I picked these half spheres up years ago and always wanted to make something with them. I have to date been unable to think of something clever to do with them.
Any suggestions would be welcomed 
I have left 2 on the table for people to handle.
Directive WiFi antennas
Are they solid half spheres
Used to work with that sort of thing, a bunch of slots and a phasing array and you will be good to go
They’re shells. I handled the sample ones yesterday. Good rigid steel, maybe 0.8-1mm thick? The larger diamter one is almost blemish free, but the small one has a noticeable ridge in it.
These things are dead useful for high-voltage lightning machines of various designs.
Failing that, a large one makes a cool novelty mirror for the bathroom 
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I think we have a winner?
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VAN DER GRAAF FTW!!!
(Discourse insists this isn’t a sentence)
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sounds great. Any one interested???
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Yes but no idea how to make one…
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Parallel series cap bank.
Let’s do it right. …
Van de Graff are fairly simply to make.
A closed loop of charge carrier about 75mm across and say 80mm long. People have their own favourite materials - vinyl, rubber, cut up PU coated nylon shower screen etc
The charge loop is mounted in a vertical PVC tube of about 100mm diameter, running on rollers at top and bottom of the external tube.
The bottom roller made of PTFE is driven by a electric motor running at about 1000rpm. Ex sewing machine motors are a popular choice. An earthed copper brush of many fine needles is positioned tangentially across the length of the roller. A popular candidate for this is one made of spread de-soldering braid.
Another unpowered roller made of nylon with it’s own needle brush is positioned at the top of plastic tube with an adjuster mounting to tension the charge loop.
The lead from the brush is connected to the inside of the charge store.
This is large conducting sphere. The larger the sphere the higher the voltage that can be stored.
The only real difficulty is finding a large sphere. People often stick two hemispherical cooking bowls together.
I have largest hunk of PTFE and two 280mm diameter IKEA bowls which I haven’t got round to assembling yet.
I haven’t seen one in action since the one in the physics lab at school!
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erm… any chance i can have some or buy some off you?
depends on what your idea is? I love them and was primarily looking for clever ideas to use them.
I would potentially be happy to share them depending on how we could use them???
Well I like the chrome finish and I was thinking it would look nice as a feature, grouped pendant lighting?