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

NW Mailing List nw-mailing-list at nwhs.org
Thu Oct 10 10:38:36 EDT 2019

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

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> 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> 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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