They are trickier to adjust than the Raleigh pamphlet indicates in that usually the rims are no longer perfectly round (50+ years later). Setting the shoe position is compromise of braking power and keeping the pad from rubbing on the rim all the time.

The shoe should be kept off the rim just enough for the wheel to spin freely with the brakes disengaged. You may have to account for flat spots in the rim when you do this by moving the shoe away from the rim a little more. If the rim is way out of round and you can't true it, the rim should be replaced. If the rim is just a little out of round, usually you can find a good compromise where the brake works OK but doesn't rub when you want the wheel to spin freely. Keep in mind that the brakes will lurch a bit if the rim is out of round. It's a judgment call when to replace the rim and when to live with the old one.