Push-Pull

[Anonymous]

QUOTE: Another thought: How many passenger terminals have a convenient and efficient infrastructure to either "run around" power or to "wye" a complete consist in a timely manner? --Hence, push-pull.

I guess that could be a reason why the local railways here havent ever really needed push-pull trains. At the main station here in Melbourne, all platforms that handle commuter trains that arent EMU types, are stub ended and arranged with a platform track, an escape or runaround track, followed by the next platform track. Cross overs connect both platform tracks to the runaround track at various points. Since all diesel commuter trains are either DMU's (RDC's) or powered by locos that can run in either direction its a simple matter of running around the trains and then recoupling.

Not sure if it can be found anywhere in the US but this particular station has fewer platforms, but each platform is longer with multiple crossovers to the middle track. In this way one platform can hold up to three seperate trains with the trains behind able to depart before the train in front by using a crossover and departing the station via the runaround track.

The only times in my experience of train travel where a push pull operation occurs here is during the evening peak when 2 complete trains a coupled together with the 2 conventional locomotives on either end both powering the train.

[CSSHEGEWISCH]

Grand Central Teminal is famous for its loop tracks on both levels and there is a loop track at Sunnyside Yard serving Penn Station. There is also a wye just south of Chicago Union Station where the BNSF main swings west and the former PRR main continues south.

However, most of the tracks at Grand Central are stub tracks and the loop at Sunnyside is used only for a handful of trains. The wye at Chicago Union Station is used to turn long-haul trains which then back into the station.

[Anonymous]

Tyson (and others, but you address ths issue in your post)--

In the US the commuter equipment uses head-end power (HEP), so running around is a costly and time-consuming problem, even if we had double ended locos. To do it, you need a crew of carmen/electricians on the ground, who have to (1) shut down the power to the train--no lights or A/C, (2) unplug the HEP cables, (3) uncouple and run around while the crew walks to the other end, (4) couple up to the other end, (5) re-plug the HEP cables and test, (6) power back up. I've seen the process take as long as 30 minutes or more on splitting of ATK trains. Aside from being prohibitively costly, generally you cannot afford the extra turnaround time necesary to do it. And with some run-throughs, like ATK's Surfliners that go through LAUPT (a stub-end terminal--so they head in and "back" out if set up for push-pull) you would leave the pax hot and in the dark during the whole process. Push-pull circumvents all that.

Your EMUs and DMUs basically accompli***he same thing, except that all the axles are powered.

Cheers, Mate!

[Anonymous]

Silly question why does it take a crew of carmen and electricians to accomplish a simple uncoupling move when the most that would be needed in the UK to do the same job is a single passenger shunter or the secondman where one exists. I suspect that the Unions are making work for themselves here!! ;-)

That said, its still at least one more wage packet and adds to the cost of loco haulage although the lack of flexibity with fixed formation trains must have a long term cost - HSTs with 7 passenger vehicles replaced trains of up to 14 in the summer on North East - South West services and the overcrowding was horrendous - its not so bad now as people don't travel by train.

As to Mr Bransons 4 car Voyagers (Vibrators!) replacing the already attenuated 7 coach formations well - I need say no more. It said nothing about passenger comfort in the low priced tender for the stock!!

[Anonymous]

45144--

It's the good ol' USA RRs. Logic is futile[banghead]

[Anonymous]

drephpe,

All our diesel commuter trains here use HEP as well. The rail company responsible for the commuter and regional passenger trains here maintains a few power cars and i occaisionally see them on certain trains but i'm not sure why they have them when the have HEP available. I suspect maybe its when the train becomes too long for the locomotive to provide adequate power. Or prehaps when special cars are attached such as a diner that may consume more power. Im not sure.

[TH&B]

It is true HEP is an enormas amount of cables, I dont know why, it's more than the MU cables to couple up locomotive units. I don't think it is a union thing, but maybe it is.

[Anonymous]

Tyson--I can answer a couple of items you brought up. First, HEP cars are useful if you have to press a locomotive into service that does not have a generator (most of these now are, of course, freight units in the US and I suspect Peter--M636C--or you can tell us if such is the case also in Oz). Second, one of the drawbacks of HEP is that the number of active pax cars in the consist is limited by the current-carrying capacity of the cables and plugs between the cars (which gets mimicked by the through cables on the cars themselves). Obviously, the generator capacity is an issue, but these are usually overdesigned for safety's sake. The cable between the HEP source and the first car sets the limit. If the train's pax consist exceeds the rating of the cables (usually given by the RR as a maximum number of cars rather than the equivalent electrical values of KVA or Amperes), then to operate the electrical systems in all the cars you have to separate the consist's electrical system in the middle of the train (to balance the load) and put either another locomotive or an HEP car on the rear end . And, as you deduced correctly, a heavy load like an all-electric diner will reduce the number of cars you can power from one end of the train. Under those conditions, you cannot connect the two halves of the train together, even if you could synchronize the two HEP generators (an absolute necessity if there is more than one AC generator), because loss of one HEP unit would drastically overload the other, tripping it out and likely damaging the electrical systems in the cars closest to it, where the greatest amount of current flows. Think of it like a tree where the generator is the root system. The trunk has to be the biggest part because nutrients have to flow through it to the entire tree, and then the branches get progressively smaller and smaller., the farther away from the trunk you get.

As to manpower, it's a work rules issue, like it or not, efficient or inefficient. 45144 makes an excellent point as to efficiencies. That was my point as well. I have literally seen it take from 1/2 hr to 1 hr and a small army to do a simple break, switch, reconnect move on an ATK consist, where the pax are stranded on the train with no power, A/C or lights. This was SOP on 21/22 at SAS for years, with the thru cars. It ranks along with the operating crews filing for and getting an extra full day's pay for a 5 minute setout of PV at an intermediate station where there is no switch crew. Even my highly valued and respected late old friend Charlie Luna of UTU fame couldn't explain the base economics of that to me. His answer, quite correctly, was that it all came down to what you could negotiate. As I said, logic is futile.

Now, that said, in all fairness, it can occasionally take a couple of people to get a balky HEP cable unplugged. These things are big and heavy (see the load discussion above as to why), they get banged around and exposed to rather extreme climatic conditions on occasion, and occasionally they fight back. That's another good reason for operating push-pull where short turns -or work rules, for that matter - are an issue. There are very few movements quicker than the operator getting off and changing ends. Even 45144's expedient and optimized switching move can't beat the time. Plus you can do it anywhere. You don't have to spend the money for a runaround track. This is particularly important in the US, where most of the passenger-related physical plant, that allowed such things even as short as 30-40 years ago, is history and would have to be rebuilt at 10-20 times the cost of what had been there and got torn out. A good example of this in the TX end of the world is Dallas Union Station, which had 10 active tracks, plus express tracks. The City Fathers tore out all but 3 and replaced them with a parking lot for the buses that never came. Now with the LRT lines and TRE, guess what are getting put back in at substantial cost?

I often wonder if we're doing the same thing to too much of the freight plant. Admittedly there are a lot of branches needing pruning, but I submit that it's a simple medical fact that a simple rhinoplasty is very different from lopping one's nose off to spite one's face-even though both can be correctly and literally classified as nose jobs.

People generally tend to be cursed with a lack of foresight, and those who have it are generally kicked off the island.

Off the soap box.[soapbox]

[TH&B]

OK that all makes sense the way you explaned it. Now my observation is that in Continental Europe push pull is very commun but they do not use such a heavy set of cables between cars. Just one not so heavy cable with 13 leads. I wonder how they can get away with so little?

ps; ever see someone pull the pin on a passenger consist without shutting the HEP off and disconecting the cables?..... ZAP!!!, burnt a big gash at the end of the coaches and the freight brakeman who was trying to show the passenger conducter how to deal with a bad order car on route (set it out that is) and he got seriously injured !

[Anonymous]

Oh, yeah 440cuin--great point!! Try that and you get a REAL fireworks show!! You (generic-not personal) never EVER break a BIG load like a train while it's still energized, unless you want to send equipment to the backshop and you and your compadres to the hospital, or worse[angel]. Unfortunately, there's no current way (bad pun, sorry-NOT![banghead]) to sectionalize a train's electrical system to remove cars without shutting the entire train down. The equipment could be added that would allow the cars between the break and the HEP generator to remain energized, but at substantial cost per car.[:(]

[CSSHEGEWISCH]

At Chicago Union Station, it generally takes about five minutes to switch over a Metra suburban consist from station stand-by power to HEP from the locomotive. Passengers already aboard the train sit in the dark during this period. Based on my observations, it takes one carman to shut off the station power, remove the cable, plug in the cable to complete the HEP circuit, and advise the train's conductor to signal the engineer to start up the HEP. As mentioned above, the cables are heavy and not too easy to plug in or remove.

In a similar vein, I remember seeing two carmen stationed at South Amboy, NJ in 1982 to change from electric (GG1) to diesel (2 E8A's) on NJ Transit trains. The carmen pulled the coupler pins, disconnected the air, steam and signal lines from the electric and then made the same connections to the diesel.

[cbq9911a]

Another push-pull operation is at the Illinois Railway Museum in Union, Illinois.

All of the steam and diesel trains run push-pull, with a conductor controling the train brakes from the rear of the train using a tailhose. They've also got a set of ex C&NW bilevels, which are run with a cab car.

[CSSHEGEWISCH]

Push-pulls definitely facilitated a detour move on Metra on June 8. Due to the derailment of the "Hoosier State" at 43rd Street, Metra Southwest Service trains detoured over BNSF and CSX. Due to the location of the connecting track between BNSF and CSX near Western Avenue and between CSX and BRC at Forest Hill, a second engine crew was used to operate over CSX from the cab of the last coach with the regular engine crew riding in the F40PH which was then trailing.