The action is fantastic, but all the freights have four or more 4400 hp diesels on the front. Even if they are DC engines will they not exceed the knuckle couplers capacity causing things to come apart? Last year I saw CP put on a show at the spiral tunnels. They had two ES44AC’s on the front and one pushing in the rear. I know that two large AC’s do not produce enough TE to break knuckle couplers, but four would certainly do that. So how does BNSF and UP do this four big diesels up front without breaking anything? Please educate me.
Thank you
Frank
PS:Could it be that they do not need all the power for the grade, but are looking for speed?
Horsepower is an expression of force and speed. Starting a train requires the highest force. Only a small portion of the total locomotive horsepower is needed to exert the force to start the train into motion from a dead stop. If all the force that could be produced by the horsepower of just a couple units were applied to a standing train of sufficient weight, it would break a knuckle for certain. The need for the full potential of the locomotive horsepower comes into play as the speed increases. As speed increases, the pulling force drops off.
Horsepower per trailing ton may be the issue here. A 4-unit, head-end power consist is capable of delivering 12,000 to 17,600 horsepower. If the train has a high hp/tt ratio, say 2.5 to 5, it’s probably a pretty short one that is protecting business in a highly competitive market segment like U.P.S., the U.S.P.S., J.B. Hunt, and the rail/ocean carriers. Now granted the train could move with far fewer ponies, but to maintain a competitive schedule, the extra horsepower is needed.
Out west, hp/tt ratios that drop below 1.0 can be pretty dicey, especially with conventional equipment. Here, an engineer has to be thinking 3-to-5 miles in advance as to the way his train will drape over the grades and then make the appropriate speed and power adjustments that will maintain maximum authorized speed without breaking the train in two.
Do remember too that when a train starts from a dead stop, an engineer will initially apply just the minimum amount of power to get the train moving. After someone in the caboose or the motion sensor built into the end-of-train device lets the engineer know that the entire train is moving, then higher throttle settings may be applied. But, again, these are applied slowly one notch at a time. Each time the ammeter on the engineer’s control stand stabilizes, the engineer then adds another notch of power until either track speed is reached or the throttle is in “Run 8,” whichever is the lesser.
There is no one formula for starting a train that works everywhere. Grade, hp/tt, and weather conditions such as high winds or wet rail, all have to be considered. An experienced hogger plugs all of those variables into the analog comput
thank you for the responses. The reason for the question was that reading on Al Krugs excellent web site he talks about three sd70MAC’s being able to break knuckle’s, as well as how a train handles over hilly territory and the in train forces. When seeing a total of four big diesels up front one begins to wonder how the knuckles stand up, specially in such territory where the video was taken. So as mentioned it is probably a lot of “tail-bone” running and the trains might not be heavy enough to create enough stress on the knuckles for them to break easily. Specially compared to the coal/ore trains where they use DPU’s.
I would never send anyone to krugs site. It is not the amount of engines that will tear a train up its how they are used. 2 dash 8s or even dash 9s will tear a train apart. its not the pulling power as much as how much slack is in the train. when you get slack in the train you haft to take it easy streaching them out.
correct, its not amount of power that rips train apart , its capabilities of linkage between seat and throttle that will prevent the train from being ripped apart.
The power on the two trains in the video are for speed not just to get them up the grade. At the speed the two trains are traveling, the locomotives are not producing enough drawbar pull to break a coupler knuckle with a steady pull. A bad wheelslip may lead to the power lunging however, and that can break coupler knuckles. All the locomotives shown in the video are DC motored.
No, it’s not always the motorman that causes the problems. You get knuckles that have flaws when they were cast, and it just takes time for the remaining portion to break. It’s also a combo of slack, grade, wheel slippage, brakes, and a plethora of other factors that can cause a knuckle to break.
Funny, but true story, I never had to replace a knuckle in line-of-road, despite heavy trains and inexperienced hoggers. Now in my small yard, I had to replace a lot. And those have been snapped by a pair of sd40-2s or a set of gp38s. Just the slack, handling without air, grade, etc is what does them in.
Correct ENR, even with all the modern computerization in AC units, there are so many factors involved with pulling knuckles. It would be very hard for someone with no freight experience to know the dynamics of running them.
Never got a knuckle myself, but according to physics, should have had a few. Then there are those who have become known as “scrap kings”, routinely yanking them at the wrong place and time. One chap pulled the drawbar AND part of the end of the car off a load of corn. At under 10 mph!
Oh nay nay! One AC motor does produce more than enough TE to do the job, if care is not used. It’s all about train dynamics. It is part of the reason for DPU, yet DPU trains still pull steel given the situation and lack of situational awareness.
thank you everybody for the information. It is very informative, never thought that there was so much involved in train handling. It does make sense, the factors involved with proper train handling sound a lot more complicated then I ever thought.
Heck, I am still learning about train handling procedures on my model railroad due to the helix[:)], I can not even begin to imagine how much is involved with the real thing.
In train forces can have other affects as well. The Beltpack/RCL is the worst at train handling, I keep saying, if Beltpack Bob(the beltpack computer) was a real hogger it would have been fired long ago. When the beltpack operator selects a speed, the on board computer wants to get to that speed NOW. I had a trainee who put the speed selector from stop to 7(MPH) shoving autoracks with the long drawbars on a curve. The in-train forces rolled the outside rail over and 14 loaded autoracks ended up on the ground. Nobody was hurt, but he learned a valuable lesson.
Knuckles do have a designed breaking strength. There are ‘regular’ knuckles and ‘hi-strength’ knuckles that are routinely used on cars in heavy haul unit train service.
One carrier limits operating head end power to 2-AC’s + 1 Dash-8 and the tonnage that can haul over a territory. In flatland territories that combo may be able to haul, theoretically, 30,000 tons…11K for the AC’s and 8K for the Dash-8. In more mountainous terrain that engine consist may only be able to handle 14,400 tons…4.9K for the AC’s and 3.6K for the Dash-8. When the power is hooked to a 18K train from flatland through the mountains either a designate helper engine or DPU is required on the rear of the train to limit the draw-bar pull and to get the train over the territory. If additional power were added to the head end, the calculated strain on the head end knuckles would exceed their calculated design strength. While the train would have the same horsepower, the stresses through the train are different depending on the location of the power within the train.
The results of slack action are magnified at slower speeds, especially under buff forces, as the leading end of a stopping train will stop quicker from a slower speed than a higher speed…when move 2-3 mph and a emergency application takes place…the head end of the train can come to a complete stop before the application can be transmitted to the rear of the train…the rear that is ‘running free’ then hits the ‘wall’ of the head end that is stopped. While I don’t have actual data to refer to, I believe more knuckles get shattered from buff forces than draft forces.
Engines being used in tonnage service that surge or momentarily lose their load and then regain their full load are no