I've noticed that the two operable steam locomotives at Dollywood have some sort of modification to the bottom of the smokebox. Is this some sort of efficiency modification like a feedwater heater?

You can see the device here:

http://farm2.staticflickr.com/1246/9230 ... 577d_b.jpg

Those were installed in 2005 or 2006 if memory serves me proper. These were placed on each engine when they had a heavy overhaul and they are an attempt to catch cinders instead of them going out the stack, best I remember there is also some heavy wire mesh inside the smokebox to help break and divert them into the square box. If you look just behind either ladder behind the first step you can see the removable covers, this was so that a small scoop can be used clean the catch box. I think it was 5 gallons a day that was caught this way but I may be wrong on how much could be taken out since my memory is a little fuzzy.

The square catch boxes are built into the smokebox where a section was removed at the bottom.

If it's what I think it is, it's some form of self cleaning smokebox. It would also have removable wire screens mounted inside the smokebox to arrest the cinders. The Brits were enthusiastic users of self cleaning smokeboxes.

Wasn't that right after the balloon stacks were removed? Also when I was at Dollywood this past year a few times 192 has been the regular power and 70 has not run this year. Is she in the shops for an overhaul or what?

Yes, the balloon stacks were removed at the same time that the smokeboxes were modified. I am pretty sure that the new stacks were copied and cast from number 71, feel free to correct me if anyone knows for sure but I am pretty certain. I do not know about 70 since I have not been able to frequent my old hangout in a while, I think the drivers had been shipped off along with the axles to points unknown but that is an unconfirmed rumour