Drawbar Pull & Tractive Effort??
woo...@rain.org
and its' drawbar pull. And, how are adhesion figures derived?
For instance, let's say a locomotive has 1750 horsepower,
63,500 pound of tractive effort at 25 per cent adhesion.
Is there a formula for deriving the drawbar pull?
mars...@angst.zko.dec.com
The adhesion figure can only be derived from experience. Typical
maximum adhesion on wet rail was 15% until computer controlled
wheel slip systems can in to existance. Dry rail 25% was a common
number and with the wheel slip systems it can be close to 40%.
Adhession essentially puts a cap on maximum tractive effort. For
example an RS-3 typically weighs 240,000lbs and has a maximum
tractive effort of 50,000lbs. So 25% of 240,000 yields 60,000 thus
adhesion should not be a factor. 15% and we get 36,000lbs thus
with wet rail adhesion is what sets maximum tractive effort.
Draw bar pull should be the same as tractive effort.
Chris
Clemens Emanuel Tillier
>1. Tractive effort is the calculated (theoretical) force exerted by a
>loco (steam or diesel) at the rim of its driving wheels.
TE is the *actual* force exerted. There's nothing theoretical about it.
>2. Drawbar pull is the force exerted by a loco at the drawbar. This
>is what pays the bills on the railroad. There is an approximate
>relation between tractive effort and drawbar pull. Drawbar pull is
>equal to the tractive effort less the mechanical, windage, and other
^^^^^^^^^^
>losses associated with the motion of the locomotive.
In a diesel locomotive (where all the wheels are powered), mechanical
friction takes its toll *before* TE is measured, at the wheel-rail
interface. In other words, increasing mechanical friction (with
increasing speed) will decrease *both* tractive effort and drawbar pull.
Hence, we do not subtract any mechanical losses from TE to find drawbar
pull. (think about where the power is dissipated).
In a steamer, there's extra axles that aren't powered so it does take some
power to overcome mechanical friction, and you have to include the effect.
>3. The factor of adhesion is simply the weight which is supported by
>the driving wheels divided by the tractive force. Steam locos were
>generally designed (there were some exceptions to this) so that the
>factor of adhesion was at least 4.0.
Right. A figure that is easier to grasp is the inverse of what you
mention, or the tractive force divided by the weight on drivers. That
gives you a number that can be compared with the coefficient of friction--
to some, this will make much more sense.
Regards, | This package contains 42 scoopfuls when
Clem Tillier | measured by weight. The precise number of
Stanford, California, USA | scoopfuls will vary somewhat with the method
ctil...@leland.stanford.edu | of scooping and the settling during shipment.
Neil Carlson
>
>What is the relationship between a locomotives' tractive effort
>and its' drawbar pull. And, how are adhesion figures derived?
>
>For instance, let's say a locomotive has 1750 horsepower,
>63,500 pound of tractive effort at 25 per cent adhesion.
>Is there a formula for deriving the drawbar pull?
>
loco (steam or diesel) at the rim of its driving wheels.
2. Drawbar pull is the force exerted by a loco at the drawbar. This
is what pays the bills on the railroad. There is an approximate
relation between tractive effort and drawbar pull. Drawbar pull is
equal to the tractive effort less the mechanical, windage, and other
losses associated with the motion of the locomotive. These are speed
dependent and they increase with speed. There are some formulas for
calculating this and they employ variables such as friction or roller
bearings, streamlining, weight of loco/tender, number of axles, etc.
3. The factor of adhesion is simply the weight which is supported by
the driving wheels divided by the tractive force. Steam locos were
generally designed (there were some exceptions to this) so that the
factor of adhesion was at least 4.0. Diesels due to the smoother
application of power can live with factors of adhesion less than 4.0.
This is especially true with the new AC diesels.
4. Horsepower comes into play when the speed at which a given tractive
effort or drawbar pull is considered. Two locomotives might have the
same tractive effort at starting or low speeds, but the locomotive with
the higher horsepower will have the greater tractive effort or drawbar
pull at higher speeds. In steam days this was the difference between a
2-8-2 and a 4-8-4 with the same tractive effort. Both could start the
same size train, but the 4-8-4 could move it a lot faster!
I hope this helps.
Neil Carlson
Santa Cruz
Clemens Emanuel Tillier
>
>My earlier comments also apply here. Plus, I want to add that the
>chief reason why TE and drawbar pull decrease with speed is due to the
>fact that locomotive horsepower is limited to some maximum value.
Yes, that is another effect; not what I was talking about.
>At a given speed the TE and the
>drawbar pull would differ by the mechanical losses.
Please give me a physical explanation of how this works in a locomotive
where all the wheels are powered. I claim (see my earlier post) that
drawbar pull equals TE minus aero forces. Mechanical losses in the
drivetrain (such as bearing friction) ARE NOT to be included in the
calculation between TE and drawbar pull. (the power is dissipated
*upstream* of where TE is defined, i.e. at the wheel rim; I can explain
this in more detail if needed.)
I know very little about AAR formulae; I'm just using physical intuition.
If I'm wrong, point out to me where I made a bad assumption.
woo...@rain.org
> Neil Carlson <n...@ix.netcom.com> wrote:
>
> >1. Tractive effort is the calculated (theoretical) force exerted by a
> >loco (steam or diesel) at the rim of its driving wheels.
>
>
> >is what pays the bills on the railroad. There is an approximate
> >relation between tractive effort and drawbar pull. Drawbar pull is
> >equal to the tractive effort less the mechanical, windage, and other
> >losses associated with the motion of the locomotive.
>
> friction takes its toll *before* TE is measured, at the wheel-rail
> interface. In other words, increasing mechanical friction (with
> increasing speed) will decrease *both* tractive effort and drawbar pull.
> Hence, we do not subtract any mechanical losses from TE to find drawbar
> pull. (think about where the power is dissipated).
>
> In a steamer, there's extra axles that aren't powered so it does take some
> power to overcome mechanical friction, and you have to include the effect.
>
> >the driving wheels divided by the tractive force. Steam locos were
> >generally designed (there were some exceptions to this) so that the
> >factor of adhesion was at least 4.0.
>
> mention, or the tractive force divided by the weight on drivers. That
> gives you a number that can be compared with the coefficient of friction--
> to some, this will make much more sense.
>
> Clem Tillier | measured by weight. The precise number of
> Stanford, California, USA | scoopfuls will vary somewhat with the method
> ctil...@leland.stanford.edu | of scooping and the settling during shipment.
>
>>>>
But, can anybody express all this in a formula that
we can plug into the simulator to represent both steam and diesel/electric
locos, which we can then plug into the Detailed Train Action Simulator model?
I've got that formula and hope to have the FORTRAN source soon. Rumor,
now in the process of being tracked down (no pun intended), has it that buried
in the bowels of DOT/FRA is a complete set of updated models used in the
current "real railroad" simulators. Rumor also has it that even though these
should be public domain due to public funding, certain interests would like to
treat them as proprietary.
All that aside, I've always felt that a good railroad sim should start with the
best set of dynamic train and motive power models that it is possible to code.
My attitude is to go models and operations first, zooty graphics last in the
computing resources allocation. You can always wait for the platforms to
catch up. But, that's probably a seperate thread discussion.
Dave Nelson
|> There are AAR formulas for the calculation of TE, and these assume no
|> mechanical losses. For steam the calculation variables include "mean
|> effective" cylinder pressure, cylinder diameter and stroke, and driving
|> wheel diameter. For a diesel the variables are traction motor torque,
|> gear ratio, and driving wheel diameter.
Do you have these formulas? I'd be very interested in them.
Dave Nelson
___________________________________________________________
Hewlett Packard email: da...@pa.itc.hp.com
ICBD fax: (415) 852-8312
1501 Page Mill Rd. phone: (415) 857-2902
Palo Alto CA. 94304
___________________________________________________________
Tim O'Connor
> What is the relationship between a locomotives' tractive effort
> and its' drawbar pull. And, how are adhesion figures derived?
I always thought the unit of measure of "drawbar pull" was horsepower
(as measured by a dynamometer car) versus "tractive effort" measured
in pounds. I don't have any figures for converting one to the other,
I'm not sure if such exists.
BUT I do think the TE is the most useful value, since train resistance
also is measured in pounds per ton. This was used by railroads such as
the SP to establish "tons per engine" back in steam days, over each and
every section of line. I think MM published a table awhile back for SP
F, AC, and diesel ratings from Dunsmuir to Klamath Falls ...
And here's some miscellaneous Resistance/TE stuff
----------------------------------------------------------------------
On a grade, gravity acts on each ton of train weight with a force of
20 lbs for each per cent grade as shown below
Percent Grade Downgrade Force of Gravity
1% 20 lb per ton (Sherman Hill)
2% 40 lb per ton (Horseshoe Curve)
3% 60 lb per ton (Raton Pass)
4% 80 lb per ton
5% 100 lb per ton (Saluda Mt)
The brake retarding force required to balance the downgrade gravitational
force is the force of gravity less the car or train resistance. The
heavier the car, the more brake retarding force is needed.
Train rolling resistance is generally taken from tables and curves based
on formulae. The most widely used of such formulae is the Davis Formula.
Rolling resistance is generally expressed in pounds per ton
R = 1.3 + (29/W) + 0.045*V + ( 0.0005*A*(V**2)/W*n )
where R = resistance in lb/ton on level tangent track
W = weight per axle in tons
n = number of axles per car
A = cross section of car in square feet
V = speed in miles per hour
Imagine a 100 car coal train on level track, approx 13,100 tons.
W = 32.5
n = 4
A = 100 (approx)
Values of R for various speeds V (SD40-2 tractive effort)
10 mph 2.68 pounds per ton approx 100,000 lbs
30 mph 3.88 pounds per ton
50 mph 5.39 pounds per ton
70 mph 7.21 pounds per ton approx 10,000 lbs
Thus a single SD40-2 can theoretically get a roll on a 20,000+ ton train
by itself (ignoring possible broken knuckles), but at 70 mph that same
engine can only pull 1,388 tons or less than 11 loaded cars!
Or looked at another way, you can see that 80-90 miles per hour induces
the same amount of resistance as a 1 percent grade!
-----------------------------------------------------------------------
By the way, for modern equipment, there is an Adjusted Davis Value ...
R(adj) = k * R(davis)
k = 1.00 for pre-1950 freight cars
= 0.85 for conventional post-1950 freight cars
= 0.95 for COFC
= 1.05 for TOFC
= 1.20 for empty, covered autoracks
= 1.30 for loaded autoracks
= 1.90 for empty, open autoracks
----------------------------------------------------------------------
And from General Electric, we have
Tractive Effort TE = (( hpe-hpa ) * 375 * e ) / V
where hpe = engine shaft horsepower
hpa = horsepower to auxiliaries
e = efficiency, often taken as 0.82
V = speed
(Note this formula ignores number of axles! Also, it's probably outdated
due to fancy new wheelslip systems that increase low speed adhesion.)
So in diesels, TE is inversely proportional to speed. True also in steam
engines, EXCEPT that horsepower in steam engines is NOT a constant. For
example, a Southern Pacific GS-4 4-8-4 produced around 5,000 horsepower
at 50 mph, but much less than that at 20 or 80 mph.
Bob
train robbery where he pulled a train overland from Martinsburg to
Strausburg, Va IN 1861. Please reply your help will be appreciated.
Bob
Norman Clubb
>
> >1. Tractive effort is the calculated (theoretical) force exerted by a
> >loco (steam or diesel) at the rim of its driving wheels.
>
> TE is the *actual* force exerted. There's nothing theoretical about it.
>
actually measure as it is being applied, has to be calculated from
(admittedly) known dimensions using a formula whose validity is not
precisely guaranteed and which makes assumptions about the steam pressure
at the piston face and (in compound locos) the share of the work done by
the low-pressure cylinders. Also, in a two-cylinder loco, the tractive
effort when both cranks are at 45 deg. to dead centre is 1.41 (root 2)
times as high as when one crank is at front or back and the other at top
or bottom dead centre. It was just this fluctuation that motivated
(mainly) European engineers to build locos with 3 cylinders and was
certainly Gresley's main argument in favour of 3-cylinder propulsion.
Best regards
Norman Clubb, Chief Engineer RSR Bewitz a.d. Thaale
Norman Clubb
>
> >1. Tractive effort is the calculated (theoretical) force exerted by a
> >loco (steam or diesel) at the rim of its driving wheels.
>
> TE is the *actual* force exerted. There's nothing theoretical about it.
>
measure as it is being applied, and has to calculated using a formula
whose validity is not precisely guaranteed. Assumptions have to made
about the effective steam pressure at the piston face and (in compound
when the cranks are at 45 deg. either side of dead centre then when one
crank is at top or bottom and the other at front or back dead centre.
this argument was Gresley's decision to concentrate on 3-cylinder
Norman Clubb
>
> >1. Tractive effort is the calculated (theoretical) force exerted by a
> >loco (steam or diesel) at the rim of its driving wheels.
>
> TE is the *actual* force exerted. There's nothing theoretical about it.
>
actually measure as it is being applied, has to be calculated from
(admittedly) known dimensions using a formula whose validity is not
effort when both cranks are at 45 deg. to dead centre is 1.41 (root 2)
times as high as when one crank is at front or back and the other at top
or bottom dead centre. It was just this fluctuation that motivated
(mainly) European engineers to build locos with 3 cylinders and was
Norman Clubb
Norman Clubb
>
> >1. Tractive effort is the calculated (theoretical) force exerted by a
> >loco (steam or diesel) at the rim of its driving wheels.
>
> TE is the *actual* force exerted. There's nothing theoretical about it.
>
measure as it is being applied, and has to calculated using a formula
whose validity is not precisely guaranteed. Assumptions have to made
when the cranks are at 45 deg. either side of dead centre then when one
WPYR
>train robbery where he pulled a train overland from Martinsburg to
>Strausburg, Va IN 1861.
Correction: This wasn't "a" train. He took dozens of engines.
The most extensive article on this that I know of is in the
November-December 1991 CIVIL WAR magazine. (The Magazine of the Civil War
Society, Vol. 9, No. 6) It is a five page article. The whole issue is
devoted to railroad matters, and is worth obtaining if you can find a
copy. The telephone number shown in the magazine is (800)247-6253. The
address was P.O. Box 770, Beryville, Virginia 22611.
This action was one of the most massive, audacious, and brilliant train
robberies ever by anybody. No one ever said that Stonewall Jackson was
not audacious or brilliant. This event really proves why.
There is also some information on this on page 46 of
MR. LINCOLN'S MILITARY RAILROADS by Roy Meredith and Arthur Meredith.
Published by W.W. Norton in 1979.
Robert G. Hilton
wp...@aol.com
Neil Carlson
(Clemens Emanuel Tillier) writes:
>
>Neil Carlson <n...@ix.netcom.com> wrote:
>
>>1. Tractive effort is the calculated (theoretical) force exerted by
a
>>loco (steam or diesel) at the rim of its driving wheels.
>
>TE is the *actual* force exerted. There's nothing theoretical about
it.
>
stand such as existed one time at Altoona, there is no way to measure
the force exerted by a loco at the rim of its driving wheels. Now if
it is calculated, is it not a theoretical value? I'm not saying that
an actual force does not exist, its just that when we specifically talk
of TE, by definition we mean a calculated value.
The force which can be measured is drawbar pull through use of a
dynamometer car. However, this measurement includes all of the
locomotive's mechanical losses as earlier described -- and it makes no
difference whether we are talking steam or diesel; they are still
there. However, they are greater for steam than for diesels.
There are AAR formulas for the calculation of TE, and these assume no
mechanical losses. For steam the calculation variables include "mean
effective" cylinder pressure, cylinder diameter and stroke, and driving
wheel diameter. For a diesel the variables are traction motor torque,
gear ratio, and driving wheel diameter.
>>2. Drawbar pull is the force exerted by a loco at the drawbar. This
>>is what pays the bills on the railroad. There is an approximate
>>relation between tractive effort and drawbar pull. Drawbar pull is
>>equal to the tractive effort less the mechanical, windage, and other
> ^^^^^^^^^^
>>losses associated with the motion of the locomotive.
>
>In a diesel locomotive (where all the wheels are powered), mechanical
>friction takes its toll *before* TE is measured, at the wheel-rail
>interface. In other words, increasing mechanical friction (with
>increasing speed) will decrease *both* tractive effort and drawbar
pull.
>Hence, we do not subtract any mechanical losses from TE to find
drawbar
>pull. (think about where the power is dissipated).
>
>In a steamer, there's extra axles that aren't powered so it does take
some
>power to overcome mechanical friction, and you have to include the
effect.
My earlier comments also apply here. Plus, I want to add that the
chief reason why TE and drawbar pull decrease with speed is due to the
fact that locomotive horsepower is limited to some maximum value.
Given this, as speed picks up, both the TE (calculated) and the drawbar
pull (measured) decrease accordingly. At a given speed the TE and the
drawbar pull would differ by the mechanical losses. You could estimate
(calculate) the TE by measuring the drawbar pull and then adding back
estimates for the appropriate mechanical losses at any given speed.
About the only time TE and drawbar pull are about the same is at
starting as there are few mechanical losses.
Neil Carlson
Santa Cruz
Bruce Harper
(Bob) wrote:
>Does anyone know any resources for information on Stonewall Jacksons
>train robbery where he pulled a train overland from Martinsburg to
>Strausburg, Va IN 1861. Please reply your help will be appreciated.
>
>Bob
Track down this book:
CALL NUMBER: E491 T95
Author: Turner, George Edgar.
Title: Victory rode the rails; the strategic place of the railroads
in the Civil War. Maps by George Richard Turner.
Edition: [1st ed.]
Imprint: Indianapolis, Bobbs-Merrill [1953]
Description: 419 p. illus., ports., maps. 25 cm.
Note: Bibliographical references included in "Notes" (p.
[377]-404)
Subject: Railroads -- United States -- History.
Subject: Railroads -- Confederate States of America.
Subject: United States -- History -- Civil War, 1861-1865 --
While it covers a number of situations and incidents involving railroads
during the War of Northern Aggression, it has a good bit of information
about how Jackson held the B&O captive at Harper's Ferry, then hauled off
what rolling stock he could get.
Bruce in Blacksburg, Virginia
--
Bruce B. Harper bha...@vt.edu
Distributed Information Systems (703)231-4360
Virginia Tech Computing Center
1700 Pratt Drive Region Director,
Blacksburg, Virginia 24060 New River Valley DPMA
Norman Clubb
Norman Clubb
WPYR
I forgot to mention in my first reply that this robbery was not the end of
Stonewall Jackson's railroad career. He gave Mr. Pope an unpleasant
surprise at the Second Battle of Manassas from behind an unfinished
railroad grade.
Neil Carlson
(Clemens Emanuel Tillier) writes in response to Carlson's comments:
>>At a given speed the TE and the
>>drawbar pull would differ by the mechanical losses.
>
>Please give me a physical explanation of how this works in a
locomotive
>where all the wheels are powered. I claim (see my earlier post) that
>drawbar pull equals TE minus aero forces. Mechanical losses in the
>drivetrain (such as bearing friction) ARE NOT to be included in the
>calculation between TE and drawbar pull. (the power is dissipated
>*upstream* of where TE is defined, i.e. at the wheel rim; I can
explain
>this in more detail if needed.)
>
>I know very little about AAR formulae; I'm just using physical
intuition.
>If I'm wrong, point out to me where I made a bad assumption.
>
>Regards,
>Clem Tillier
Clem,
Our discussion on this topic centers around the definition of TE. This
is a much abused term and perhaps through this abuse it has aquired a
meaning beyond what was originally intended. My interpretation of it
is the traditional (and perhaps older) meaning -- it is a calculated
quantity.
Let me cite a source for this. I refer to Ralph Johnson's (chief
engineer at BLW) book "The Steam Locomotive" page 137. "the term Rated
Tractive Force (TE) means the calculated, theoretical starting force,
and all other tractive forces will be designated by their respective
speeds."
The calculations for TE whether at starting or at speed do not include
any allowances for mechanical or windage losses. It strictly
determines the theoretical force a given locomotive could be capable of
applying at rim of a driving wheel. At starting this is based on the
physical parameters of a locomotive. At speed it is usually based on
the prime mover HP (boiler HP for steam; BHP for the diesel engine)
from which the resultant force is computed.
TE was intended as a design specification or figure of merit by which
one could compare the likely performance of various locomotives. With
this understanding, there really is no need to include mechanical or
windage losses. The more important figure is drawbar pull which
includes all such losses. It is what produces revenue for the RR.
This discussion originally began when a subscriber (Woodman) asked
about the relationship between TE and DB pull. There is no simple
answer to that question as TE is calculated and DB pull is real and
measurable. My attempt in explaining it was to show that a calculated
relationship could be developed if allowances are made for mechanical
and windage losses. A subsequent posting (O'Connor #7803) touched on
this when he referenced the work done by W. J. Davis, Jr. in developing
mathmatical relations to predict mechanical and windage resistance to
motion. I would refer you to that posting.
With regard to diesels, there are still mechanical losses which are not
considered in the calculation of TE. At starting this includes journal
friction which is chiefly a function of axle weight. But once in
motion, rolling friction (concussion, flange resistance and
oscillation) and windage losses become important. Grant it, a steam
locomotive has many more of these losses than a diesel with its
unpowered axles, plus the valve motion alone on a large steam engine at
speed can easily absorb 200-300HP.
I hope this helps to clarify my statements on this topic. If you would
like to discuss it further, E-mail me back. I'm at Stanford every
couple of months and we could get together over a cup of coffee!
Neil Carlson
Santa Cruz
P.S. If you're interested, I'm pretty sure there is a copy of
Johnson's book at Stanford. Try the Green Library or Stanford
Auxilliary Library (SAL) stacks.
Bob Smart
>In article <3u5v1k$r...@ixnews6.ix.netcom.com>, bobs...@ix.netcom.com
>(Bob) wrote:
>>Does anyone know any resources for information on Stonewall Jacksons
>>train robbery where he pulled a train overland from Martinsburg to
>>Strausburg, Va IN 1861. Please reply your help will be appreciated.
>>
>>Bob
Working from memory most of the locomotives & rolling stock was destroyed when
Jackson had to abandon Harpers Ferry. This was done by igniting the loaded coal
cars and other flammable stock and running the locomotives off a destroyed
bridge into the Potomac. At least one smaller engine was hauled down the line
to Winchester then over the valley turnpike south to Stanton(?) Check any
history of Jackson. I liked 'They called him Stonewall' a pretty standard book
that I have seen in many libraries. I'm swamped at work right now but if you
need more pointers I'll try to dig them up. There is a new history of Jackson
that I have at home but haven't had a chance to read ( author was Fraswell??)
the section on the locomotive heist.
The basic story is this The confederates occupied the south bank of the Potomac
from Harpers Ferry past Martinsburg. The B&O ran with Stonewalls forebearance
on that stretch. Stonewall told the B&O that the loaded trains made too much
noise at night and that they would have to be run only in daytime. The B&O
complied. Then Stonewall said the empties were too noisy at night. The B&O
obliged by running everything during the day. One day he dispatched troops toi
each end of the line he controlled. The troops on the east end only stopped
eastbound trains the troops on the west end stopped westbound trains. Soon the
whole double track line was full of stopped trains!. He then burnt the bridges
and tried to figure out what to do with all the trains. some rolling stock and
at least on locomotive were sent south.
Bob Smart ( bsm...@rational.com)
Alex Schneider
da...@pa.itc.hp.com (Dave Nelson ) wrote:
>In article <3u4svh$h...@ixnews6.ix.netcom.com>, n...@ix.netcom.com (Neil
Carlson ) writes:
>
>|> mechanical losses. For steam the calculation variables include "mean
>|> effective" cylinder pressure, cylinder diameter and stroke, and driving
>|> wheel diameter. For a diesel the variables are traction motor torque,
>|> gear ratio, and driving wheel diameter.
>
Steam locomotive starting tractive effort T =
0.85 P x C**2 x S / D
where P = boiler pressure in pounds per square inch
C = cylinder diameter in inches
S = cylinder stroke in inches
D = driving wheel diameter in inches
Source: Locomotive Data, The Baldwin Locomotive Works, 1923.
rodrigo.s...@gmail.com
I'm doing a thesis coursework in the railroad industry and I'm just begun getting familiar with this data.
How did you came up with the 100,000 & 10,000 lbs in the example below?
Thanks
Adam H. Kerman
>I'm doing a thesis coursework in the railroad industry and I'm just begun getting familiar with this data.
>How did you came up with the 100,000 & 10,000 lbs in the example below?
>>10 mph 2.68 pounds per ton approx 100,000 lbs
>>30 mph 3.88 pounds per ton
>>50 mph 5.39 pounds per ton
>>70 mph 7.21 pounds per ton approx 10,000 lbs
>>Thus a single SD40-2 can theoretically get a roll on a 20,000+ ton train
>>by itself (ignoring possible broken knuckles), but at 70 mph that same
>>engine can only pull 1,388 tons or less than 11 loaded cars!
>>Or looked at another way, you can see that 80-90 miles per hour induces
>>the same amount of resistance as a 1 percent grade!
were these articles? Where did you find them? Didn't your thesis come
due since the time this thread began and long before you posted your
followup?
I have a feeling that the formula was explained if we could read the
articles for ourselves.
If you're going to participate and post to Usenet, please do not top post
and please cite correctly.
Stephen Sprunk
> rodrigo.s...@gmail.com wrote:
>> I'm doing a thesis coursework in the railroad industry and I'm just
>> begun getting familiar with this data. How did you came up with the
> I can't find either precursor article in this thread. Exactly how
> old were these articles? Where did you find them? Didn't your thesis
> come due since the time this thread began and long before you posted
> your followup?
>
> I have a feeling that the formula was explained if we could read the
> articles for ourselves.
1995. Here is the specific article quoted:
Message-ID: <3u6rpc$4...@info-server.bbn.com>#1/1
S
--
Stephen Sprunk "God does not play dice." --Albert Einstein
CCIE #3723 "God is an inveterate gambler, and He throws the
K5SSS dice at every possible opportunity." --Stephen Hawking
Adam H. Kerman
>On 31-Mar-14 08:37, Adam H. Kerman wrote:
>>rodrigo.s...@gmail.com wrote:
>>>I'm doing a thesis coursework in the railroad industry and I'm just
>>>begun getting familiar with this data. How did you came up with the
>>>100,000 & 10,000 lbs in the example below? ...
>>I can't find either precursor article in this thread. Exactly how
>>old were these articles? Where did you find them? Didn't your thesis
>>come due since the time this thread began and long before you posted
>>your followup?
>>I have a feeling that the formula was explained if we could read the
>>articles for ourselves.
>A few seconds with Google Groups shows he replyied to a thread from July
>1995. Here is the specific article quoted:
>Message-ID: <3u6rpc$4...@info-server.bbn.com>#1/1
knows that the indexing function has been broken for a great many years.
Of course I tried searching with Message-ID, but didn't turn up anything.
I also used Howard Knight's search, found nothing, which led me to
suspect that the articles in the thread had expired many years ago and
that he'd missed his thesis deadline by a lot.
Stephen Sprunk
> Stephen Sprunk <ste...@sprunk.org> wrote:
>> On 31-Mar-14 08:37, Adam H. Kerman wrote:
>>> rodrigo.s...@gmail.com wrote:
>>>> I'm doing a thesis coursework in the railroad industry and I'm just
>>>> begun getting familiar with this data. How did you came up with the
>>>> 100,000 & 10,000 lbs in the example below? ...
>>>
>>> I can't find either precursor article in this thread. Exactly how
>>> old were these articles? Where did you find them? Didn't your thesis
>>> come due since the time this thread began and long before you posted
>>> your followup?
>>>
>>> I have a feeling that the formula was explained if we could read the
>>> articles for ourselves.
>>
>> A few seconds with Google Groups shows he replyied to a thread from July
>> 1995. Here is the specific article quoted:
>>
>> Message-ID: <3u6rpc$4...@info-server.bbn.com>#1/1
>
> Stephen, it's really special that your search worked for you,
> but everyone knows that the indexing function has been broken for a
> great many years. Of course I tried searching with Message-ID, but
> didn't turn up anything.
Message-ID, which used to work. Here is a direct link to the thread:
https://groups.google.com/forum/#!searchin/misc.transport.rail.americas/Drawbar$20Pull$20$26$20Tractive$20Effort$3F$3F/misc.transport.rail.americas
Here is the specific article:
https://groups.google.com/forum/#!original/misc.transport.rail.americas/hbR5cGl9ACw/eR3shbzPpfYJ
However, since I'm sure you'll find a reason to complain about that too,
here is the full text of the article he replied to:
>
> 10 mph 2.68 pounds per ton approx 100,000 lbs
> 30 mph 3.88 pounds per ton
> 50 mph 5.39 pounds per ton
> 70 mph 7.21 pounds per ton approx 10,000 lbs
>
> Thus a single SD40-2 can theoretically get a roll on a 20,000+ ton train
> by itself (ignoring possible broken knuckles), but at 70 mph that same
> engine can only pull 1,388 tons or less than 11 loaded cars!
>
> Or looked at another way, you can see that 80-90 miles per hour induces
> the same amount of resistance as a 1 percent grade!
>
>
> By the way, for modern equipment, there is an Adjusted Davis Value ...
>
> R(adj) = k * R(davis)
>
> k = 1.00 for pre-1950 freight cars
> = 0.85 for conventional post-1950 freight cars
> = 0.95 for COFC
> = 1.05 for TOFC
> = 1.20 for empty, covered autoracks
> = 1.30 for loaded autoracks
> = 1.90 for empty, open autoracks
>
> ----------------------------------------------------------------------
>
> And from General Electric, we have
>
> Tractive Effort TE = (( hpe-hpa ) * 375 * e ) / V
>
> where hpe = engine shaft horsepower
> hpa = horsepower to auxiliaries
> e = efficiency, often taken as 0.82
> V = speed
>
> (Note this formula ignores number of axles! Also, it's probably outdated
> due to fancy new wheelslip systems that increase low speed adhesion.)
>
> So in diesels, TE is inversely proportional to speed. True also in steam
> engines, EXCEPT that horsepower in steam engines is NOT a constant. For
> example, a Southern Pacific GS-4 4-8-4 produced around 5,000 horsepower
> at 50 mph, but much less than that at 20 or 80 mph.
> I also used Howard Knight's search, found nothing, which led me to
> suspect that the articles in the thread had expired many years ago and
> that he'd missed his thesis deadline by a lot.
so I don't see any reason to think he is 19 years late finishing his
thesis. Perhaps he ran across the thread while doing research but
didn't realize he was reading/replying to such an old article, or he
figured that the author was still around and could continue the
discussion, or that someone else here could, etc.
Adam H. Kerman
>On 31-Mar-14 11:42, Adam H. Kerman wrote:
>>Stephen Sprunk <ste...@sprunk.org> wrote:
>>>On 31-Mar-14 08:37, Adam H. Kerman wrote:
>>>>rodrigo.s...@gmail.com wrote:
>>>>>I'm doing a thesis coursework in the railroad industry and I'm just
>>>>>begun getting familiar with this data. How did you came up with the
>>>>>100,000 & 10,000 lbs in the example below? ...
>>>>I can't find either precursor article in this thread. Exactly how
>>>>old were these articles? Where did you find them? Didn't your thesis
>>>>come due since the time this thread began and long before you posted
>>>>your followup?
>>>>I have a feeling that the formula was explained if we could read the
>>>>articles for ourselves.
>>>A few seconds with Google Groups shows he replyied to a thread from July
>>>1995. Here is the specific article quoted:
>>>Message-ID: <3u6rpc$4...@info-server.bbn.com>#1/1
>>Stephen, it's really special that your search worked for you,
>It would have worked for you too, if you bothered trying.
I searched for the Message-ID in Google Groups and got nothing.
>I was unaware Google Groups has now screwed up even searching by
>Message-ID, which used to work.
truly unaware of is how searching a database works, and how poorly it
functions when the indexes aren't built and maintained.
Since you're being an asshole, the rest snipped unread.
Stephen Sprunk
> Stephen Sprunk <ste...@sprunk.org> wrote:
>> On 31-Mar-14 11:42, Adam H. Kerman wrote:
>>> Stephen, it's really special that your search worked for you,
>>
>> It would have worked for you too, if you bothered trying.
>
> You sure do have a reading comprehension problem. I just stated that
> I searched for the Message-ID in Google Groups and got nothing.
that's how I found the Message-ID in the first place!
>> I was unaware Google Groups has now screwed up even searching by
>> Message-ID, which used to work.
>
> There are a great many things of which you aren't aware.
> What you are truly unaware of is how searching a database works, and
> how poorly it functions when the indexes aren't built and maintained.
I doubt this particular problem has much to do with indexes, though.
> Since you're being an asshole,
need to argue with me, so who's the asshole?
> the rest snipped unread.
You complain you don't have the original text, and then when I provide
the original text, you throw a tantrum and ignore it. How mature.
Adam H. Kerman
>On 31-Mar-14 13:16, Adam H. Kerman wrote:
>>Stephen Sprunk <ste...@sprunk.org> wrote:
>>>On 31-Mar-14 11:42, Adam H. Kerman wrote:
>>>>Stephen, it's really special that your search worked for you,
>>>It would have worked for you too, if you bothered trying.
>>You sure do have a reading comprehension problem. I just stated that
>>I searched for the Message-ID in Google Groups and got nothing.
>I searched for the Subject and the original thread was the first hit;
>that's how I found the Message-ID in the first place!
the References header; no searching required.
The rest snipped unread.