Steam & Excursion > How much power to the early steam locomotives develop?

I'm well aware of how much power a "modern" steam locomotive can develop -- for instance, I've heard the 844 or 4449 develop something in the range of 4000-5000 hp, while the "Big Boy" would perhaps be rated at 6000-7000 hp or so.

But seeing some steam tractors operating at the Oregon Antique Powerland show, made me wonder. . .just how much power did the early steam locomotives develop? For example. . .how much did the "Jupiter", one of the engines at Promonitory, develop?

I've never seen any figures for the early engines. . .and I'm thinking it probably wasn't too much more than maybe 100-200 hp.

Anybody have any good numbers?



Edited 1 time(s). Last edit at 07/28/14 13:56 by Narniaman.

I wonder if people at Kloke could provide some info. I don't know how much testing of that nature has been done on Leviathan but I bet you could at least get precise dimensions from them to do some math.

Cheers,Dave

I am by no way an expert on locomotive performance, but here are some comparison numbers from a railroad that I know.

Unfortunately, steam locos weren't usually rated by horsepower but rather tractive effort in pounds. I know that on the Wabash, 4-4-0s built in the 1880s and 1890s were rated at 12,000 to 14,000 pounds tractive effort. In comparison, a Wabash USRA light 2-8-2 was rated at about 50,000 pounds. And a Wabash 4-8-4 built in the early 1930s was about 71,000 pounds. Now, you have to consider that the cars were smaller and lighter in the days of the 4-4-0s too, so the trains would be a bit longer than you might think. In my book, "Railroading on the Wabash Fourth District", I've included diagrams with statistics of most of the Wabash diesel and steam locos plus tonnage ratings for that line. On the flat end of the Fourth a USRA Mike rated 4,000 tons, while a two unit EMD F7 diesel combo rated 7,140. (A 4-8-2 would rate 6,000 tons, not as good as the two F7s.) In Chapter Two, as told by a hogger that started on this line in 1897, with the 4-4-0s, drag freights were rated for 1,000 tons and high class freights 1,000 tons "double-headed". But these were ratings in ideal weather to judge the number of cars a train could safely handle, but outside temperature, winds, slippery rail and grades could drop this rating considerably.

As experts will tell you here, speed was a factor too as certain locos had more power in a given speed range than others as it does when we compare steam with diesel. Also, smaller drivers often equated to more tractive effort than larger drivers, all other things being equal.

I will yield to others here who know more about this than I do, but hopefully these comparisons will help you get a feel for how powerful the old tea kettles were.

Victor A. Baird
http://www.erstwhilepublications.com/



Edited 5 time(s). Last edit at 07/28/14 11:43 by wabash2800.

Wabash2800 has pretty much nailed the TE of early locomotives.

Short Line Enterprises ex-Dardanelle & Russellville 4-4-0 No.8, built by Cooke L&M Co. in 1888 weighs in at 40 Tons has 17" Bore x 24 " stroke, Driver Diameter of 58". It's tractive effort is calculated as 14,230 lbs.

The standard formula in T=(.85 x P x d^2 x s) / D

Where:
T = Tractive Effort
.85 is the standard constant representing effective boiler pressure
P = Boiler Pressure
d = Cylinder Bore
s = Cylinder Stroke
D = driver diameter

An engine similar to the Central Pacific's Jupiter should have approximately 11.500 lbs. of TE. It most likely had a boiler pressure of 130 lbs. and 60" drivers with a 16" bore & 24" stroke. It would also have weighed 30-32,000 lbs.

Another factor in the calculation is adhesive weight of the locomotive. The factor of adhesion is nominally 20-25% of the weight on drivers.

All of these factors were well known by the 1860's and were a determining factor in the overall dimensions of a steam locomotive. Too much TE for a given adhesive weight meant the engine was too slippery. Too little and it couldn't start a train.

Too small a boiler and no fireman could make enough steam. The SP learned this lesson with their 4-10-0 "El Gobernador."

One more factor to consider is gradient. On straight and level track it takes between 4-6 lbs. of force to move one ton with friction bearing trucks. On a 2% grade it takes approximately 45 lbs. of force to move the same ton. This factor is one of the reasons the Transcontinental Railroad was required to have a maximum effective grade of 2.2%.

Basic info taken from the 1875 edition of Forney's Catechism of the Locomotive.

I have a reprint of the 1906 Locomotive Catechism by Robert Grimshaw. This book gives
a couple of formulas for calculating a locomotive's horse power one of which is as
follows:

Cylinder diameter in inches squared times the speed in miles per hour times average
steam pressure in the cylinder in pounds per square inch times the length of the
stroke in inches. Divide this by the driving wheel diameter in feet times 4500.

So for the Central Pacific's Jupiter moving at 25 MPH we would have (using cylinder steam pressure
as .85 X boiler pressure as described in the previous post):

(16 X 16 X 25 X .85 x 130 x 24) / (5 x 4500) = 785 Horse Power (rounded to nearest
whole number)

For the Central Pacific's C.P. Huntington moving at 25 MPH the formula gives us 285 Horse Power.



Edited 1 time(s). Last edit at 07/29/14 15:07 by C.P.Huntington.