When building complex robots, one of the common needs is to compute the ratio of gearings in order to exactly tune the interaction of the movable parts of your machine. With all the different gears around and the sheer number of possible combinatioins, this is not always a trivial task.
Yesterday, though, I ran over a most wonderful web page by Sariel, a LEGO® aficionado from Poland well-known for his sophisticated TECHNIC inventions. Amongst other things, the page allows to select any combination of TECHNIC gears and displays the resulting gear ratio.
Great stuff and most helpful indeed!
Try it out (and do not forget to browse also the other intriguing pages of Sariel's web page).