Was Re: Roller Bearings and the Y6-b, Now Y6b Development

Thu Oct 10 12:20:36 EDT 2019

The N&W was serious about roller bearings they even put them on the bell turnings,   One note I have read that rollers were four to five time as expensive.

Larry Evans

From: NW-Mailing-List [mailto:nw-mailing-list-bounces at nwhs.org] On Behalf Of NW Mailing List
Sent: Thursday, October 10, 2019 10:39 AM
To: List NWHS <nw-mailing-list at nwhs.org>
Subject: Was Re: Roller Bearings and the Y6-b, Now Y6b Development

All,

N&W instead of expanding the speed capability of the Y Class they created the A Class to take care of Fast Freight, flatter districts and the occasional heavy passenger train.  Later they realized that a single engine type to do all freight jobs would be better for the railroad operationally and financially.  N&W started investigating the Y7 for this role, assuming larger drivers and abandoning compound operation was necessary to meet the objective of a general purpose freight locomotive.

I propose that in about 1930, N&W could have sped up the compound 58" drivered Y Class to allow it to also do everything that the Class A did as well so that the Class A would have never been designed or built.

There are 2 issues to a Y class doing the work of an A. 1. Maximum speed and 2. Drop off of drawbar pull at higher speed.

With respect to 1. The size of the low pressure cylinders and lack of ability to balance them for 70 mph is the issue. Dividing the 2 huge lp cylinders into 3 reasonable sized lp cylinders on 120 degree separation would likely have allowed 70 mph balancing.  

Also the volume of the lp cylinders is driven by the volume of the hp cylinders. The hp cylinders size on the Y class is driven by tractive effort requirements for the 4 axles of the hp engine.  The lp engine due to size and the starting valve has no issue producing as much tractive effort as needed. Changing the wheel arrangement to 2-10-6-4 would have helped in allowing smaller hp and lp cylinders and balancing while keep TE high.

Also the 3 cylinder  lp engine with less torque variation in a rotation should allow the lp engine to produce 25000 pounds of TE per axle vs 20000. So a 3 lp cylider Y class should have been capable of 180000 to 185000 pounds of TE versus 160000ish pounds of rating TE for a Y5 Y6.

The second issue is drop of of drawbar pull at higher speed.  This is an issue of steam flow and pressure drops. A 3 cylinder lp engine and also reducing the cylinder sizes in general will help this tremendously.  But having 2 piston valves per cylinder with the longest practical travel lap and lead will greatly improve middle range and top end power without hurting the low end.  High lead in valve gears can make a locomotive slippery at low speed so variable lead based on cutoff like DRGW did would be appropriate based on what the N&W did with the Y Class. 

The live and intermediate steam piping from the dome through the superheater throttle  and cylinder steam ports should have cross section of 25% of the cylinder faces not 8-10% on the Y class. 

Also the Y class need more  steam chest volume about 125% of the cylinder volume.  

More superheat like 850 degrees Farenheit would have helped but probably required saturated steam cooling of the valve liners.

Also resuperheating of the exhaust steam to the lp engine would help.  More feedwater heat extraction using a 2 stage setup with open and closed type stages. Basically adding a 2nd shell and tube stage to a Worthington FWH would work.

When finished with this you would end up with a loco of similar weight and size but have 70 mph top speed 185000 pounds TE and likely 7000 drawbar horsepower on the same coal and water consumption as a Y.

And in the end Stuart Saunders would have dieselized anyway.

John Rhodes 

On Thu, Oct 10, 2019 at 8:10 AM NW Mailing List via NW-Mailing-List <nw-mailing-list at nwhs.org <mailto:nw-mailing-list at nwhs.org> > wrote:

I'd like to throw another possible reason - roller bearing rods have large hubs and may have interfered with the clearance limits on  the lower part of the N&W's load gauge.  With the Y6's 58" drivers and 32" stroke, there's not a lot of room  for a roller bearing rod hub.  IIRC, load gauge interference was a problem with the P&LE's 2-8-4's and they had conventional solid bearing rods and 63" drivers.

Dave Stephenson

On Wednesday, October 9, 2019, 9:58:26 PM EDT, NW Mailing List <nw-mailing-list at nwhs.org <mailto:nw-mailing-list at nwhs.org> > wrote:

Bill 

      If you’re a Trainorders member (I am not)you can go back and read Wes Camp’s writing on this subject recently . Very interesting  There were

a lot of reasons why probably it never happened . 

Larry Evans

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