Gyroscope explanation without maths.

[tonyfoale]

Tony, yes one can click on your link and view your .PDF and it works .
But if you try to save it so that you can view it later it downloads as .html
which on the next viewing does not display correctly so the document is unreadable.

I think that you are using Chrome's save, in which case it will offer you .html. Look for a download button in the top right corner, that should save as a PDF.