Push-Pull

[Anonymous]

Hey,

I was just curious about the use of push-pull trains nowdays. I dont know about everyone else but to me a train thats effectively running backwards with the locomotive pushing the cars just seems unnatural. I always think that it is unsafe although i have no technical basis for it other than backing a train at speed on a model layout always ends in disaster.

Anyway, what is the fascination with push-pull in the US with diesel trains? Why dont they use a bunch of of DMU's like they used to? or a combination of powered and unpowered cars?

Just curious to see why they like running trains backwards [;)]

[CShaveRR]

Here in Chicago, we wouldn't have it any other way!

First of all, these trains replaced conventional locomotive-hauled passenger trains (DMUs or RDCs never quite caught on for commuter service here). With push-pull trains, the power is kept on one end, eliminating the time and expense of moving it from one end to the other just to keep it on the front. That would mean several extra moves at the terminal, involving backing the train out, running around it, then backing it back in for the next departing run.

Also, think about the commuters--sometimes over a thousand on each train--having to get off and walk along the platform at the terminal, past a locomotive that is running at high speed to keep the electricity on in the cars. We railroad employees are required to wear ear protection around locomotives, and these are noisier than most--and smelly, if the ventilation system isn't working just right. With the locomotives at the far end of the platform, the customers are spared all of this.

[passengerfan]

Push Pull saves time if engine pulls one direction and pushes the other their is no need to turn consist at terminals or for the engine to run around consist after being turned. Push Pull is used extensively in Commuter operations and in certain western Amtrak trains SAN JOAQUINS, CASCADES and others. None of the really long distance trains use push pull as the Amtrak Superliners are not equipped with tram lines, necessary for push pull operations. Amtrak California cars equipped with tram lines as are the talgo consists with a power unit at one end and former power unit at the other. Amtrak tram lined many of the Amcoaches and the single level Pullman Standard cars from the early yeras of Amtrak. The new Acela trains operating in the northeast corridor have a power unit at each end so are bi-directional. Canada runs push pull in Montreal, Toronto and Vancouver commuter services. Hope this answers your question.

[Anonymous]

QUOTE:
Canada runs push pull in Montreal, Toronto and Vancouver commuter services. Hope this answers your question.

Yup, Westcoast express running from Mission to Vancouver is all push pull - the loco pulls on the way to vancouver then pushes back to mission in the afternoon.

All GO transit in Ontario is push-pull as well.

[Anonymous]

But the train tends to strugle more up a hill and puts a hell of a lot stress on the lead motor.A DPU on ether end of the train will tend to strugle more than just having 2 locomotives on the point,the end result is a slower train in worm dpu mode.
But there is a good side to the use of dpu's,it gives extra brake pipe AIR through out the train incase of an emergency.BNSFfan.

[BaltACD]

Push-Pull also permits quick turnaround of the trains in a destination/origin terminal. The engineer/operator walks from one operating end to the other while the train is unloaded and reloaded and the train is ready to depart within 10/15 minutes or less.

[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 !!

[Anonymous]

Ok you win.BNSFfan.

[trainfan1221]

Push-pull has been the main thing here on what are now the NJTransit main lines since the days of Erie-Lackawanna. It is something so normal we don`t even think twice about it. It eliminates the need to turn around, since there aren't too many facilities for this anyway, and it keeps the engines from being all up front in terminals like Hoboken. This way they are on the far side ready to head outward.

[Anonymous]

RE: Superliners in push-pull (well, almost)....the Heartland Flyer FTW-OKC runs push-pull almost every day. Uses a GE for power and an "F40 baggage car" for the cab on the other end. They wired the consist with MU cables and dedicated the cars. Have seen it a couple of times bidirectional.

By the way, bidirectional diesel was a winning concept ATK had to be dragged into kicking and screaming, as usual. 1st on the San Diegans where they tried to short the consists of overfilled trains claiming inadequate power, until a couple of PailRac/URPA guys (now both deceased) in SoCal convinced them that they could just as easily put a locomotive on the other end as put a cab car there.

[Anonymous]

So does METRA.

[Kozzie]

Hi Tyson from Dave up in "Brizzo"

Haven't heard from you for a while. [:)]

I think the use of push-pull is so different for us lot here downunder because most of our commuter networks are EMUs, with ones that were loco hauled (like us here in Brisbane) phased out over the years. I think it's a case of what you're used to. [swg][swg]

Dave
(Kozzie)

[TH&B]

In Europe push-pull is also commun, but they use buffers and chains as couplers and sometimes coaches would twist their frames if the springs in the buffers were uneven, especialy on longer heavier trains !

In the US there is a central draft gear so this should not be a problem.

[TH&B]

In Europe push-pull is also commun, but they use buffers and chains as couplers and sometimes coaches would twist their frames if the springs in the buffers were uneven, especialy on longer heavier trains !

In the US there is a central draft gear so this should not be a problem.

[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

[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]

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".

[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.

[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

[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

[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?

[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.

[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.

[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 !

[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.

[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

[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.

[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.

[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.

[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