Free Rotation of an object with no linear movement

[Anonymous]

I am looking to put the 2 platforms above each other and allow the top platform to rotate (about any axis) as it pleases whilst having the center of both objects stay aligned. Ive grounded the base plate however I cannot seem to find how to constrain the top plate so that its center is always above the bottom plate and the sides just go up and down. This will be used in the design of a stewart platform. The holes i placed in the platforms do not need to be there, I only put them there to try to align the objects. Any help is appreciated.

Regards,
Jayden.

Edit: Basically I want the top plate to be able to acheive all of the movements it acheives when you are using "Free Rotate" option. 

[Frank-Oosterwaal · Accepted solution]

Hi Jayden,

Look at the screencast.

Constrain the center point to the axis and it will always stay in the center.

Add more constrains to limit more freedom degrees if needed.

For example, if you want to limit the height constrain the center point to the top plane (XZ) with a offset.

We can't open your trail2.iam if you don't attach the parts needed in the assembly.

If you want, attach everything and we'll show you how to do it in your assembly.

[Anonymous]

Thank you so much this is exactly what I was looking for. I have already done it with my pieces now, sorry for not attaching them. I am very grateful 🙂