In the new edition of Trains (Nov 07) the article titled "Hauling Gas". In the article Tom Danneman was riding with the crew up Evaro hill on the Montana Rail Link...and the train stalled. The Crew's solution was to UN -MU the power, and run them independently, like the old days of double heading steam.
My question: why did this work?
Is it because the anti-slip will decrease power to all units in the consist when it prevents wheel slip...so the advantage of the first unit drying the rail by passing over it is lost? By running the units individually, the second unit can take advantage of the dry rail created by the passing of the first unit?
Or is there some other aspect of MUs that causes this?
....Fellows, I'm another one doing the wondering what gave them the extra power....TE....limited slip function, or what, to make the difference. And to start on the hill and accelerate to 10 mph....!! That was a figure that was difficult for me to understand. From stalling to 10 mph running.....with the same two engines...??
Quentin
I have not seen the article but the most likely reason this worked is there was some problem with the mu electricals on one of the units or the MU cable was defective.
The anti slip systems are completely out of the engineer's control and are loco specific. That is each locomotive takes care of it's own wheel slip correction so a reduction of power on the lead unit does not have any effect on the powere applied to trailing locos. Now the nit pickers can say that the lead loco dropping it's load will increase the load on the trailing units causing them to slip and then add to the problem. The reality is still that the anti slip on the lead loco does not control the anti slip on any of the trailing units.
beaulieu's response also warrants reading. What he is saying can be true but it is not likely what happened in this situation.
arbfbe wrote: I have not seen the article but the most likely reason this worked is there was some problem with the mu electricals on one of the units or the MU cable was defective.The anti slip systems are completely out of the engineer's control and are loco specific. That is each locomotive takes care of it's own wheel slip correction so a reduction of power on the lead unit does not have any effect on the powere applied to trailing locos. Now the nit pickers can say that the lead loco dropping it's load will increase the load on the trailing units causing them to slip and then add to the problem. The reality is still that the anti slip on the lead loco does not control the anti slip on any of the trailing units.beaulieu's response also warrants reading. What he is saying can be true but it is not likely what happened in this situation.
The article noted that after they successfully surmounted the hill they were crossing, they re-attached the M.U. cables and continued on in M.U. operation for the rest of the trip...so you are likely mistaken in your assumption (which was a good, logical one by the way).
Thanks for the vote of confidence in my assumptions. I really do have some experience with MU locomotive operations and have hands on experience with what is likely to go wrong in a number of situations. A broken connection in the MU cable or connection box or within the locomotive can cause all trailing units to operate at a reduced throttle setting. This might be a real pain in the hind end when the train is fully loaded on a mountain grade such as Evaro Hill but not pose much of a problem when the train is running down the river between Paradise and Pipeline. Then the train returns empty or with a short load of cars from Woodlin and the lead unit in 8 throttle and the trailing units in 5 or 6 throttle is enough to handle the lighter train.
Note that on the return the trailing unit for the westbound trip will now be the lead unit for the eastbound trip. The same MU connections will be used so it would be interesting how well the units performed and what the effective throttle positions in the units when the lead unit was in Run 8 really turned out to be.
I likely would not have even posted what I did here but sometimes the technical discussions on this forum get way too far from reality account posts and speculation from people who have absolutely no background with the equipment or operations to make the wild eyed claims they add to the post. No one seems to want to wait and see if someone who knows can claify the question before some one MUST add yet another speculative and baseless resolution to the post.
The lead unit drops its load and this increases load on other units. this is true but its because of the sudden demand on those units. as you say the wheel sleep or traction controll is local unit only not train line or M/U. and i have had consist that we had to do this to get up a hill. reason was M/Ued one unit dropped its load and quit working after notch 6 while the other pulled hard in notch 8. i needed the power so after seperating the m/u cable we ran them seperate up hill crested the grade and then re m/ued them and went on with no more trouble.
UP_North wrote:My guess would be the fact that with the SD70ace there is no need to worry about short time ratings and with the SD45 there is. At those speeds, I'm sure the SD45 was running in the red and they had to notch down to let the SD45's traction motors cool down. By disconecting the MU cable they could run the 70ace in the 8th notch while running the Sd45 at a lower throttle setting to avoid exceeding the short time rating of the SD45 and toasting the traction motors.
Never too old to have a happy childhood!
That is a pretty good guess but MRL has modified the circuitry in the Dash 2 units so they can be used with the ACe units and derate their load when the newer units get below the short time ratings of the older unit's traction motors. There is no need to say anything about that modification at this point. Some of you know why.
My answer involved only a small amount of guessing, clearly reading the RH column on page 49 the SD70ACe is slipping (shuddering). It states that the shudders (slippage) is occuring more frequently and that speed is falling until the train stalls. The reason the trains stalls is because the wheelslips are happening so often that the computer is reducing the power to the front locomotive truck to recover traction. Clearly the Engineer feels that he can get more power out of the SD70ACe by running it at a lower power setting. With both locomotives linked by a MU cable doing so will reduce the power and TE produced by the trailing SD45. By unplugging the MU cable and sending someone back to operate the throttle, they can get more out of the SD45.
Simply put, what I am saying is that a SD70ACe running in throttle position 7 and a SD45 in throttle position 8, will pull harder than if both units are in throttle position 8 and the SD70ACe is slipping badly. Under the poor rail conditions experienced, the SD70ACe is pulling harder on the drawbar in Run 7 than it is in Run 8.
For Wabash1, you are not supposed to operate the locomotive in higher than Run 4 with the Reverser centered because there is no load on the Traction Alternator.
beaulieu wrote: My answer involved only a small amount of guessing, clearly reading the RH column on page 49 the SD70ACe is slipping (shuddering). It states that the shudders (slippage) is occuring more frequently and that speed is falling until the train stalls. The reason the trains stalls is because the wheelslips are happening so often that the computer is reducing the power to the front locomotive truck to recover traction. Clearly the Engineer feels that he can get more power out of the SD70ACe by running it at a lower power setting. With both locomotives linked by a MU cable doing so will reduce the power and TE produced by the trailing SD45. By unplugging the MU cable and sending someone back to operate the throttle, they can get more out of the SD45. Simply put, what I am saying is that a SD70ACe running in throttle position 7 and a SD45 in throttle position 8, will pull harder than if both units are in throttle position 8 and the SD70ACe is slipping badly. Under the poor rail conditions experienced, the SD70ACe is pulling harder on the drawbar in Run 7 than it is in Run 8.For Wabash1, you are not supposed to operate the locomotive in higher than Run 4 with the Reverser centered because there is no load on the Traction Alternator.
yes you are right in that a high horse power unit will pull better in notch 6 than notch 8. and in cases like the one mentioned it would be better disconnecting the m/u jumper. not sure what you mean by operating a engine in notch 4 ( no such thing as run) with the reverser centered. If you are sitting still brakes on reverser centered, you can have the throttle in notch 8 with no harm to anything, when you are doing this you are to drop the gen field switch. this is what the ns pays me to do. so if they are wrong call them im sure they be glad to fix the problem.
wabash1 wrote: yes you are right in that a high horse power unit will pull better in notch 6 than notch 8. and in cases like the one mentioned it would be better disconnecting the m/u jumper. not sure what you mean by operating a engine in notch 4 ( no such thing as run) with the reverser centered. If you are sitting still brakes on reverser centered, you can have the throttle in notch 8 with no harm to anything, when you are doing this you are to drop the gen field switch. this is what the ns pays me to do. so if they are wrong call them im sure they be glad to fix the problem.
Hmm, picked this out of a SD60 Operator's Manual, the warning note was in the section labeled "Pumping Up Air" but seemed to apply more generally.
" Throttle may be advanced to No. 5 if necessary. Engine should not, however, be run unloaded (as in pumping air) at speeds beyond throttle No. 5 position."
The "Pumping Up Air" section described placing the generator field switch in the "Off" position, and the Reverser handle in the "Neutral" position. Which is also how you would also set up to cool traction motors on locomotives with mechanically driven traction motor blowers.
I was wrong on the position "4" it is "5". I seem to remember something similar in the SD40-2 Operator's Manual, but I can't find my copy right now.
Sorry, Wabash 1, the only control the lead loco has over the trailing units is the position of the throttle handle. It has no other communication method with the other units. There is no way for it to tell certain locos in the consist not to be in the same throttle position as it is in. The trailing units have their own wheel slip systems which can reduce the load for a short time. I am not sure how the overload system on the MRL SD45-2 units is set up to function but it does not take any information from the lead loco than throttle position and reverser direction.
Placing the throttle in a higher position with the reverser centered to cool the traction motors after they have been in the short time rating is common with the older units where the cooling blower is a direct connection with the engine crank shaft. There is no NEED to use idle 8 though the more air the better, eh? I will have to open up the doors on an ACe one of these days to see if the TM cooling is still direct connected to the engine shaft. I am thinking there is no longer one large central blower and each truck or traction motor is cooled with smaller blowers with an electric motor powering each and control of the speed assigned to a computer. In that case, there is no need to rev up the engine unless the main alternator at idle does not quite provide enough juice to power the cooling fans. If that is the case, the computer will recognize this and increase the engine rpms accordingly.
I am on vacation for a couple of weeks here so I have no way to interview the parties involved for more detail. Perhaps later we can put all the speculation to rest.
beaulieu wrote: wabash1 wrote:yes you are right in that a high horse power unit will pull better in notch 6 than notch 8. and in cases like the one mentioned it would be better disconnecting the m/u jumper. not sure what you mean by operating a engine in notch 4 ( no such thing as run) with the reverser centered. If you are sitting still brakes on reverser centered, you can have the throttle in notch 8 with no harm to anything, when you are doing this you are to drop the gen field switch. this is what the ns pays me to do. so if they are wrong call them im sure they be glad to fix the problem. Hmm, picked this out of a SD60 Operator's Manual, the warning note was in the section labeled "Pumping Up Air" but seemed to apply more generally." Throttle may be advanced to No. 5 if necessary. Engine should not, however, be run unloaded (as in pumping air) at speeds beyond throttle No. 5 position."The "Pumping Up Air" section described placing the generator field switch in the "Off" position, and the Reverser handle in the "Neutral" position. Which is also how you would also set up to cool traction motors on locomotives with mechanically driven traction motor blowers. I was wrong on the position "4" it is "5". I seem to remember something similar in the SD40-2 Operator's Manual, but I can't find my copy right now.
wabash1 wrote:yes you are right in that a high horse power unit will pull better in notch 6 than notch 8. and in cases like the one mentioned it would be better disconnecting the m/u jumper. not sure what you mean by operating a engine in notch 4 ( no such thing as run) with the reverser centered. If you are sitting still brakes on reverser centered, you can have the throttle in notch 8 with no harm to anything, when you are doing this you are to drop the gen field switch. this is what the ns pays me to do. so if they are wrong call them im sure they be glad to fix the problem.
well so you guys quit trying to pin me down, i will be more exact with out looking things up.
1) the engine in question was a sd45 and short time rating. i said i am not worried about short time rating as long as its moving but if i do stall and over heat the traction motors i will stop be in notch 8 and cool them down. you must remeber that pumping air and cooling the motors is 2 differant things altogether. in which no matter what you do going past notch 5 wont do anything but waste fuel your pumping as fast as you can in notch 5 what little extra you get abouve that is not worth the waste of fuel. but cooling traction motors ive been instructed to make sure i am in notch 8 for 15 min to cool these motors down , and if i remeber right that is for dash 8 and 9 engines.
2) the only communication between engines is what throttle notch to be in or dynamic if so equiped when to sand and headlights brake applications and direction of travel. for what its worth i have seen engines load the same amps but seperate them they sometimes load more not always.
3) i cant rember what else was said , i have agreed with some of the things you have said just not all and even added to it. I am not a know it all and dont try to be, oh one thing that was not mentioned is that if you have a 2 or 3 unit consist and lets say the rear unit started slipping ( it happens) that unit will start sanding and make all units sand. have a good day.
Oh, I didn't think of that. You're probobly right. I had thought is was because the SD70's wheelslip control wasn't letting it run at full power, while the SD45 could, because it didn't have the advanced wheelslip control.
We fried a couple of traction motors when they "ran away" - ran faster than track speed. They were in a trailing unit, so the engineer didn't notice. Management's answer was to doublehead, or at least place an engineer (most of us are volunteers, so cost isn't an object) in each unit to monitor things.
I read some time ago about the NYC discovering that one axle on some unit or another was running at a merry 100 mph - while the rest were doing around 60..... This apparently went on for some time.
Larry Resident Microferroequinologist (at least at my house) Everyone goes home; Safety begins with you My Opinion. Standard Disclaimers Apply. No Expiration Date Come ride the rails with me! There's one thing about humility - the moment you think you've got it, you've lost it...
tree68 wrote: We fried a couple of traction motors when they "ran away" - ran faster than track speed. They were in a trailing unit, so the engineer didn't notice. Management's answer was to doublehead, or at least place an engineer (most of us are volunteers, so cost isn't an object) in each unit to monitor things.I read some time ago about the NYC discovering that one axle on some unit or another was running at a merry 100 mph - while the rest were doing around 60..... This apparently went on for some time.
that is why they came up with ( for lack of better wording) series forestalling, in which the mp15 and sw1500 was working and running much faster than the rest of the units in a train, they have a switch to use that limits what the unit is doing and its called series forestalling, it limits in notch 8 ( if remeber right been long time) and protects the traction motors from over heating,ive always had these engines shut down or isolated. Never needed them for power on the main.
I remember reading that some units had an optional control that when set to "
downrate" position would reduce the lead unit one notch, alowing the lead to run at a lower
power setting than the trailing units
this reduced slipping by the lead , since the lead dressed the rail the trailing units had better
grip on the rail and could hold more power
notch 8 inthe lead cab told the lead run7 but the trailing ran run 8 per position sign on the m.u.
A.K. Cummings wrote:My assumption was that it was done to prevent wheel slip. If the engines are controlled separately, the engineer of each can push the throttle as agressively as makes sense. In other words, if the second engine is in throttle 7 and its wheels slip, the engineer then can simply throttle back and keep it in throttle 6 if that results in the wheels holding steady. Meanwhile, perhaps the lead engine is able to hold to the rails in notch 7 or even 8, resulting in each engine generating its maximum pulling power short of slipping. Does that make sense to any of the engineers out there?Andy CummingsAssociate EditorTrains MagazineWaukesha, Wis.
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