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Reaching crusing speed

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Reaching crusing speed
Posted by tstage on Saturday, June 6, 2020 1:39 PM

Greetings,

I'm going preface the following by saying that I realize that there are a number of variables involved with any guessmate so I will try to limit those as best I can.

I was operating a 13-car freight train on my temporary layout this afternoon using two different locomotives: An EMD FTA-B (2,500 HP) and a USRA 2-8-2 Mike.  With my NCE Power Cab and some programmed momentum, I used the incremental buttons to slowly bring each one up to speed when the thought occurred to me: "How long would a xx-car train take to reach a given speed?"

So, limiting the locomotives to the aforementioned and using an identical load of cars for each one - in ballark figures:

  1. How long would it "reasonably" take for a 50-car train of 40' boxcars to get up to 60 MPH from a dead start?
  2. What would the time difference be pulling empty vs fully-loaded cars?

Let me also preface this by adding that the weather conditions are 68 degrees and dry and the track is level and straight.

I hope that helps and that the variables have been limited to reasonable terms.  If not, I will try and narrow them down further.

Thanks,

Tom

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Posted by mbinsewi on Saturday, June 6, 2020 3:31 PM

I have my favorite place to watch CN trains, it's a siding named Midway.  I watched SB trains depart, from a stop, many times.  

It doesn't seem to matter if it's a stack train, or manifest, and using Google maps and the measuring distance feature, by the time the lead loco is about 1800 ft. down the line, it's moving at 30mph +, and accelerating rapidly.

By the time the DPU passes me, it's moving at it's usual track speed of about 48-50 mph., according to the transmission from the nearby defect detector.

This doesn't have much to do with your scenario Tom, just thought I add what I see.

Mike.

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Posted by DrW on Saturday, June 6, 2020 4:29 PM

Interesting question. Some benchmark values for 0 - 60 mph acceleration (unfortunately only marginally relevant to your question):

Bugatti Veyron  2.3 s

Boeing 777  < 6 s

High-speed train  20 - 30 s

VIA passenger train  ~ 80 s

Southern Pacific GS-4 with excursion train  ~ 5 min

In the video about the GS-4, they did not show the whole train. Thus, I do not know about the tonnage involved. However, I think your hypothetical train would fall into this range.

 

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Posted by Overmod on Saturday, June 6, 2020 5:50 PM

There are in fact actual answers apart from sarcasm to this kind of question.

One way to get to an approximation that does not involve calculus is to get a drawbar/speed diagram for the power from someone like Ed, plug the numbers for your train consist into the Davis formula to get train resistance, and quickly look at acceleration between a few sets of speed points, say 5mph apart.  This will get you within a few seconds of the true 'smoothed curve' of acceleration while acknowledging that the diesel 'part' will help acceleration down low and the steam engine proportionally more as it gets up toward the peak of its horsepower curve.  Note that the corresponding acceleration profile will be very far from linear, with initial acceleration being comparatively slow (limited by the steam-engine cyclic and diesel traction-motor restrictions) and higher speed being more quickly reached.

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Posted by BigDaddy on Saturday, June 6, 2020 5:56 PM

mbinsewi
by the time the lead loco is about 1800 ft. down the line, it's moving at 30mph +, and accelerating rapidly.

That's 20 feet of HO track.  More power to you if you have that kind of space.

Henry

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Posted by doctorwayne on Saturday, June 6, 2020 8:59 PM

I have, not counting double track, yards, and industrial sidings, more that a couple hundred feet of track, but none of it is suited for high speeds.  I believe the highest posted limit is 45mph, and most trains would be hard-pressed to achieve it before reaching an area with lower posted speeds.

There's not much in the way of hypothetical performance when grades and curves limit both speed and tonnage.  I run some fairly heavy trains, with multiple locomotives, and the hope is that they'll get from point A to point B without stalling or having to double a hill or two.  I find that challenge more interesting than speed, but that's just a personal preference.

Wayne

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Posted by mbinsewi on Saturday, June 6, 2020 9:28 PM

BigDaddy
That's 20 feet of HO track.  More power to you if you have that kind of space.

No Henry, I do not have that much space on my layout.  I'm talking about REAL CN trains,  starting from a full stop, and getting the green light to proceed.

Mike.

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Posted by OldEngineman on Saturday, June 6, 2020 9:43 PM

Number of cars. Weight (loads or empties). Grade. Number of engines and what KIND of engines you have. All kinds of variables.

I had SEOP's (Selkirk-Oak Point) southbound on the Hudson line, 130+ cars, just about 100% loads, 13,000+ tons, with 3 B23-7's for power (2,200 each). The Hudson line is about as flat as a table top, but you could barely get track speed (50mph) from them after 10-15 miles with a train like that, if at all.

On the other hand, coming home from a run with WNCH-99 (Danbury stone train), 4 engines (usually B-23's), 40 empties, South Norwalk to New Haven you could zip right along.

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Posted by xdford on Sunday, June 7, 2020 1:21 AM

Hi there 

Mikes approximation is probably about right for a mainline train. The limits are the weight of the train, the horsepower of the motive power, track curvature etc. as OldEngineman pointed out. 

My own layout is a 4x8 so that 1800 feet is about a lap by which time I am doing 30-40 smph.  I similarly allow a lap for braking - I'm on DC with inertia throttles with braking control.

What you have to consider is what LOOKS right on YOUR LAYOUT and operating scheme for YOU but well done for asking. Most of us cannot hope to operate in aircraft hangars and have the space for running but a reasonable attempt at trying to emulate what you see will pass for realism ... which is what you are trying to achieve,

Good Luck

Cheers from Australia

Trevor 

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Posted by gmpullman on Sunday, June 7, 2020 3:33 AM

Good topic.

As Overmod points out there are formulas for train resistance and of course, ruling grade and curvature, temperature and weather conditions all playing a role in getting the train moving.

Another variable I might add is simply —just how quickly does the operating railroad want that train to get over the division and at what risk is there if it doesn't?

A great deal of operating "lessons" were learned in North America during the high-traffic times of WWII. After the War, of course, equipment was beat, track maintenance was deferred to varying degrees and the railroads were beginning to "see the light" of the coming Diesel age. Some roads, the PRR notably, didn't have the capital to sink into major steam locomotive repairs. 

My point is, some roads were moving thousands of carloads a day along with some spots of high-density passenger traffic. The locomotive assignments (the Power Desk) knew what the requirements of each day's train was and would try to match power to the train if at all possible.

Mostly this was a redundant task as the makeup of most trains, no matter if a loaded coal drag or a fast mail and express train or even a limited such as the Century, was fairly stable so particular locomotives could be reliably assigned.

The shop forces, engine crews, dispatchers and operators could pretty much know how things were going to play-out during their "trick". There was redundancy in the trackage for the most part as well with higher speed passenger and mail trains usually run on specified tracks (usually the inner pair) and the slower freight on another. Both the Pennsy and the New York Central could boast a four-track main for nearly their entire routes between Chicago and New York.

This reduced "some" of the risk of, say a poorly steaming engine or a particularly heavy train from delaying the faster trains or "plugging-up" the railroad with a breakdown or stalling.

Once the "downsizing" era of CTC and longer trains, fewer crews, more multiple-unit diesels and, recently, no one on the rear-end it became increasingly more important to have reliable power, properly maintained and able to get a train over the division (which is also now double or triple what it was in the steam days) without delay.

Much of my observations were during the later Penn-Central years and I couldn't believe some of the waste, poor decisions and lack of equipment and maintenance were having on the operation.

I remember seeing the mail trains, #5 & 6 with four, five and sometimes six E7 and E8s on the head end. P-C didn't want this train to suffer any delays if at all possible. The thing is, at any given time, a quarter of those engines could be off-line, traction motors cut-out, and the train limping along at 45 or 50 rather than the authorized speed of 80.

I recall, too, some of the early GE's that crews didn't care much for (to put it kindly). All the specs were there, but they just wouldn't "load". In other words, rev the prime mover but power would take a slow journey to the traction motors. "Eight-and-wait" the engineers would say. It took a while for GE to get their reputation partially back.

Many times I've seen the entire railroad (i.e. both main line tracks) blocked by one train that "dies" while crossing over (broken knuckle, air hose, dragging brakes, etc) and everything stops for thirty miles on either side of the tie-up. So, if you have an underpowered coal drag somewhere in there and traffic is so backed up there's no way around it, everything is going to move at the speed of that raggedy-old coal drag.

Several times, too, I've seen crews outlaw just outside their terminal. Likewise this ties up the whole railroad while a new crew is taxied out to the train.

What this has to do with "getting up to speed" is that any one of these delays causes a ripple effect that sometimes can't be recovered from. You might have a good set of power but if you have to slow down or stop often, recovering your "track speed" can be a real challenge.

Fortunately, the nasty Penn Central days are in the past. I've heard some more recent (horror) stories about the legacy of Hunter Harrison and his "Precision Scheduled Railroading" but I'm not all that familiar with those tales of woe.

There were certainly some times when I was able to ride some of the Central's Flexi-Van trains or their ML (Multi-Level) auto trains and we ran fast and delays were to a minimum. These, the mail trains, UPS trains and some of the auto parts trains were their bread and butter. These trains got the newest and most reliable engines and there was some explaining to do if they were held up for any reason.

Another example of "fast freight" was the Santa Fe's experiments with the "Super-C" run from Chicago to LA, 2200 miles in 40 hours.

 ATSF 100 and 102 FP45s with SUPER C starting inaugural run, Corwith Yard, Chicago, IL  on January 17, 1968 by Marty Bernard, on Flickr

Sometimes, it was the preference of the engineer and his operating habits that would determine how quickly you got up to track speed. I remember guys talking about a few "hot-shots" that would have every drawbar stressed to the max when getting under way. Others would take a more cautious approach and ease into the load while keeping the ammeter in the green.

One of my favorite hangouts back in the day was Canton, Ohio on the PRR Chicago-Pittsburgh main line. About 11 PM the eastbound Broadway would come roaring into the station, and with brake shoes screeching come to a quick halt.

In a matter of minutes, the four E's on the head end would come to life and — like race horses out of the gate — get that fourteen to sixteen car train headed east like nobody's business. By the time the last car passed by she was already up to about 35 or 40. Canton sat in a low spot so those E's could be heard working on out of there, run 8, for the next ten or fifteen minutes or so.

Good Luck, Ed

 

 

 

 

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Posted by gregc on Sunday, June 7, 2020 10:19 AM

here's an answer

Plot illustrates train speed vs time (minutes) at max HP of 2500.  Train tonnage is 1750T, 35 50T cars.  Max usable HP is limited by max tractive effort at low speeds based on loco weight of 247,200 lb and at higher speeds based on Armstrong's full car resitance chart.   This is for level track and full cars.

the number of cars was reduced to 35 in order to reach ~60 mph, at which point train resistance roughly equals tractive effort.

horsepower is 32572 (pounds-force)  lbF * ft / min.  Drawbar force is HP / speed (ft/sec).  while HP may be constant (assumed), the drawbar force dimishes with speed.

i'm sure there are other factors affecting the outcome

greg - Philadelphia & Reading / Reading

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Posted by selector on Sunday, June 7, 2020 2:22 PM

Rolling resistance, tonnage trailing, weakest coupler in the bunch, condition of the track, posted limits or work areas where there's a slow order, meets when the siding one will take is exactly one car longer than your consist without fowling, reports of a bad axle might cause a pucker,...

Tom, it's a great question, and from the answers it would appear to warrant an entire disseration, or at least a thread. Smile

I think you must be like me when it comes to running our toys.  I set all locomotives to anywhere from 50% of the range for CVs 3 and 4 and on up to about 90%.  Northern types with modest trains of 8-12 cars would get the low value, while my Y6-b, I1-sa and 2-10-2 gets the higher value.  My practice is to twist my encoder knob right up to my top speed for the track and tonnage and watch everything unfold via digital magic.  Cool  My 4-8-4 will take maybe 20 feet and 40 seconds to reach 79 scale mph from a standing start, and my Mallet will lift its tonnage over the same distance, but take 90 seconds, and end at 40 mph.

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Posted by ATLANTIC CENTRAL on Sunday, June 7, 2020 9:53 PM

gregc

here's an answer

Plot illustrates train speed vs time (minutes) at max HP of 2500.  Train tonnage is 1750T, 35 50T cars.  Max usable HP is limited by max tractive effort at low speeds based on loco weight of 247,200 lb and at higher speeds based on Armstrong's full car resitance chart.   This is for level track and full cars.

the number of cars was reduced to 35 in order to reach ~60 mph, at which point train resistance roughly equals tractive effort.

horsepower is 32572 (pounds-force)  lbF * ft / min.  Drawbar force is HP / speed (ft/sec).  while HP may be constant (assumed), the drawbar force dimishes with speed.

i'm sure there are other factors affecting the outcome

 

And that is pretty good answer.

Without doing any math I was going to say that 50 cars, 2500 tons, would likely not hit 60 mph with that motive power, but would be able to go 45 or 50 mph and get there in about 10 minutes.

The B&O used two Mike's on 3500 ton trains leaving Baltimore. The ruling grade to Brunswick is about 1.3%. Speeds around 50 were typical from what I have been told.

I don't care for throttle momentum that has long settings. My Aristo throttles do have a "ramp up" time even when set on 0 momentum, but that is pretty quick, maybe 2-4 seconds from zero to full throttle.  

Even on a big layout, our distances are too short for anything too fussy here.

Sheldon

    

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Posted by SeeYou190 on Saturday, June 13, 2020 10:00 AM

I know nothing about the physics of this topic, so I will stay out of that part.

I do watch trains in Atlanta and a couple of other places in Georgia.

When NORFOLK SOUTHERN assembles a train in Atlanta, and it leaves the facility, it has a severe speed restriction for the first part of the trip. Then it gets to speed up to 35-40 MPH for a while. Once it clears Buford, it can ramp up to serious speed and tool on down the line.

My question would be how often do train crews really get to open the throttle and accellerate a train at maximum capability? I would imagine this would not be the encouraged way to run a train unless upcoming terrain would make maximum accelleration preferable.

-Kevin

Wink Happily modeling my STRATTON & GILLETTE RAILROAD. A Class A line located in a personal fantasy world of semi-plausible nonsense on Tuesday, August 3rd, 1954.

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Posted by gregc on Saturday, June 13, 2020 12:08 PM

SeeYou190
My question would be how often do train crews really get to open the throttle and accellerate a train at maximum capability?

why not use maximum HP/tractive-effort to maximize acceleration up to the speed limit?

greg - Philadelphia & Reading / Reading

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Posted by gmpullman on Saturday, June 13, 2020 3:03 PM

gregc
why not use maximum HP/tractive-effort to maximize acceleration up to the speed limit?

 

 

There can be consequences.

Cheers, Ed

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Posted by SeeYou190 on Saturday, June 13, 2020 4:07 PM

gregc
why not use maximum HP/tractive-effort to maximize acceleration up to the speed limit?

Fuel savings. Safety. Equipment wear and tear. Company operating rules. Best practices. Being proffessional on the job. Noise ordinances. Courtesy.

I don't know.

Why do you respond to my question with another question?

Why not surface a submarine as quickly as physically possible?

Why not accellerate a class 8 truck at full throttle every time just to reach 70 MPH?

Why not launch the Space Shuttle if it is already fueled and on the launchpad?

-Kevin

Wink Happily modeling my STRATTON & GILLETTE RAILROAD. A Class A line located in a personal fantasy world of semi-plausible nonsense on Tuesday, August 3rd, 1954.

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Posted by gregc on Saturday, June 13, 2020 5:22 PM

SeeYou190
Why do you respond to my question with another question?

because I don't know and am curious

and while i would be interested in what the best approach is, i'm also interested in why.  So I specifically asked why max acceleration wouldn't be best approach.

max drawbar force and hence acceleration is at lowest speed and would be the point that a coupler might break as Ed illustrated and could be limited if necessary (max HP < value below some speed).

i had been told that at least for an automobile, the best fuel efficiency is by maximizing acceleration to get to top gear as quickly as possible.    So I'd be curious to know if the most efficient HP for a diesel locomotive varies with speed.

greg - Philadelphia & Reading / Reading

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Posted by BRAKIE on Saturday, June 13, 2020 7:33 PM

Some of the old head engineers I work with would "put the whip to 'em' and be up to track speed within five minutes without any undue heavy slack..

Larry

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Summerset Ry.


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Posted by SeeYou190 on Saturday, June 13, 2020 8:02 PM

gregc
i had been told that at least for an automobile, the best fuel efficiency is by maximizing acceleration to get to top gear as quickly as possible.

That is untrue. Rapid accelleration results in terrible economy.

This might be true in a foreign country with small cars that have 1.3 liter engines, but with our over-powered American cars, nope.

If you have a manual transmission, and accellerate slowly, and skip the last gear down to get to top gear, you will see a fuel efficiency increase in stop and go traffic. It is a lot of work, and accelleration will suffer. Not worth it.

-Kevin

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Posted by ATLANTIC CENTRAL on Saturday, June 13, 2020 9:50 PM

SeeYou190

 

 
gregc
i had been told that at least for an automobile, the best fuel efficiency is by maximizing acceleration to get to top gear as quickly as possible.

 

That is untrue. Rapid accelleration results in terrible economy.

This might be true in a foreign country with small cars that have 1.3 liter engines, but with our over-powered American cars, nope.

If you have a manual transmission, and accellerate slowly, and skip the last gear down to get to top gear, you will see a fuel efficiency increase in stop and go traffic. It is a lot of work, and accelleration will suffer. Not worth it.

-Kevin

 

Greg,

With automobiles, a steady cruising speed provides the best fuel economy.

Many drivers, espeically out here in the rural suburbs, have the bad habit of accelerating slowly, but almost constantly over a long distance, until they reach their "speed of fear" or encounter a condition that requires them to slow down.

Example - the speed limit on a rural road is 50 mph, they turn onto the road and moderately accelerate to 45, then they slow their rate of acceleration, but over the next several miles find themselves going possibly as fast as 65, until they catch up with another car, come to a stop sign, etc.

This behaivor is very bad for fuel economy.

It is much better to accelerate moderately to your desired cruising speed, in this case let's say 55 or 60, then hold that speed as constant as possible/practical.

The engine runs at its leanest and highest efficiency at a steady speed/load.

So Greg, that is likely what you heard someone saying/trying to explain about quick acceleration and automobiles.

Very hard aggressive acceleration is very bad for fuel economy and steady cruising afterwards will not offset those losses.

I can tell you all about the fuel economy extremes of the hot rods I have built over the years.............

Even today, I drive a large 4800 lb. car, with 360 HP, lots of torque, and twin turbo chargers, that will go from 0-60 in 5 seconds, OR, it will get 24 mpg on the highway carrying 7 people. But it will not do both at the same time........

Kevin, as for trains, every region is different in terms of how much open trackage there is, what the track conditions are, and how often engineers can push their trains to the speed limits.

But around here, we have both AMTRAK and CSX within sight and parellel to US 40 for a number of miles and it is easy to pace trains with your car and know how fast they are going.

Quite often CSX freight trains between Baltimore and points north are traveling at 50-60 mph. It is a bit of an adrenaline rush to be sitting at the grade crossing in downtown Aberdeen MD when a freight train comes thru at that speed. It happens nearly every day.

And AMTRAK trains get right up to their 88 mph limit.

Sheldon 

    

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Posted by gmpullman on Saturday, June 13, 2020 11:41 PM

Train Handling Rules: Every railroad has a set of specific rules applied to train handling. That busted drawbar shown in the previous photo may have cost an engineer a week or two of furlough time. Or his/her job.

 CSX_rules-train by Edmund, on Flickr

 

Training, learning from engineers that have handled the route, knowing your train (weight) and how it will react to grades, and curves, dynamic braking (bunching slack) or use of air (stretching the slack) where are the laods/empties, weather and dozens of other variables will determine just how much power will be.

Chapter 34 here scratches the surface:

http://rgpcops.net/images/abth.pdf

 

Read through that book and you'll at least get a little feel for what's at play.

34.2.1: Starting/Accelerating Train

34.2.1 Starting/Accelerating Train Rule Updated Date January 20, 2012 

On level and ascending grade: On descending grade: Advance the throttle to a position sufficient to hold the train when necessary. Release the automatic brake. Use the lowest throttle position possible to start the train. It may be necessary to retard starting acceleration by use of the independent brake. Allow the locomotive load meter to stabilize before advancing the throttle to the next higher position. Once the train is moving, do not increase the throttle until the locomotive load meter stabilizes. To accelerate, advance the throttle slowly, one notch at a time to avoid excessive draft forces. In curved territory, use only enough power to start the train to reduce the possibility of string-lining in curves because of excessive lateral forces.

If the train will not start, reapply brakes, reduce throttle to idle, and determine the cause. Applying power on a standing DC locomotive longer than necessary will damage traction motors.

1. 2. 3. 4. 5. With the independent brake fully applied, activate the dynamic brake. Release the automatic brake and wait for all brakes to release and slack to adjust. On heavy descending grades the automatic brakes may remain applied. Gradually reduce the independent brake until the train begins to move. Release the independent brake as the dynamic brake becomes effective. Adjust dynamic brake to allow train to accelerate.

Nothing is left to chance. Enginemen are frequently evaluated for train handling and reprimanded for failures to use company set guidelines. Today more than ever with in-cab cameras and recording instruments that give real-time analysis to any manager or other authoriized employee. No more flying by the seat of the pants. 

Good Luck, Ed

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Posted by BRAKIE on Sunday, June 14, 2020 3:46 AM

Ed, Back in the day alot of the old engineers wold "shake 'em loose" meaning the would use enough throttle to move until the engine stalled from the slack,they would stop and reverse until the stack was in,then,stop, use more throttle to pull ahead until the engine stalled farther then the first time and this was repeated until the conductor or rear brakeman let the engineer know the caboose rolled on that last move and with this information the engineer was assured the brakes was fully release.

I don't know if this was proper proceedure but, it was widely used on the PRR and N&W.

Engineers being evaluated is nothing new.

A ARFE would ride along to watch a engineer operate a engine and his train handling skills. In fact my Grandfather stopped his train once and told a young ARFE in some colorful words to run  this engine since I'm not doing my job right!  With that the ARFE stood behind Grandpa and didn't utter another word.

My understanding is this young ARFE was nitpicking and Grandpa had enough of that foolishness. Usually ARFE was former engineers but,this one was a high offical's son that was appointed the job with nothing more then basic engineer training.

How he got by without his monthly throttle time remains a mystery to me..

Larry

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Posted by gmpullman on Sunday, June 14, 2020 5:22 AM

BRAKIE
Ed, Back in the day alot of the old engineers wold "shake 'em loose" meaning the would use enough throttle to move until the engine stalled from the slack,they would stop and reverse until the stack was in,then,stop, use more throttle to pull ahead until the engine stalled —

Hi, Larry

I was just reading a story about a wreck on the NYC in Oneida, NY on October 19,  1950 where a box car door was rocked loose and fell flat across the westbound passenger main right ahead of #21 headed to Cleveland at 85 miles an hour. A local freight with 126 cars had made three attempts at getting started when the door came loose on an automobile box car 56 in from the head-end.

The engine truck rode on top of the door, flipped the Hudson 5422 on her side, killed the fireman instantly and the engineer died an hour later. Ten of the eleven passenger cars derailed and several structures in town were destroyed including two of the crossing shanties. The crossing watchman survived but had to be pulled out of the rubble.

Taking slack was sometimes necessary, especially with solid bearings — even worse in cold weather — but when you're stalled it was the only option.

Regards, Ed

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Posted by wjstix on Monday, June 15, 2020 11:52 AM

tstage
I was operating a 13-car freight train on my temporary layout this afternoon using two different locomotives: An EMD FTA-B (2,500 HP) and a USRA 2-8-2 Mike. With my NCE Power Cab and some programmed momentum, I used the incremental buttons to slowly bring each one up to speed when the thought occurred to me: "How long would a xx-car train take to reach a given speed?"

Note that it would take a different amount of time depending which engine was used. A diesel has more power 'up front' to start a train with, while a steam engine needs longer to get up to speed. That's why many steam engineers had trouble with pulling out couplers when they first started using diesels on freight trains.

In the OP's question, note that an A-B set of FTs and a 2-8-2 had about the same amount of pulling power. However, even if the steam engine had more horsepower than the diesel, it would still take the steam engine longer to get up to track speed.

Stix

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