Good LEGO CAD Design Software with Technic elements and animation I'm taking computer engineering in Gr. 11 right now and our final project is to create a robot with the first version of Mindstorms. My partner and I are making a sumo robot for the class competition. We don't have the required parts at home such as gears and technic pieces and we're not allowed to take home the pieces.

We're using LEGO RCX 1.0 with 2.0 firmware and mostly technic pieces. Is there some type of CAD software that lets me test to see if the gears do what I want it to? I know LDD does this to an extent but they don't have the RCX 1.0 pieces, and placement of pieces is frustrating.

Also, I have the .dat files for LDraw, is there a way to import those parts into LDD?
Take a look at SR 3D Builder. I have not used this software myself but it looks like it may do what you need. It's free (for non-commercial use) and you can import your LDraw files.

Here is a link to some videos on YouTube

See below for the features list (taken from the website)


NEW Support for Piston - Rod mechanism
NEW Support for Linear Actuators and Shock Absorbers
NEW the Animation Console to easily create and animate your technic
models
Towball, HINGES and GEARS SUPPORT! Take a look to the Gallery  to see
what I mean
Connection Solver for quick connecting hinges and rotating parts
Support for RACKS and steering
Support for ANIMATED FLEXYBLE PARTS
Belt Generator with real connections
Now with GROUP management
New exclusive MirrorBuilding features  for quick build of symmetric
models. MUST TRY !!
Enhanced instructions editor to easily modify the order in which bricks are loaded in your model and/or take photos while building
Complex gear driven hinges support (quadrilaters deformation and
steering)
Great fully 3D building envinronment with reflection and
transparencies
You will see your model during loading time and can pause for
instruction steps
You can modify and save models (lDraw/MLCad .dat compatible format)
Fast selecting/moving/adding/removing you'll never see in MLCad
Copy/Rotation/Deletetion/Color change of single or multiple brick. Undo/Redo functionality
Real connections detection, not always the same near brick positioning
Brick selection by Block (means that solid connected bricks can be selected at once)
Grid positioning to speed up positioning of pieces
Automatic and precise positioning and orientering of most bricks according to connection detection 
Automatic detection of rotation axles
You can easily load model from other known programs: it supports the
following formats

.dat files
.ldr files
.mpd files (only a few metacommand are currently supported)