The Yahoo CAD_CAM_EDM_DRO group
(home page) has had threads comparing the various CAD packages. Searching the archives cand give you a lot of good information.
Pro/ENGINEER is a complex 3d CAD program. Pro/MECHANICA is a related mechanical simulation package capable of not only simulating the parts movement relative to the other parts in the assembly but calculating the fatigue life, stress, deformation, and thermal conduction of the parts being designed.
web page
The free subset of Pro/Desktop (itself a simplified version of Pro/ENGINEER) is available at
download web page
It is an interesting program but it requires a lot of practice and time to make it do what you want the first time. If the simple simple version is not enough there is another option.
Student Editions of Pro/ENGINEER and/or Pro/MECHANICA and related software are available for "personal or educational use" (no student ID is required) at
pro educational store web page or
JourneyEd web page. The prices are very low compared with the commercial prices of these products with few restrictions. (e.g. Pro/ENGINEER and Pro/MECHANICA is available for $150 while list price for commercial use is $34,000 )
If only I had time to learn to use programs this complex, I am sure that they would be useful.
The JourneyEd site has educational pricing on products from other comnpanies which require current student or faculty status to purchase or use. These include Solidworks, Adobe software, and many others. (A community college welding course could come in handy.)