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?

2 Answers 2


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
  • 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)
  • 1
    How would I import pieces? I have a version of LDraw with the old technic motors but when I try to set that as the default LDraw folder, it says that there's no image folder
    – Alex
    Commented Jun 10, 2012 at 20:15
  • Never mind. I didn't set the types to display from base types to all types. I found the 9V mini-motor. But the problem now is that the model is missing its casing
    – Alex
    Commented Jun 10, 2012 at 20:29
  • 1
    @AlexYan I have not used the software, but a google search took me to this forum post:eurobricks.com/forum/index.php?showtopic=30348&st=30. The advice that may help you is "the error is generally risen when you have chosen a destination folder for the Part Library different from the default c:\lDraw and you already have the c:\lDraw folder on your HD. To fix the problem, use the <File>.<Setup Directories> option to choose the correct folder you install the part library to. If you can't remember it, search your hard disk for the "Conns" folder. Its parent folder is the correct one!"
    – mcqwerty
    Commented Jun 10, 2012 at 20:29
  • 3
    @AlexYan I'm the author of SR 3D Builder. If you have any trouble or question just email me and I will try to help you Sergio
    – user891
    Commented Jun 13, 2012 at 21:32
  • Is there an alternative for macOS High Sierra?
    – osman
    Commented Apr 5, 2018 at 23:42

Edit to update: It looks like the NXT version of RDS only really supports the "Tribot", and has partial support for the "ShooterBot", but does not have a simulation of it.

I know the original Microsoft Robotics Studio supported building robots using the RCX bricks - although the latest version has been upgraded to NXT and it has simulation tools too for testing your robots prior to building and deploying your code.

As the core components should be the same (gears, beams, etc.) you should be able to get a reasonable way through testing even if the final code has to be written elsewhere.

I know some people have had success upgrading the RCX samples to newer versions of RS, but I'm not sure if anyone's tried it with 4.

  • 1
    Wow. Didn't know that. I'll take a look
    – Alex
    Commented Jun 12, 2012 at 23:14

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