Empty (tare) weight of 611's Auxiliary Tender?

Thu Jul 9 07:39:44 EDT 2015

Dave:

Thanks!  This kind of detailed information is extremely helpful and  much 
appreciated.

Dave Phelps

In a message dated 7/9/2015 3:51:50 A.M. Eastern Daylight Time,  
nw-mailing-list at nwhs.org writes:

Dave, 

I have to limit my comments  because I was on the research car for two 
days, and the final numbers have not  been run.   However, I can address the 
conservatism of N&W's testing  procedure back in 1945  from  work I did years 
ago.  The often  quoted 5,028 DBHP at 41 mph was actually made in a series of 
tests that were  designed to measure the economy of raising the steam 
pressure to 300  psi.  As a result, in order to hold constant speed with constant 
load  (1,065 tons), the 300 psi tests were run with a shorter cutoff than 
the 275  psi tests.  So the word "maximum" doesn't seem to be a very 
descriptive  adjective to apply to the DBHP reading.  I don't believe N&W used it  
in the test report either.   Also the unit evaporation rate I estimated  for 
the test was about 77 lbs of water per SF of direct heating surface.   
Baldwin  recommended 80lbs/SF DHS as a nice achievable figure for daily  working. 
 So, you can draw your own conclusions about whether the  sometimes-heard 
5,200 DBHP maximum at 45-50 mph is over the top or not.   I don't think it 
is.  The J's were body-builders in a very stylish  outfit!

Dave Stephenson

____________________________________
 From: NW Mailing List via NW-Mailing-List  <nw-mailing-list at nwhs.org>
To: nw-mailing-list at nwhs.org 
Cc: NW Mailing List  <nw-mailing-list at nwhs.org> 
Sent: Wednesday, July 8, 2015 2:07  PM
Subject: Re: Empty (tare) weight of 611's  Auxiliary Tender?

Based on the information from Ken,  below, and Dave Stephenson in his 
response, I calculate that the auxiliary  tender required about 370 drawbar 
horsepower to be kept moving at 26 mph on  the 1.34% grade.  This includes the 
following assumptions:
- The "Modified Davis" train  resistance formula gives a reasonable answer 
(it's sort of the "industry  standard", so that should be safe...)
- The Auxiliary Tender was still  full
- The measurement was on tangent track  (this assumption is mandatory since 
I had no information regarding specific  location with respect to a curve) 
OR the quoted grade was compensated.
- Yes, of course I added grade  resistance to the rolling resistance.

Added to the 4400 DBHP the NS Research  Car is quoted as having measured, 
this compares favorably with the  slightly over 4500 DBHP  in the N&W curve 
reproduced in  Col. Jeffries' book, and is just about on (as close as you can 
read the curve)  the curve Classic Trains published (on-line) in 
conjunction with their special  issue on 4-8-4s.

Several relevant conclusions, in no  particular order:
- There have for years been "whispered" thoughts that the N&W's  published 
capabilities for the J were...um...conservative.
- Spencer did a super job!
- "The Old Girl" hasn't lost a step!

Thanks to Ken and Dave for their assistance!

Dave Phelps

In a message dated 7/8/2015 1:41:37 P.M. Eastern Daylight Time,  
nw-mailing-list at nwhs.org writes:

Dave   

The best I can do is off NS' diagram sheet for the 250001 and 250002,  last 
updated was 1-22-1991, which states an average light weight of 143,650  
pounds.

Ken Miller

On Jul 8, 2015, at 10:31 AM, NW Mailing List via NW-Mailing-List  wrote:

Could some kind soul please provide the empty (tare) weight of 611's  
current auxiliary tender?

I need the information to complete the input data to calculate, using the  
modified Davis train resistance formula, how much the addition of the  
auxiliary tender impacts the drawbar horsepower measurements reported from the  
NS Research Car during the recent excursions.  Then, a valid comparison  can 
be made with the N&W curve reproduced in Col. Jeffries' book, and  the curve 
Classic Trains published (on-line) in conjunction with their special  issue 
on 4-8-4s.

Thanks in advance,

Dave Phelps

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