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The SD-80MAC is probably the most popular and strangest of all modern Conrail locomotives. An interim 5,000hp locomotive trapped between the 4,000hp SD-70MAC and the 6,000hp SD-90MAC, the SD-80MAC found a home only on Conrail. Needing high-horsepower, high-tractive-effort locomotives in the mid-1990s for hauling coal over the Pittsburgh Line and the Boston Line, Conrail turned to General Motors Locomotive Group's (GMLG) for their new 5,000hp SD-80MAC. All units were delivered with a 5,000hp prime movers.Technically speaking, the SD-80MAC runs a whopping 80'-2" between couplers and is powered by a two-stroke, 710G3B 20-cylinder prime mover, the first locomotive to use a 20-cylinder engine since 1975. The fuel tank capacity on the units is a staggering 5,900 gallons. It's been reported that due to the large two-stroke engine, the SD-80MAC sucks fuel like it’s candy. This entire powerful package rides on unique HTCR radial, self-guided trucks with 45" diameter wheels. Conrail estimated that two SD-80MAC's could do the work of four traditional DC locomotives, thereby significantly reducing operating and maintenance costs. Truly a monster of a locomotive and the ultimate in form following function!
They're Here ran the news headline in Conrail's employee magazine, Inside Track, in their January/February 1996 issue. On November 20, 1995 in Buffalo, New York, Conrail took delivery of the first partially complete SD-80MAC from EMD. From there it quickly made its way down to the famous Juniata Locomotive Shops in Altoona, Pennsylvania, where shop crews completed the unit's construction and applied a new Conrail paint scheme befitting such a special breed of locomotive. As Inside Track reported, "They represent the most dramatic advance in railroad power technology since the change from steam to diesel power nearly a half-century ago." On December 6, 1995 the completed unit, CR 4100, officially joined the roster during a dedication ceremony at Juniata, which featured the locomotive charging out the shop doors like a star football player and bursting through a paper Conrail banner. On hand were representatives and officials from EMD and Conrail. You can read more about the ceremony and view photos from the day by downloading They're Here (272K 
) of the one page article pictured to the rightRight on the heels of 4100, 4101 rolled out of the shops. After a brief period of in-shop testing, Conrail placed this pair into actual mainline testing between Conway and Altoona beginning in January 1996. Since the testing was successful over the Pennsylvania mountain range, Conrail sent the pair to the railroad’s other tortuous mountain mainline, the Boston Line. After all, Conrail ordered these locomotives specifically for hauling freight over them.
In May 1996 the last of Conrail 28 SD-80MAC’s, CR 4127, unceremoniously rolled out of the Juniata shops. Even though Conrail purchased the two demonstration units from EMD, numbering them CR 4128 and CR 4129, 4127 would remain the last SD-80MAC constructed.
As the locomotives began rolling out of the paint shop, Conrail began placing them into service. The plan was to assign each locomotive to a particular business unit. The Intermodal Unit was to receive six units, the Unit Train (Coal) Unit was to receive eight units, and the CORE Unit or general freight network was to receive fourteen units. This meant that railfans could see the new locomotives powering just about any type of Conrail mainline freight train.
Of course, you had to live near the line over which the locomotives operated. Since I lived at the time in eastern Pennsylvania, my chances of spotting an SD-80MAC early on were pretty darn good. After hearing stories of the engines operating in mighty pairs on the lead of heavy coal drags out in the western mountains of the state, I finally got to see them in my placid foothill region. It was a cold, late winter afternoon when I heard the sound of two SD-80MACs working off in the distance. I expected to see the high-class locomotives powering one of Conrail’s more dignified freight trains, such as a high-priority coal drag or an especially long intermodal. Standing trackside at CP-Wyomissing Junction on the famed Harrisburg Line, a small group of us dedicated railfans awaited the train's arrival. I deemed it too dark for photos, so I resigned myself to simply watch and admire as many details on the locomotives as possible. Since the train was heading east and had the green signal to take the steep downhill grade that everyone called "the connection" to the Belt Line around the city of Reading, I knew it would have to slow to at least 35mph. Plenty of time to admire the might of the new engines!
As the clean engines, the cleanest engines I had ever seen on late-era Conrail, rounded the curve approaching Wyomissing, goosebumps began forming on my arms. Now I am not one to sentimentalize my railfanning experiences--at least not too much--but I actually was excited to see these engines in person. There is nothing quite like seeing 80 feet of 5,000 horsepower bearing down on you so close that you could actually reach out and touch them. Even as I write this piece, five years after the event, I can still visualize that evening. If only I had been more prepared for what happened that evening.
Expecting to find the SD-80MAC's leading a high-priority train, my jaw literally dropped as the train rounded that distant curve approaching the junction. Sure the engines were clean, as I have mentioned, but the train behind them was one of the dirtiest, lowest priority trains on the Conrail system--PIMO. Argh! The one Conrail freight train I could not stand. 100+ beaten gondolas carrying coil steel, sheet steel, and scrap steel. Did I mention it carried steel? Did I mention it had gondolas? For some unknown reason that probably stems back to a traumatic episode in my childhood having involved gondolas, I hated trains made up of nothing but gondolas. OK, so PIMO occasionally did contain some mixed fright on its head-end. Whoopee! It was still a gondola train to me. That it ran between Pittsburgh and Morrisville, PA was not important to me either, not that it had to be. Of all trains, I grumbled, why this looser?
"Because that’s what Conrail bought these things for," a kindly railfan next to me intoned. Oh yeah. I had forgotten. PIMO was probably one of the heaviest trains Conrail operated. Sure, coal trains are heavy. But steel is heavier. Probably the only thing at the time heavier was an iron ore train that ran through our area. If the SD-80MAC’s could handle the sheet steel, the coil steel, and the scrap steel of PIMO, then these trains could handle anything. And handle the steel they did!
Slowly the pair of SD-80MAC’s approached then rolled past me. The moment I saw them, I was glad that I was unable to snap photos. Too often I’m so concerned about getting my photos just right that I never actually get to see what I’m shooting. As the train trails off in the distance, all I can remember having seen was a bunch of blue boxes fully focused in my frame at f16 with a shutter speed of 1/250th of a second. But this evening was different. Not being able to shoot photos allowed me to actually stand and enjoy the scene, taking notice of the entire railroading experience. And what an experience it was. I knew from magazine photos that SD-80MAC’s were long, I knew that anything 80 feet long is...well...long. When you combine this length with the SD-80MAC’s rather angular, functional appearance, all creeping downhill, you have an awesome locomotive. I was impressed, this coming from a fellow who still prefers standard cab locomotives over widecabs any day. As the engines slipped past me and disappeared past the old double-mast signal protecting the junction, I stood in silence for several seconds. We all stood in a moment of silence. We had seen our first Conrail SD-80MAC, and were pleased.
But life as a railfan watching massive SD-80MAC's is one thing. Running them every day as your job is quite another. When the locomotives were still new to the system, Conrail placed them in dedicated pairs of SD-80MAC's. If other locomotive classes had to be included in the consist, then the operating department dictated that the SD-80MAC's be placed at the rear of the lash-up. Conrail based this decision on the known operating conditions of AC locomotives. Conrail feared that if an SD-80MAC were leading a consist of traditional DC locomotives, that the SD-80MAC would burn out the traction motors of the trailing units. In locomotives the prime mover (engine) generates electricity via an enormous alternator. The alternator in turn electrically powers traction motors in the locomotive's trucks. These electric motors give the locomotive its traction and speed. If you send too much power to the motors, they burn out, bringing the locomotive to a grinding halt. Conrail executives didn't like that idea, therefore the SD-80MAC trailing unit rule.
Now, traditional direct current (DC) powered locomotives must keep moving at a minimum speed. If they go below this minimum speed for too long a time, they risk burning out their traction motors. If they climb a grade that is too steep for them to handle, especially with a heavy train spread across several other grades, they risk stalling. Even though the train is barely moving up the grade, the alternator is still pumping electicity into the traction motors as if the engine were running at Notch 5, a mainline throttle setting.
Now when traction motors are about to burn out due to stalling or slow speed, the lead engine limits the electrical load of the struggling engines. If the locomotives fall below a minimum speed for too long, which in technical terms is called a locomotive's "minimum continuous tractive rating," the lead engine might possibly shut them down. Every locomotive model has its own tractive rating. What makes AC locomotives unique is that they can completely stop or stall without any fear of burning out their traction motors. If you were to put an SD-80MAC in the lead of traditional DC-powered locomotives, the SD-80MAC would never worry about the traction motors of its trailing units burning out. It would be unable to sense such problems since it doesn't have to worry about such things on its own locomotive, possibly causing a serious accident. Such a is the type of situation Conrail wanted to avoid when it passed its AC trailing unit rule.
In reality, however, Conrail never had to worry about its worst fears coming true. According to Tim Frederick, who spoke with an engineer working the coal fields of the former-Monongehela lines, Conrail routinely placed its SD-80MAC's anywhere in the consist without fear of burning out the traction motors on older locomotives. Since Conrail equipped all their trains with plenty of power on the MGA lines, engineers did not have to worry about stalling out on the grades. Plus engineers working the MGA lines had been well educated about the potential for burning out motors and how to properly operate their new AC locomotives. As a result, there really wasn't any concern about placing the SD-80MAC's in the mixed consists, even though the trailing unit rule was still technically in effect.
So that wraps up the SD-80MAC technical information, their operating conditions, and their impact on an semi-impressionable railfan. Originally, Conrail wanted to have many more SD-80MAC's than the meager 28 of the original order. They even placed an order for an additional 30 units, doubling their fleet once you take into account the two demonstration units they bought from EMD. Then merger-mania struck the railroad. With the pending merger looking like a done deal, NS and CSX forced Conrail management to change the order to SD-70MAC's and SD-70's. Neither railroad wanted more of an "oddball" locomotive model running around their properties, thereby ending the short production life of the SD-80MAC.
To this day the Conrail SD-80MAC remains the most popular locomotive class among modelers and railfans. Every month since the Conrail Cyclopedia came online in 1998, the SD-80MAC pages have remained the most popular. Even if I had one photo online, the section would get hundreds of visitors a month. I hope you have enjoyed this brief visit with Conrail's mighty giants.
Thanks to: Tim Frederick and his dad, who is head of Conrail's mechanical engineering department, for info on operating characteristics of the SD-80MAC and a few other details.
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