This is amazing 
Preserving these yo-yo physics pamphlets is pure gold. Thank you, everyone, and know that we support the Internet Archive in so many ways, and I know people there personally.
However – I think these were written when yo-yos were all made of simple wood? The physics have not changed, but the materials – and what we can do with them – definitely have. A lot.
I mean, I like Pumping Wood, don’t get me wrong, but there’s a reason we don’t build a lot of things out of plain old wood any more..