Why would railroads use two back-to-back diesels on some short or local trains when one engine can do the job? For example, during the F-unit era, photos always show an A-A or an A-B unit combination when they were used even for short trains that a single engine could handle. I recently saw two Soo Line GP38-2s on a ten-car branchline train.
Do railroads just sometimes assign two particular diesels together that always do the same jobs on branchlines ?
The easy part first.
Why 2 engines on a local? Simple they may leave the yard with 10 cars but,by the time they finish their run there may be 30 or more cars in the train’s consist.
As far as A/B or A/A on a short train the train may have enroute switching to do with several pickups and another reason the A/B may have been drawbared together…Of course it could be to keep a even locomotive balance in the division’s terminals.
Today some locals operate with a engine on both ends to eliminate time consuming runaround moves and for stubbed end industrial leads(branch)…This also eliminates a caboose needed for a long reverse moves out of a indudtrial lead.
The semi-weekly NS local here would drive you nuts. Its a pair of SD70s and the longest train I’ve seen was five cars.
Way back when the diesel engines were the new kids on the block, many railroads doubled up on them just to make sure they would make the trip! Most people today don’t realize that the reliability on those engines weren’t all that great…
Actually EMD was the best locomotive made back then…Alco was good but,subject to mechanical problems and was bought by some roads to keep EMD in pricing in check.When GE release their U25B it gave less then stellar performance but,was still superior to Alco…
Sadly Alco’s Century line of locomotives failed in sales against the GE products due to Alco’s on going mechanical problems with the Century line of locomotives.
Back to back engines may be assigned to have an engine facing forward on both legs of a turn.
There may be pickups on line.
If its a through freight they may be positioning the power. This train may be short, but the next assignment may be a longer train.
It may be the power is used on a local because its handy. The PRR used Baldwin sharknose passenger units on a local because the engines were laying over between passenger runs.
It may be cheaper to use two big road units that aren’t doing anything else than to assign a small unit for a train that only runs one shift a day.
They could have a bad plan.
Gidday, I’ll stand corrected, but I thought that one reason that diesels were doubled was that as a single unit they lacked the tractive effort and adhesive weight of the steam locomotive they were replacing.
Cheers, the Bear.
Not just two units on the front - sometimes they run push-pull with a loco on each end of the train. When I lived in Hatfield PA, the local up the former Reading Bethlehem Branch from Lansdale ran this way. No need to try to run looking backwards (hard on the neck - though some locos have dual controls and can be worked either way), plus no issues switching facing or trailing point sidings, since with a loco facing each end, it’s always a trailing point to one of them.
One day they were spotting a center beam flat of lumber near where I lived, and the really poor track condition finally bit someone. The car stayed on the rails, but it leaned over so far that it was the rest of the train standing on the main that kept it from actually falling over. The crew walked around a lot and tried a few things, eventually they gave up,locked down the lead loco, climbed in the cab of the trailing one, and headed back to Lansdale. Next day a large crane came in and pulled the lumber flat upright so it could be delivered and the rest of the train pulled out of the way. WOuld have been a long walk back if both locos were on the head end of the train, there was no runaround here and no movign the cars standing on the main, they were well jammed by the tilted flat.
–Randy
Hi upjake!
There are quite a few reasons why railroads run two locomotives on a train when only one is needed. First, a 2000 HP GP38-2 can typically handle at least 2000 tons unless there are some major grades on the route. So two together could easily handle 35 to 60 cars depending on the total train tonnage and the tonnage profile of the line they are on. As someone mentioned before a train might leave with only ten cars but at some point the engines might bring back or be coupled to 40 cars at some point during their tour of duty. That is one instance when two locomotives would definitely be needed.
Another reason is that many locomotives are directional with only ditchlights on the shorthood end. Two back to back engines would solve the problem when returning to their assigned terminal. All an engineer has to do is “swap ends” and make the other unit the lead unit when the train reaches the turning point. Turntables and wye tracks are few and far between these days.
A third reason is as an engineer I’m not going to brake up a MU consist when I don’t have to. If I don’t need the additional power I can always isolate an engine in the consist to conserve fuel. When you MU engines together you have to couple four air hoses and one big jumper cable. Set the trailing units in trail position, release all handbrakes, make sure all electrical switches are in their proper positions and then run a brake test. Frankly I don’t know many engineers that will go through all that work if they don’t have to.
Hope this helps out.
Tim
NS Locomotive Engineer
Actually that would depend on the locomotive tonnage rating and percentage of grade-a mean grade could be .5% on a curve.
I worked locals that had a single GP9 pulling 18 cars.I worked urban locals that had SD9 and 14 cars.
Now I worked a turn that used a H24-66 simply because of the tonnage-we had 40 empties and returned with 50 loads of lime stone.
As long as a engine could handle the tonnage then it could be used solo.
Now weather plays a part as well during the winter 2 locomotives may be require to handle the same tonnage as one locomotive in the spring,summer and fall,add slick rails from rain and ice then tractive effort can be reduce.
It would depend on what they were replacing. An A-B set of FT diesels had roughly the same pulling power as a typical 2-8-2 steam engine. So a train that required one 2-8-2 would probably need two 1st generation diesels to replace it.
As noted, practicality can be an issue too. I grew up on a dead-end branch line, and the railroad often ran back to back EMD switchers on the trains so that when they reached the end of the branch, the engines could run around the cars and the engineer could move to the formerly trailing diesel and be facing the front of the train again as it headed back to where it started.
On mainline trains, railroads generally try to keep 2 or 3 unit lash-ups set up so the outside engines face away from each other, to they can be kept together and work either direction without needing to be turned on a wye or loop.
Here in northern Michigan trains are pretty scarce as are customers. In two years I have seen three trains. Great Lakes Central brings one car from Cadillac to Williamsburg six miles east of Traverse City. All three trains have had two GP38 engines. They come into Traverse City and split the engines. The car is taken between engines on a branch that requires the train to go back the way it came (basically a switchback). The engine on what is now the front is also positioned to switch the car into the lumberyard siding. Since there is no way to get the engine on the front of the train the crew switchs to the other engine to pull the car and second engine back to Traverse City where the two engines are reunited and the car is then taken back to Cadillac. Only logic I can see is possibly a rule not allowing crews to push a car when there are grade crossings or some similar reason even though 5mph would be a breathtaking speed for this railroad.
hey where on the NS are you located?
I know that the engines from EMD were so good that the engines meant for freights were being used on passenger trains.
To answer the question though, there are a multitude of reasons. Extra help, unit failures, avoiding the run-around, and so on…
avoiding the run-around
Actually we would avoid a run around if possible but,back then we had a 3 man ground crew(conductor/2 brakeman) that made such moves simple and there was no need for a engine on both ends of the train-remember the caboose/cabin was occupied by the conductor and rear brakeman and all the rear brakeman would need to do is swing off the cabin and unlock and line the switch for the run around move.The head brakeman would uncouple the engine and unlock and line the other switch for the run around move and swing on the engine as it rolled by to help with the switching.-------------------------
The second unit was usually needed for the tonnage.Again we may have left the yard with (say) two GP7s and 6 cars but,we may return with 30 or more.
Even back in the day railroads wouldn’t assigned two locomotives to a local due to the extra cost involved.
Gidday, Larry and Stix, I appreciate your comments.
Unless its a personal experience I generally like to have something to quote from, but couldn’t find one at the time I made my original comment. This one is not the one I was thinking of, I am developing a memory like a sieve, but this one is from the book, long out of print, “Engine Pass - New Zealand Railways” by D.B.Leitch.
…"With 660 hp the De would have made an admirable job of heavy shunt work, or of short branch line trains, but instead they were expected to cope with main line traffic, usually with a single engine.As such they were far from an unqualified success and grossly underpowered for such duties. On suburban trains they were almost never better, and often worse than the old steam engines they replaced…"
Note: The De class were the first diesel-electric locomotives employed on the New Zealand Railway in 1950.
By using this quote I am by no means wishing to re-ignite the steam vs diesel debate as David Leitch makes quite clear that these loco’s were clearly misused by management, I suspect that other railroad managements elsewhere, in trying “to get more bang for their buck” made similar mistakes.
Cheers,the Bear.
I suspect that other railroad managements elsewhere, in trying “to get more bang for their buck” made similar mistakes.
Absolutely! There was a lesson that railroaders soon learn.It may take 3 diesels to pull the same train as a 2-8-4!
However,that was acceptable since the diesels was cheaper to operate and they could eliminate thousands of roundhouse and steam back shop jobs—and eventually the fireman’s job…
You see in the eyes of railroad management it never was about steam vs. diesel(that’s a railfan/modelers argument)…It was about cutting costs,eliminating jobs and closing back shops and where applicable roundhouses…
It took a while for some railroads to “get it right” with diesels. Some like Chicago & NorthWestern, didn’t use their diesels efficiently at first, and ended up buying more diesels than they needed. Later they realized their mistake and became much more efficient in handling diesel assignments. New York Central didn’t buy enough diesels, and over-estimated how much they could get out of each diesel, and struggled for a while in getting enough engines where they needed to be to pull the trains they needed to pull. Plus of course, railroads often bought from several builders, meaning they had to keep spare parts and such for several different builders.
A good example of the steam/diesel comparison was the New York Central, who in 1945 bought it’s new 4-8-4 “Niagara” type passenger engines at the same time it rec’d several A-A sets of GM E-7 passenger diesels. The Niagara could do the same job with the same availability as an A-A set of E-units if it was meticulously maintained…but the diesels didn’t need to be meticulously maintained - they required fewer manhours in the shops and roundhouse, so were more efficient to operate.
Nope. Diesels are much heavier than steam locomotives. Around 30 tons per axle. In fact that’s why some railroads kept smaller steam locomotives like 2-6-0s, 2-8-0s and 4-6-0s for use on light tracked branch lines well after dieselization of mainlines because they had lower axle ratings than even the lightest diesels.
Diesels have higher tractive effort than steam because except for A-1-As, all their weight is on their driving wheels and because electric traction motors can apply all it’s power at low speed while a steam engine only generates maximum power at it’s maximum rpm.
To continue the Niagara vs PA discussion, a later, more accurate, analysis determined that, to equal the over-the-road performance of the 6000 hp 4-8-4, the honest diesel would have required 3 units, not two. (Note the earlier comment about NYC overestimating what diesels could do.)
The same thing applied to many first and second generation diesels. Tractive effort STARTS trains, but horsepower gets them over the road. It took a pair of F3, F7 or early road switcher units to equal the over-the-road performance of even a mediocre 2-8-2. As for superpower…
Then, too, many first generation carbody diesel sets were coupled with drawbars to get around `a crew in every unit’ laws and union agreements. Then, as now, it really was all about cutting costs and getting more bang for the buck.
And now for the ultimate overpowered train. BNSF westbound, east of Mojave, CA. - 6 big 6-axle units, seven empty (I think) gons. More powered axles than unpowered axles! (Obviously balancing power, since the eastbound climb over Tehachapi Pass is both longer and steeper than its westbound grade.)
Chuck (Modeling Central Japan in September, 1964 - with frequent doubleheaders, steam, diesel and mixed)