design

How would you make a pivot that would allow motion in an arc around a tube of a larger diameter by a tube of a smaller diameter? The pivot must be able to be moved along the larger tube for adjustment.

Some starting ideas:

I discovered this really cool software called AutoDesk Sketchbook Pro 2010. Its great for putting your concept ideas down. I have to get use to drawing with a stylus yet. I am going to use this on my project ideas at school. Its pretty inexpensive also. Here is my first attempt at drawing something.

I have a paper & pencil sketch of my robotic design and I was wondering if there is anyway to easily create a CAD model by scanning my sketch into the computer. I user Google SketchUp and Alibre Xpress (yeah I'm cheap) and I can't afford anything "more advanced".  If there's anyway to do this, I would love to know, or if you could point me to a tutorial, that would be greatly appreciated.

I have a fairly strong background in code development, but I would like to build a stronger knowledge in curcuit design. I can read a datasheet and learn how to hook up a certain component, but when it comes to using a specific component for a use other than it is designed for I lack the knowledge to know when to use a capacitor, flyback diodes, etc.

I'm not positive this is the right place to post this.  Admins please move it if I'm asking in the wrong place.

As said in sociatyofrobots.com, designing is the most important stage of robot building. I spent no time designing Turpis, and that's most likely why it turned out so bad. However, I'm an awful artist, and I need to find a more efficient way to plan. I've tried my hand at Sketchup, and it is uncooperative with my computers. Are there any easy-to-use free software out there?

Thanks,

Brennon