The largest American steam locomotives were trhe Big Boy 4-8-8-4 and the Challenger 4-6-6-4's, but I briefly saw a mention of a larger class with three sets of main drivers, making it something like a 4-6-6-6-4. Was there such an engine?
Good golly, Molly!shaygetz said:The Virginian and the Erie both had what are called "triplexes". The Erie's was a 2-8-8-8-2 and the Virginian's was a 2-8-8-8-4. Both were not too successful because of the massive amounts of steam needed for the relatively low returns in tractive effort. Here's a link>>>
http://www.dself.dsl.pipex.com/MUSEUM/LOCOLOCO/triplex/triplex.htm