Is there any software that I can use to design simple machines? For example, setup a motor to a threaded rod to make a linear actuator and connect that to a knife for example. I saw some videos for CAD software but It looks like that kind of software was for designing a gear or what not as opposed to connecting things together.
A major plus would be free and works in linux.
There are many programs that do this but most are very expensive.
I believe Google Sketch Up (name?) is OK though and that's free.
Be prepared for a looooong learning period with any 3D package.
Rob
Take a look at FreeCAD (FreeCAD download | SourceForge.net). Sounds like it's more or less what you're looking for.
captainandcoke:
Is there any software that I can use to design simple machines? For example, setup a motor to a threaded rod to make a linear actuator and connect that to a knife for example. I saw some videos for CAD software but It looks like that kind of software was for designing a gear or what not as opposed to connecting things together.
There is quite a bit of mechanical analysis and simulation that can be performed in some modern parameteric CAD software. For example, motion simulation and finite element analysis (for stress, strain, and other physical load analysis) are very possible, and in some cases even thermal analysis. However, you do have to either build or aquire the 3D model and associate the relevant physical properties with it. Although some packages have built-in libraries of common materials, etc... to make process a bit easier.
Still, what you seem to be looking for would be the mechanical version of Fritzing, something both easy to use and still free. Unfortunately, I'm not aware of anything like that...
Edit: Typos...