Thanks for the update.
I thought the contact time vs. stick speed graph was particularly interesting. I assume that the time was measured with with the high-speed video. I don't know of any theory that predicts that shape of dependence.
Was this a laminated tip?
Perhaps up to the the inflection point, the upper layer(s) of leather compress (with max compression being reached over shorter intervals as the cue velocity increased); then after the inflection point, with sufficient velocity a relatively inflexible barrier formed by a glue layer is overcome and lower layers start to compress more quickly?
Just a thought ...
Re-edited: "more quickly" added at the end for clarification. (The lower layers must have been compressing before the suggested deformation of the boundary layer - otherwise it would be a minimum rather than an infection point. What could be happening is that the deformation causes this compression to speed up, perhaps because the barrier is no longer spreading the force so effectively.)
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