About this 3D model
Still out of plastic... This has to happen though! A Van de Graaff generator is essentially a box, a tube and a ball with some gubbins that connect it together and move the charge about. A box, tube and ball are easy. With a 3D printer, so are the gubbins. When I get more plastic (3 days from now!) the beast will come to life. In the UK, the ball can be picked up from homebase from about £20.