I asked one of the crew when they were in Rock Springs last year why they use a diesel, and he told me that they use it more for dynamic braking than anything else.
Murphy’s Law is this ANYTHING that CAN HAPPEN WILL HAPPEN. Just because something should NOT happen does not mean it will not ever Happen. I dad had a Brand new Motor blow up on him one time the Crank was wrong in it the Pistons were wrong the Cam was installed Backwards But it ran for about 20 miles then it went BANG so bad they had to replace the hood and the ENGINE.
Anything Mechaincal WILL FAIL at somepoint and it will be a failure we never Figured will happen.
OK, I’ll admit to being old and slow at times, but what do they need dynamic braking for on a steam run. It’s pulling a passenger consist, not a two-mile long freight. At any rate, I remember reading an article in “Trains” years ago by Steve Lee concerning running the 3985 on freight, and Steve said you use the train brakes to stop, not the locomotive brakes.
Now if the diesel is there for the purpose of protection power I can understand that, however protection power can always be stationed at various places along the line, or run ten to fifteen minutes ahead of the steam run. That’s what was done on the C&O 614 runs on New Jersey Transit back in the 90’s.
While I can’t speak to UP practices, the primary braking system that engineers are being instructed to use is Dynamic Braking, especially with AC engines having extended range Dynamic Braking that is effective to a much lower speed than the earlier versions used.
Once upon a time (when fuel was ‘cheap’ and plentiful) powered stretch air braking was the preferred method as it gave a more comfortable ride to the Conductor & Flagman in the caboose. Since today’s EOT’s don’t care all that much about ride quality and minimal fuel use is a priority, Dynamic Braking is being taught as the primary braking medium. Plus when you get a ‘kicker’ when using the air brakes, now you have a train to inspect. - and the track time that that requires.
To BaltACD: Your explaination certainly make sense, at least as far as modern freight operations are concerned, and I thank you for it. However, with 844 we’re talking about running a 1940’s era train, the locomotive plus the passenger consist. so it would seem to me that if you’re going “old school”, you’ve got to go “old school” all the way irregardless of modern operating practices. But as you said, you’re not familiar with UP’s practices, so don’t think I’m trying to start an argument with you, I’m just trying to puzzle this one out.
To use an analogy with something I’m VERY familiar with, modern smokeless gunpowder burns a lot cleaner and a lot more efficiently than the old black powder does, but you don’t dare put it in a muzzleloader! If you do, when the gun goes “BOOM!” so will you!
I don’t know UP practices, especially when it comes to operating with the steam engines, with that being said, I would expect that they would be relying to some extent on the dynamic brakes of the diesel - when you are relying on a particular braking system - and it does not provide the speed reduction that is anticipated then the air brakes are the only thing that is left. Just like trying to brake a car on ice or wet grass - when you don’t get the retardation you expect, you would swear the car is powering on. With a train, even a passenger equipment train, if you don’t get the expected braking power at the expected point and if you are going downgrade at the time you could be getting very close to runaway speed where the fully applied air brakes on the train don’t have enough braking power to get the tonnage of the train stopped on the grade.
Read a NTSB report of a CSX coal train that ran away down 17 Mile grade - only had dynamics on one of the three engines and train speed got to 17 MPH -
I believe the diesel for dynamic braking may be at least partly to save wear on train brakes. I remember reading in an article (probably Trains but might have been another magazine) several years ago a steam crew discussing saying they figured if they ran without the diesel for a particular trip (I think it was UP via Feather River canyon; but that was at least ten years ago) they would have to replace the brake shoes for the entire train.
When 2 or more locomotives are MU’d together, is there a test routine to ensure that all the hot pins are properly connecting?
For that matter, since nearly all road locomotives are now computer controlled, should the industry replace the current MU system with a one or two wire system that simply allows the computers to communicate with one another much like the radio based system used to communicate with a trailing locomotive? Or has that been done and my understanding of the system outdated?
From what I have seen in videos, this train consisted of #844, two auxiliary tenders, the diesel helper, and six passenger cars. If the diesel were under full power, and if the automatic brakes were put into emergency, could that diesel produce enough tractive effort to prevent the train from stopping with all of its brakes fully applied?
Here is another question. Suppose you have the six passenger cars standing still with their brakes applied to the maximum pressure such that their wheels would slide if they were pulled hard enough. Then suppose you tie on the diesel and pull as hard as it can pull. Which of the following will happen?
A) The diesel will slip its wheels and not be able to move the cars.
[quote user=“Bucyrus”]
From what I have seen in videos, this train consisted of #844, two auxiliary tenders, the diesel helper, and six passenger cars. If the diesel were under full power, and if the automatic brakes were put into emergency, could that diesel produce enough tractive effort to prevent the train from stopping with all of its brakes fully applied?
Here is another question. Suppose you have the six passenger cars standing still with their brakes applied to the maximum pressure such that their wheels would slide if they were pulled hard enough. Then suppose you tie on the diesel and pull as hard as it can pull. Which of the following will happen?
A) The diesel will slip its wheels and not be able to move the cars
Okay, if the diesel were able to drag 600 tons with wheels sliding, how likely would it be for the drawbars / couplers to withstand that amount of pull against the resistance that would result from 600 tons being dragged while sliding on its wheels?
No problem at all - I am certain the engineering types can calculate the math involved, however dragging 600 sliding tons around does not really create that much force on the draft gear system.
Figure on a 250K lb Knuckle and your only at 1.2 Million Pounds total weight behind you unless it derailed your fine. I am guessng that the Knuckle was only at 50% loaded or LESS.
I am looking at it This way. I would put 1850FTlbs of Tourque Multiplied by Gearing to Over 1 Million pounds of Force with my Transmission and send it down a Driveshaft. What held that driveshaft to my Rear End Gear 4 5/16 bolts in the U Joint and their Straps. I never Broke one even when I would shockload them way over their Limit what gave way first the Freaking Welds on the Driveshaft. Last one I did break was from my Foreman flooring an Overpowered Cummins that had 850 HP in the low side of the tranny He bent it like a Pretzel.
Just because something is Supposed to be the Weakest Link does NOT MEAN IT WILL BE.
First guess would be 25% of 600 tons-- right? A driver that’s trying to rotate will slip when it’s exerting somewhere around 25% of the weight on it, so…
Or: a train is sitting on a 20% grade with brakes locking the wheels. Will gravity be enough to slide the train down the grade?
(Next question; how much less force is needed to keep it sliding, compared to what’s needed to start it sliding.)
That is indeed the next question. At the slowest speed of startup, the brake friction and the diesel helper tractive effort is the highest, and then both taper off as speed increases. So would the locomotive tractive effort be able to overcome the brake resistance at 45-50 mph? My guess is: “Yes.”
[B)] Ed; I know what you speak of. I had a " jack shaft" turn into a drill rod when the truck was on a wet spot , the wheels slipped and I moved forward and when the front drivers hit dry pavement , instant drill rod at 350.$$ plus labor.~~~~ Lesson learned.
Cannonball
If you mean, would the AC44 be able to pull the train at 45-50 mph with all the wheels sliding except its own, my guess is no. You think 30000 lb tractive effort would pull all those sliding wheels?
I don’t know what to think about that.
I am just trying to invent a plausible therory of what could have happened. It seems to me that there are two plausible explanations for the wheel flattening:
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The engineer inadvertenly left the locomotive brakes applied with a service or emgency applicaiton of the automatic brake.
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The engineer was unable to stop the train with an emergency application of the automatic brake with the locomotive brakes released; and therefore he applied the locomotive brakes as a last ditch effort to add enough braking to stop the train.