I used the example of empty coal cars compared to loaded coal cars to eliminate differences of car types. Instead let’s say we have a long train of empty any kind of cars. The question is still- does a longer train of empties require more HP than a short train of loads of the same trailing weight in a highly curving grade?
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When the trailing tonnage does not limit drawbar problems the amount of HP can determine the max speed the train can make. discounting wind say a train on flat land such as FEC can make 20 mph with 4000 HP, If that train wants to make 40 MPH then it would need 8000 HP. 60 MPH 12000 HP, But the train uses about the same HP hours to cover a distance.
Of course when starting a train 12000HP cannot be applied when first starting ans it could break a knuckle but more applied as speed increases.
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A long train going around curves creates more drag than a shorter train of the same weight and would require more horsepower to maintain a given speed.
This is also noticeable when descending a grade. A long train is easier to control when going through curves than when on tangent track.
Mark
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Thanks for the great information I now have a better understanding of why the number of engines vary so much from train to train. I learned that a lot has to be considered from the ruling grade, available horsepower, speed the train will travel, maximum speed limitations on different cars, weather, leaves on the rails, areas with curves, empty or full cars, and DPU locations. Thanks to Jeff and others who added an attachment - some things are easier to understand when you have something to look at. One last thought after searching for the title of the person responsible for assembling the train it showed “trainmaster” or “Conductor”. So it seems unless you are replacing a crew that was timed out when the engineer and conductor report for work they will assemble their train following the railroad’s rules. Is that how it works? The Trains Forum contains a wealth of experience and knowledge - thank you all for helping me by answering my questions.
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When assembling a manifest (mixed freight train) at the originating yard, the yard master directs the switch engine on how to switch the cars to build blocks of cars for the same destination on the different tracks.
Once finished building the blocks, the blocks are moved to the departure tracks. (Some small yards may not have such tracks and trains are assembled from the class tracks.) Depending on length, multiple blocks in order will be placed on the departure tracks. A train might only need one track or it may take several tracks to hold it. The placement on the track(s) is also directed by the yardmaster. Using the computer before moving cars, he can build the train on paper. The computer will flag any placement error requiring correction and placement of DP engines, if needed. Once the computer is happy, the cars are moved over.
On the departure tracks, the car department does the final mechanical and initial terminal air brake tests. Most larger yards can do the air test with a stationary air plant. Once everything is ok, the tracks are released to allow the train to be assembled from the tracks and depart.
The road engines might be moved to the train by hostlers who just move power to and from the engine servicing facility. As a cost cutting measure, most of those jobs are gone. Now road crews do that. The road crew, having got their paperwork and instructions on what order to assemble the train, do so. Do a final set and release of the train and leave.
Jeff
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Jeff, That clears up the process. Thank you.
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Do you know DJ of the DJsTrains youtube channel? He’s a CSX engineer out of New Castle. I think his real name is Dominic “something Italian”.
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Train length can be a double edged sword. Yes, there is increased resistance as a long train is moving through multiple curves at the same time.
There are geographical conditions where a long train is a benefit. Akron on the B&O New Castle to Willard line is one such location. Akron hill is a 1% +/- grade on both sides of Akron Jct, which at one time had a 10 MPH speed restriction. Trains, in either direction, descend the mile long grade to move the entire train through Akron Jct. at 10 MPH and then climb the other side up the 1% grade - without the benefit of a ‘running start’. Heavy trains of less than a mile in length frequently stalled as they had to pull the entire weight of their train upgrade with a start at LESS than minimum continuous speed. Long trains had the benefit of gravity pushing the rear end of their train down the grade as the head end was cresting the grade.
The current 4K+ HP AC traction locomotives when coupled under MU control have sufficient tractive effort to exceed the strength of freight car knuckles. Carrier rules dictate how many and what kinds of power can be On Line during the handling of any train. By the same token there are also Carrier Rules specifying how much Dynamic Braking power can be utilized.
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“does a longer train of empties require more HP than a short train of loads of the same trailing weight”
Same total weight on more axles, with more air resistance – RRs have always known a given tonnage of loaded cars roll easier than the same tonnage of empties, on curvy rail or straight. That’s why many RRs used “adjusted tonnage” ratings. Look at the back page of this IC timetable
A 4-8-2 was rated at 11325 adjusted tons northward to Chicago, meaning 9825 actual tons in 100 cars, or 8325 actual tons in 200 cars, or 6825 actual tons in 300 cars. But apparently Gilman to Clinton has a steeper grade, so a lower rating, and also a lower adjustment for empty cars, since the steeper the grade the more important actual weight is.
Note that IC claimed some rebuilt 2100-class 2-8-2s could take a 120-car 10475-ton coal train north to Chicago, which includes a 0.3% climb from Kankakee. Goes to show you can’t always believe tonnage tables.
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Some countries have experimented with using lasers to burn off the leaves. Do any US freight locos have them?
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The Long Island is the only railroad I remember testing the laser system.
GE had a promising-looking supersonic hot-air blower at one time, back in the era of onboard flange-lubricating sticks and TOR dispensers. One use was to blow traction sand and other material off the contact patches before the TOR went on – this was not the same device that cleared the rail just before the lead locomotive. If you thought the prime mover noise was irritating for hours on end – try Thunderscreech-class noise…
The problem with leaves is not ‘autumn leaves on the track that could be blown off’. The wheels compress the leaf matter into a dense plastic-like substance that then has an astonishingly slick surface when wet, much like a Slip 'n Slide from Hell. You need serious power to flush, blow, or burn that stuff off a railhead without leaving detritus behind…
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I worked with DJ a number of times back around the time of the Conrail split and have seen him at train shows occasionally.
Mark
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Tonnage charts are not ‘exact’ engine limits. Some engineers, with some trains can exceed them. Other engineers with other trains can fail with a lighter train.
Back in the days of steam, and really up to the late 1980’s the weights of all trains were the yard clerks ‘best’ estimate. In general terms the weight of empty cars was guesstimated at between 25 and 30 tons per car. Loaded cars were estimated at between 60 and 80 tons per car. In the late 1980’s the Class 1 carriers car and train data systems became sophisticated enough to capture the light weight of cars from UMLER (Universal Machine Language Equipment Register) which has myriad facts concerning EVERY car that all carriers have in Interchange Service in North America; the computer systems at that time were also able to extract the loaded weight of contents from the carrier’s revenue billing systems and marry that weight with the UMLER lightweight to give an accurate weight for each car in trains for most cars in trains. There are a couple of exceptions, vehicles moving in auto racks are not billed on weight. Intermodal trailers and containers are not billed on weight of contents.
Train consist lengths and weights today are the most accurate they have ever been.
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I appreciate everyone contributing. I thought this was an interesting question, and it’s turned out to be interesting answers. It’s great to have railroad workers willing to contribute!
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Those charts also assume an engine is running to as built manufacturer specs. And most of us know what age does …
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Not to my knowledge. It’d be cool if they did though. HAHA! PEW PEW PEW! Take that leaves!
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Engines are figured to run as good as the day they left the factory and the weather is always sunny and 75 degrees no matter the time of year.
Jeff
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To expand a bit: LIRR has used a laser system since 2017. Metro-North adopted the idea, and has now snazzed it up with a wrap.
There appears to be a deplorable lack of PEW PEW PEW in operation, though. Perhaps some strobes and a fog machine could be added for effect…
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Tonnage ratings the carriers use have never been set at the absolute maximum for each class of power. I don’t know what adjustment factor is used.
What I know from experience. Ninety car coal trains had two Dash-8’s for power between Atlanta and Waycross. There are undulating grades between Atlanta and Manchester, GA. In dry weather the Dash-8’s could handle the trains without issue, however, throw in rain or a heavy frost and they would stall on one of the grades. Instructions were that IF rain or frost was to be the issue, Atlanta was to add an additional unit to the train. Some days there weren’t enough engines available to add.
When the AC traction engines became the standard, the issues with 90 car trains went away. Both the Dash-8’s and the AC’s had nominally 4K HP, the mechanics of AC traction at the rail was that much better.
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This is why the ‘effective tons per axle’ metric previously mentioned here comes in. As better forms of slip and traction control are proven, and better AC control and motors are used, it is relatively easy to adjust that figure so that the ‘sum of axle ratings’ gives you the power to move a given train resistance acceptably on a given ruling resistance.
Something you and Jeff might be familiar with: it was my understanding years ago (without official confirmation) that UP would keep locomotives in service with inoperable fuel injectors (the number I was given was up to four on a 16-cylinder engine). I don’t know whether there was some formula for derating such units, or it was just ASSumed that the governor would feed a bit more fuel to the remaining injectors to hold rpm in MU.
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