Has anyone got a clue as to how to get the gear/sprocket off of a Elgin rear hub? It looks like there is a ring that screws on and holds it on ,but when you take it off nothing happens and you eventually loose the ring. Is the gear screwed on too ,or pressed on ,or what . Hoping someone has a clue. Also can you just swap the two gears and make it a skiptooth or is something else involved? help!