The inner workings of a mechanical calculator

I wasted so much time last night watching videos of mechanical calculators (it started with this one dividing by zero). I've never seen a mechanical calculator in person and I guess with the abundance of digital technology around me I just never really put much thought into what a calculator was like before circuits were involved. Well, I can conclude that they are awesome and very noisy machines and of course, I want one now.

The video above shows how the calculator works on the inside, but if you just want to see the machine doing calculations, check out the video below. Complicated, but totally sensible and wonderful!

This one is just as cool!