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Spotters Guide

IDC 001

Confused about the differences between a GG20B and a GG10B? Want to know what makes a Green Kid a GK10B? Was that an RP20BD you just saw, or something else? What makes a genset locomotive a genset? Heck, what's that NRE thingy? 2GS-something, or 3 or ten? Want a little help?

Well, suffer no more (I hope). This section will strive to explain what makes each model, well, each model, using exceprts from a 17-page spotter's guide I put together. You can also download the complete Guide by following this link or clicking on the icon at the left. Warning: 3.2 megabytes.

The expanded version of the online spotter's guide now encompases models built by NRE, MotivePower, Brookville, and others, as well as Railpower's hybrids and gensets. For roster information on the Railpower hybrids, see the home page for this website at For roster information on the Railpower, NRE, MotivePower etc. gensets, see this site's companion,

The online version of the guide is divided up into sections, with a photo at left to illustrate each one. For a larger view, click on the photo. The links on the model numbers lead to the rosters for each. I hope this comes in handy. Enjoy!

RPRX 2001

Hybrid: Railpower GGS2000D

This is the prototype unit is numbered RPRX 2001, and named “Emerald”. The most noticeable difference in the RPRX 2001 is the very low long hood, which stands at roughly half the height of later productions models. The newer units have larger diesel generator sets and more batteries. The 2001 also has a slightly different cab shape than production models, most notably the flat face where the front and rear windows are located. (On production models, the cab face has a slight but pronounced peak to it.) The 2001’s rear cab windows are also much larger than the production models. Also the nose and end of the long hood are of a slightly different shape when compared to production models. The car body sides don’t have any louvers like other versions do. Instead, the batteries are vented from the top.

KCS 1869

Hybrid: Railpower GG20B ph. II

Note: I am going along with popular convention here when I reference the first production GG20B’s as Phase II locomotives. I believe the so-called Phase I model would be the GGS2000D prototype. The Phase II GG20B encompasses all models built between 2004 and early 2006. It is most easily distinguished from later versions by the rows of vertical louvers along the sides of the long hood. Louver count is also a spotting feature between the GG20B  and GG10B models, but we’ll cross that bridge in the next section. The diesel generator unit is housed at the end of the long hood, where the horizontal louvers are located. There is a small exhaust stack on the top of the hood, along with nine small round vents centered on the top of the hood above the batteries.

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Hybrid: Railpower GG20B ph. III

The so-called Phase III GG20B was introduced at the beginning of 2006. The biggest difference between the ph. II and ph. III units are the lack of vertical louvers on the long hood, and the inclusion of much larger air vents on the top of the hood over the batteries. I am not sure if it is a specific spotting feature or just an option on specific units, but all of the Phase III units built so far have only one window in the cab doors. Most (but not all) of the Phase II units have a second, smaller window below the larger one in both doors.

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Hybrid: Railpower GG20B ph. IV

In late 2006, Railpower made a minor change to the GG20B model at the behest of Canadian Pacific, equipping it with a larger diesel generator, rumored to be 500kW as opposed to 250kW in the other production models. The result was what I have called the Phase IV GG20B. The most noticeable difference between the ph. III and ph. IV models is an enlarged section at the end of the long hood that houses the larger generator. There are also two exhaust stacks over the generator in the models built so far. As of late 2006, Railpower had constructed two of these units, CP 1704 and CP 1705. Because of the termination of the CP contract, neither unit was delivered.

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Hybrid: Railpower GG20B Variations

Several variations on the GG20B theme have been built, most notably the first four units built for BNSF in late 2005. (See figure 4 below.) All four units are phase II GG20B’s. The BNSF units were built as remote control platforms, and don’t have cabs per se. The electrical panels on the units are still in their original locations inside the “cab”, and a small portion of the cab is retained for that purposes. There is even a cab door on the front face of the enclosure.

Another variation is the locomotives built for Union Pacific (UPY 2300-2319) Those locomotives were converted using retired General Electric B30-7 and B30-7A locomotives, which are slightly longer than EMD’s GP9. They also have the very distinctive GE two axle trucks rather than some variation of the Blomberg truck that the other units ride on. The UPY units are split up between two orders. UPY2300-2309 are phase II units built in 2005, while the 2310-2319 are phase III units being delivered in 2006. See the photo above of the ph. III GG20B for an example of the UP configuration.

At least one locomotive so far, BNSF 1205, is in the process of being converted to run on fuel-cell propulsion instead of a diesel generator. No official model designation has been given to this unit yet.

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Hybrid: Railpower GG10B

The GG10B is a 1,000 horsepower version of the Green Goat switching locomotive, and shares numerous features with its GG20B cousins. The GG10Bs built so far have the same cab and hood configurations as a Phase II GG20B. The biggest spotting difference between the two is found in the vertical louvers on the sides of the long hood. The GG10B has seven sets, while the GG20B has 14. Also, the GG10B has five vents on the top of the long hood, directly above the batteries, while the GG20B has nine.

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Hybrid: Railpower GK10B Prototypes

The GK10B is a smaller cousin of the GG20B and GG10B switchers. As they are called Green Goats, then the smaller ones logically would be Green Kids, right? The biggest difference between the GK10B and the GG10B is the platform – where the Green Goats are built on an EMD GP9 frame, the Green Kids are built using an EMD SW or similar style switcher as a base. The first three GK10B’s were built from ex-Canadian Pacific SW1200’s, and retained a very EMD SW-like appearance, including the rounded switcher cab on the end of the unit, and the same overall height of the long hood.  About the only thing to distinguish the early Green Kids from their EMD SW counterparts is the lack of louvers in the long hood, and the lack of large exhaust stacks on the top of the hood. The early Green Kids also lack the SW’s taper at the cab-end of the hood, and the radiator fan housing at the other end.

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Hybrid: Railpower GK10B Production Model

Railpower’s Green Kid model came of age in late 2005 with the delivery of Railserve 356, the first “production” GK10B built. The unit, built on a former BN (ex-Frisco) SW9, basically looks like a shortened GG10B. Railserve 356 features a similar (if not the same) cab as the GG-series locomotives, and a shorter but similar long hood. Like the GG10B, the GK10B has seven rows of vertical louvers by the batteries, and the four rows of horizontal louvers by the diesel engine. The nose is also similar, but shorter. Like the GG conversions, the Green Kid retains a lot of its SW personality from the frame line down.

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Hybrid: RP20BH Prototype

The RP20BH is Railpower’s hybrid version of its 2,000 horsepower road switcher. It uses a pair of 667hp diesel generators and a smaller bank of batteries for propulsion. A prototype for the RP20BH is under construction as of mid-2006 in Schenectady, NY. Externally, the RP20BH is very similar to the RP20BD. The most obvious difference between the two is the RP20BH’s pair of vents over the battery compartment at the front of the long hood. Because the BH has two diesel engines and the BD has three, the configuration of stacks on top of the hood is different as well. Like the RP20BD, the RP20BH is to be built using retired second-generation EMD GP-series road switchers as platforms.

Hybrid: RP20BH Production Model

To date no productions RP20BH locomotives have been produced. Given the differences between prototype and production model RP20BH's, I'd expect a similar variation in the RP20BH.

KCS 1869

Genset: Railpower RP20BD Prototype

The RP20BD is the only locomotive built by Railpower that is not hybrid. Rather than using a diesel generator and a bank of batteries to achieve its propulsion, the RP20BD uses three 667 hp diesel gensets in sequence, starting and shutting down each one as needed for traction. The carbody design of the RP20BD shares several features with the other Railpower locomotive models, including very similar (if not identical) cabs and short hoods, and similar styling in the long hood. The RP20BD units are designed to be built atop a larger EMD road switcher type frame, including the GP30, GP35, GP38, GP40, GP50, etc. The prototype was built on an ex-Canadian National GP40-2.

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Genset: RP20BD Production Model

Union Pacific received the first production RP20BD locomotives in late Sept. 2006. The units vary from the prototype in several aspects. First of all, the UP units lack the large radiator section at the end of the long hood. In lieu, it appears that the radiators are incorporated into each motor assembly. They also have a much sharper angle to the nose and short hood sections in front of the cab. The UP units were also built on former GE locomotives.

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Genset: RP14BD

Norfolk Southern is the first taker so far for Railpower's first entry into the twin engine genset locomotive market, the RP14BD. When completed by TMS from kits provided by Railpower, the RP14BD will feature two Deutz engines for a total rating of 1,334 horsepower. The first two units are being built on retired SW1500 switcher frames, though frames like the EMD GP9 and similar can be used as well.


Genset: NRE 2GS14B Prototype

National Railroad Equipmen set the locomotive market on its side with the release of UPY 2005, a center-cab switcher with two Cummins QSK-19 diesel engines under the hood. The Genset locomotive was born. While both engine/genset combos were low-emissions rated, the unit achieved further emissions reductions by using only one of the two when the additional power wasn't needed.

The 2005 was built on the frame of a former SP MP15 switcher. So far, the center-cab design hasn't been repeated.


Genset: NRE 2GS14B Production Model

A total of four 2GS14B two-engine genset locomotives have been built, plus a demonstrator unit for NRE. The production version of the 2GS14B has a more conventional road switcher layout, with both gensets together under the long hood, and the cab toward the front.

Like the prototype, the productions units use a pair of Cummins enignes, for a 1,400 horsepower rating. Of the five produced so far, three have been built on recycled EMD GP-type frames. The other two were built on brand new framses, as has been done with the 3GS21B's.


Genset: NRE 3GS21B

National Railroad Equipment's 3GS21B genset locomotive looks quite a bit different from the Railpower RP20BD, but the technology is similar. Like the RP20BD, NRE's 3GS21B uses three diesel engines for propulsion. In this case, the engines are Cummins QSK-19's, rated at 700 hp each, for a total effective rating of 2,100 hp.

Operation is very similar to the RP20. The first 60 units built are for the Union Pacific for use in Los Angeles, CA, where the twin-engine prototype 2GS14B can be found. The very first unit, UPY 2701, was delivered in late December, 2006.

Unlike Railpower, which uses stripped locomotive frames for its conversions, the GS21 is built on an all-new frame, though the first unit built appears to be using recycled Blomberg trucks, and possibly a recycled fuel tank as well. The locomotive has a radically different cab configuration than the Railpower units, with much smaller windows, and a taller short hood.


Genset: Brookville CoGen

Brookville Equipment Co. of Brookville, PA has perhaps the most ambitious view of the multi-engine concept, taking it a few steps further. Their CoGeneration line of road switchers is being designed not only to run with multiple engines, but to have the option of electric or battery power built in as well. The CoGen line also features regenerative braking that generates power for the systems while braking at speeds down to 0.6 mph.

The prototype un it in the CoGen line was built using Maine Central 259, an EMD GP38. The unit features three Cummins QSK-19 engines for power. Those engines are rated at 700 hp each, giving the unit an agregate horsepower rating of 2,100. Brookville literature mentions the use of all-new construction frames, but the first one is definitely a recycled unit.

Visually, this unit is quite a bit different from any other genset offerings, in that it has a more conventional height long hood, larger radiator fans, and the stock-looking EMD cab and nose.

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Genset: MPI-Wabtec MP21B

Though most commonly associated with LNG and larger single engine locomotives (see the next sections below for more details) Wabtec subsidiary MotivePower Industries of Boise, ID is in the process of preparing a three-engine genset switcher for the market.

The MPI/Wabtec version will be similar in appearance to the Railpower RP20BD (which should help muddy the waters up a little more in the spotting department...) but will use a trio of 700 hp Cummins QSK-19 engines, for a combined total of 2,100 horsepower.

In the summer of 2007, MotivePower created a test bed unit for internal use on the frame of a former New Jersey Transit GP40FH-2. The prototype is expected to be complete by Nov. 2007, with production scheduled for early 2008.

MPI has also mentioned that a two-engine, 1,400 hp model is in the planning stages.

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Not a genset: Morrison-Knudsen MK1200G

In the early 1990’s, Liquified Natural Gas (LNG) was in vogue as an alternative to the emissions of diesel fuels. Several railroads experimented with LNG conversions, most notably the Burlington Northern railroad. In the middle of this movement, Idaho-based MK turned out four prototype LNG-powered switchers, two for the Santa Fe and two for the Union Pacific. The MK1200G stands out from the Railpower units by having the larger radiator and two fans at the end of the long hood, and the single large stack for the LNG-powered prime mover. The units also have very different patterns of air grilles on the side of the long hood, and some subtle differences in the cab shape.

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Not a genset: MPI MP1500D and MP2000D

MotivePower created a line of 1,500 horsepower and 2,000 horsepower Caterpillar-powered switching locomotives, classed as the MP1500D and MP2000D respectively. The units bear quite a bit of similarity to the MK1200G, with the large radiator fans at the end of the long hood. One common theme among all of these offerings is the recycling of retired first generation diesel frames. In many ways, the business model set by the MK1500 and MK2000 is similar to Railpower’s conversion model of today.


Not a genset: EMD/MPI GP15D and GP20D

In cooperation with MPI-Wabtec (MK’s latest incarnation), EMD catalogs the 1,500 horsepower GP15D, which basically looks like the MP2000D. Like the MP2000D, the GP15D is easily distinguished from Railpower’s units by the large exhaust stacks and the two large radiator fans at the end of the long hood. Some variations also have dynamic brakes, which makes them look even less like Railpower units.


Not a genset locomotive: MPI MP20C-3 and MP20GP

MotivePower is remanufacturing retired SD45 locomotives with 2,000 horsepower Detroit Diesel engines for Pacific Harbor Lines and giving them model designation MP20C-3's. They have also remanufactured 2nd generation Geeps for PHL and Union Pacific, giving them the model designation MP20GP. Though they are low-emissions locomotives (and even say so on the side of the hood) they use a single engine and therefore aren't part of this site.

For corrections, questions or to contribute photos, please e-mail me at: Thanks!

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