SHERMAN HILL & BIG BOY

SHERMAN HILL SUMMIT

AND

UNION PACIFIC BIG BOY LOCOMOTIVE

Research of topics under discussion at the 8 am coffee hour at

Wescoats Corner & Five Points Arbys.

The 1885 era of the Union Pacific railroad's saw locomotives

struggle to move trains of 3600 tons over the Wasatch mountains between Ogden, Utah and Green River. Wyoming.

These mountains held the 176 miles of track beginning at

Ogden,Utah, sitting at 4300 feet above sea level, climbing the Wasatch

Range, to 7300 feet at Aspen tunnel, then down to Green River,

Wyoming, sitting at 6100 feet above sea level.

On occasion Union Pacific had to combine three or more steam

engines to assist heavily loaded trains over the Wasatch mountains.

Early 1940's when the Union Pacific was enjoying a period of

high earnings and profits, the company under a new president , William

Jefferies, ordered built, an locomotive that could pull 3600 tons over

the Wasatch Range unassisted..

Also on the mines of American manufacturers and transportation

managers was the eventual entering of the United States in World War II

which was already putting additional traffic on the heavily traveled

Ogden - Green River route.

In Omaha, Nebraska's Union Pacific's Department of Research &

Mechanical Standards, Otto Jabelmann, calculated that 135, 000 lb.,

of 'tractive effort' was needed for the engine ordered built for Jefferies to

achieve it's goal. The engine was quickly designed and the American

Locomotive Company agreed to build such a locomotive. These new

engines were given trade numbers of “4000 Class” and were to be named

Wasatch series, however, a worker wrote “Big Boy” on the front of the

first engine as it was being built and that name 'stuck'. Union Pacific

already had the Challenger built in 1936, but Big Boy was larger,

heavier and required Union Pacific to lay heavier rails and realign curves.

With the tender Big Boy was the largest steam locomotive built that could

operate on existing standard gauge railroads.

But wait, an interruption, “tractive effort', what is that? Calls for another research period. So it be.

PAGE TWO

Tractive Effort, or Tractive Force, a mechanical engineering term,

refers to the total traction a vehicle exerts on a surface or the amount

of total traction parallel to the direction of motion. Got that down and

understood ? I bet.

Railroad engineering holds the term 'tracfive effort' is used to

describe the pulling or pushing capability of a locomotive.

The term tractive effort is starting tractive effort, continuous

tractive effort, and maximum tractive effort, and are related to common

mechanical factors , input torque to the driving wheels , the wheel

diameter, coefficient of friction between the driving wheels and the

supporting surface, the weight added, is the factor of adhesion that

determines the maximum torque that can be applied before the onset of wheelspin or wheelslip. Starting tractive effort, is the tractive force

generated at standstill, determines the train weight a locomotive can

set in motion, maximum tractive effort is the highest force under a

condition not injurious. Continuous tractive effort is the tractive force

to be maintained , before the system overheats. “Power at rail” is a

railroad term for the available power for traction or the power available

to propel the train.

We intend to have Warren explain this “tractive effort” thing to us

in more detail so perhaps the following will be some help .

An estimate tractive effort of a steam locomotive can be obtained

from the cylinder pressure, cylinder bore, the stroke and diameter of the

wheel . Torque depends on the driving rod angle made with the tangent

of the radius on the driving wheel. The driving force is torque divided

by wheel radius, thus: d = d2 sp / w X 0.85.

OK Lets get back to Big Boy, a 4- 8-8-4 locomotive, the only one

to be so, the front leading truck, had 36 inch wheels, following were 8

wheels, 68 inches, the drive wheels, driven by a piston to each 4 wheel,

followed by 8 more drive wheels identical to the first. Under the cab was

a 4 wheel trailing truck with 42 inch wheels. Each set of 8 drive wheels

had its own frame and was articulated which allowed Big Boy to handle

20 degree curves. Number 4000, the first Big Boy locomotive delivered , was on track by 5 September 1941.

PAGE 3

All Big Boys were 132 feet, 10 inches long, the engine being 85

feet, 9-1/2 inches long, the tender was 47 feet, 5 inches long. The height

of the locomotive was 16 foot, 2-1/2inches. Locomotive and tender were

a maximum of 11 feet. 6 inches wide. The weight, engine was 772,250

pounds, 436,500 tender for total of 1,208, 750 lbs . Almost 605 tons.

The tender, named 'centipede' because of it's 14 wheels, each one 42

inch tall. The tender could carry 64,000 lb of coal. It also carried 25,000

gallons of water in a rear compartment. Big Boy was designed for a

top speed of 80 mph. Seldom did it ever exceed 50 mph and over the

mountain it was down to 12 mph. At a speed of 41 mph there was 6290

hp at the drawbar. Each drive wheel rotated 202 times a minute. This called

for 12,869 cu ft of steam every minute.

The cab had four seats for a three man crew. An Engineer, fireman, and breakman. In 1944 the class 2 Big Boy cost $319,600.

The Ogden to Green River 76 mile run would take at least four hours,

uphill, a clime of 2500 feet. Under full steam the Big Boy consumed

22,000 lb of coal ans 12,000 gallons of water per hour.

As diesel locomotives became the prime mover, Big Boys soldiered

on and were the last steam engines used in regular service. There had

been 17 Big Boys locomotives total in operation for 20 years.

Sherman Hill Summit is the highest point of the Union Pacific

Railroad's First Transcontinental Railroad at 7247 feet. It had first

been named Lone Tree Pass and Evans Pass. The town of Sherman was

a train stop where engines were changed, had a roundhouse, turntable,

water tank, and section houses. There were maybe 100 residents of

Sherman, a general store, post office, school, two hotels and two saloons.

Abstract: Wikipedia, and William Pearces' Old Machine Press, www,

by Harrison H, September 16, 2018, for

www.iinni,blogspot.com and facebook's

Harrison H page.

Abstract: (if you want to call it that OK) September 15, 2018,

by Harrison H. from Wikpedia to www.iinni.blogspot.com

& Facebook