The age of steam really turned up the ante on mechanical power that could be directed to any task.  Unlike wind, or even water, steam was on demand and “controllable”. Our modern day vehicle engines are the air-pumps that derive very closely from steam.

But often the power needs to be be geared up or down, and transmissions are the mechanical genious that handles that.

The next two pictures are from bycicle parts, just ad demostration on how far one can take an idea.

First, the Rohloff 14 gear internal gear hub.  One look and you will be amazed at the sheer audacity of this component, and shocked by its quality and price.

And then the rather curious, and no less impressive NuVinci Continuously-Variable Bicycle Hub.

Click on the pictures, follow the links. This is very interesting bits of technology.