I just started using LDD, and I have been trying out a few things that I couldn't do with the limitations of my Lego collection. One thing that has me caught up is that I can't seem to get the technic gears to interact with the Toothed Bar piece. I know this is possible in real life, but I was wondering if it is possible to do on the computer.

In the project I have, I want the lever to be turned and the platform attached to the Toothed Bars to go up or down. Right now, only the gears on the axle spin when rotated.

example project

2 Answers 2


The LEGO Digital Designer software does not have the ability to simulate the interaction of gears.

There is a similar software program called SR 3D Builder that does have this capability.


LDD is a design solution for static models. It is not a functional simulation tool. The gears turn with the crank handle if they are associated to the same group, but that is only because the gears, the axle and the handle share the same rotation point. The toothed bar does not share that same rotation point (and is likely not part of your "group" that contains the handle, axle and gears) and hence does not turn. If you made it part of the group, it would rotate around the center of the axle, which is not the effect you are looking for.

  • I have seen some videos where people get systems of gears to work, but that does not work when I try it either. Is there specific mode that I need to use to get something like that to work Oct 7, 2016 at 19:56

Not the answer you're looking for? Browse other questions tagged or ask your own question.