When attached to a motor, are the new worm gears big enough (large enough diameter) to correctly engage one of the equally new rack gears.
My question arises because I worry that the motor case will interfere with the motion of the rack gear.
I want to use a worm gear directly attached to a motor as the pinion gear in a rack and pinion set-up.
I do not believe the worm will work with the Rack gear as your describe above. The worm itself is small enough in diameter that your assumption is correct; direct driving a worm with a Vex motor will cause the motor housing to interfere with the rack.
You can however position the worm such that the motor is clear of the rack (utilizing additional gearing/shaft/whatever).
It should be noted that the worm does NOT mate very “cleanly” with the rack. Your mileage may vary.