cold weather roller bearing friction

[userfriendly]

A 160 car coal train has 640 axles and 1280 roller bearings not including locomotives.
I've noticed that in very cold weather a 25% increase in fuel consumption.
For example 5,000+ liters instead of 4,000 on a 130 mile run.
Each car weighs 143 tons (2,000 lbs tons).
Snow can add to the weight of each car.
Cyclonic action of the wheel flanges against the rail as the train slows
is another source of parasitic friction loss.
At low speed it would make sense that the lubricant in the wheel bearings will cool.
TOR, top of rail friction modifiers become less effective as the temperature drops.
If it takes .75 horsepower per ton during summer operation to climb a 1.2% grade at 9mph ,
how can we accurately predict the horsepower requirement of the same train as the ambient drops?

 

[Olas]

Without knowing the visc. of the lube being used and how it reacts to temp change, we can't predict with much accuracy..

Going off the reported fuel usage, it looks like you need an extra 25% horsepower when it's cold and 25% less when warm.

 

[Boomer]

I have a photo in a book taken in the 1930's of a steam engine pulling a freight stalled in winter on the Rockville Bridge north of Harrisburg, PA. This bridge crosses the Susquehanna River and is the longest stone arch bridge in the world. At each end there is an approximate 90 degree turn. According to the caption, the stall was caused by the engine being unable to overcome the stiffness of the grease in the bearing boxes of the cars. So what goes around, comes around!

 

[FowVay]

Grease is like motor oil in the sense that it comes in different viscosity ratings for the climate the component is being used.

Grease ratings range from NLGI 000 through NLGI 6. Most common that we generally see is NLGI 2.

Maybe the rail service should be consulting with a lubrication specialist to [censored] their needs and make changes during the extreme cold climates. A 25% reduction in efficiency is surely costing them more than just fuel.

 

[Food Scientist]

Is this a homework problem?

 

[userfriendly]

Yea, sort of a self-induced homework project.
The train described weighs almost 23,000 tons.
The locomotives are GE AC44s.
They can put 4,400 HP to the rail down to 9.6 MPH,
then traction becomes iffy.
Traction/power can be moved to the axles that
are not slipping from the ones that are.
Curves add to the wheel flange frictional losses.
More so closer to the power.
Locomotive arrangement is two up front, two close to
the middle and one at the back pushing (2-2-1).

I know we have one BITOG member in Calgary.........

 

[MolaKule]

Originally Posted By: used_0il
A 160 car coal train has 640 axles and 1280 roller bearings not including locomotives.
I've noticed that in very cold weather a 25% increase in fuel consumption.
For example 5,000+ liters instead of 4,000 on a 130 mile run.
Each car weighs 143 tons (2,000 lbs tons).
Snow can add to the weight of each car.
Cyclonic action of the wheel flanges against the rail as the train slows
is another source of parasitic friction loss.
At low speed it would make sense that the lubricant in the wheel bearings will cool.
TOR, top of rail friction modifiers become less effective as the temperature drops.
If it takes .75 horsepower per ton during summer operation to climb a 1.2% grade at 9mph ,
how can we accurately predict the horsepower requirement of the same train as the ambient drops?


How about doing a course interpolation on a graph?

Assume 0.75HP/Ton for summer and 0.94 HP/Ton for winter.

Take your end points of extreme high and low temps on one axis verses the horsepower extreme high and low points on the other axis.

Any intersection of one variable with the curve should give you the other variable's value.

FowVay is right, you need a lube expert to find or formulate you a high level EP, lower viscosity grease for winter.

 

[userfriendly]

A couple of guys can push an empty rail car once it is moving in the summer, but not in
the winter.
If the added resistance is caused by the cold lubricant in the winter then
we only have to add the extra horsepower the roller bearings require.

The extra horsepower required would be the same whether the car was loaded at 143 tons
(286,000 lbs) or empty at 32 tons.

For that reason hp/ton cold / hp/ton warm doesn't work as well as it should.
Or at least not as others so far think it should.

Actually by writing this out and reading the responses I'm starting to identify
the problem in determining "winter haulage rates".

 

[ragtoplvr]

It is not uncommon for a diesel engine to lose efficiency in cold weather. Winter blends of diesel tend to have lower BTU content.

This might be part of the increase in fuel consumption.

Rod

 

[userfriendly]

Thanks ragtoplvr;
I can pull up the horsepower hours at the completion of a trip
and overlay it on a previous trip with an identical train, but
contrasting ambient.
The colder it is, the more horsepower and fuel the trip requires.
The efficiency of locomotives and other industrial engines can
be expressed in pounds of fuel per horsepower hour, or it's
metric equivalent.
Generator output is usually around 5,000 HP at 1050 RPM.
Auxiliary HP to run heaters, headlights and the air pump
can be as high as 300.
After electrical and other efficiency parasites take their share,
4,400 HP is delivered to the rail.
On a nice warm day on straight track, the flange effect and bearings
consume almost nothing, and you can determine the horsepower
requirement of a train climbing a grade by using the formula
of 33,000 lbs of lift over time.
A grade of 1% is considered steep for railway purposes.
That means for every 100 feet traveled, one foot of elevation is ascended.
Operating locomotives are not added into the weight of a train.

How much horsepower would be required for a 23,000 ton train
to ascend a 1% grade at 10 MPH?

 

[Shannow]

Originally Posted By: used_0il
How much horsepower would be required for a 23,000 ton train to ascend a 1% grade at 10 MPH?


Vertical speed is 0.1MPH, or 0.044m/s

Excluding friction, just dragging 23,000 (I used Tonnes) vertically at 0.044m/s against gravity has me calculating 10MW, or 13,500hp.

 

[MolaKule]

Suggestion:

Avoid all curves and hills.

 

[CrawfishTails]

Originally Posted By: Shannow
Originally Posted By: used_0il
How much horsepower would be required for a 23,000 ton train to ascend a 1% grade at 10 MPH?


Vertical speed is 0.1MPH, or 0.044m/s

Excluding friction, just dragging 23,000 (I used Tonnes) vertically at 0.044m/s against gravity has me calculating 10MW, or 13,500hp.


Only a bitoger would exclude friction....

 

[d00df00d]

Originally Posted By: CrawfishTails
Originally Posted By: Shannow
Vertical speed is 0.1MPH, or 0.044m/s

Excluding friction, just dragging 23,000 (I used Tonnes) vertically at 0.044m/s against gravity has me calculating 10MW, or 13,500hp.


Only a bitoger would exclude friction....

Pretty sure that was just to give an idea of scale, not to imply that friction is actually worth neglecting.

 

[CrawfishTails]

Originally Posted By: d00df00d

Pretty sure that was just to give an idea of scale, not to imply that friction is actually worth neglecting.


Yep, its really to give a lower limit on power required. Friction can only be estimated or obtained thru measurement at track conditions. Estimating a 10% friction, you can multiply Shannow's answer by 1.1, but who knows?

 

[Shannow]

I think it's better to exclude friction, state it, and provide a lower boundary for the answer than to make up a number an claim it as more accurate...that's the realms of BITOG

Rate of change of potential energy is always a good start for something needs to be "at least this big".

 

[Yah-Tah-Hey]

Those are sealed roller bearings, right? I don't ever recall seeing a grease zerk on any of our 100+ coal car wheel bearings. . I presume the bearing manufacturer specs a grease to serve across a wide temperature range. In years of power generation experience, I don't think I recall ever hearing anyone mention anything about friction loss due to wheel bearing grease. There were too many immediate problems to be concerned. UP didn't have a problem getting the train to the plant, but once our own coal handling people got in the cab, all bets were off.

 

[userfriendly]

The friction loses are not a percentage of the train weight,
but has more to do with bearing and track induced loses.

I mentioned that a couple of guys can keep an empty rail car
rolling in warm weather by pushing it on level straight track.

A total of 8 wheel bearings requiring virtually no resistance.
Cool those bearings to -40C, and I wouldn't be surprised if they
require 1 hp each at 10 MPH to turn.
The friction losses of 1 HP per wheel would be the same whether
the car was loaded or empty.

HP calculation? At 10 mph, one mile takes 6 minutes or one tenth
of an hour. In 6 minutes the train has climbed 528 feet.

What would someone who is interested in ballistics say about that?

 

[userfriendly]

I forgot a decimal point.
The above should read 52.8 feet ascended
in 6 minutes, or 528 feet in the course of an hour.

Locomotive power is also expressed as "tractive effort"
or pulling power, being a mechanical draft horse.

This effort, measured at the draw bar goes up
as speed goes down for a given horsepower, or working rate.

Exceed the shear strength of the draft gear and it will break.

Two locomotives producing a total of 8,800 HP at 9.6 mph
exerts a pulling force that is very close to the draft rating
of the couplings.

 

[Wagonmaster261]

Train is too darned big.

Although with the DPs it is roughly 2 11,500 ton trains coupled together. What is to say the air brakes are fully released? DPs help with multiple air sources throughout the train instead of just from the head end.

Quote:
If it takes .75 horsepower per ton during summer operation to climb a 1.2% grade at 9mph , how can we accurately predict the horsepower requirement of the same train as the ambient drops?


Easy. Pretend it is summer out. Run the equipment to the breaking point. If it doesn't get over the hill, ask for a helper. After a few times of clogging the main with trains that won't make the hill, run smaller trains in winter that will make it.