Union Pacific used to run freights with two DD40X and two fast forty SD40. What was the tonnage and or number of freight cars when these freights ran Salt Lake City to LA. Gary
Impressive units as always:
https://www.railpictures.net/photo/597818/
https://www.railpictures.net/photo/560242/
https://www.railpictures.net/photo/560241/
https://www.railpictures.net/photo/510105/
https://www.railpictures.net/photo/488177/
https://www.railpictures.net/photo/639202/
Did UP always run them in pairs or were three unit DD40X sets also seen on the mainline?
Three and sometimes even four unit Centennial consists were commonplace during their earlier years.
I believe the appearance of high speed geared SD40-2's in the mid 1970's is what largely ended that practice, with what fans nicknamed a "Fast Forty Sandwich" (Centennials braketing a SD40-2H) becoming the new norm as Union Pacific sought fuel savings at the expense of some performance.
And when a number of them were briefly reactivated in the mid 1980's as business rebounded after the 1980 recession (Which first put these successful but well worn units into storage), one seemed to be typical in an engine consist from the pictures I've seen. A possible consequence of their high mileage and their extended stay in the desert that reduced reliability when they came back out?
Three units:
https://www.railpictures.net/photo/71209/
https://www.railpictures.net/photo/55026/
https://www.railpictures.net/photo/143722/
https://www.railpictures.net/photo/270867/
Classic Fast 40 Sandwich:
https://www.railpictures.net/photo/225862/
https://www.railpictures.net/photo/221394/
https://www.railpictures.net/photo/221297/
https://www.railpictures.net/photo/261760/
https://www.railpictures.net/photo/302505/
https://www.railpictures.net/photo/317063/
https://www.railpictures.net/photo/382656/
https://www.railpictures.net/photo/378674/
https://www.railpictures.net/photo/402291/
The DD40X's were supposedly just two SD40's glued together end-to-end, but they still look much larger than that - see this photo:
Thanks, kgbw49 for posting those many links - fun to look at this morning! Too bad I missed them when they were in their prime.
- PDN.
More like two GP40's glued together...
Don't forget the "A" in DDA40X.. the whole unit put out 66oo hp so not really two SD40s or GP40s glued together.
I thought the "A" stood for an A (cab) unit. Weren't there some DD40 B units?
I also thought - with no basis that I can recall - the "sandwich" was a Fast Forty SD45 on each side of a DD40A? Might be some photos of that configuration someplace.
What's odd - in any of these configurations - is putting a 6-axle unit in with essentially multiple 4-axle units. Even if the SD40s were geared up for a higher speed range, that would seem to negate the need for the extra weight and axles. Since diesels are horsepower-limited, once above starting range the SD40 would perform about the same as a 4-axle GP40. It's not like the added 2 axles and weight of the SD40s was going to be enough to start a train that the DD40A's plus the same number of GP40's couldn't start, or to go up a grade that the DD40's + GP40's couldn't get up.
Link to a data sheet on the DD40's:
http://www.thedieselshop.us/Data%20EMD%20DDA40X.HTML
It shows the minimum radius as 57 degrees, which is roughly 100 ft., and as such is not credible. For something that huge, about 20 degrees is more believable.
Wonder what the inside curve overhang is for that? Probabaly not much more than for a full-length passenger car, but it would be something to see.
Paul_D_North_JrI thought the "A" stood for an A (cab) unit. Weren't there some DD40 B units? I also thought - with no basis that I can recall - the "sandwich" was a Fast Forty SD45 on each side of a DD40A? Might be some photos of that configuration someplace. What's odd - in any of these configurations - is putting a 6-axle unit in with essentially multiple 4-axle units. Even if the SD40s were geared up for a higher speed range, that would seem to negate the need for the extra weight and axles. Since diesels are horsepower-limited, once above starting range the SD40 would perform about the same as a 4-axle GP40. It's not like the added 2 axles and weight of the SD40s was going to be enough to start a train that the DD40A's plus the same number of GP40's couldn't start, or to go up a grade that the DD40's + GP40's couldn't get up. Link to a data sheet on the DD40's: http://www.thedieselshop.us/Data%20EMD%20DDA40X.HTML It shows the minimum radius as 57 degrees, which is roughly 100 ft., and as such is not credible. For something that huge, about 20 degrees is more believable. Wonder what the inside curve overhang is for that? Probabaly not much more than for a full-length passenger car, but it would be something to see. - PDN.
GP40's and the DD40's would be putting 750 HP to each traction motor. The SD40 would only be putting 500 HP to each traction motor.
The carriers have found that when you try to put more than 750 HP through each traction motor on a locomotive it tends to become 'slippery'.
The hope of the 6000 HP AC locomotives was that they could use their 1000 HP per traction motor to move intermodal trains at higher speeds - as speed requires HP. The length and wind restiance on today's intermodal trains created more pulling tonnage than the 6000 HP AC's could handle without slipping, thus the short life of the 6000 HP AC's. They were found to be real slippery when used in max tonnage unit train services.
Never too old to have a happy childhood!
DD35s were B units, and DD35As were A units of 5000 hp each. UP bought 15 DD35A units and 27 DD35 units in 1965. (UP bought 47 DDA40X “Centennials” - aka “Big Jacks” - Of 6600 hp each from 1969 to 1971.)
https://www.railpictures.net/photo/656152/
https://www.railpictures.net/photo/580046/
https://www.railpictures.net/photo/551298/
https://www.railpictures.net/photo/530104/
https://www.railpictures.net/photo/528886/
https://www.railpictures.net/photo/378673/
https://www.railpictures.net/photo/373996/
https://www.railpictures.net/photo/271019/
https://www.railpictures.net/photo/3549/
Ulrich Don't forget the "A" in DDA40X.. the whole unit put out 66oo hp so not really two SD40s or GP40s glued together.
It's the "X" as SP had a few SD45X's rated at 4200HP. The Centennials were numbered in the 6900 series as the original plan was to have a total of 6900 horsepower, but were de-rated to 6600HP before placed into service. Half of 6900HP is 3450HP which is just shy of the 3500HP for the GP50/SD50 (the last EMD domestic designs with the 645 engine).
I do remember passing a scrap metal truck headed south on I-15 with a side fram from a DD truck gloriously visible.
Yeah, after your earlier correction I was thinking that the DD40A was more like 2 GP50's glued together. More accurately, at 3,300 HP something between a GP40 and a GP50, but there never was a GP45 - and would it have had a 3,600 HP V20 like its big brother, the SD45?
I was also wondering what the ride would be like on that looong wheelbase. Probably the engines had the best of it, being at the middle. The crew is still over the front truck, and would still feel a low joint somewhat, but I bet even that is smoothed out quite a bit by the wheelbase of that 4-axle truck.
Paul_D_North_JrMore accurately, at 3,300 HP something between a GP40 and a GP50, but there never was a GP45 - and would it have had a 3,600 HP V20 like its big brother, the SD45?
I don't think most of the 'sophistications' that allowed the GP50's rating were available during the Centennial era -- most of us gleefully acknowledging that to be really fortunate considering how the GP50 experience generally turned out.
If I recall correctly, the 'derating' was related to cooling efficiency. I wouldn't be surprised to find that Don Strack or Will Davis has a definitive account.
I was at MOT last Sunday, looking carefully at the primary and secondary suspension of those four-axle trucks. It is surprising (to me) how little lateral is allowed in the axlebox arrangements, but there is a very well-developed spring arrangement between the truck bolster and the frame, which I suspect gave relatively good controlled ride quality for a Flexicoil truck -- certainly no worse than an SD-40 of equivalent vintage. I'm a bit surprised that the dampers of the -2 series were never fitted to these trucks, considering the high speeds UP used in this era.
If I remember correctly, there would be no "GP45" to compete with U36Bs precisely because the 20-cylinder engine would be too long to fit on a 4-axle frame, with all the other 'stuff' an EMD design requires, and still achieve proper weight balance without overloading. This is much the same argument we have for the C4 designs that use some variant of idler-axle trucks but retain three axles per truck frame -- the combination of length, weight, and packaging requires at least one three-axle truck (as in some 2000 and all the 2400hp FM cab units, and as it turned out the FL9), and in the interests of parts commonalty and service training alone, it makes sense to standardize on two.
Paul_D_North_JrI was also wondering what the ride would be like on that looong wheelbase. Probably the engines had the best of it, being at the middle. The crew is still over the front truck, and would still feel a low joint somewhat, but I bet even that is smoothed out quite a bit by the wheelbase of that 4-axle truck.
Our community is FREE to join. To participate you must either login or register for an account.