Electro-Diesel motive power for HSR development

(This thread is started as a continuation of the discussion of Gas Turbine locomotives for HSR operations.)

Electro-Diesel motive power has been used in some countries since the 1940’s; principally to allow for uninterrupted operations of electric based services (Overhead, 3rd rail, locomotive or EMU) beyond the reach of the electrical supply. This technology is currently being revisited by Britain’s Network rail as a method of improving service in newly electrified regions.

In the modern mode, HSR sets are primarily distributed traction EMU’s with a single pantograph and transformer. Diesels can be used to provide traction current when:

1. the set operates beyond the overhead, allowing for an uninterrupted service at ends and on branches of an electrified core region. Studies have shown that passengers do not like changing trains or the perception that that they are not being offered a consistent, best quality through service.

2. during construction, when electrical supply may be intermittent. This allows newer cars to provide an early, improved service and generates additional traffic and revenue.
3. during an emergency, sets are not stranded due to the lack of motive power. Currently, such planning is on all operators mind.


The discussion is oriented around the best method for providing this diesel power (head-end, dual-end or in the middle), the economic aspects of a mixed propulsion system (what to do with the diesels when electrification is 100% for example?) and the power to weight ratio required to provide a reasonable service in the “off wire” mode.

For this to work in hsr , ( i believe most of the e.g in england are probably 100mph max ), you would need to look at the weight problem of 2 sets of power supply . Its probably doable , i would imagine both end cars need to have a diesel engine or transformer or both . traction motors would need to be distributed amongst all cars .
you would need a high speed diesel , perhaps several based on a truck engine ala genset switchers . I would imagine they would produce high frequency high voltage a.c from the attached generator , reticfy then invert it to usuable traction power . on the electric side i would imagine they would do the same thing . instead of a heavy 60 hz transformer , they could also reticfy , invert , and use a much lighter high frequency transformer . ideally both the diesel and cantenary supples could use the same rectifier , inverter , transformer .
ideally all track near stations would be electrified , to use cantenary power for accerlating / regen braking .if this was done perhaps the deisel engine could be smaller , been sized to maintain track speed , rahter than to accllerate the train etc .
Wouldnt be cheap though , i would think the extra cost would approach the cost of cantenary for short to meduim distance hsr .

The weight is obviously the crux of the matter. Diesels appear to be roughly twice as heavy as GTs for example, for a given output, and straight electrics with no prime movers (or fuel tanks) are obviously at a great advantage.
does a much heavier train set built around several heavy engines bump up the weight and cost of the track and roadbed? I suppose it does, but I have no basis for estimating.
wouldnt it be better, in the planning stages to improve system reliability, than to over build and compromise with a "hybrid" in order to accept the inevitability of forced outages ?

as an analogy, we ride in elevators in tall buildings, believing that if the power goes out we might be stranded in the elevator.
To reduce that risk, building designers dont buy elevator cars with emergency engines built into in them and shafts designed to accomodate that so they can motor themselves to the ground floor, what the do nowadays is provide the elevator control system with highly reliable back up power supplies.

From what I've read, the "damage to the tracks" argument is something like this:

Heavy, Acela-type trains do a lot more damage to pristine, HSR-grade tracks used exclusively for passenger rail than comparable lightweight European/Asian trains. HOWEVER...

I forgot who told me or where I read it (I think it was somewhere on this site), but apparently the added wear & tear caused by Acela-type trains is NOTHING compared to the maintenance cost of trying to keep a pair of tracks actively used by dozens of mile-long coal/limestone trains per day suitably aligned and maintained for 125mph passenger trains as well.

Put another way, heavy Acela-type trains increase the wear and tear on tracks, but heavy freight trains utterly destroy them.

I used to be a really big fan of 110/125mph ISR for Florida, particularly along CSX between WPB and Auburndale. Then, someone (on this site, I think) pointed out to me that 98% of the freight CSX runs along those tracks consists of mile-long limestone trains from quarries in West Dade -- trains that are so heavy and destructive, FEC won't allow them anywhere NEAR its tracks. Basically, he said that heavy freight trains would do so much damage to 125mph passenger tracks, it would actually be cheaper in the medium (~25-year) run to triple-track the corridor and keep the limestone trains away from the other two tracks. Or, if double-tracked, keep the limestone trains far away from the "passenger" track, and just write off the other track as a long siding that can be used by passenger trains at low speed to allow passing.

“track damage” is getting away from the subject.

All rail services cause track wear and locomotives with nose hung motors are some of the worst culprits for cracks and heat tempering. I don’t know of any evidence that diesel traction is harder on the rails than electric or that Gas Turbines are lighter than diesels in this application. Certainly distributed electrical traction with many powered axles provides better acceleration and less track wear than the Acela style approach.

My understanding from reading the FRA definitions is that HSR implies dedicated and differently (higher standard) maintained track. Not to say that HSTs would not run “HSR emerging” track, but they would be subject to restrictions and obviously need to meet crash standards for mixed traffic operations. Pure passenger HSR such as the DesertXpress, would be exempt.

Does rail weight have anything to do with it? i.e. would going with a 286K or even 312K standard on high-speed lines shared with freight mitigate the wear-and-tear problem significantly enough to allow compromises on trainset weight? The less overdesign required to make them lighter the easier it's going to be to choose from a more diverse range of equipment for HSR purchase needs.

“Does rail weight have anything to do with it?”

It is irrelevant to this discussion.

My early career was in rail testing and if the answer was as simple as “fright trains bad”, “passenger trains good”, I would have quickly been reduced to minimum wage.
There are lots of factors effecting rail performance and traffic weight is one of them but to state that diesels cause more damage that electrics is a vast simplification. Most locomotives, regardless of power type or range weigh approximately the same. IMHO, it is the design of traction motor linkage that is the critical factor.

Back to the original topic of this thread and F-line’s comments on the availability of commercial equipment for HSR in general:

While the is USA is having this healthy discussion on the introduction of high speed rail services, most other countries are contemplating the “next generation” (the phrase used by Britain’s Network Rail chairman) of equipment and how to best improve its rail operations. There is much wisdom to be derived from the mistakes of those first European systems and the US has the opportunity to “jump” to generation two by looking at the offerings of the major players in the international arena as they gear up to meet European demand.

As an interim step, the US could consider purchase (probably be paid to take it away) of obsolete HST stock (220km/h) from Europe as a learning exercise in HSR operations

^^^ The problem with European stock (obsolete or otherwise) is that under current federal laws, it can't share tracks at all with freight trains. In Europe, it's understood that you don't literally want freight and passenger traffic sharing the same track, but with proper electronic control systems, you can live with a policy that keeps them apart, and allow them to occasionally tiptoe around each other to get into established city train stations.

In America, that's not good enough. If the trains aren't Acela-type "tanks on wheels", they literally can't run on rails with any possibility of ever encountering a freight train, no matter how remote. For example, in Europe, especially Germany, it would be 100% legal to build 4 tracks where the two inner tracks are for passenger trains (not necessary 180mph high-speed, but comfortably in the 200-250km/hour range), and the two outer tracks are for freight trains. The inner pair might have periodic flyovers where there are freight yards to allow movement between the sides during the day, but out in the middle of the countryside where there might be a spur that gets used once a week, they can just build a switch to allow freight trains on one side to get to the other when no passenger trains are approaching. In America, that would be utterly and completely illegal.

It's crazy, because we have no qualms about allowing a mile-long freight train to cross paths with a subcompact car with little more than a pair of flashing red lights and a pivoting wood stick, but the idea of allowing freight trains to cross the path of a passenger train -- even with electronic controls to cut power to the passenger train so it can't physically RUN within a mile of the crossing point, and to prevent the switch from actuating if there's a passenger train anywhere near the block -- is absolutely taboo.

This, more than anything, is the main reason why any passenger rail project in America (high-speed or otherwise) ends up with a price tag that makes the Apollo Space Program look cheap. There's literally no cost-benefit sanity check, and any HSR line that used European stock would have to be 100% separate and Shinkansen-like to legally exist in America.

The new Hitachi bi-mode trains which will replace some of the long serving diesel High Speed Trains in the UK will be 5 coach units with a pantograph at one end and diesel power units under the 3 centre carriages for operation beyond the limits of the overhead lines.

As to freight trains running on the same tracks as high speed passenger trains, that's certainly the case on the UK East Coast Mainline where 125mph expresses share tracks with freight. High Speed 1 is also planning to operate freight trains at night when the 186mph Eurostars are not running.

"diesel power units under the 3 centre carriages"

Interesting. Can you provide a reference to that design? I had not associated the Agility trains with under car diesels.

Chafford1 wrote:The new Hitachi bi-mode trains which will replace some of the long serving diesel High Speed Trains in the UK will be 5 coach units with a pantograph at one end and diesel power units under the 3 centre carriages for operation beyond the limits of the overhead lines.

As to freight trains running on the same tracks as high speed passenger trains, that's certainly the case on the UK East Coast Mainline where 125mph expresses share tracks with freight. High Speed 1 is also planning to operate freight trains at night when the 186mph Eurostars are not running.

The important thing about freight on the HS1 is that it will bring UIC gauge freight trains to London, probably to a depot in Dagenham.

"diesel power units under the 3 centre carriages "

I found this reference in another thread (http://www.railroad.net/forums/viewtopi ... 11#p637750) on this forum:

http://www.agilitytrains.com/assets/pdf ... ed-1_5.pdf

The diagrams at the bottom of the second page clearly show that the Hitachi/Agility proposed replacements for the IC125 program are conventional
consists with power cars and distributed electric traction under a proportion of the revenue cars. No under floor diesel units.

I find some aspects curious in this design.

1.The driving/cab ends to not appear to have traction motors.
2. There is a 25kv power bus on all the consist layouts even though this is in theory, not necessary.
3. It is not clear from the diagrams if the electric version of the cab car is designed for revenue service or is simply an empty power car.
The flashy video on the Agility web site seems to show passenger windows in the cab cars.

In terms of this discussion, the 5 & 10 car Bi-mode diagrams shown would be examples of electro-diesels capable of 140mph.

paulmartinsmith wrote:"diesel power units under the 3 centre carriages "

I found this reference in another thread (http://www.railroad.net/forums/viewtopi ... 11#p637750) on this forum:

http://www.agilitytrains.com/assets/pdf ... ed-1_5.pdf

The diagrams at the bottom of the second page clearly show that the Hitachi/Agility proposed replacements for the IC125 program are conventional
consists with power cars and distributed electric traction under a proportion of the revenue cars. No under floor diesel units.

I find some aspects curious in this design.

1.The driving/cab ends to not appear to have traction motors.
2. There is a 25kv power bus on all the consist layouts even though this is in theory, not necessary.
3. It is not clear from the diagrams if the electric version of the cab car is designed for revenue service or is simply an empty power car.
The flashy video on the Agility web site seems to show passenger windows in the cab cars.

In terms of this discussion, the 5 & 10 car Bi-mode diagrams shown would be examples of electro-diesels capable of 140mph.

A lot of water has passed under the bridge since those documents were released. The final versions will now have undercarriage diesel engines.

I'll pass on more details as soon as I have them.