One of the best chain rack and pinion designs I have seen in FIRST was on the ChiefDelphi 2000 robot. Its purpose was to entend and retract their boom-like arm.
Here is a picture.
I wish I could find a picture of the back face of the robot. This view would show that 2 van door motors drove a chain up and down. The chain was attached to two aluminum tubes and was wrapped, serpentine-like, between sprockets on the 2 motors.
Can anyone from CheifDelphi give us a better picture of this?
This machine was and still is a thing of beauty. It is my favorite robot in all of FIRST, for all time. This design feature was just one of its strong points.
Andy B.