F125 vs. Charger Tractive Effort

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CSXfoamer1997

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The F125's will generate 4700 HP with a 20-cylinder engine and have a starting tractive effort of 315 kN to pull up to 10-20 bi-levels with one unit.

The Chargers will generate 4400 HP with a 16-cylinder engine and have a starting tractive effort of only 290 kN to pull only up to 5 bi-levels with one unit.

Why would the F125's have more tractive effort than the Chargers if they have almost the same amount of horsepower?

And had the engine in the Chargers had 20 cylinders, it'd generate 5500 HP. And why do they have 16 cylinders instead of 20?
 
Because 20 was not necessary to meet the performance requirement specified for it. Putting in a bigger engine adds to the cost, which probably would have made them lose out on the bidding.

As for how many cars can be pulled, that has to do with pulled with what sort of acceleration. If arbitrarily low acceleration and speed is acceptable then quite a huge number of cars can be pulled. So one needs to look at those two numbers to make an apples to apples comparison.
 
Sounds like a bogus number of Bilevel cars pulled. Both engines.

Tractive effort has little to do with horse power. You can fry the DC motors if you apply too much power / amps. Start for a stop you have HP to spare, that why Frieght Engines can use slugs. Only after you reach (X) speed do the slugs stop use the HP and the power is used to turn the mothers tracton wheels only.

Number of Cylinder is a weight and maintenance issue.
 
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likely to be ac not dc traction, but bad things can still happen with an improper "takeoff" the point about slugs in freight service is great, passenger aficionados might not realize they exist agree on the number of cars pulled being bogus for both.
 
likely to be ac not dc traction, but bad things can still happen with an improper "takeoff" the point about slugs in freight service is great, passenger aficionados might not realize they exist agree on the number of cars pulled being bogus for both.
It'll definitely be AC. No DC powered locos have been made since 2010.
 
The F125's will generate 4700 HP with a 20-cylinder engine and have a starting tractive effort of 315 kN to pull up to 10-20 bi-levels with one unit.

The Chargers will generate 4400 HP with a 16-cylinder engine and have a starting tractive effort of only 290 kN to pull only up to 5 bi-levels with one unit.

Why would the F125's have more tractive effort than the Chargers if they have almost the same amount of horsepower?

And had the engine in the Chargers had 20 cylinders, it'd generate 5500 HP. And why do they have 16 cylinders instead of 20?
By selecting a 16 cylinder engine, Siemens was able to offer a lighter and less expensive locomotive. Siemens underbid EMD and MotivePower by about $1 million per locomotive in winning the contract.

Surprisingly enough, the public documents for the Mult-State Locomotive Procurement are still available on Illinois DOT's website. The summary of the evaluation of the 3 bidder's proposals is the 2nd link on the list under Final Offer Evaluation Report. Lots of information on the specs and what the terms were available in the linked documents.

EMD protested the contract award, but since little has been heard about it since, I figure the protest was denied and dropped. The EMD protest letter has EMD's estimates or more accurately their claims on acceleration performance of their proposal vs Siemens design which might interest you. The letter was publicly available at the time of the protest. A google search using the document name turns up a copy here on scribd. The bottom line with regards to 125 mph speeds, that both the EMD 125 and Siemens Charger will take a long time to get from 110-115 mph to maxing out at 125 mph because of their power limits.
 
likely to be ac not dc traction, but bad things can still happen with an improper "takeoff" the point about slugs in freight service is great, passenger aficionados might not realize they exist agree on the number of cars pulled being bogus for both.
It'll definitely be AC. No DC powered locos have been made since 2010.
This statement is too broad for me to consider as fact without further information. There have been genset locomotives built since then, and I'm unsure whether they use AC or DC for generating and parallel load sharing.
 
The number of engines also has to do with a rail line's profile. For instance, the SL could easily run with a single engine between NOL and HOS because it's virtually flat all the way, except for the Huey P. Long bridge over the Mississippi River which is a 2% grade on both approaches. I'm sure none of us want to stall on the Huey P. 225' above the water due to lack of power. :eek:
 
Number of cylinders doesn't tell the entire story anyways. They both have similar total displacement at 95 and 105 liters for the Charger and F125 respectively.
 
Design engineers can only estimate what will happen. It will take actual testing to compare how each loco does thru its speed range and for the many different trailing tonnage ( cars ). One loco may take say 6 cars to 60 mph in x time and the other X+Y time. But 6 cars behind 1st loco to 120 might take T time and 2nd take T-S time. Then again 12 cars might provide entirely different results. The power vs time curves can get quite complicated.
 
Practically everyone uses AC induction motors for "traction motor" (railroad) applications; brushless DC permanent-magnet motors are an alternative, but very rarely used. Another question would be MOSFETs or IGBTs for controlling the motors, though I get the impression that IGBTs have won out.
 
Tractive effort has little to do with horse power.
This is a misleading statement. Once you get above the rated continuous speed, tractive effort has EVERYTHING to do with horsepower, as the horsepower rating dictates the max tractive effort at any given speed above the continuous speed rating. This is why, ultimately, the 300 HP difference between the F125 and Charger locomotives doesn't mean much at speeds above 100 mph. If one does the math, at 100 mph, that difference in horsepower results in 1,125 lbs of TE difference between the two locomotives, which is close to nothing in the grand scheme of things.

The truth to the original statement is that starting tractive effort is not governed by HP, but rather by adhesion and the locomotive computer. Because of the way the math works, at 0 speed, you could theoretically have infinite TE, regardless of HP rating, but that would make no sense, since the wheels would slip for eternity. So the solution is to limit tractive effort at low speeds just enough that the wheels do not slip, but not so much that it needlessly hinders starting acceleration. With this in mind, again, the difference between the F125 (71k lbs) and Charger (65k lbs) is negligible (6000 lbs TE).

In the grand scheme, both locomotives would be able to perform their assignments just fine (6-8 cars @ MAS of 90 mph). For higher speed operations (125 mph), they're planning to bookend the consists anyway, so you'll have at least 8000 HP for traction after taking into account the HEP requirements. That's the equivalent of a single electric locomotive on the NEC, and one of those can handle 12-14 cars @ 125 mph easily.
 
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