Looking at the Dec '09 edition of Railfan and Railroad and came across The Camera Bag section...The "All Jim Boyd" Issue. There is a picture at the bottom of page 62 which shows Northwestern Steel and Wire 0-6-0 #10 working the NS&W Mill in January of 1980 with its rear driver set disconnected.
What would be the reason for this? Would such a move waste more steam, as it were even though the weight of the engine remains the same and now 3 sets of drivers have to compensate for the work the last set is not doing? Seems that this engine would now 'eat' a lot more fuel working harder.
Why would they do that?

CORRECTION: The engine in question was originally an 0-8-0 not an 0-6-0. Its GTW #8327. My first post would have made her an 0-4-0...sorry!

Remember that by this time they were pretty much keeping these engines running with minimal maintenance. Likely they broke a crank pin or had a similar problem on one side. Rather than repair that problem, they just removed the rod on the other side to compensate, effectively making the engine an 0-6-2.

The locomotive wouldn't have worked "harder" with one fewer set of drivers, but it would have been a lot more "slippery". OTOH they may not have been taxing the engine's abilities with the loads they were switching so this may not have been a problem.

This was discussed in a thread or two a while ago.

See thread titled: "Status of GTW 8305 (NS&W 05) and read my posting towards the bottom... J.David