odd photo

Tue May 19 07:17:17 EDT 2015

Lynn - 

All the low-pressure cylinders of the Z-1s and Z-1as and Z-1bs were the same size – 35 inches.  The difference is in the valves.  The slide valves were the flat-top assembly on the top of the cylinders; the slide valve assemblies could be separated and removed from the cylinders.  The rounded tops denoted piston valves; these cylinder/valve assemblies were cast in one piece.   One of the Z-1as sold to the Tennessee Central (1396) had piston valves; one of the Z-1as sold to the Interstate (the former 1422, I believe) also had piston valves.

Where did you get the idea that any of the Z’s had cast frame/cylinder assemblies?  None of the Z’s were so equipped; they all had built-up bar frames with separate cylinders.  The only N&W engines equipped with one-piece frame/cylinders were the As, Js, S-1s, S-1as, rebuilt Y-5s, Y-6s, Y-6as and Y-6bs – 202 locomotives.  

Lynn – you need to not out-think this thing.  None of the Z’s had cylinders that were any more huge than the others.  They ALL got their boiler pressure raised to 225.  They were excellent engines.  But none got cast frames or roller bearings.

EdKing

From: NW Mailing List 
Sent: Monday, May 18, 2015 10:22 PM
To: nw-mailing-list at nwhs.org 
Subject: Re: odd photo

I don't know why my fingers went to the "L", shoulda been the "Z"
I have an NKP model L1a, Confuscious say I'm Confusced...

yah, they're compounds, I relooked, I have a model of the Z1a, scoured the Prince pics, there are apparently 2 versions of a Z1a, one pic has just HUGE front cylinders vs the earlier Z1a, perhaps this was the remod back to the slide valve but not changing the  front 2pistons as they were the one piece frame/cylinder body, maybe they shoulda called it the Z1A, (vs Z1a...see what I did there, huh huh)  when you say that its "Z1AAAaaaeeeeee"

They mention some clearance issues with the front cylinders like that. 

The book also mentions since the Y's displaced the Z's in mainline running they got bumped to switching service and some mine runs, been trying to figure out how to use my model, now I know with along the M2c's I have.

-Lynn-

On 5/18/2015 8:23 AM, nw-mailing-list-request at nwhs.org wrote:

        Subject: Re: odd photo 
        From: NW Mailing List mailto:nw-mailing-list at nwhs.org 
        Date: 5/17/2015 8:58 AM 
        To: nw-mailing-list at nwhs.org 

  Lynn:

  Please re-read Prince's book.  The Z1s, a and b, (not "L") were ALL compound engines.  The Z1 and Z1a were built with slide-valve low pressure cylinders.  Those rebuilt to Z1b got piston valve low pressure cylinders; there may have been other improvements, too, but others more knowledgeable about such details can fill that in.

  There was one (1) fully simple Z, class Z2, No. 1399.

  This link http://www.steamlocomotive.com/2-6-6-2/?page=nw is helpful.

  Dave Phelps

  In a message dated 5/17/2015 8:08:42 A.M. Eastern Daylight Time, nw-mailing-list at nwhs.org writes:
    I can verify reading princes book 1331 is the lowest numbered engine to get the treatment from an L1a to an L1b. N&W is no stranger to reworking their engines, The point is about the L1b it has low pressure front cylinders, while the L1a is basically a full simple engine.
    This is about grinding on the mountains to move that coal at low speed. The simple engines could move faster. The reason why is the larger cylinders at higher speed cause reverse pressures which does not work well for higher speeds, but low speeds are fine, why the Y class compound development, drag that freight over them mountains.
    N&W could probably pick and choose the best engines in condition to take the modification and last many more years, and that they did with all of their steam lineup, but again other lower end steamers met the scrappers torch while steam technology advanced.  The Roanoke shops were very talented keeping the steam fleet alive why many of the older engines lasted to the end. M2c's built in 1917 still working in 1958? wotta run.

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