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Old January 29th, 2013, 06:37 PM   #241
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24 Jan 2013 :
TSB Concerned About the Risk of Derailment of Heavy Passenger Locomotives on Lower Classes of Track
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Old February 1st, 2013, 02:04 PM   #242
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2 questions:
  • Why are the newer locomotives 'typically heavier'? Shouldn't a passenger locomotive be as light as possible?
  • Why do 4-axle freight locomotives not suffer the same problem?
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Old April 11th, 2013, 05:16 PM   #244
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Quote:
Originally Posted by M-NL View Post
2 questions:
  • Why are the newer locomotives 'typically heavier'? Shouldn't a passenger locomotive be as light as possible?
  • Why do 4-axle freight locomotives not suffer the same problem?
A locomotive must not exceed a certain axle load. In Europe it is around 20 tons/axle. I do not know the numbers for North America, but they should't be much different.
Locomotives should be heavy. Weight turns into traction. This is especially valid for freight trains, but also for heavy passenger trains. In Europe, passenger Trains are usually about 10-15 coaches long. In the US, I have seen passenger trains that are 30-35 coaches long, and i can imagine, it is the same in Canada. Such trains need a heavy locomotive or two lighter ones, to have traction. Especially on mountain tracks, a light locomotive might not be able to put the train in motion.
Same thing is true for freight locomotives. Light, 4 axle locomotives will not be able to pull heavy freight trains on their own. freight trains are often pulled/pushed by 3-6 locomotives.
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Old April 11th, 2013, 06:18 PM   #245
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NA passenger cars are also ridiculously overweighted, so they require heavier locos.
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Old April 12th, 2013, 01:58 PM   #246
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Quote:
Originally Posted by mpeculea View Post
A locomotive must not exceed a certain axle load. In Europe it is around 20 tons/axle. I do not know the numbers for North America, but they should't be much different.
In Europe 22,5 t/axle is normal (TRAXX/Vectron/Prima II all weigh in at around 90t). In NA they are much higher, both the passenger GE Genesis P42DC and the freight GE ES44AC have axleloads of 32,5 t/axle.

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Originally Posted by mpeculea View Post
Locomotives should be heavy. Weight turns into traction.
Not entirely true, you still need bigger traction motors to actually generate those higher forces. As a rule of thumb a modern locomotive can deliver about 35% to 42% of it's weight (in kN!) as tractive effort. The above mentioned 90t TRAXX/Vectron/Prima II can deliver around 300 kN of starting tractive effort, the 122t P42DC only 280 kN. For 280 kN 85t would have been enough, therefore you could consider that massively overweight. The TSB article mentioned that the new generation NA passenger locomotives would be even heavier, so hence my question why? It is true though that these lighter loco's will be more prone to skidding.

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Originally Posted by mpeculea View Post
Same thing is true for freight locomotives. Light, 4 axle locomotives will not be able to pull heavy freight trains on their own. freight trains are often pulled/pushed by 3-6 locomotives.
Yes they will, you just need more of them to reach the same adhesion weight, which is the reason you won't see that often.

Your explanation does not adress the fact that a higher axle load also increases the dynamic stress on the tracks, especially at higher speeds. In fact, double the weight result in more then double the dynamic forces.

My second question also remains: Why would a similar weight 4-axle freight locomotive be less prone to derailing then a 4-axle passenger loco. The only thing I can come up with is a different wheel shape and not having truck rotation dampers on freight locomotives.
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Old April 12th, 2013, 02:53 PM   #247
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Quote:
Originally Posted by M-NL View Post
Not entirely true, you still need bigger traction motors to actually generate those higher forces. As a rule of thumb a modern locomotive can deliver about 35% to 42% of it's weight (in kN!) as tractive effort. The above mentioned 90t TRAXX/Vectron/Prima II can deliver around 300 kN of starting tractive effort, the 122t P42DC only 280 kN. For 280 kN 85t would have been enough, therefore you could consider that massively overweight. The TSB article mentioned that the new generation NA passenger locomotives would be even heavier, so hence my question why? It is true though that these lighter loco's will be more prone to skidding.
When the train is put into motion, traction (measured in the coupling) is not as important as the torque put in the wheel by the engine. The more powerful the engine, the more torque it will put out. You need a huge amount of torque to actually put a train in motion. If the engine is to light, the torque put by the engines into the wheels will exceed the friction momentum, and the wheels will skid. After the train has gained a bit of inertia (somewhere between 5 and 10 kph), traction in the coupling is what matters, in order to accelerate. So the smaller traction of the P42DC will translate into weaker acceleration.
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Old April 14th, 2013, 03:32 PM   #248
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Traction (measured in the coupling) = The torque put in the wheel by the engine. Where else would it come from?

I'm sorry but your explanation still doesn't explain why a North American locomotive is 1.5 times heavier then it needs to be for the performance it delivers and why the newer ones will be even heavier.
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Old April 14th, 2013, 03:59 PM   #249
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Due to massive train lengths and weight here, locos must be heavier than usual in the hopes they withstand head-on collisions with each other, I think.
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Old April 16th, 2013, 01:39 PM   #250
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I've read that several times and a lot of people at the TSB and FRA seem to have the same opinion.

If you collide head on with a 15000t freight train I don't think it would make much difference if your own weight is 90t or 122t. Same story for a head on collision between 2 passenger trains both travelling upwards of 75mph. In both cases the results won't be pretty.

But the NA railroad community can't ignore the fact that passenger trains constantly need to drag enormous weights around for the very unlikely event of a collision. That uses a lot of extra fuel and create extra wear on both the track and the rolling stock. But it's how they want it to be.
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Old April 16th, 2013, 02:59 PM   #251
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I wonder how much longer loco anti-collision attributes must remain excessively heavy here
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Old May 28th, 2013, 10:05 PM   #252
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Country's national passenger services operator recently got this year's int'l airail concept award
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Old June 1st, 2013, 11:43 AM   #253
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Old June 1st, 2013, 03:47 PM   #254
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That was close... How it was possible at all?
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Old June 1st, 2013, 07:20 PM   #255
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The recording itself hails from the 1990s.
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Old June 1st, 2013, 07:54 PM   #256
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Well, back in early 90s in ex-USSR countries was utter chaos and povetry, so dismantling main beam lamp of locomotive after the ride was common practise - because if it's stolen during the stop - the replacement would be impossible to find... And without the main beam locomotive surely may not be operated. But even then, interlock fail that resulted into possibility of head-on collision would be an national-wide sensation.
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Old June 12th, 2013, 04:55 AM   #257
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Today's :
CORRECTED-Canada watchdog wants tougher safety rules for trains
"(Corrects 10th paragraph to show CN is already rolling out automatic systems in the United States, and not in the United States and Canada, as first sent) ..."

I wonder if the 'report' even mentions that the watchdog's recommendation has been issued three times the past ten years
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Old July 7th, 2013, 01:25 AM   #258
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Learning of crazy derailments all the time becomes more and more sickening, this country's a banana republic.



Auto pilot hauling 73 cars of crude had halted near Lac-Mégantic's old town centre last night. It's said that for reason/s unknown the automatic consist started rolling backwards, then derailed, and at least 4 of the cars exploded, levelling half the town centre , and the fire has been raging out of control now for more than 10 hours already. Lots of crude is fouling the nearby river, coming from other punctured cars. 1 dead, possibly 60 missing.

This negligent practice is criminal ...
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Old July 8th, 2013, 03:25 PM   #259
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Old July 8th, 2013, 03:27 PM   #260
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Anyhow, Friday night's train was not auto-pilot. Leaving the locos running, the driver parked the train in the village of Nantes a few miles up slope from the historic lakeside town of Lac-Mégantic, went to the hotel nearby to sleep for the night, but after a couple of hours all the cars somehow uncoupled from the locos. Fire retardent was to arrive finally Saturday evening. The fires were extinguished yesterday evening. Much crude continues to spill into the Chaudière River and the Mégantic Lake itself. 5 dead, at least 40 missing. Packed bar trackside to be focus of search for human remains.
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