Mike,
According to the small book about the 346 put out by CRM (Locomotive 346 The First Hundred Years by Dirk Ramsey and George E. Lawrence) the engine did not receive the half flanges until after the wreck on Kenosha Pass on July 25, 1936. The lack of flanges is considered one of the causes, whether correct or not, and is blamed in large part (combined with the speed of course) for this accident. Page 11 is where the topic is discussed and the book states that "C&S engine crews were not fond of the C-19's because they were prone to derail when working up grade...the engine's lateral motion beating on the badly worn rails the center two pairs of blind drivers tended to slide off the rail." It goes on to say that nothing was done to remedy the problem because all the derailments were at relatively low speed until the derailment of the 346 which killed engineer McGowan. During the shopping to repair the damage from the wreck the engine received the special flanges. There is no mention in the book whether or not the other two C-19's on the C&S also received the flanges at this time or not.
Daniel