DAFT AS A BRUSH.

Last weekend I fell for the charms of a young lady. She is doing some design course in Glasgow and had been round a few engineering companies to get a very strange table made. Needless to say they were not enthusiastic as she only had colour washed sketches and engineers are not at all keen on colour washed dimensionless drawings especially when presented by a young lass with a ring through her nose and her trousers arse hanging out. One of them suggested I had time on my hands and enjoyed messing with such stuff. I had never seen anything quite like it. This isn't her drawing but shows the general idea. She had wires, maybe a posh synthetic Kevlar/Carbon fibre cord would work. Who knows?

Her design is for a work station and is supposed to be elliptical in plan view. I did point out it will be a bit wobbly but looking at the job I think with enough tension on the chains the wobble could be reduced to a quiver. The original idea was to use cast iron....apparently it is all the rage. Hers, if she gets the finance to build it, will be fabricated. I pointed out that casting is very expensive for a one off and a prototype at that. The innocence of youth.

I have made a start on the job.

This is the base the horizontal bit can be laser cut in 10mm plate and the vertical bit MIG welded on from 8mm cold rolled strip. It measures 900mm x 400mm so the waste on the base would be horrendous. Probably make it in three pieces, maybe five. TIG it together and give it a good polish. No one would know. This is an oblong as it makes it easier to pick up centres for the support structure. One has to have equal tension on all four chains which is a real laying out bugger of a job. I wonder if she would settle for a triangular table. I doubt it as when I suggested an equilateral triangle she was making those funny noises women make....Like a snuffling up the nose whilst speaking and applauding ones efforts sort of thing. I think it means. 
"I understand you are doing your best but try harder."

I searched all over for a CAD drawing of chain but ended up having to create it as chain makers don't seem to give CAD images away. No need, unless you have an arty farty person as a client. This chain is to spec as they do provide a drawing. 

It will require four of these toggles to connect the chain to the top and bottom rings, The top ring which I've yet to construct will carry a sheet of either 6mm or 8mm posh glass cut to fit or so I'm told. I will need a fifth one of these to connect a short chain to the bottom support arm and another similar with a screw tensioner on it to go on the top one. 
Bearing folk are wonderful they give CAD stuff away.

This is perhaps overkill but I can see the chains having to take one hell of a load, at least 500kg if not a 1000kg. This is from AST Bearings but most bearing manufacturers supply CAD models. This bearing costs about a fiver if you buy fifty. If she popped round and smiled they'd most likely give her one.....Please excuse the expression.
I still have to create the support arms and the top ring. I'm trying to work out how best to fabricate them as there are many hours of machining and welding already. I will get the rest done before the weekend and then the fun starts with the FEM. Not the artist you pervs, FEM stands for Finite Element Method it shows stress/fail points in fabrications. Freecad supports FEM and once I get my tiny brain round how to use it I will find I have to pop a mini Acrow prop under her table or re-design lots of bits of it. I have a new project that has inspired me. Should be done with working drawings for a week on Sunday. 
I may be daft as a brush but Clive was unusually perceptive when he volunteered me for this job. I'm enjoying it.

This is the latest from Andrew Lawrence.

Have fun and smile at the stupid world we live in.