Proper Mecanum Setup

I know there are a few threads on this already, but I want to be for certain I understand. I have seen mecanums are to be set up in an X formation and this is what I took from it. [Edit: Top=Front, Right=Right, Bottom=Back, Left=Left]

Can someone please confirm this is correct? Thanks in advance.

Assuming you are looking at the robot from the top, yes this is correct.

Yes, that’s how it should look when looking downwards on the machine. It should look like an X from the top, and an O from the bottom.

This is because mecanums need to apply forces in a circle to turn. An O touching the ground can create four vectors which rotate about the center, but an X can only create four vectors which cancel by pushing towards or away from the center.

I thought x on the floor can still generate the same appropriate vectors but required more “intervention” with the standard code, reversing directions of wheels etc…

Pretty sure my team was at this point at one time…

These papers discuss this topic well:

mecanum X & O square & rectangle
mecanum force vector analysis

Click on the links corresponding to these titles on this page:

Note that when most people talk about X & O orientation they tend to talk about a bird’s eye view, whereas Ether in these papers refers to a worm’s eye view. An X viewed from the top is the same setup as an O viewed from the bottom, and vice versa.

No amount of code will “fix” the issue. The mechanics of an O-oriented mecanum drive as viewed from the top will result in less optimal turning than an X-oriented mecanum drive. This is explained in the papers.