Push-Pull

[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.

[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]

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.

[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.[:(]

[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]

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]

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]

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.

[Anonymous]

45144--

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

[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]

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!

[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]

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.

[daveklepper]

In the case of Amtrak, motors were not retained, for the simple reason that the control wiring through the cars is not designed to handle traction power, only control circuits, so any motors on the control cab wouldn't have any way of drawing power from the diesel at the rear. Dave

[rrock]

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.

[Anonymous]

And more push-pull......

1. LIRR basically started the converted loco cab unit approach when it demotored and de-engined a bunch of FA's and stuck them on the rear of their diesel-hauled trains.

2. Texas Utilities' (now TXU Energy, for those of you in deregulated states) lignite mining subsidiary runs several dedicated intermediate-haul electric and diesel railways at power plants where the unit trains operate push-pull with Ortner rapid discharge hoppers and NO loop tracks (just point-to-point), using a cab car on the rear and radio control rather than MU cables down the train. They've been doing it successfully for over 20 years with little or no significant problems, including radio control from the single (!) operating crewman on the ground and from the tipple controller at loading. Of course, their union is IBEW, and I guess they just didn't know that everybody knows it couldn't be done.

3. The GRR/GREX dump train (these get sold and/or leased out all over the country) can also be set up for push-pull operation.

[TH&B]

Yes they are depowered. The only "cab cars" that are powered I've seen are the British Gatwick Express push pull trains, there the cab car is powered.

[daveklepper]

Amtraks cab cars are completely depowered. I think all are, without motors. Otherwise you would need high current heavy cables and very cumbersome jumpers, like between diesel switcher "cows" and their "calves", not jsut the normal weight signal and communication cables. Dave

[CSSHEGEWISCH]

Push-Pulls on VRE are no different than long-standing operations in the Chicago area, including the multiplicity of grade crossings, except on the IC main line. On Chicago gallery bi-levels, the engineer's control cab is on the upper level, which still doesn't provide a whole lot of protection.

[TH&B]

Refering to the picture of the p-p freight, didn't WC run short p-p freights with those air dump cars with a cab at one end (radio controled)?

MU trains dont always have better traction then p-p loco hauled, it does very much depend on types and designs. mu's have lighter axle loads and some mu's have one in 3 or 4 axles powered so this causes wheel slip easiy, other types will have 1 in 2 or 1 in 1.5 axles powered or even ALL axles powered, these types will have better traction then loco hauled.

In Europe and England I've been on mu's that were delayed cosiderably because of wheel slip, I've seen helper (or banking) engines on mu's due to grade and rain. The only diesel electric hauled passenger train I've ever been on that had bad wheel slip was a GP-9 with 10 six axle heavy weight coaches !

[FJ and G]

Push-pull on VRE is an extremely dangerous way to do it, with the many grade crossings and the lack of protection for the engineer during the push mode.

[CSSHEGEWISCH]

As a rule, the traction motors have also been removed from the F40PH's that were converted to control cabs. Leaving the traction motors in place would only contribute dead weight as there would be no practicable way of supplying electric power to them through the train (the cables would have to be quite heavy) and the additional tractive effort would only be useful at low speeds, similar to yard and hump slugs.

[Anonymous]

QUOTE: However, note that Amtrak's "cab cars" are often ex FP-40's that retain the safety feature of a cab-body diesel locomotive on the point.

I wasnt aware they did that. All i knew of push-pull was with one "locomotive looking" locomotive at one end and then a string of passenger cars, the last one having some driving controls and such in it. This is just based on what i have seen of the Amtrak California system. So some push-pull trains have what appears to be 2 locomotives(one at either end of the train) except one of those locomotives has actually had its prime mover, generators, and what-have-you taken out? So basically a shell on trucks with only the driving controls in the cab? I think if thats the case then seeing trains that have an EMD F unit on either end would probably look quite good. Plus i'm sure the carbody could withstand a collision much better than the cars could.

When they use these ex-diesels do the trucks retain their traction motors so they can be powered by the locomotive at the other end of the train?

[Anonymous]

As to push pull accidents there was a lot of discussion around this in the UK when the Glasgow Edinburgh PP hit a cow on the line at Polmont. For a real indication of the weight of a loco still pushing the horrific ICE (Loco at both ends) smash in Germany is worth studying. The coaches did indeed get concertinered as the leading loco hit and collapsed a bridge.

It just doesn't bear thinking about.

That said the UK runs 10 of 1000 of miles push pull quite happily

[Hugh Jampton]

QUOTE: Originally posted by athelney

Push -Pull technology was used widely in UK on the west coast mainline betwee London -Glasgow. Loco was on the front pulling to Scotland and reverse coming back . This is now being done away with,now Virgin have got their Pendolino tilting train car sets. I believe some push- pulls still operate but are going the way of the dodo !!

Plenty of push-pull sets are still in operation, and have no intention of going away. The East Coast Mainline from London to Edinburgh via Doncaster, and the East Anglia network in Essex, Suffolk and Norfolk both rely heavily on p-p operation.

There is even an example of push-pull operation in freight operations, albeit on a closed system with relatively short trains. Rheinbraun operate a number of open cast lignite mines in Germany and move both the overburden and lignite on a specially designed rail system that uses push-pull operations. There is a picture of one of their trains and a short description at:
http://mercurio.iet.unipi.it/pix/picmonth/2001-11.html

[daveklepper]

Two other matters: Yes, USA railroads did buy diesels with cabs in both directions. Remember that the first freight diesels were four-unit A-B-B-A drawbar coupled Electro Motive FT locomotives, each unit 1350 HP, for a total of 5400 HP, about equal to a large Mallet, possibly somewhere between a Challenger and a Big Boy, and breaking up the consists and providing couplers and jumper cables and sockets came later. Then came the transition to road-switchers, which have little difficulty in running in either direction, and today you will see usually cowel units, the modern freight power, in back-to-back configuration. So why buy the extra control equipment and cab amenities? Then, with the passenger equipment, originally we had articulated one-directional trains (Zephyr, Green Diamond, City pof Denver), except for the New Haven (NYNH&H) Comet, which was bi-directional, like today's Acela trains (and of course the North Shore Electroliners). With a locomotive at the front and a round-end or beaver tale or whatever observation car at the rear, the whole train has to be turned, and EMD E-units looked great matching their trains, and a cab at the back would of spoiled it a bit. (OK, I know, the GG1 also looked great and it had two cabs, and so did the other electrics!) Now, with push-pull operation, the second cab isn't of much use.

Israel Railways has a whole slew of Alstom double-end streamline cab unit diesel electcrics (with EMD diesel engines). They are used on Alstom push-pull comfortable single-level trains that have a cab-hotel power car on the other end, and with AdTranz double-level commuter trains, again with a cab-hotel-power car on the other end, and with a string of 20 years old and older Yugoslavian (bought new 1967), ex-British Mark II, ex-TEE 1960 stainless, and other trail cars, and then an old coach bringing up the rear converted to a head-end power car without cab and not push-pull. Occasionally, an old EMD road-switcher will substitute for the Alstom on the last variety of trains. And there is also quite a fleet of Danish Flexiliners IC-3 articulated diesel mu's, like Amtrak tested Chicago -Milwaukee and LA - Las Vegas. These are four-truck three-section cars with two underfloor diesels, and a unique swingout front end that permits coupling cars while providing both a wide weather protected passegeway between cars and a central engineer console and wide front window for the front and rear cars.
i've seen as many as four in a single train, and also just one by itself.

[daveklepper]

The safety factor is much the same for a push-pull as for mu's, because the weight of the train behind the first car doesn't increase hugely when the last car is a locomotive instead of an mu car, and any accident invariably has the engineer shutting off power and applying brakes. However, note that Amtrak's "cab cars" are often ex FP-40's that retain the safety feature of a cab-body diesel locomotive on the point. After my earlier response, it was pointed out to me that SEPTA has returned to buying mu electric cars, possibly because they like the improved acceleration that gives a higher top overall schedule speed on multi-stop commuter runs. Metro North has stayed with electric mu's for electrified lines and diesel and dual-mode push-pulls for everything else, after their last Budd RDC's were retired. Generally, the diesel runs have stops further apart with more express running. Metro North did try the Budd self-propelled vehicle "SPV", nicknamed the seldom propelled vehicle because of its problems, and it was not a success, so even the short consist shuttle runs today are run push pull. Kind of waste to see a 3000+ HP diesel with only two coaches. Of course, this is the kind of market the new Colorado Railcar is supposed to address, and tests have shown it delivers great fuel economy, and there is a Canadian firm that seems to be doing a good job in remanufacturing old Budd RDC's with Cummings? or Caterpillar? diesels. By dual-mode diesels I mean those equipped with third rail shoes and the ability to run a straight dc-power electrics to run a through service to Grand Central Terminal. Amtrak and the Long Island Rail Road have similar dual-power diesels for Penn Station service. The Long Island seems to be going largely push-pull also. It had a fleet of depowered "power cars", ex EMD F-units and ex-Alco FA's, where the or a diesel served only to provide "hotel power" (lights, heat, air-conditioning), and a new road-switcher pushes and pulls on the other end. I think they are going now with pretty much the same equipment Metro North has, in other words coach-cab-cars, and have been retiring their "power cars." Their new passenger road diesels, like Metro North's provide "hotel power".

[Anonymous]

hmm thanx guys

Down here we dont have any push-pull trains. We only have conventional locomotive hauled, DMU, and EMU sets. However here all the locomotives used on passenger trains can run in both directions, ie with a cab at either end. I dont know why the Victorian Railways did it different but ever since we had our first mainline passenger diesels they were like that. The '"B" class was the first and it was basically a shorter version of the EMD E units but with a streamlined cab at each end. Why didnt roads in America think too much of locos with dual cabs? surely there couldn't have been that much of a difference in price? or maintenice? so is was reasonably quick and simple to run around the train at the destination.

Back to push-pull, i would think they would not be particularly safe in an accident? For example in the event of a head on collision with something there would still be a 100 tonne locomotive pushing from the rear. Would this not cause a severe concertina effect when the front car has hit something? unlike the locomotive the cars are much lighter and more likely to crumple upon impact. Am i right in assuming this? Has there ever been a collision involving the driving car of a push-pull train?

This photo shows an EMU that hit a locomotive at a major train station here. Fortunately there was no one on board the EMU! Take a look at the truck under the EMU to get a better idea of how long the car was before it hit the locomotive.

http://www.vicsig.net/photo.php?filename=20030204-sss-394m-n463-3.jpg

[daveklepper]

MU's, even with some trailer cars added (with control wiring through, of course) is best for performance, because there is more wieght on drivers, less tendency to slip in adverse weather, and generally better braking and acceleration. This is true for both electric mu's and diesel . But the down side in maintenance. Any "power" whether mu car or locomotive, has to be inspected more frequently and obviously is more expensive to maintain than a trailer or regular coach. That is why SEPTA (the Phily area commuter a dn transit authority) and New Jersey Transit have generally bought coaches for push-pull and locomotives to match instead of mu cars in recent years. Also, first cost is obviously much less. An mu car is simply a coach that is also a low-horsepower locomotive and can cost 150% - 200% the cost of a regular coach. So push-pull gets the operational simplicity of the mu train at reduced costs. Yes, there is more wear on draft gear and couplers and yes there is more wear on the outside rails of curves. Just like with pusher locomotives on long freight trains on heavy grades. But not so much as to begin to eat up the savings. Dave