Software: Invention of simple mechanical devices

Until you mentioned the simulation I would recommend Turbo Cad 2D or 3D. 2D is free if I remember.

However, doing mechanical simulation, it probably will require an arm and a leg. So I would first invent one of each of those (arm and leg) so you can replace what you loose to get the software you need.

Try these links:

http://www.alibre.com/xpress/software/alibre-design-xpress.asp

http://www.instructables.com/group/cad/

Graficalc

From http://www.inventbetter.com/

Download and register the trial version then wait for the upgrade offer (about $100 instead of $1000)

Moray is a wireframe modeller (shareware) (100 euro$) and is able to animate and do inverse kinetatics. It puts out text files that can be rendered in the freeware pov-ray.

Moray www.stmuc.com/moray

Pov-ray www.pov-ray.org

Chris