need some help with animating a tricky joint

[Will1337]

i cant seem to figure out how to get these joints to work together. Should i be using the pin-slot joint?  is there a better way to do an increasing diameter slot joint? would you even call it that?

[davebYYPCU · Accepted solution]

You were fairly close, Ground the back plate, 

motion Link the rotation with the slider distance, these numbers are close to it, might need further tweaking.

[Will1337]

Thanks again!