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  • General discussion about locomotives, rolling stock, and equipment
General discussion about locomotives, rolling stock, and equipment

Moderator: John_Perkowski

 #805960  by trainwayne1
 
In reading a Trains article about slugs, a question comes to mind. Using a hypothetical situation, a TOFC or stacks of 8000 tons requires X amount of tractive effort from 12 axles to get started and pull a portion of the grades on its route, but 2 4 axle 3000 hp units will be able to maintain speeds on the balance of its run. Would the use of a slug powered by both 4 axle units and equiped to be able to be on or off line at the engineers will be more economical that the use of 6 axle units for the whole route?
 #805962  by timz
 
I guess that's what SCL did in the late 1970s (except they weren't doing it on intermodal trains), so it must not be pointless-- but as far as us fans can tell there would be no advantage, aside from maybe less wear on the track with B-Bs instead of C-Cs?
 #806352  by Allen Hazen
 
Two 3000 hp units for 8000 tons seems a bit low for intermodal speeds: my guess is that most stack trains have closer to 2 hp/ton than the .75 hp/ton this would give. Which may be why we don't see road slugs on intermodal trains: by the time you have enough power to get the train over the road at the desired speed you will usually have enough units on the point to give you all the tractive effort you need WITHOUT adding extra powered axles.

But the general point is interesting. When SCL bought its MATEs units (road slugs -- with fuel tanks and provision for reprovisioning the slug mothers' tanks en route -- built new by GE and used with U36B mothers), the write-up in "Trains" speculated that the idea was at most marginally cost-effective. At the time a CC diesel apparently cost about 20% more than an equivalent BB unit, so a MATE would have to cost less than 40% of what a complete U36B did for a U36B-MATE-U36B combination to be competitive in first cost with a pair of U36C. The rule of thumb in those days were that the diesel engine, the electrical gear, and the rest of the locomotive were roughly a third of the cost each, so a MATE (four traction motors worth of electrical plus most of a "rest") probably cost a third or more of what a complete BB locomotive would... and, in operation, gave you another set of couplers and m.u. connections and ... to worry about. So I suspect there wasn't much savings.

It would be interesting to hear details from someone who knew the actual prices and what SCL's reasons for initiating the experiment but not going on with the idea after the two initial orders of MATEs were.
 #806419  by trainwayne1
 
Allen...since you've divided the cost by thirds.....
"The rule of thumb in those days were that the diesel engine, the electrical gear, and the rest of the locomotive were roughly a third of the cost each, so a MATE (four traction motors worth of electrical plus most of a "rest") probably cost a third or more of what a complete BB locomotive would... and, in operation, gave you another set of couplers and m.u. connections and ... to worry about. So I suspect there wasn't much savings."

Wouldn't the lack of a diesel engine be a third LESS of the cost?
 #806617  by Triplex
 
Note the comparison is two locomotives and a slug vs. two locomotives, not three.
 #806702  by Allen Hazen
 
Factory-built slugs are rare: I only know of two groups (CP yard slugs from MLW in 1950s, CN ?hump? slugs from GMD in the ?1970s?) besides the SCL GE-built MATEs. I assume this means that most railroads have decided they are not economically worth-while. I'd love to know more about what SCL's thinking was in ordering MATEs. Note that some of their MATEs were single-ended, so a single U36B+MATE was the operational equivalent of a pair of U18B (or a pair of late first generation units: GP-9 or RS-11). I think this sort of combination was used in low-speed "Bone Valley" phosphate service, and may have seemed like the best way to get the efficiencies of second-generation power for this low-speed service.

What might help in figuring out what the thinking was would be some comparison prices: U36B, U18B, MATE. Anybody have anything?

My "guesstimate" was figured on the basis:
-- Two U36C would cost the equivalent of 120% of two U36B (based on a remark in an old "Trains" article)
-- A MATE would have, in comparison with a U36B, (i) no engine cost (ii) a relatively small proportion of the electrical cost (two motors, no generator, no control system or very simple one, some cabling) (iii) something less than full "locomotive mechanical portion" cost (frame, trucks, fueltank, drawgear..., but no cab and ?no air compressor?). So it ***might*** be under 40% of the price of a U36B (to justify ordering double-ended MATEs) or ***maybe*** less than the difference between the cost of a single U36B and that of two U18B (to justify single-ended MATEs).
But these are ROUGH APPROXIMATE GUESSTIMATED figures, maybe not even in a small enough "ballpark" for understanding SCL's thinking.
 #806744  by trainwayne1
 
Triplex..."Note the comparison is two locomotives and a slug vs. two locomotives, not three."

I used that comparison based on the number of axles and total tractive effort. I was also assuming that a lighter intermodel train would be adequetly powered for a great portion of its run with 2 3000HP B-B locos, using the slug only where it was needed, which means that the machinery and four axles of the slug would be subjected to a lot less wear and tear while in a pure off line rolling mode, while 2 C-C units would be working all the time. I guess a lot more detailed cost and other factors would have to be examined and compared to get an accurate answer
 #808919  by v8interceptor
 
trainwayne1 wrote:Triplex..."Note the comparison is two locomotives and a slug vs. two locomotives, not three."

I used that comparison based on the number of axles and total tractive effort. I was also assuming that a lighter intermodel train would be adequetly powered for a great portion of its run with 2 3000HP B-B locos, using the slug only where it was needed, which means that the machinery and four axles of the slug would be subjected to a lot less wear and tear while in a pure off line rolling mode, while 2 C-C units would be working all the time. I guess a lot more detailed cost and other factors would have to be examined and compared to get an accurate answer
That is a big assumption given that the majority of intermodal trains run with considerably more than 6000HP. Generally the big class one RRs power stack trains with at least 3 4,000-4,400 HP units and I don't think it can be argued that they are overpowered. The advantage of road slugs is in heavy haul service under 25 M.P.H. With a fast intermodal train you want all the HP you can get at speed. The trend in the industry is for longer,heavier trains, and has been since doublestacks replaced TOFC as the preferred intermodal method...
 #809465  by John_Perkowski
 
Having watched plenty of fore and aft coal (and now grain) on both BNSF and UP , my personal guess is a full-up unit has more utility to today's Class One operators than does a road cab and slug combo
 #812696  by 10more years
 
I hate slug-mate consists. Now that I feel better by just having said that, I've wondered why, with the technology we have available why doesn't the engineer have the ability from the lead locomotive to remotely shut down, isolate, start every engine in his consist from the lead locomotive. Not only that, but to also see on computer displays what each engine is loading. The electronics can't be that complicated.
 #813374  by CN Sparky
 
10more years wrote:I hate slug-mate consists. Now that I feel better by just having said that, I've wondered why, with the technology we have available why doesn't the engineer have the ability from the lead locomotive to remotely shut down, isolate, start every engine in his consist from the lead locomotive. Not only that, but to also see on computer displays what each engine is loading. The electronics can't be that complicated.
From a safety point of view... the Engine control switch is a better idea. Some of the crews I have to deal with don't even know what buttons to push to control the DP power they're driving...

Now the latest locomotives running with computer screens usually have a Consist monitor where you can see what each unit is doing... run/isolate... and how much load they're contributing. But only the newer ones do this... ie the CN Evo's (2220-2309) and SD70M-2's (8000-8024, 8800-8914). They can't pick up what older units in the same consist are doing...
 #815773  by v8interceptor
 
10more years wrote:I hate slug-mate consists. Now that I feel better by just having said that, I've wondered why, with the technology we have available why doesn't the engineer have the ability from the lead locomotive to remotely shut down, isolate, start every engine in his consist from the lead locomotive. Not only that, but to also see on computer displays what each engine is loading. The electronics can't be that complicated.
CONRAIL had much of it's SD40-2 fleet equipped with a system built by Harmon called SELECT-A-POWER which enabled the Engineer to do exactly what you suggest when operating a consist of units equipped with the feature. It makes sense for road trains but for local work and switching I don't see how it's a better idea than Slugs...
 #816633  by RDGTRANSMUSEUM
 
Conrail had most of the road locomotives equipped in the 1980's with select-a -power. i worked for them in 90's and no one used the feature. If you had a good set of powere you just ran with that,there is enough to keep you busy with a train, let alone taking units on and off line all the time playing with buttons.
 #818597  by v8interceptor
 
RDGTRANSMUSEUM wrote:Conrail had most of the road locomotives equipped in the 1980's with select-a -power. i worked for them in 90's and no one used the feature. If you had a good set of powere you just ran with that,there is enough to keep you busy with a train, let alone taking units on and off line all the time playing with buttons.
I do recall reading that when the SD40-2s with the feature were first delivered, there was an informal(and questionable) competition between engineers in some of the districts as to who could operate particular trains with the lowest number of units "online"...allegedly this led to damaged traction motors on overloaded units..