Locomotive pulling power

Overview

Locomotive pulling power has always been of interest to large scale railroaders, I believe because we have grades and curves more severe than the real thing.

There are many debates about pulling power, and things that seem to affect it. This page will attempt to look into some of this and present some helpful data.

I may add sections on techniques to increase pulling power, and point to specific mods on specific locomotives.

Actual measurements

Chuck Naeser has over the years kept track of a consistent method of measuring pulling power and documenting what he has found, so most of the following information is courtesy of him.

He uses a fish scale, (pictured below), but I also need to mention he uses a consistent method of preparing the conditions to get repeatable results. He uses brass track, not oxidized aluminum (more traction) or stainless steel (more slippery in my experience).

fishing scale

Recently, Chuck noticed that the basic relationship between loco weight and pulling power did not make sense for all locos, in particular a USAT Hudson.

Chuck reasoned that the weight on the leading and/or trailing trucks could have a significant effect. Therefore, he designed a setup to isolate the weight on these wheels:

 

weight on trucks

Notice by keeping the loco level there should be minimal effect on the weight distribution as measured.

Chuck has been keeping track of his measurements and I twisted his arm a bit to present his information here, where it can help a number of people, and also present some interesting observations.

In the table below, Chuck has added columns to address the weight distribution, and see if there is a more consistent relationship between the weight on the driving wheels and pulling power.

Note that there are still some measurements to be made, those will be marked with ??. This table will be updated as time goes on.

 

Engine Weight Performance

 

Make / Model

 

Number of powered axles


Number of wheels with traction tires



Number of non powered axles


Gross Weight - entire loco (lbs)


Net Weight - powered axles only (lbs)

 
% of weight not on driving wheels

 

Pulling Power (lbs)

Pulling power as a % of gross engine weight


Pulling power as a % of net engine weight

 LGB                  
 AT&SF diesel  6 1 0 9.4  9.4 0 2.5 27  27
 F7A diesel  4 1 0 8.75 8.75 0 3 34  34
 2-6-0 Mogul  3 1 1 7 5.75 17.9 1.5 21.4  
 2-6-6-2 Mallet SV  6 2 2 9.8 8.6 12.2 3 30.6  
 0-4-0 Stainz  2 1 0 3.7 3.7 0 1 27  27
 0-4-4 Forney  2 1 2 7.6 ?? ?? 2.75 36  
 Aristo-Craft                  
 2-8-2 Mikado  4 0 2 11  ?? ?? 4.5 41 41
 2-8-8-2 Mallet  8 0 2 14 13.5 3.6 5 35.7 35.7
 Bachmann                  
 Climax  4 0 0 7.3  7.3 0 2.25  31 31
 2-8-0 Consolidation  4 0 1  10.1  ?? ?? 3.25  32  
 2-8-2 Mikado  4 0 2 13  ?? ?? 3.75  29  
 2 truck Shay  4 0 0 9.6  9.6 ?? 2.5  26 26
 Accucraft                  
 2-8-2 K28 Mikado  4 0 2 12  ?? ??  3.5 29  
 2-8-2 K27 Mikado  4 0 2 17.5  ??  ??  4.75 27  
USA Trains                  
SD40  6 4 0 10.4  10.4 0 3.5 34 34
SD70  6 0 0 11  11 0 4.5 41 41
SD70 (Dirk)  6 12 0 19.38  19.38 0 8.5 44 44
F3A  4 4 0 7.5  7.5 0 3.25 43 43
F3B  4 4 0 6.9  6.9 0 3.75 54 54
F3AB 8 8 0 14.4  14.4 0 6.75 47 47
GG1  6 0 4? 34 28.6 15.9 8 23.5  
4-6-4 Hudson  3 0 4 25 22.3 10.8 5 20  
                   
 Average       12.3     3.9  36.3 37

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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