You'll find more pictures, the LDraw design, a guide for building the ball and comments on alternative designs here.
This model uses 180 long axle pins (part number 11214) . Instead you could also use regular axle pins and friction pins.
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These types of files are created with the LDraw system of software. You will need to install compatible software to open and view the instructions. A full list of available software is on the LDraw site.