The kids' problems are just beginning. While Mrs. Higgin's Singer is nearly 100 years old, the gap between early 20th century and 17th century manufacturing technology and techniques is vast—particularly for under-experienced would-be twin engineers not yet in high school. David turns out to have a head for organizing and management, and keeps the project moving forward with an able assist from his Grandma Higgins. She eventually bankrolls a big piece of the company, while David figures out how to make it pay. Sarah has a grasp of finance beyond her years, and teams with David—which he minds, not a bit.