Hot answers tagged mechanical
Would this solve your problem? Depending on the direction of the input, only one axle will turn.
You can use a large gear (3649) with connector pegs (970607) attached like this: Then you can attach the 6x6 plate on top.
There's actually a specialized part to accomplish this task. Take a look at the Technic Turntable (2855): This part can be used to create sturdy rotating platforms that can be controlled by gears. It consists of two parts (2855 and 2856) that snap together to allow for smooth rotation about the center. Here's an example from the classic Mobile Crane set: ...
Ok, I have managed to build a working cam mechanism using LEGO Technic. Only thing missing is a big enough spring or elastic band to pull the entire assembly upwards - Still thinking through that part but sharing in the hopes that others can take my idea further (My current best thought is to have rubber bands on the outside of the mechanism pulling the "...
Here is a possible implementation using this exact part: Video . There are also several other solutions with different pieces if you need more inspiration or explanation: Animated GIF, 4 wheel steering, Top-down view.
What you can do is use an old-style spring loaded missile, the rubber tip is soft enough to let you trigger the launcher without putting the missile back in, and you don't need to trigger the launcher to lock the missile. I you press the flat bar at the top it works about 90% of the time.
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