They are on all formats SolidWorks ProE Inventor and more on
www.3DContentCentral.com. Use the keyword "Tetrix" . Select the file format, year of software (you can go back a few years) and download to your harddrive. Unzip the file.
If you have SolidWorks you can drag/drog a 3DContentCentral part right into the graphics window.
To link to the folder where you put all your robot components, from the Design Library, use Add Folder location, browse to your robot component folder on your desktop - this will save you alot of time when creating assemblies.
Before you start your assemblies - really think about symmetry, mirror component and component pattern. Build the sub assembies as you would physically assemble them.
If you need SolidWorks for FTC, go to
www.solidworks.com/SponsoredDesignContest
Marie