This is a question we can play with a bit, triggered by the E-8 "what if" question.
What specific qualities would you build into a modern, passenger locomotive? What technology would you use, and how would you use it?
Just offhand, I would want a locomotive with the power capability of a GG-1 to haul a passenger train fast- but with the ability to pull a freight train, too. I would want a locomotive that would not have to be turned to face forward. I would want a locomotive that could use overhead wire, third rail, or run on it's own under diesel power.
And the railfan in me says that we absolutely HAVE to have something that looks worthy of taking the consequences of a trespassing charge, just to get a telephoto lens shot.
How do you think something like that would look? How would you design your "dream" locomotive to be practical, economic, comfortable to operate, and efficient?
I see three distinct applications for passenger locomotives: commuter, corridor and long distance. Technology for all three cases would be a diesel electric hybrid, and while third rail would be a relatively easy add-on (and maybe 1500VDC overhead?), allowing for operation off of high voltage AC would involve some serious trade-offs. The HEP should be run off an inverter to allow more flexibility in operation of the prime mover.
A commuter locomotive would be designed for rapid acceleration to track speed, with the propulsion system designed to produce 8,000 to 10,000 drawbar HP for about a minute at a time - and be able to provide similar levels of braking horsepower. Prime mover would be in the 3,000 to 4,000HP range.
A corridor locomotive would be designed for slower acceleration and higher top speed than a commuter locomotive, propulsion system designed to produce 6,000 to 8,000 drawbar HP for up to five minutes at a time (cresting hills, etc). Prime mover in the 4,000HP range.
A long distance locomotive would use the hybrid subsystem for a mild assist for a half hour to an hour (e.g. supply HEP from battery for that period of time while the prime mover supplies power for climbing a hill - such as Raton pass). Prime mover should be in th 4,500HP range.
- Erik
How do you think something like that would look?
NJ Transit recently tried to get a RFP for a dual-mode unit that could run on AC catenary wire. No offers. Now, reportedly, they are trying for an EMU/DMU combo (inspired by similar operations by Denmark's Flexliner and others), and this after the agency has gone hell-bent for leather in an anti-MU direction for a decade or so.As for freight operation, Conrail certainly knew that the only places that diesel-electric locomotives couldn't go were tunnels, and underground/covered passenger stations, that had limited ventilation. That helped them with their (IMHO misguided) decision to abandon electric ops (as well as the GN/MILW precedent thereof).
CSSHEGEWISCH wrote:The specs suggested by erikem seem overly complicated and make the engineering issues involved in a dual-power design seem simple by comparison. While these specs look good on paper, we need to ask if they can be achieved in the real world, how much would it cost to meet them and are they really necessary.
IMHO (well maybe not so humble...) a hybrid commuter locomotive has some attractive features - one is the potential of increasing short term power for acceleration and another is fuel savings from recovering braking energy.
As for design complexity, let's assume AC drive with permag synchronous motors and IGBT inverters. Tractive effort will depend almost solely on current of the inverter output. The effective (low frequency) voltage of the inverter output will scale with the speed. At low effective voltages, the average inverter input current is much less than the average output current (most of the current is recirculated through the local bypass capacitors) assuming a constant input voltage. The only thing that prevents generation of full torque at full speed is whether the power source can supply the current - which isn't possible with a reasonable sized diesel engine. There's little that would prevent the motors from exerting full braking effort at top speed other than the lack of a place to dump the power coming out of the inverter.
There are a couple of ways of supplying the current over and above what available from the traction alternator. One way is to hang a huge capacitor in parallel with the inverter input. The first problem is that the presently available capacitors (e.g. Maxwell Ultracaps) have an energy density roughly a factor of ten lower than what's needed - but there are groups claiming that a 10X improvement is possible - and EEStor is claiming even higher energy density for their ceramics (I'll believe it when they start shipping product). The second problem is that the cost of these capacitors are presently ~10X too high, though costs are expected to decline. The other way of supplying the current is to hang a battery on the inverter inputs. Li-ion has both the power and energy density necessary, but with a very limited cycle time (which can be increased by drastically reducing depth of discharge). This latter approach is being taken by GE, though I suspect the limits on power are set by the battery (battery designed for high energy density rather than high power density).
What I have glossed over is a means fo monitoring the health of the battery (including state of charge). Another complication is that the traction alternator voltage will have to follow the charging/discharging of the batteries or capacitors.
Similar arguments could be made for the corridor locomotive, but I would concede that the long distance locomotive might best be achieved by stuffing the biggest/baddest engine possible in the carbody.
JT22CW wrote: How do you think something like that would look?Look at a photograph of empty railroad tracks, and you'll know NJ Transit recently tried to get a RFP for a dual-mode unit that could run on AC catenary wire. No offers. Now, reportedly, they are trying for an EMU/DMU combo (inspired by similar operations by Denmark's Flexliner and others), and this after the agency has gone hell-bent for leather in an anti-MU direction for a decade or so.As for freight operation, Conrail certainly knew that the only places that diesel-electric locomotives couldn't go were tunnels, and underground/covered passenger stations, that had limited ventilation. That helped them with their (IMHO misguided) decision to abandon electric ops (as well as the GN/MILW precedent thereof).
The primary drivers in CR's decision to drop electrics were:
1. The inability to come to an agreement on how to split the power bill.
2. The high cost per car-mile imposed by Amtrak for freight.
3. The existence of decent, alternative routes between Harrisburg, North Jersey and Philly.
4. A surplus of diesel locomotives due to declining traffic levels in 1980.
To a lesser extent, there were some economies taken in locomotive utilization and reduction in facilities and manpower.
As far as I know, tunnels and stations were never an issue. The only tunnels of significance I can think of are the B&P and Virginia Ave tunnels. Neither of these are a problem operating diesels.
-Don (Random stuff, mostly about trains - what else? http://blerfblog.blogspot.com/)
erikem wrote: CSSHEGEWISCH wrote:The specs suggested by erikem seem overly complicated and make the engineering issues involved in a dual-power design seem simple by comparison. While these specs look good on paper, we need to ask if they can be achieved in the real world, how much would it cost to meet them and are they really necessary.IMHO (well maybe not so humble...) a hybrid commuter locomotive has some attractive features - one is the potential of increasing short term power for acceleration and another is fuel savings from recovering braking energy.As for design complexity, let's assume AC drive with permag synchronous motors and IGBT inverters. Tractive effort will depend almost solely on current of the inverter output. The effective (low frequency) voltage of the inverter output will scale with the speed. At low effective voltages, the average inverter input current is much less than the average output current (most of the current is recirculated through the local bypass capacitors) assuming a constant input voltage. The only thing that prevents generation of full torque at full speed is whether the power source can supply the current - which isn't possible with a reasonable sized diesel engine. There's little that would prevent the motors from exerting full braking effort at top speed other than the lack of a place to dump the power coming out of the inverter. There are a couple of ways of supplying the current over and above what available from the traction alternator. One way is to hang a huge capacitor in parallel with the inverter input. The first problem is that the presently available capacitors (e.g. Maxwell Ultracaps) have an energy density roughly a factor of ten lower than what's needed - but there are groups claiming that a 10X improvement is possible - and EEStor is claiming even higher energy density for their ceramics (I'll believe it when they start shipping product). The second problem is that the cost of these capacitors are presently ~10X too high, though costs are expected to decline. The other way of supplying the current is to hang a battery on the inverter inputs. Li-ion has both the power and energy density necessary, but with a very limited cycle time (which can be increased by drastically reducing depth of discharge). This latter approach is being taken by GE, though I suspect the limits on power are set by the battery (battery designed for high energy density rather than high power density). What I have glossed over is a means fo monitoring the health of the battery (including state of charge). Another complication is that the traction alternator voltage will have to follow the charging/discharging of the batteries or capacitors. Similar arguments could be made for the corridor locomotive, but I would concede that the long distance locomotive might best be achieved by stuffing the biggest/baddest engine possible in the carbody.
A hybrid commuter locomotive is a great idea! When you consider a GE locomotive takes 80 seconds to get to full load and more than a full minute just to get to 1/2 load, you're not exactly blasting away from the platform after each stop. Add in AC traction and you could start to get MU-like performance out of locomotive hauled trains.
Given that most of the energy consumption on many commuter trains is used up accelerating the train (versus overcoming rolling, curve, grade and aero resistance) and that energy is just burned up stopping, you should be able to get some really impressive fuel economy gains.
Anybody care to sharpen their pencil and take a stab at it?
This hybrid locomotive would have an incredible amount of gear crammed into its carbody and it sounds like a maintenance nightmare, not unlike D&H 1403 in the steam era. I'm wondering if the initial and ongoing expense of procuring and operating such a locomotive would be justified for saving a few minutes of schedule time plus the ancient issue of the fuel/maintenance trade-off.
CSSHEGEWISCH wrote:This hybrid locomotive would have an incredible amount of gear crammed into its carbody and it sounds like a maintenance nightmare, not unlike D&H 1403 in the steam era. I'm wondering if the initial and ongoing expense of procuring and operating such a locomotive would be justified for saving a few minutes of schedule time plus the ancient issue of the fuel/maintenance trade-off.
For a locomotive with AC traction motors, the extra gear would either be a battery pack or capacitor bank attached to the bus connecting the output of the traction alternator with the inverter inputs. These could be put in the space currently taken up by the dynamic braking grid and fan (been told that weighs about 3 tons). The capacitor solution would be my first choice if caps with sufficient energy density could be developed, as capacitors are almost maintenance free (especially ceramic). Batteries would require more maintenance and Li-ion batteries have a spectacular (and dangerous) failure mode.
With currently available batteries or capacitors, a hybrid locomotive would not make economic sense (figure $2 to $6 million per locomotive using Maxwell Ultracaps), but prices are trending downwards. At the moment, the ultracaps are starting to look interesting for LRV's & rapid transit (more frequent stops and lower top speeds).
The key issue with economics is whether it would be cheaper to electrify or go to hybrids with electric like performance. Right now, i'd say electrification is cheaper, but 5 years from now???
Something else to consider, most R/C planes are now electrically powered and a man carrying electric plane was shown at Oshkosh.
Agh! I do see your point and having spent some of my misspent youth turning wrenches on locomotives I'm preternaturally opposed to all things electronic and mechanical that break, but here's point another you might not have thought about: that few minutes of schedule time is extraordinarily valuable on a commuter railroad because it is trying to pack a tremendous amount of capacity into a tiny amount of time. A few seconds matters because it means the railroad can operate more trains on the same track in a given amount of time, a savings in both fixed plant and equipment. If the alternative to adding capacity is buying another main track at $5 million/mile (nice open country, no right-of-way costs), $25 million/ mile (city streets), or $100 million/mile (tunneling under city streets), the hybrid locomotive even with all of its extra gadgets and maintenance is awfully cheap. Capacity costs are collossal on a commuter railroad if you have to acquire privately owned right-of-way or if you have to tunnel -- L.A. Red Line cost a staggering $5.6 billion for 17.4 miles.
For example, a client recently asked if we could find any way to cut travel times on a new commuter line. We looked at the property and the equipment for several days and decided it would be feasible to increase the unbalance on curves by 1" to get 5 more mph out of the curves, then ran the train performance model to look and see if this was meaningful after acceleration and deceleration times. Time saved was about 80 seconds each way and the client was thrilled because that meant the existing equipment could squeeze out one more round trip per rush hour, saving the client having to purchase another train set at $4 million, plus another operator and his relief, another space in the carbarn, heavier dispatching workload, more spare parts, yadda yadda.
RWM
There are few possible basic design variations that could be considered for a hybrid commuter locomotive.
One would be based on a conventional six axle AC frt locomotive. The weight of the energy storage devices could be offset by reducing the thickness of top and bottom sheets of the frame, which is currently how the locomotives are ballasted. 35% adhesion would mean that the locomotive could manage 2 mph/sec acceleration on a trailing tonnage over 5X the locomotive weight, or roughly 14, 70 ton coaches. This would give EMU like performance. I could see this type of locomotive being well suited for the big Metra, LIRR, NJT and MN trains. It would be overkill for the smaller VRE, MARC, TriRail trains.
Another would be a conventional 4 axle DC locomotive as mentioned previously. A mild hybrid.
The third approach would be to use a smaller diesel engine and more energy storage. For example, if you want 4000 HP performance, but you spend 1/2 your time accelerating and the other half braking or stopped, you'd only need a 2000 HP diesel engine on the average. You could base the design of such a locomotive off the gen-set locomotives that are currently in vogue.
Why a locomotive? With an emu or dmu, or even a combination, you can divide all that heavy technical stuff over all those axles. More powered axles would be even better for a more balanced / even acceleration, or not?
greetings,
Marc Immeker
marcimmeker wrote: Why a locomotive? With an emu or dmu, or even a combination, you can divide all that heavy technical stuff over all those axles. More powered axles would be even better for a more balanced / even acceleration, or not?greetings,Marc Immeker
Cost. It's generally cheaper to have a few, big things than lots of small things. Transit acceleration only demands 2 or 3 mph/sec (< 0.1G) so adhesion > 10% that an EMU or DMU can provide is a waste.
Railway Man wrote: CSSHEGEWISCH wrote: This hybrid locomotive would have an incredible amount of gear crammed into its carbody and it sounds like a maintenance nightmare, not unlike D&H 1403 in the steam era. I'm wondering if the initial and ongoing expense of procuring and operating such a locomotive would be justified for saving a few minutes of schedule time plus the ancient issue of the fuel/maintenance trade-off.Agh! I do see your point and having spent some of my misspent youth turning wrenches on locomotives I'm preternaturally opposed to all things electronic and mechanical that break, but here's point another you might not have thought about: that few minutes of schedule time is extraordinarily valuable on a commuter railroad because it is trying to pack a tremendous amount of capacity into a tiny amount of time. A few seconds matters because it means the railroad can operate more trains on the same track in a given amount of time, a savings in both fixed plant and equipment. If the alternative to adding capacity is buying another main track at $5 million/mile (nice open country, no right-of-way costs), $25 million/ mile (city streets), or $100 million/mile (tunneling under city streets), the hybrid locomotive even with all of its extra gadgets and maintenance is awfully cheap. Capacity costs are collossal on a commuter railroad if you have to acquire privately owned right-of-way or if you have to tunnel -- L.A. Red Line cost a staggering $5.6 billion for 17.4 miles. For example, a client recently asked if we could find any way to cut travel times on a new commuter line. We looked at the property and the equipment for several days and decided it would be feasible to increase the unbalance on curves by 1" to get 5 more mph out of the curves, then ran the train performance model to look and see if this was meaningful after acceleration and deceleration times. Time saved was about 80 seconds each way and the client was thrilled because that meant the existing equipment could squeeze out one more round trip per rush hour, saving the client having to purchase another train set at $4 million, plus another operator and his relief, another space in the carbarn, heavier dispatching workload, more spare parts, yadda yadda. RWM
CSSHEGEWISCH wrote: This hybrid locomotive would have an incredible amount of gear crammed into its carbody and it sounds like a maintenance nightmare, not unlike D&H 1403 in the steam era. I'm wondering if the initial and ongoing expense of procuring and operating such a locomotive would be justified for saving a few minutes of schedule time plus the ancient issue of the fuel/maintenance trade-off.
Excuse me for my puzzlement here, but I can't determine how the time savings of 80 seconds per trip allows a set of equipment to get in one more round trip per rush hour unless we're talking light rail or rapid transit and very short distances between terminals or turnarounds.
Hmmm... based on what y'all are saying I think that we would be looking at a diesel electric taking power from storage batteries rather than a direct link from inverter to traction motors. Does those kinds of batteries currently exist? Could they provide the acceleration needed to pull a commuter train in a timely fashion?
The problem I see with multiple unit train sets is that they take away flexibility from the railroad, and they are a service nightmare. If one brake system on one car breaks (like the ACELA brakes did), the whole trainset goes out of service. My thinking is that designing the "perfect" passenger locomotive would provide the flexibility to replace that locomotive with another if it broke down, rather than deadline the whole train.
The problem, as Marc put it so well, is providing even traction effort over the length of the train itself, as well as evening out the weight of the train by so doing.
Here's another question to stir the pot... Would this perfect passenger locomotive have three axle trucks or two axle trucks? On the one hand, it's my understanding that three axle trucks provide more tractive effort... but on the other hand, three axle trucks don't work so well on a lot of track, and one would hope that we are designing (in our heads) a locomotive that can go anywhere and do anything... efficiently.
Keep up the good work, fellas, it's interesting conversation...
For commuter rail its hard to beat electrification using either electric locomotives or electric MU equipment. The demands of rapid acceleration and deceleration coupled with short frequent trips have "electric" stamped all over them. There is a good reason that every concentration of serious commuter rail in the world outside the United States is in electrified territory. I'm quite familiar with the electrified operations of the JR (Japanese Railways) and I'm not speaking only of the Shinkansen high speed trains. Every day in Tokyo and Osaka and several other major cities literally millions of people travel by commuter rail not only to and from work but everywhere else as well. It's how school children get to school.
In Tokyo each train consists of ten cars with three or four power cars per train. The rest are trailers. Power is from overhead catenary with pantographs. Train intervals during rush hour are five minutes or so and even during non-peak periods train invervals are seldom further apart than fifteen minutes. Schedules are exact, meaning to the minute (you can set your watch by them) and delays are very rare. A singe ten car commuter train in Tokyo will carry more than 1,000 people. That's mass transit. Getting around on the trains and subways in Tokyo is one of the real joys of visiting that city.
The Shinkansen is of course the ultimate way to travel long distance. For travel between Tokyo and Osaka it beats the airlines hands-down. Other intercity trains in Japan are not Shinkansen but are instead the original meter gauge using conventional electric locomotive hauled or electric mu equipment and all but the most infrequently used are electrified. The same high quality service, always on time.
With the exception of the shinkansen, there is no great technological breakthrough here, just good maintenance and good railroad practices. The newer commuter rail and subway equipment is using inverter driven AC traction but the vast majority is still conventional DC traction motors with conventional control systems. Again, well proven equipment with impeccable maintenance and inspection.
JR is blessed with a very dense population setting but probably more importantly, people in Japan appreciate the blessing of good public transportation. (Paying $4.50 per gallon for gas and having to drive on very congested and narrow roads with non-existent or very expensive parking probably has something to do with it, too.)
What would it take for the United States to get serious about electrification? I suppose that continued and growing oil shortages and ever more costly fuel will sooner or later force a re-evaluation of using the railroad as a practical means of public transportation. And I am convinced that the vast majority of this new and revitalized service will be electrified service.
Electrification has looked good on paper ever since B&O electrified the Baltimore tunnels in 1895. Unfortunately, it IS a massive expense and that is one of the things that shot down dozens of proposals and shut down most of the small electrifications after dieselization. Headways in suburban operations are also going to have to get a lot tighter before stringing catenary can be justified.
As far as the price of gasoline forcing people out of their cars, the most recent surge indicates that it isn't going to happen anytime soon.
oltmannd wrote:A hybrid commuter locomotive is a great idea! When you consider a GE locomotive takes 80 seconds to get to full load and more than a full minute just to get to 1/2 load, you're not exactly blasting away from the platform after each stop. Add in AC traction and you could start to get MU-like performance out of locomotive hauled trains
erikthered wrote:Here's another question to stir the pot... Would this perfect passenger locomotive have three axle trucks or two axle trucks? On the one hand, it's my understanding that three axle trucks provide more tractive effort
CSSHEGEWISCH wrote:Electrification has looked good on paper ever since B&O electrified the Baltimore tunnels in 1895. Unfortunately, it IS a massive expense
As far as the price of gasoline forcing people out of their cars, the most recent surge indicates that it isn't going to happen anytime soon
JT22CW wrote: oltmannd wrote:A hybrid commuter locomotive is a great idea! When you consider a GE locomotive takes 80 seconds to get to full load and more than a full minute just to get to 1/2 load, you're not exactly blasting away from the platform after each stop. Add in AC traction and you could start to get MU-like performance out of locomotive hauled trainsGot any room on board the engine frame? Any way to make it light enough to fit on B-B trucks? Can you guarantee low MDBF for new technology?Diesels like the PL42AC already use AC traction. The LIRR has a new problematic fleet that has AC traction, too. Probably the most successful new diesel with AC traction is the P32AC-DM that Amtrak and Metro-North use.The last GE used in commuter service before the Genesis was the U34CH, correct? However, that was a C-C dual-service locomotive (i.e. as built for the Erie Lackawanna) with a hefty starting TE of 90,000 lbs. erikthered wrote:Here's another question to stir the pot... Would this perfect passenger locomotive have three axle trucks or two axle trucks? On the one hand, it's my understanding that three axle trucks provide more tractive effortConsider which kind of "three-axle truck" you mean. A1A-A1A is like B-B, insofar as having two traction motors (and one unpowered axle in the middle); C-C has all axles powered, but the USA doesn't seem to be able (or willing) to readily balance this for high speed (overseas, electric C-C motors like Deutsche Bundesbahn's Class 103 operated at 125 mph). CSSHEGEWISCH wrote:Electrification has looked good on paper ever since B&O electrified the Baltimore tunnels in 1895. Unfortunately, it IS a massive expenseOnly seems to be a massive expense in the USA, doesn't it? The irony there is that most railroad electrfication technology was developed in the US.There are many degrees of electrification. Among the oldest is the low-voltage DC third-rail, which requires substations every two miles or so; high-voltage AC electrification (e.g. the 25kV 60Hz between New Haven CT and Boston MA) can have substations as far apart as 20 miles.As far as the price of gasoline forcing people out of their cars, the most recent surge indicates that it isn't going to happen anytime soonSince more rail is not being invested in, people will continue to be forced to use and abuse their cars. However, the dreaded falloff in consumer spending is the side-effect (to which the band-aid "economic stimulus package" has been fielded to stave off temporarily).
Trade fuel and DB for energy storage on a 4 axle. If real estate is a problem, there's always the GP40TC style frame. That would give you a "mild" hybrid.
OR
build an A1A-A1A six axle on a light frame (thin frame top and bottom cover plate - its' only as thick as it is for ballast). Energy storage devices becomes the ballast. AC traction so you only need 4 powered axles to get you 2mph/sec acceleration on a decent sized train. This would be a "wild" hybrid.
MTBF on new technology? What? We should never develop anything new because it isn't mature technology right out of the gate. That's oxymoronic.
Our community is FREE to join. To participate you must either login or register for an account.