As an aside: I'm not exactly a mechanical engineer, but based on the diagram at the beginning, I think there's an aspect of a swing-set that the author's not co

As an aside: I'm not exactly a mechanical engineer, but based on the diagram at the beginning, I think there's an aspect of a swing-set that the author's not considering (although maybe it's mentioned in some of the papers referenced at the bottom)- namely, the fact that the seat is suspended by a _chain_, which you can pull or push to affect your motion. As far as I can tell, this article assumes a _rigid_ swing system. I don't have the physics chops to work out how that would affect the results this article worked out, but I have to imagine it'd make it possible to get the swing going faster, sooner.