Simulate Solar System: How to keep earth axis in one plane during revolution

[jakobried0]

I want to make a simple animation of the earth's revolution around the sun. However, I am now stuck with setting up the correct joints. The things I have done so far are:

1. Create sun, earth, earth's axis and earth's rotation path as individual components.

2. Create as-built joints between:

sun - earth: earth rotation around the sun

sun - axis: axis rotation around the sun (together with earth)

earth - axis: earth rotating around it's own axis

However, when earth and its axis are rotating around the sun, the axis doesn't stay in one plane e.g. faces to the sun with always the same site. 

This, of course, is wrong and I would like to change that. 

How can I solve this? Did I already make a mistake when setting up the joints between the components? 

Here you can see the current design:

Thanks alot in advance!

[jhackney1972]

Please attach your model so the Forum users can help you better.  If you do not know how to attach your Fusion 360 model follow these easy steps. Open the model in Fusion 360, select the File menu, then Export and save as a F3D or F3Z file to your hard drive. Then use the Attachments section, of a forum post, to attach it.

[jhackney1972]

You have not supplied your model so I created a rough one for you to demonstrate the process.  Open my model, expand the Joints folder and right mouse click on Earth Around Sun Revolve Joint.  Choose Animate Joint Relationship to see the motion you want.  You will be able to see what I did by looking at the timeline.  Let me know if you need further help.  Model is attached.

Edit: Corrected attached model so the Earth rotates CCW around Sun

[jhackney1972]

Did my solution fit your needs?  If so please select the Accept Solution icon on my post.  If you have other questions or need further help please ask.

[pavmed]

This is possible to solve using two additional intermediate "virtual" components - (1) simply a line replicating distance between eartch center and sun center - let's call it "leg" (2) component without any contents - call it "cage"

You then make such joints:

1. Sun center - revolute around vertical - leg point A

2. leg point B - revolute vertical - cage

3. sun center - planar with disabled rotation - cage

4. earth- revolute around earth axis - cage

this makes cage turn around sun without changing it orientation - just XY movement at exact distance from sun.

And there'll be earth turning around its own axis inside cage.