Solved! Go to Solution.
The trick to setting up this constraint is to correctly select both parts. The first will be the rotational part. It should already be free to rotate about an axis and constrained to a fixed face. Then select the translational part by picking an edge representing the axis of translation. Open the attached ZIP. Drag the red "post" on the "pinion wheel" and the "rack" will translate.
I must be missing something as I am trying to delete all of your constraints and get the same results but I am failing. Can you please up load a screen shot recording or several pictures, because if it is something very particular I need to figure out my systematic error. I have attached my assembly of where I tried to recreate what you did but failed so you might be able to shed some more light on the subject. Thanks in advance.
In the attached image, I am selecting the cylinder face as the FIRST SELECTION (shown on left).
I am then selecting the linear edge of the rack as the SECOND SELECTION (shown on right).
Doing so uses the circumfrential length as the ratio between the rack and pinion.
Michael - forgetting the translational constraint for the moment...
...in my example, the pinion is constrained to the face of the base plate as well as to the axis of the hole. The base plate is grounded. The pinion can be dragged rotationally.
The rack is touching the pinion face. It is constrained to the face of the base plate and it is flushed to the edge. It can be dragged back/forth.
Now: add the translational constraint and then drag the pinion to see the rack move by the circumfrential length/ratio.
Is all of that working for you in the example assembly when you open it?