ONLINE
STORE
"ASK THE BACH MAN"
FORUM
PARTS, SERVICE,
& INFORMATION
CATALOGS AND
BROCHURES

Welcome, Guest. Please login or register.
Did you miss your activation email?
October 14, 2019, 07:06:50 PM
Home Help Search Login Register
News: Check out the photo gallery link above or >click here< to see photos of recently announced products!
+  Bachmann Message Board
|-+  Discussion Boards
| |-+  Large
| | |-+  Tractive pulling power
« previous next »
Pages: [1] Print
Author Topic: Tractive pulling power  (Read 354 times)
mickeykelley

View Profile
« on: July 16, 2019, 06:44:37 PM »

Just as a curiosity, has anyone ever tested the tractive power of the various Spectrum units, the 2/3 truck Shay, Climax, 2-6-6-2, Heisler, K-27 and C-19?  The. Compared that to real world specs?  Just curious.
Logged
Kevin Strong


View Profile WWW
« Reply #1 on: July 20, 2019, 11:22:10 PM »

Drawbar pull is usually measured for the reviews in Garden Railways magazine. They use a rough estimate of 1.25 ounces of drawbar pull per car, so a locomotive with a drawbar pull measured at 2 pounds would be (by their estimates) able to pull 26 cars on straight and level track.

A quick survey of some of the Bachmann locos based on GR reviews:

C-19 - 2 pounds = 26 cars
K-27 - 2.5 pounds = 32 cars
2-truck Shay - 2.5 pounds = 32 cars
2-6-6-2 - 2.5 pounds = 32 cars
Climax (early version) - 1.1 pounds = 13 cars
4-4-0 - 1.4 pounds = 17 cars
2-6-0 - 1.4 pounds = 17 cars
0-4-0 - 1 pound = 12 cars


Now, about translating that to the "real world?" We need to consider a few things, but first and foremost is the weight of the average cars being pulled and the grades being climbed.

Here's a link to the 1885 Baldwin catalog, which has photos and builder's data for many narrow gauge locos.
https://archive.org/details/illustratednarro00baldrich

Consider the Baldwin 8-18D, which is the Bachmann "centennial" mogul. (The fancy one in the pretty colors.) On the flat and level, the loco is rated at 895 tons. On a 3% grade, that drops to 70 tons.

The 10-26E is the C-19. On the flat and level, it's rated at 1630 tons. Get that same loco on a 3%, and it drops to 130 tons.

Note also that the introduction of just a half of a percent of grade reduces the tonnage by over half.

That's the numbers, so how does that translate into cars? That depends on the weight of the car. Early freight cars (c. 1870 - 1900s) were low capacity, so maybe 10 - 20 tons each fully loaded. Later cars could weigh upwards of 40 tons each.

Let's look at the C-19, then, and take an average car weight of 25 tons (the capacity of a D&RGW box car).

"By the book"

Flat - 1630 tons = 65 cars
0.5% - 655 tons = 26 cars
1.0% - 395 tons = 15 cars
1.5% - 275 tons = 11 cars
2.0% - 205 tons = 8 cars
2.5% - 160 tons = 6 cars
3.0% - 130 tons = 5 cars

Here's the mogul:

Flat - 895 tons = 35 cars
0.5% - 335 tons = 13 cars
1.0% - 215 tons = 8 cars
1.5% - 150 tons = 6 cars
2.0% - 110 tons = 4 cars
2.5% - 85 tons = 3 cars
3.0% - 70 tons = 2 cars

When you compare the numbers for the prototype compared to the models, the prototypes can outpull the models on the flat and level (based on GR's estimates), but with the introduction of even half of a percent grade, the models can outpull the prototypes. Consider also that the model locos are all "geared locos," so they are not nearly as affected by grades as the prototypes. A model loco that can pull 15 cars on the straight and level can handle half that up a 3%.

So, the question for the modeler is whether we tailor our trains to reflect how the prototype would respond to those grades, or whether we just want "typical" trains regardless of the terrain on our railroads. Two car trains may look ridiculous, but they may be prototypical.

Later,

K
Logged

mickeykelley

View Profile
« Reply #2 on: July 20, 2019, 11:56:16 PM »

Thanks Kevin.  That was very informative and really kind of what I was interested in.
Logged
the Bach-man
Administrator


View Profile
« Reply #3 on: July 21, 2019, 09:20:25 PM »

Kev!
What a great analysis!
Thanks a lot!
Best,
the Bach-man
Logged
Pages: [1] Print 
« previous next »
Jump to:  
Powered by SMF | SMF © 2015, Simple Machines Valid XHTML 1.0! Valid CSS!