Is there any need to doublehead electric multiple unit trains? If so how can it be done? i.e an AB AB consist of married pairs.
By double-head, you mean two train crews. The answer is NO. Not in regular service. MU equipment by definition is meant to pass power control and braking (and communications and door control and even lights on and off) between units just like two or more diesels “MU” with each other and are contrtolled from the cab of the lead locomotive. When cars are built as married pairs, like most Metro North and LIRR mu’s. thjey work equally welll AB-BA, AB-AB, BA-AB, and BA-BA, ON METRO NNORTH AND LIRR and most other systems. This is OK because there are controls at the “far” end of both the A and B cars. This is true of nearly all married pair arrangements.
ON the other hand if A cars have all the controls and B cars are blind trailers or blind motors without controls, then obviously an A must be at the front, and at the rear too if there aren’t loops or wyes at the terminals/
IN emergencies, incompatibe equipment, equjipment with differing control systems, may be coupled together and require a crew in both sets, but usually the head group will simply pull the rear one as trailers.
The Japanese railroad system (now split up and privatized) runs 3, 4, 7 and 10-car EMU trains, made up by mixing and matching 3-car and 4-car sets.
The sets consist of:
- 3 car. Control trailer, motor(no controls), motor with controls.
- 4 car. Control trailer, motor(no controls), trailer(no controls), motor with controls.
No matter the number of cars, and no matter that there is no passage between sets, the crew consisted of a d’raiba, who operated the controls in the lead car cab and a conductor, who rode the cab of the car showing markers and operated the doors. I presume that is still the case.
The only time an MU train would have two crews aboard is if the train split at some intermediate point, with sets going to two different destinations. This was rare when I lived in Japan and may have been eliminated since - by increasing passenger traffic which would justify two separate long trains.
Chuck
Methinks there may be a mis-speak in here somewhere.
Yes, electric locomotives can be lashed together into a single unit, and is done to increase the tractive force. But this is called “MU”, and the units are “MU’d”. This of course was impossible with steam locomotives which needed a crew in both units, and THIS is what double-heading means.
In the past when a helper was needed, it used to have a second crew in it, but now railroads use “distributed power” which can place units at the front, middle and/or end of the train all under the control of the locomotive engineer in the front of the train, and with no additional crews on board.
LIRR runs trains with D/M locomotives at each end of the consist with only one crewman.
ROAR
MU means multiple unit. It could mean control, as in several locomotives or powered cars controlled from one point. Two or more locomotives, either electric or diesel, are controlled usually from the front cab. Also, powered cars as in subway or, in the US, commuter trains with several cars with motors controlled from one cab or throttle, are referred to as MU. Most are electric, some, like the NJT River LIne, are diesel. Therefore your question:
There, in effect, is no such thing as double heading multiple unit trains…usually the total number of cars are tied to one controller. Some cars are single cars, others are motor car and a trailer semi permenantly coupled. SEPTA has some cars that can operate as a single car train; light rail vehicles the same. Usually most electric trains are in minimum two car trains and usually up to 12 cars, rarely if ever going beyond that number.
By the above definition, electric locomotives, therefore, are not MU’s.
But the term doubleheaded is another matter. Double heading technically means two independent locomotives operated by two seperate crews. That was the way things were done with steam and steam-diesel combinations. Modern day multiple unit controls, however, allows for two or more locomotive, diesel or electric (but usually all diesel or all electric, MLW did have diesel and electric combinations, but that is the only one I am sure of) controlled from one throttle or cab. Sometimes there are locomotives which cannot be mu’d with others, often usually foriegn road power; but that is becoming more and more rare, or locomotives which are just plain not so equipped. Two locomotives, diesel or electric, which cannot be mu’d would have to be double h
I appreciate your time and effort in your response. When I used the term doubleheading I simply meant more power. I was particularly referring to subway cars and commuter trains. I meant adding a double ended single electric múltiple unit car to an AB AB married pair. Will that add more power? Then you add another A unit like AB AB AAAIs there even any need to apply this concept to mu’s?
Thanks to all of you for your informative response.
I am not sure if you are confused or making things more complicated than they are. Multiple unit trains like subway and commuter trains, and some light rail vehicles, are coupled together and controlled from one point with the cars with motors propelling the train. SEPTA’s Arrow III cars, I think, can run as a single car in trainsets usually up to 12 cars. There are some sytems that have a motor and a trailer car semi permanently coupled (married pairs) with controls at opposet ends of the set and more than one set can be coupled together with control cabs at opposite ends. Introduction of a seperate locomotive to an MU set is done only when the trains set is inoperable. I don’t know of any cases where a locomotive can be tied into an MU trains control system…at least not here in the US.
I remember speaking with an ABB Vice President several years ago about a diesel unit providing electric power to an train set with motors on each car. If I remember he indicated that such and idea was being developed or was in practice someplace in Europe. He also added that because of the US standard of heavy loading guage…basically, the ability to withstand collisions and protect people and cargo…it, along with several other concepts, are not able to be practically applied to our railroads.
I feel you are confused by AB and A units and A1A units. A unit is a cab unit, B is a booster. YOu can have a combination of A and B units to make up a locomotive set, usually control
It depends on the A car. If the A car was the detached power car from a married pair, then it would add power to an AB AB A consist. However, 50 years ago the EMUs on the NYC and the LIRR were all power units, and were only expected to power themselves and the occasional baggage car at one end of the train (and in the case of the NYC, an RDC for service beyond 3rd rail). In other words, a car like that would not necessarily have added much to the hp per car ratio.