I’m going to build a spin art painting machine - the only bit that puzzles me about the construction is how to hold down the card onto the turntable while it is spinning, without obstructing part of it from being painted.
How is it done in production-line spin art machines?
The ones I have seen for 3x5 cards have nothing. The user just tapes it on the back (with a little loop, like you do to a poster on the wall). This also allows the card to be placed off center for added fun.
Thanks for the ideas. In the end, I drilled a few shallow depressions in the face of the turntable, and into each of these I pressed a little nugget of white-tak (that stuff you use to put posters up on the wall - also that stuff you use to remove small circles of wall paint when you take posters down). That worked really quite well.
Build details and initial results can be seen here, if anyone is interested.