Weve got another one of those threads where everyone assumes what everyone else means, havent we? Im beginning to think it might be handy to have a forum glossary somewhere; even if the definitions arent scientifically accurate, it would be nice if everybody knew what everyone else meant in the context of this forum. (Translational spinner would be another good one to add.)

Jim: Going off Richards definition, I suspect the points in question are of the mathematical infinitely small variety used in two elephants connected by light inextensible string examples (as much of my maths A-level was).

That is, a single point connection doesnt constrain movement to a single axis - its a ball and socket joint. Put two ball and socket joints on the flipper and you have the equivalent of a conventional hinge. So its a double point so long as it constrains the axis of rotation of the flipper.

But, to be honest, I have no idea what Im talking about. It depends whether were talking about the flipper in three dimensions, or a two-dimensional diagram of it in the plane of its motion. Christian seems to be going with the latter interpretation, Richard with the former. The numbers are plausible either way around.

(I got called an anorak on LBC radio recently. Youd never guess...)

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Fluppet