Here is a very basic guide I did up a while ago:
http://www20.brinkster.com/antweights/How%20To%20Build%20A%20Simple%20Antweight.htmlhttp://www20.brinkster.com/antweight...le%20Antweight. html

Here is a guide with some pictures Simon Windich Made:
http://windisch.co.uk/electra/howto/build_a_robot.htmhttp://windisch.co.uk/electra/howto/build_a_robot.htm

Hope this helps
Regards
Ian