular slots.
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or search router radius rod woodworking for more hits.
A round bottomed slot would spread the loads better but require greater precision whereas a slightly oversize flat bottomed slot would give more leeway for inaccuracies. Might be nice to try the round bottomed one on some scrap to see how it goes. Varnished MDF may end up being the best surface as it has such a fine grain and with balls virtually filling the improvised race then the loading per ball could be low enough to prevent deformation of the slot base.
Absolute accuracy not critical as long as both halves are identical so do one after the other without any rod adjustments.
Yes, the garage window frame was me and the router is still in said garage. Though it was valuable for that particular job it's had very little use since.
It didn't come with a radius rod but it should be straightforward enough to make one. If the ball race approach isn't satisfactory for whatever reason I'll certainly give this method a go. I was thinking of a round-bottomed slot, hence my slight concern about the accuracy of the cut.
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