Trains: Diesel engines but electric motors

daymobrew

When I lived near San Francisco a friend told me that the local train service trains had diesel engines that charged batteries and an electric motor drove the wheels.
I was told that the diesel engine is tuned to be very efficient/effective. We know that electric motors have acceleration advantages over diesel motors.

I emailed CalTrain last week but they have not replied confirming the setup. The fleet info page mentions 'generator' for most of their locomotives.

Does such a system sound realistic our was I misinformed?
If so, would it be an effective method of providing the benefits of electric trains without the need for the overhead wiring infrastructure?
I realise that a diesel/electric loco would not be able to carry passengers, unlike the current DMU carriages.

mikedragon32

http://travel.howstuffworks.com/diesel-locomotive.htm

markf909

I used to commute regularly on that service, when I used it a few years back it was all standard GM locomotives, dont know the type.
Subsequent to me leaving the Bay Area, Caltrain invested in what is known as the "Baby Bullet" service, a limited express from SF to San Jose, I wonder are these the kind of locomotives you are refering to?

Ham'nd'egger

Not saying anything yay or nay but I am sure that it would be possible, if a bit of a waste of space within the power units to hold engine, generator unit and battery units. Certainly, no mention of such a unit on EMD's website.

dmeehan

i loved the way the caltrain conductors announced each station, almost singing it :-)

"Our next station stop is Bbbbbrrrrrrrrroadwayyyyyyyyy" (Broadway, that is)

BendiBus

Not sure about the batteries but diesel locos are actually diesel-electric.

The diesel engine runs a generator. The generator provides electricity to traction motors which turn the axles.

daymobrew

dmeehan wrote:

"Our next station stop is Bbbbbrrrrrrrrroadwayyyyyyyyy" (Broadway, that is)

Or make divorce comments about the Bay Meadows stop (it's a former horse track).

From reading the responses it sounds like I was somewhat mistaken and that the Caltrain locos are probably diesel/electric.
So, would these be good for DART-like services on the Maynooth/Kildare/Dundalk commuter lines? Would they be cheaper than overhead electric infrastructure? What are the disadvantages?

Occidental

daymobrew wrote:

So, would these be good for DART-like services on the Maynooth/Kildare/Dundalk commuter lines? Would they be cheaper than overhead electric infrastructure? What are the disadvantages?

You can't run them underground between Heuston and Spencer Dock.

BrianD

daymobrew wrote:

When I lived near San Francisco a friend told me that the local train service trains had diesel engines that charged batteries and an electric motor drove the wheels.
I was told that the diesel engine is tuned to be very efficient/effective. We know that electric motors have acceleration advantages over diesel motors.

I emailed CalTrain last week but they have not replied confirming the setup. The fleet info page mentions 'generator' for most of their locomotives.

Does such a system sound realistic our was I misinformed?
If so, would it be an effective method of providing the benefits of electric trains without the need for the overhead wiring infrastructure?
I realise that a diesel/electric loco would not be able to carry passengers, unlike the current DMU carriages.

Is this not the way that all diesel locomotives work including the Irish Rail fleet? Diesel engines that power electric traction.

Boston has a cheap mans underground line (Martin Cullen would approve) on the Silver (Airport) Line. Electric-Diesel buses operate the line. Underground they work on electric engines powered by overhead cables. Once overground the diesel engine fires up and the bus drives down the highway to the airport.

Mec-a-nic

markf909 wrote:

Subsequent to me leaving the Bay Area, Caltrain invested in what is known as the "Baby Bullet" service, a limited express from SF to San Jose, I wonder are these the kind of locomotives you are refering to?

CalTrain upgraded the tracks (& signaling?) to allow more trains per hour, and the 'Baby Bullet' service is just the regular locos except they only stop at main suburbs.
It cuts 30mins off the normal 90min SanJose-SanFran trip.
(Less time to surf the web...) :rolleyes:

Ham'nd'egger

Occidental wrote:

You can't run them underground between Heuston and Spencer Dock.

DART's are capable of running underground, they were specified to be capable of this when ordered way back when. All it would take is for either the tunnel to have overhead clearance for a powerline and pantograph or for DART's to be fitted with a third rail underneath to pick up electricity with.

The main advantage of electric power is quick acceration and deceleration, low maintainance, low pollution levels and quick turnaround. Against it is the capital cost of the electrical systems and the relative inflexibility of it, which is why it is more common on suburban systems and highly used mainlines.

Diesel Electric is the norm for locos as it lightens axle loads on engines compared with pure diesel locos, as well as vastly better acceleration rates and general economy reasons. Most railcars tend to be diesel engined alone as it allows for smaller flatter bus-like engines that can be run in tandem with other car sets if and when required.

markf909

Mec-a-nic wrote:

CalTrain upgraded the tracks (& signaling?) to allow more trains per hour, and the 'Baby Bullet' service is just the regular locos except they only stop at main suburbs.
It cuts 30mins off the normal 90min SanJose-SanFran trip.
(Less time to surf the web...) :rolleyes:

Well they got these loco's in, which are different than the ones I used to commute on back in the day.

Red Alert

All of IE's current locos (with the exception of a few low-speed shunters and branch line locos in the 1970's) right from the now-scrapped ones to the 201's are Diesel-Electric drive. Mechanical gearboxes become hard to build once you get up to very high power levels. Depending on the wiring setup you can get a lot more 'gears' (or ratios) from Diesel-Electric drive.

You can actually get so-called DEMU's (Diesel Electric Multiple Units) which are allegedly a lot more pleasant than DMU's. However they tend to run in Power Car / Trailer Car formations.

Using the engine/battery/motor combination would lead to losses - unless the train had some other reason (like a short stretch underground) it would be uneconomical to do this.

bk

I must say the Caltrain service is excellent. Very fast, smooth, comfortable and relatively cheap. Lovely clean double decker carriages.

It shocked me that during rush hour they were still nearly empty!! In Dublin you would be packed in like sardines, just goes to show how much they love their cars over there.