Here's one I'm in the process of doing. I'm using a cheap mechanical pencil and a piece of paper I pulled from the copier.

http://img395.imageshack.us/img395/4374/cycle2eq5.jpg (http://imageshack.us)

Dude, ur shading is perfect!

WOAH!! Tons of detail man.. This looks like it will be killer once its finished.. The shading is insane

The tank looks like it's floating above the frame, rather than being attached. Otherwise, looks great.