I have two machines. Black headed Singers. One is a 15- as indicated on a little metal piece under the singer badge. It was in a treadle cabinet. It has a spoked hand wheel and is highly functional. I came upon a 15 with a potted motor and broken hand wheel. When we got the hand wheel off we saw the end of that shaft was broken, as in post #25. I am trying to make one electric machine. I don't know if the motor works or can be fixed.