Difference Between a Y6a and Y6b

southern154 · **Joined:** Mon Jun 24, 2013 12:54 pm **Posts:** 320

The title speaks for itself, what is the difference between the two?

Tom Davidson · **Joined:** Sun Dec 29, 2013 6:07 pm **Posts:** 203

Visually, the most striking spotting feature is the feedwater heater. Y-6b's used a Worthington type SA, which featured a small "box" ahead of the stack, plus a water pump on the left side. Earlier Y-6's and Y-6a's (as well as other N&W 2-8-8-2's) used the earlier Worthington BL feedwater heater, which featured a very large assembly on the left side.

There may have been other differences as well.

Tom

Overmod · **Joined:** Thu May 24, 2012 1:37 pm **Posts:** 2492

Initially there were firebox differences; at least some of the Y6a's, including the one that has been preserved, received the larger firebox. Technically the air-compressor layout was different because the pumps balanced the older BL feedwater heater.

There were also a number of small improvements intended to make maintenance easier and more direct -- I will see if I can find a more specific list.

I think that only a subset of Y6b's had the small oval 'racetrack' smokebox door arrangement. Someone more familiar with N&W power will know the definitive story.

whodom · **Posted:** Fri May 29, 2015 12:03 pm

I think the Y6a's also had conventional bearings on the tender axles while the Y6b's had all rollers.

Overmod · **Joined:** Thu May 24, 2012 1:37 pm **Posts:** 2492

Quote:

I think the Y6a's also had conventional bearings on the tender axles while the Y6b's had all rollers.

An interesting point. The only diagram I have for a Y6a (p.54 of Norfolk & Western Steam, the last 25 years) indicates 30T/22,000 gal, "6-1/2" x 12" journals'.

2156 has plain tender bearings, and in fact needed attention to one of them during the recent move to Roanoke.

As a "sort" of preservation issue -- I'd have thought that N&W would be swapping out plain-bearing trucks for roller-bearing trucks on whatever power remained in service after steam started to be phased out. On the other hand, if I were donating a locomotive for 'dea' preservation, I might consider leaving plain-bearing trucks on it and saving the (expensive and more-easily-serviced) roller-bearing trucks in revenue service as long as possible.

Mark Jordan · **Joined:** Fri Nov 07, 2008 11:21 am **Posts:** 490

As a "kinda-sorta" N&W enthusiast and modeler, I'll paraphrase what already has been said, and add a teeny bit:

1) Feedwater heater in top of smokebox vs left side of boiler.
2) Air pumps on each side of boiler (Y6b) vs two on right side (Y6, Y6a).
3) Friction bearing tender axles.
4) Smokebox door ***

*** The "small oval" smokebox door on early Y6b's was later replaced with a standard door as used on Y5, Y6, Y6a engines. All Y6b's were updated.