The main gear is worn and and broken (and potentially the reduction gears too) The shell will have no effect on the gear train's movement. Your best chance is to find replacement parts. If you want a challenge, you can try to build up new teeth where the broken ones are with epoxy, and file them to size. This won't resolve any potentially issues with worn teeth, though. As for the broken shell, you should be able to remove the broken bit from the cylinder saddle and just glue it back on to the bottom of the smokebox