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Old October 12th, 2012, 04:12 PM   #141
Momo1435
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It's not that simple, the main problem with full dual power locomotives is that they are extremely heavy. The dual mode ALP45 is almost 40 tons heavier then the electric ALP46, in percentages it is almost 40% heavier. This is because the electrical system in a diesel electric loco is much more straight forward then in a electrical loco. It doesn't need the same big and heavy transformers that are used to transform the current from the overhead wire into a current that is most suitable to power and electric motor. With a dual locomotive you need the heaviest parts of both diesel and electric locomotives, making them as heavy as they are.

This extra weight hurts the performance of a locomotive, it's not a big issue for commuter trains since the overall weight of the train isn't that high. But with heavy freight trains it's a different story. The energy saved by using electric power on some difficult lines might not weigh up against the extra energy that is needed to haul the extra weight. The 40% extra weight could add between 1 and 3 percent extra weight to a complete freight train depending on the total weight. That doesn't sound much, but on a 2,000 km / 1,200 miles trip this can make a big difference in fuel costs.

Another issue is that the axle load will also be much higher, not all tracks will be strong enough to cope with such heavy locomotives and the track maintenance costs will also be higher.
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Old October 12th, 2012, 05:11 PM   #142
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I disagree about extra weight hurting the performance - this is much more of an issue with passenger trains. For freight extra weight = extra tractive effort (from rest), hence why so many freight locos are ballasted. An extra 40 tons is nothing compared to the total weight of many freight trains. For the sake of argument, if the freight train was on a poorly aligned route, and only travelled at a maximum of 20 mph, and it kept having to slow down and accelerate, then it is technically possible that the extra 40tons of ballast in the loco saves fuel. Unlikely to happen in reality of course, but it illustrates the point.

The axle load is of course an issue. So is the added complexity of the system. Being able to return current on descent through regenerative braking is only possible if there is another train that can use it - less likely on short unconnected sections of electrification.
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Old October 12th, 2012, 06:26 PM   #143
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Well, as far as I know, all powerful diesel locos in the US are heavily ballasted,
so it would just be a matter of trading the ballast weight for the additional
equipment, and your dual-mode loco is ready. What I don't know is whether
one can still find some space in a current diesel loco design to install the
required transformers, inverters, ventilation, and so on, that a dual-mode
loco would require.

In Europe, mountain lines were among the first to be electrified, because at
that time, steam engines did not have enough tractive effort at low speed
to win against the grades. Nowadays it would be a pure economical calculation.
Has it been done already ? With the mindset being so much
against electrification over there, I'm not sure. Remember places like
Cascade tunnel, where electrification was in place, and locos available,
but all that was blown away anyway right after diesel came into place...
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Old October 12th, 2012, 07:08 PM   #144
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Basically it depends on if the added weight of all the electrical equipment outweighs the ballast or not. For the ALP45 the weight increase was 40 tons, but for a heavy diesel locomotive this could easily be more. Especially since the space is an issue, if the whole locomotive has to become bigger because of it. And that's of course the case since you still want to have the same power output as a diesel loco. Plus you need full electric power since the trains are heavy and you only use it when the most power is needed. This will further increase the weight of the locomotive, before you know it a 6 axle locomotive will weight more then 300 tons.
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Old October 15th, 2012, 09:01 AM   #145
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Weight can't be an issue. In Europe we have several 3500 to 4000 hp locomotives that are limited to a 22,5 ton axle weight (even a 5000hp one, but it has a hydraulic transmission). That leaves plenty of weight to add a transformer. If properly designed the transformercasing can be a structural element of the frame.

Space may require a redesign and some rethinking. Using 2 smaller engines instead of 1 big one could be a solution (leaving you the option to run on 1 engine if you need less then 50% power). This could also be an advantages as far as EPA demands go. A smaller engine is easier to get clean. Also consider that you will be running electric when power is needed, thus you can considerably reduce the size of the fueltanks.

You could even go so far as to lower the diesel power of the locomotive. You do not need it once the train is in motion on flat country and at the spots you do need it you install overhead wires.

I think you should forget about the current generation locomotives and think outside the box here. A return to cab units instead of hood units, which I think look better anyway, but that's personal.

As far as economics go: Technology can now provide solutions that were unfeasible just 20 years ago. Also environmental demands have gone up the last 20 years and will continue to get more strict. Also noise restrictions may become a factor in the near future. It may become to expensive to retain the current designs.
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Old October 15th, 2012, 09:10 AM   #146
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Quote:
Originally Posted by M-NL View Post
Space may require a redesign and some rethinking. Using 2 smaller engines instead of 1 big one could be a solution (leaving you the option to run on 1 engine if you need less then 50% power). This could also be an advantages as far as EPA demands go. A smaller engine is easier to get clean. Also consider that you will be running electric when power is needed, thus you can considerably reduce the size of the fueltanks.

You could even go so far as to lower the diesel power of the locomotive. You do not need it once the train is in motion on flat country and at the spots you do need it you install overhead wires.
DB is ordering Diesels with four engines for use on both regional passenger trains, and freight trains. They indeed intend to only run all or just some of them depending on the load demanded. Bombardier is going to build these locomotives, and they will have easy exchangeable power packs.
Another evolution is the development of power electronics that will allow locomotive engineers to do completely away with the transformer. It will be interesting to see if this finds its way in to multi mode locs too.
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