OK. This ongoing project for a DIY kneeling chair is well on its way now. Here’s the schematic of the parts I’m using and the relevant dimensions. You could call it ‘plans’ or ‘blueprint’, but I’m not making any claims in that area!
Also refer to the next article (Part #3) here.
EDIT: Please note the dimension in yellow… this corrects an error I discovered when I put the seating section together (it originally said 110mm).
I spent today (had most of the day off in order to get this going) trimming the parts. Last week I used an angle grinder to take the 3m lengths of 30mm box and 1½” round steel sections down to manageable pieces. The diagram below shows roughly how the parts will fit together – I’ll put up a better drawing with dimensions later.
Basically, there are two seat struts (A) parallel to each other, and two knee struts (B) the same. The seat struts are closer together and fit inside the knee struts in a distorted X shape. I’ll use the spacers to make sure that the struts are the right distance apart.
You can see how those seat support struts (Aa) I mentioned in Part #1 will work. The original chair didn’t have these, so you can imagine how weak it would have been. In order to accommodate these struts I increased the size of the seat plate from the original, though the hole spacings will be the same. At a later stage I’m going to build my own upholstered seat and knee pads, but for the time being I’ll just transfer the ones off this existing chair (hence the hole spacings).
Anyway, I ended up using a good old hacksaw to cut the 45º angles. It was far less hassle then I’d imagined (from metalwork days back in school). I must confess I used the angle grinder and a coarse grinding wheel to trim the ends, though. I finished/squared these off with a metal file.
EDIT: If you came to this page from a search engine, don’t forget to look for Kneeling Chair Project parts (#1), #2, #3, and #4 (plus a couple of updates) using the site search facility. This project is now complete and there are drawings/blueprints in the other parts.