Rotation that keeps upright

Hello, I am currently programming a fairground ride and I want the seats where people sit to have a target rotation of being upright but I want it to transition to this rotation. The Axis I want it to rotate on the x axis. I do not really know if someone could help me. Here is an image to explain what I am looking for:

As you can see, I want this to rotate on the ride. If you want to look what the ride IRL is like, its called danter’s air.

Thanks.

Make the chairs children objects of the arm and rotate them locally.

chair.transform.localRotation = Quaternion.Euler(new Vector3(chair.transform.localEulerAngles.x + (Time.deltaTime * speed), 0, 0));

your ride hierarchy would be : base > long horizontal arm > spinning hand > rotating chairs

each would be rotating in local space using similar code to the above example.

You could skip all this and make an animation. That would probably be even easier/more control/better performance. Your code would be starting/stopping the animation

https://unity3d.com/learn/tutorials/topics/animation/animation-view?playlist=17099

Something like this, i would skip mecanim and use legacy.