I saw a picture in a book on crossbows of a modern prototype crossbow with the prod mounted on a rack and pinion with the rack running down the middle of the stock and the prod attached to the pinion gear.the string was then attached to the trigger pin while the bow was relaxed and the bow was then cranked up to the desired tension.With modern materials you could make a pretty strong crossbow with this design without making it too heavy.Would still be usable by a person unable to cock the present crossbows.Never saw one for sale,but it seemed interesting at the time.The builder claimed his prototype was adjustable in pull weight to 300 pounds.
