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As we are working on SR2, we are leveraging as much as we can from SimplePlanes. This unassuming part has been an absolute game-changer in SimplePlanes.
It's a simple motor that can drive rotation between two connected parts. Players have used it in SimplePlanes to make things like swept wings, retractable landing gear, rotating turrets, and even walking robots. Here's a rocket where I connected the side boosters to rotators that respond to roll:
Like most other parts, the rotator has several properties that can be customized in the game. You'll have the ability to change its speed, range of motion, activation group, etc. You can also connect it to any available input axis, which allows making very complicated designs.