pic: Diagonal View
 

Re: pic: Diagonal View
 

Correct me if I am wrong, but this looks like a passive wheel with and encoder attached to it. So when you move it tracks the distance. I assume that you would use two of these on a robot, one in an x axis and one in the y axis (assuming you are looking at the field from above).

Re: pic: Diagonal View
 

Great job with the CAD work. I can critique the design a bit:

You're going to have all kinds of trouble with the sliding link. A good rule of thumb for sliding joints is that the ratio between bearing length (in the direction of sliding), and bearing diameter (or spacing) should be greater than 2:1, otherwise when one side starts to grip a bit, the whole bearing will twist and jam. You've got hardly any bearing length in this sketch, so jamming would be a real concern.

Another good rule of thumb is to prefer rotating joints to sliding joints - so if you can redesign this to use a trailing arm, you'll have more chance of success.

Re: pic: Diagonal View
 

Is the plan to rely on the weight of the wheel to keep the wheel in constant contact with the ground? I was looking for some sort of spring device for that purpose. Even without binding as noted by nuclearnerd, I would be concerned with it "skipping" and sliding along the wheel direction rather than rotating.

But it is a nice design, our team had considered some way of using a tracking wheel for measurement last year and didn't go through with it. We were accurate enough on Mecanum wheels, and timing alone (with gyro angle corrections) to do a 3-stack autonomous.