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Thanks Gary,

I couldn't find any patents relating to this on google. However, I've found an original 1947 paper by Brown and Nassau which has some more detail. the Luykx and Brown papers attached. Tantilising but frustrating, since  neither paper includes a complete diagram or picture of the full device. I would be grateful if you and anyone with the maths could take a look and give any advice on how to build a protype from the graphs and information provided.

My understanding is 2 identical quadrant grids on opposide sides of an opaque board, with 2 transparent moving quadrants pivoted at the corner, mirror images.

I'll probably have a play around with different combinations,  hoping to hit on a working structure.

Any advice would be welcomed.

this looks like an interesting and obviuosly little known alternative to the Bygrave, using graphic, not slide rule or calculation  methods.

Best wishes

Francis

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