I was reading the recent Trains story about the push for converting more old units into slugs for both yard and road service. The thing that has always struck me about slug conversions is why do they have to gut the locomotive in the first place? Why wouldn't it make sense to have locomotives set up to be able to operate in "slug mode" when needed, but also available for regular service when needed? Wouldn't that be a real fuel savings and also make a versatile fleet? They have to ballast the slugs after they remove the prime movers and other gear, so why not leave it there and just set it up to bypass the prime mover etc. when you don't need the added horsepower. Imagine a string of 4 locomotives pulling a train, shut one unit down and have it in slug mode. If the need for more horsepower arrises, have an auto-start feature that would fire up the prime-mover and switch the unit over to regular mode. The unit could be shut down for half the ride, but still be there for the section of the run that it's needed. I also would think that they are going to be running out of good GP-38's to convert to slugs when they still need them for local work almost system wide.
Steve Carlson
I assume the answer is cost. They don't have to maintain the additional components.
I've often thought that the next generation of Locomotives may in fact be a common electrical grid similar to what you describe. basically treat the traction motors of all units as one system and the Diesel generators of all units as another system and add and subtract both as needed.
That's a pretty complex thing to do though.
My assumption is that the units chosen to be 'slugged' are ones wigh prime mover or main generator problems, or units which are being cannibalized. The unit which has the poorest maintenance expense/operating hour rating will give up its better pieces to put another unit back in service. The bad prime mover or generator will be sent to a recycling facility and the new slug will be ballasted, fitted with power cables and put to work where needed.
Since the 'do nothing' alternative would be a repair using more expensive parts and a known maintenance problem standing on the spare loco line, the bottom line impact is clear.
Chuck
It could also be a fuel consumption or emissions issue.
The engine could work perfectly well, but consume more fuel than another and thus not be worth it.
The confusing part is that not all railroads assign these values equally, so while BN and ATSF rebuilt their 30s/35s to be better units, CSX turned them into road slugs.
SteveC I was reading the recent Trains story about the push for converting more old units into slugs for both yard and road service. The thing that has always struck me about slug conversions is why do they have to gut the locomotive in the first place? Why wouldn't it make sense to have locomotives set up to be able to operate in "slug mode" when needed, but also available for regular service when needed? Wouldn't that be a real fuel savings and also make a versatile fleet? They have to ballast the slugs after they remove the prime movers and other gear, so why not leave it there and just set it up to bypass the prime mover etc. when you don't need the added horsepower. Imagine a string of 4 locomotives pulling a train, shut one unit down and have it in slug mode. If the need for more horsepower arrises, have an auto-start feature that would fire up the prime-mover and switch the unit over to regular mode. The unit could be shut down for half the ride, but still be there for the section of the run that it's needed. I also would think that they are going to be running out of good GP-38's to convert to slugs when they still need them for local work almost system wide. Steve Carlson
Conrail had a fleet of SD40-2s equipped with the Harmon Select-a-power feature which allowed individual units in a consist to be brought on or offline as required. O.C the units were not electrically connected as a mother-slug pair would be. I believe the Locotrol DPU system allows for the same mode of operation.
There a couple of patents I've read online (one held by Railpower industries, the other by an Electrical Engineer associated with the GE Hybrid GEVO project) that describe road slugs equipped with auxiliary diesel engines (and energy storage systems) that operate in a similiar manner to what you describe. So maybe it's an idea whose day will come:
http://www.google.com/patents/about?id=qnTSAAAAEBAJ&dq=railway+vehicle+system
"I Often Dream of Trains"-From the Album of the Same Name by Robyn Hitchcock
In a similar vein, NS is beginning to cut down GP38's to road slugs not that differnent than those of CSX, also using GP40/GP40-2 mothers. Type of service may be a factor, too. CSX slug sets tended to work in transfer, mine run and local freight service, all of which are generally low-speed operations. ATSF may have also had more shop capabilities than most roads, so upgrading the GP30/GP35's and others was a logical progression from the CF7's and GP7/9 upgrades.
Well, but BN farmed them out to MK and VMV...and EMD.
Only SP of the Western railroads ever went in for road slugs in the modern era. I don't recall theirs lasting more than a few years either.
IIRC the few SP road slugs stayed on the roster until the UP merger. The last I was sure of Central Oregon and Pacific had one or two of the former SP slugs.
The UP has at least a few slugs. This one was at North Platte in the summer of '09. Sorry about the pic quality:
I see a number of valid reasons for using "SLUGS" in services from yard duties to road service.
Every railroad is in quest of its' Holy Grail', if you will. That being lower OR's achieved by cutting costs
whereever they can. Balancing maintenance costs to horsepower vs fuel costs, and so on.
The question is " Why slugs now?" Possibly a Federal Government anxious to feed monies into programs
that create "GREEN ANYTHING" while they look for successes to excite their constituents (ie; entice folks to get
out and VOTE--mainly for those in power.)
Found the following link with a couple of relative comments
to be of interest here. http://www.globegazette.com/news/local/article_509dd5a2-96e0-11df-a93b-001cc4c002e0.html
referenced comments regard the Iowa Northern Railroad; FTA: "..The company could save up to $500,000 per year in fuel costs by running the slugs,
Sabin said. He plans to add four more units within a year. Six slugs in service could cut the company’s per-car fuel use in half, he said.
Three of INR’s standard diesel-powered engines were converted to “mother units” to power the slugs. For long-distance, low-speed hauling,
the slugs will make the trains much more efficient, said William Magee, INR assistant general manager of engine mechanics.
The engines were designed for higher speeds and have more horsepower than was needed.
“Frankly that horsepower was being wasted,” Magee said. Now that extra horsepower runs a generator that helps power the slug..."
Further from the article; "...A federal grant of $303,800 from the American Recovery and Reinvestment Act of 2009 helped pay for both units..."
[From the e-Edition of the Globe Gazette of July 24.2010 article by John Molseed ]
Another reason for slugs now might be this. Think of the slugs as the Battery unit of the Hybrid units that might be coming out soon. Use the Battery for the Ballast then when the unit is producing more current than can be used then feed the excess into the battery. Then when you need the Slug for Accleration or what ever. You will have it.
edbenton Another reason for slugs now might be this. Think of the slugs as the Battery unit of the Hybrid units that might be coming out soon. Use the Battery for the Ballast then when the unit is producing more current than can be used then feed the excess into the battery. Then when you need the Slug for Accleration or what ever. You will have it.
Some of the Green Goats that Railpower built for NS & BNSF were set up to operate in Mother-Slug configuration as described...
I imagine they've all been rebuilt again as "straight" slugs due ot the GG battery woes...
Many of the Green Goat hybrids have been rebuilt to gensets.
As was said, due to battery issues.
I'm not in the least surprised that road slugs grew in popularity. What has confused me is why they seem to regularly be teamed up with GP40s rather than GP60s.
Granted there are more GP40s out there, but still.
And it may be that the railroads that own those units are simply not interested in Slugs. I'm thinking primarily of BNSF and their GP60Ms and straight 60s. and B upgrades.
ATSF used to use 2300HP 4 axle units for everything. one would think that a 3600 HP 4Axle+ slug might give you the same performance.
At the very least, some of the Protolance guys over on the MR side of the site might be able to use such a logic as a valid motive power plan.
Those 2300 hp GP39's you mention deliver about 575 hp/axle. A 3600 hp(like the old SCL U236B) put out about 900 hp/axle. With the GE 'MATE' slug attached, the hp/axle is about 450. SCL used these combos pulling rock/phosphate trains in Florida. CSX uses their GP40/slugs to pull mine local coal trains - both good examples of lower speed operation. One of the problems with slugs is matching the 'load' to the power source. As speed increases, there is a lot of Back-EMF generated and some complex shunting or even disconnecting of the slug's traction motors is done. At that point, you are basically pulling extra weight.
Jim
Modeling BNSF and Milwaukee Road in SW Wisconsin
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