Currently I am using the free version of Google Sketchup to do some 3D modelling of a project. The software seems to not be well suited to the purpose, I want to model fixed solid objects, but in sketchup when you model two objects, say a motherboard tray and a standoff the two objects become a single object, and any edits to say the MB tray, distort the connected objects like the standoff. I am new to this sort of software and I expect there to be a learning curve, but it seems overly complex than what my needs are. Are there any good Sketchup learning resources targeted to our needs? Are there any alternatives that can be recommended?