I recently took some pictures of my dolly rig to show everybody, since a bunch of you have been interested in this. Hopefully, you might be able to build something of a similar design based upon these pictures.

By use of a bunch of gears, I rotate the handle just once, and the big red T section moves an extremely small increment. Because it's so consistent, this allows me to animate amazingly smooth camera movements. I usually put my tripod onto the T and my camera onto that.

If you make such a thing, just make sure that the gears are arranged in such a way that a big turn of the handle comes out as as small of a movement you can get at the other end.

If you wish to see this in action, I have a pretty good example of a shot made with this in I Am The Darkness.