McFarlane. Otherwise known as Franklin W. Dixon. Well, one of them.
From the Globe and Mail:
Under the pen name Roy Rockwood, McFarlane subsequently produced seven novels in the syndicate's Dave Fearless series, then moved on to write more than 20 Hardy Boys novels.
For most of these, he was paid a flat fee of $100 per book and, although the novels sold many millions of copies and were translated into 50 languages, he earned no royalties. A well-preserved first edition is now worth about $1,500.