THE TUNNEL MOTOR - and EMD's Extended Fight with Thermodynamics

 

    Southern Pacific had a unique problem in the late 1960s and early 1970s. While most other roads had success operating EMD's latest line of road locomotives (at the time, the 645 line), SP was running into trouble on its mountain routes. EMD's SD45 (of which SP had over 300) were overheating in tunnels and snow sheds at an alarming rate. Even stranger still, GE's new U33C was not having any issues at all with overheating and was operating perfectly fine through the road's many bores and sheds. What was going on here? SP embarked on a quest to find out, and so began the saga of the "tunnel motor", or EMD's never ending quest to meet SP's demanding operating conditions.

    First, an extremely simplified discussion of thermodynamics and how EMD radiators perform compared to GE radiators. Pictured here will be an SD45 and U33C, however the following description applies to almost all of EMD's GP/SD line and GE's Universal line with a few notable exceptions (covered later on in this post). 

    EMD's SD45 draws cool radiator air from around the shuttered intakes at the rear of the unit. When extra cooling is necessary, the radiator automatically regulates itself using the radiator shutters and fans. In the case of the SD45, two banks of three radiator cores with two separate sets of shutters and three distinct fans are present. One fan activates, then one set of shutters, then one fan, then the other shutters, then the third fan, when necessary. When little cooling is necessary, the two rear fans are used as an air intake while the shutters remain closed. At maximum notch, full load, the engine can sustain itself with all three fans running and both shutters open.

    GE's U33C has one central fan and six radiator cores. Air is drawn from vents on the side of the hood, below the radiator, and drawn upward over the cores. Mounted directly at the top of the cabinet, the radiator fan pushes air over the cores upward. Using a fluid valve to regulate water flow, the radiator allows more or less water through depending on necessary cooling. At maximum notch, full load, the engine sustains itself with the fluid valve completely open and the fan at max speed. This eliminates the need for shutters as well as requires only one engine driven fan (compared to EMD's three electric fans.) 

    One last notable bit of engine tech is the exhaust. On both the SD45 and U33C, a single exhaust stack expels engine exhaust directly upwards. On the SD45's 20-645E3, this stack is positioned on the generator end of the engine (closer to the cab), while on the U33C's 7FDL16E the stack is on the auxiliary end (adjacent to the radiator).

Relative heat diagrams for the U33C and SD45 in an enclosed space.
Notice how the U33C's intake is much lower, and gathers cooler air.

 

    The trouble begins under load in tunnels. Operating in open air, both the U33C and SD45 work as intended; both units expel hot air upward and intake cold air from the engine air intakes without issue. However, when inside a tunnel, it was found that SD45s were inhaling hot air as a combination of engine exhaust and hot radiator air due to the close proximity of the radiator intake and fans to the radiator exhaust. This problem was not extended to the Universals, as their lowered cool air intake was able to intake colder, lower air than the hot rising exhaust from the engine and the already spent hot radiator air.

    SP was a firm believer in improving a product as much as possible, and went to EMD with their findings. In response, EMD developed the "Tunnel Cooling Modification" which reoriented the radiator to be more akin to GE's design, placing the cores at the very top of the hood and placing the fans underneath them blowing upward. Depending on installation, a different configuration was used; on the SD45T-2, three fans are present, on the SD40T-2, only two are necessary. On EMD's tunnel cooling modification, in place of the fluid valve regulator present on the Universal, shutters placed above the cores were used, opening as cooling was necessary. 

Builders photo of SSW 9163

Exposed radiator cores behind
open shutters; a solid photo
of how the Tunnel Motor style
radiator was oriented.

    EMD would eventually make changes to their radiators to make them perform better in enclosed spaces. Effective after 1975, baffles between the separate fans and requiring the shutters to open immediately upon fan activation (rather than drawing air through the other fans, which would be significantly hotter than the air around the shutters) were made standard on the Dash 2 line and all future models with the same radiator design, continuing to the present. Tunnel cooling modifications were offered on the 50 Series of the 1980's, however no purchasers optioned it (SP was not interested in the 50 Series and DRGW's one order of SD50's was a duplicate of a Seaboard order).

    The "tunnel motor" radiator seemed to be more than satisfactory to SP, as they purchased 247 SD45T-2's and 239 SD40T-2's from 1972 to 1980, with DRGW also purchasing a handful of SD40T-2's during the mid-1970's (Rio Grande had similar troubles with their EMD products in similar circumstances). Eventually, after merger with DRGW, SP owned all built tunnel motors, operating them with distinction well into the 2000's on UP. Some were exported to South America, others were sold into secondhand service, and a select few were donated to museums (at least one SD45T-2 and two SD40T-2's).

An MP15DC. The radiator intake is clearly
noted at the front face of the hood.
Craig Garver photo

    While SP was dealing with their troubles in tunnels, EMD encountered a similar issue with their smaller power and overheating; however, unlike the road switchers, the switcher and light road switcher units had a completely different radiator design. Originally introduced in the late 1930's on their S and N line switchers, EMD's switcher radiator draws air from the front and exhausts upwards, across the cores.

 

    This presented a similar issue to the road switchers, but in a different context: when two switchers were run front-to-front (usually SW1500's or MP15DC's), the radiators could not draw enough cold air to keep the engine cooled, leading to overheating. This was most exacerbated on roads using them in road service (namely P&LE, among others) where units would overheat each other facing towards themselves. As it turned out, the tunnel cooling modification was called upon here, where a downsized version of what was present on the SD's was used in place of the standard forward facing radiator fan. Found satisfactory, the tunnel cooling style radiator was made standard on the switcher line. The MP15AC was the first switcher to employ this cooling setup in 1975, and all further locomotives of this caliber made by EMD (such as the GP15 and MP15T) would carry the "tunnel cooling" style radiator standard.

An MP15AC. The radiator has been completely
reoriented, however the rest of the unit is
largely the same on the outside.
Craig Garver photo

    GE never changed their radiator setup in any dramatic way, simply iterating upon it and upgrading it with improved components and customer preferred options. Replacing the shaft driven fan with an electrically blown fan, moving the radiator cores upward in the body, and generally simplifying construction were among the many improvements GE made to their radiator design, up until today's Evolution line locomotives. Ironically, despite the roads findings, the Universals were disliked after the mid 70's recession and were operated minimally by an ailing Southern Pacific. While the U33C's of the 1970's were retired early, EMD's SD45T-2's and SD40T-2's had long and legendary service careers on SP, DRGW, and UP, so it's important to remember the key role GE had in the creation of an icon of western railroading in the late 70's and 80's.

GE'S SUPER 7

A group of MGA's Super 7-23B's huddle together at Brownsville, PA in between jobs
John Benner photo

 

     By the 1980's, GE had firmly entrenched themselves as a viable and solid locomotive builder, and had an impressive catalog to go with it. Having built massive fleets of road units across nearly 30 years by that time, it was no surprise that GE's reputation for solid road power and good parts supply was unparalleled and would pave the way for their eventual defeat of EMD as the dominant force in the North American locomotive market. However, one market they had not been nearly as successful in was the lower horsepower market. Ironically, despite first producing small switchers for industrial customers and light duty work, modern GE had trouble convincing customers to buy their smaller products (since the Universal line GE had been offering a locomotive in the 1800-2300 HP lineup, well into the 80s, however the only ones ever built were the U18B, U23B, and B23-7 almost entirely for Class I railroads). Their most common low horsepower locomotives, the U23B and B23-7, were both purchased by operators with very specific horsepower bracket needs (such as ATSF, SOU, and PC/CR).

WP U23B #2251 would become GECX 2001.
It was one of a handful of Super 7's rebuilt by M-K Boise.
Vic Reyna photo, Craig Garver collection

    At the same time, many Class I railroads had stockpiles of very old, very worn out locomotives, and studies performed by EMD and GE found that there was a possible market for rebuilding old locomotives as a cheaper alternative to buying new power. For EMD, who had a significantly larger catalog of old equipment to rebuild, they took several GP9's and produced the BL20-2, a 4 axle, 2000 horsepower frame up rebuild of the previous locomotive with a new carbody and modern engine/generator upgrades. The first BL20-2 rolled out in August 1992, and two more followed the next month. While EMD had the advantage of most roads already owning their older equipment, GE's old locomotives were almost exclusively sitting in scrap piles at their Erie, PA plant, as their lifespan was significantly shorter than a comparable EMD locomotive of the era. 

Little Rock, Arkansas was the final resting place
for many GE products purchased by WP and UP.
Murray Lewis photo

 

    Studying their most popular models across the Universal and Dash 7, GE took a handful of traded in Universals on the property (a few U23B's from Western Pacific plus a U33C from Southern and a few 6 axle U's from Milwaukee Road), stripped them down to the frame, rebuilt and retooled the engine-generator sets, all new wiring and SENTRY wheelslip control, and gave them new Dash 8 equivalent carbodies. Having studied ATSF's SF30C of 1986, GE moved various subsystems inside the hood to make the Universals more equivalent in layout and tech to a comparable Series 7. The U23B's kept their 2250 HP rating, while the miscellaneous 6 axles were unified under 3000 HP, with the units emerging from rebuild dubbed "Super 7" for their equivalence to a Series 7 with new Dash 8 technology.

GECX #3000 rests at CNW's Proviso Yard on September 18th, 1995.
GE often sent their 6 axle Super 7's out on lease and warranty coverage service to customers.
Sam Carlson photo

 

    The Erie plant was at record capacity, so to make space for more Dash 8 orders being fulfilled at the time (GE was about to roll out the widecab for the very first time with the Dash 8-40CW and wanted as much production capacity as possible), GE purchased the former Montreal Locomotive Works factory to help alleviate congestion at Erie. GE also contracted some production to Morrison Knudsen of Boise, who produced several of the 4 axle Super 7 demonstrators. GE did not end up producing nearly as many Super 7's as intended, with the majority of 6 axle production being completed in Mexico by FNM shop crews using GE supplied kits. MLW was shortly thereafter closed, with the signing of NAFTA on the horizon being an important factor.

Before the delivery of 52, RS 51, 50, and a GE
coverage unit (2002) lead a W/B.
Bill Kalkman photo

    The first Super 7's were sent out in 1989 to demonstrate across North America. GE offered the 6 axles as warranty coverage on the side as well as demonstrators while the 4 axles went barnstorming across America to every class 2 railroad that was willing to test them. Major 4 axle demonstrators included Indiana Railway, Iowa Interstate, Missouri Pacific, Chicago Central, Roberval and Saguenay, and Monongahela, with the latter two generating orders of 2+1 (RS had two orders) and 10 (MGA's were on lease from GE) respectively. 

The 6 axle demonstrators spent time on the CNW, UP, BN, ATSF, and FNM, only generating orders from FNM. FNM would come to own the frightening majority of Super 7's built, using their extensive fleet of U30C's, ex-SP and ex-D&H U33C's, U36C's, U36CG's, C30-7's, and even a handful of C36-7's as rebuild cores. FNM would eventually run out of cores and buy a solitary order of Super 7-30C's in 1994 without cores, with GE responding with a microprocessor equipped, Dash 8 carbody and frame, 3000 horsepower "Super 7" built in 1994. 

GECX 5000 on the BN. Where the air cleaner would be on an M630 has
been replaced with dynamic brake equipment, and the air cleaner has
been moved below it.
Flickr user RRARTIST1 photo

 

Renumbered, but not repainted,
DL 3000 is resplendent in GE
paint. This unit was essentially
unchanged from BCOL.

Flickr user GCL 392 photo

    At the same time as FNM began purchasing rebuild kits en masse, GE purchased two M630's from BC Rail with the intent of developing a Super 7 equivalent for ALCO/MLW products. BCOL #705 and #706 arrived at Erie, with 705 being the first to go under the knife. While the M630 was electrically very similar to the Universal line, its frame, trucks, and layout were completely different, and instead of developing a Dash 8 carbody for the unit, GE simply reused the MLW built body with a general rebuild and rewire. GE also replaced the air filter cabinet with a new, modern air filter with GE's electrically blown dynamics present in other Super 7's and Dash 8's. Emerging as GECX #5000, the lone M630 Super 7 was sent off to demonstrate on FNM. For reasons unknown, the unit never made it to Mexico, and lay stored in Texas for a period of time until it was returned to Erie. GE sent it out a handful of times as a leaser, and gave 706 a minor rebuild and used it for testing, but both units would be orphaned for their entire time at Erie. Both units were sold to Delaware Lackawanna in the mid-2000's, with 5000 becoming 3007 (and garnering the nickname "The Brain" for its uniquity) and 706 becoming 3000.

    By 1993, the Dash 9 was introduced and the Dash 8 was quietly deprecated. While Super 7's would continue to be rebuilt by shops in Mexico with kits from GE, and FNM had one final order of microprocessor equipped units on the horizon, the Super 7 program was completed, with a final customer list of RS, MGA and FNM (later Ferromex). What became of them after the programs completion was varied depending on owner:

Bill Kalkman photo

• Roberval and Saguenay gave their Super 7's a long prolific life, from 1990 until 2023, when they were all three replaced by a handful of ex-CSX SD70ACe's and leased GP38-2's. The trio were scrapped in 2019.
  

 

 

• Monongahela's leased units went on to Conrail in 1993 after the merger of the former into the latter, where they operated virtually unchanged on the now former MGA route. The 1999 dissolution of Conrail into Conrail Shared Assets had the Super 7's split between CSX and NS, where CSX shoehorned them into service alongside equivalent B23-7's while NS did away with theirs very quickly. Two of them went to the Arkansas and Oklahoma Railroad, where they operate to this day, five went to Ohio Central, and the rest went to Providence and Worcester. OHCR's five units and PW's three were on the EPA "kill list" of non-complying G&W equipment to be destroyed following the January 2023 settlement of a lawsuit, with all eight intending to be torched within the following years. As of March 2024, Ohio Central's are still present and running on the property while PW's are stored serviceable.

A broadside shot of PW 2215.
After being purchased by G&W, PW's three units moved around
to various other roads, with 2215 here going to Connecticut Southern.
David Blazejewski photo

 

• FNM's massive fleet continued to operate well into the 2010's and 2020's, with the vast majority of the fleet soldiering on in road train service in Mexico. After privatization, the fleet went to various owners, including TFM and Ferromex, however they continue to be active road power across the country. 

FXE 3735 is still in its original rebuild paint in July 2023!
Note the Super 7 text on the hood, a staple of original Super 7 paint.
Carlos Moran photo

 

    EMD did not fare any better than GE with the rebuild-lease market. The BL20-2 demonstrator trio failed to generate any orders at all, with the three units being sent into leasing service by a joint GATX-EMD partnership, where they remain today. Meanwhile, while Universals are all but dead in secondhand and thirdhand ownership, early EMD products continue to motor along the Class 3's and industrial owners of North America. 

Ohio Central 4092 and 4093 roll along the Muskingum River
outside Zanesville, Ohio.
Scooter Hovanec photo

 

    It is easy to look at the Super 7 and deem it a failure due to the very small number built for North America, but it is worth noting that GE was not preoccupied with their construction at all. Outside of the demonstrators, the units were entirely contract built, and GE passively generated mileage for their own units by leasing and warranty coverage. While EMD only built 3 BL20-2's, GE built 16 Super 7-23B's for two customers and themselves, plus selling hundreds of kits to FNM to rebuild their own fleet of 6 axle GE's. At the same time as the Super 7's passively made themselves, GE had the time to upgrade Erie, develop new locomotives in the Dash 9 and AC4400CW, and bring their products to a wider market across North America. Ultimately, compared to unrebuilt Universals and given their lengthy service life, it's hard to say GE "failed" with the Super 7.

In the beginning...

 This is the first post on my new blog, Mr. Doggard's Magic Diesel Blog. I'm still getting the hang of this stuff, so bear with me for a bit.

Here you will find a collection of information on some models of diesel electric locomotive which I have collected over the last several years. While my specific interest is General Electric locomotives, I also have collected data on EMD, Baldwin, Lima, ALCO, and others, and intend to post varied and interesting content on this blog depending on what I have at my disposal.

I can also, occasionally, post off topic discussion (which will be tagged as such) relating to my other interests or various personal topics. As well as an archivist and modeler, I am a hobby writer and a big fan of video games.

Thanks for checking out my blog.

        - Doggard