California Northern 504 on the UP Roseville Yard Deadline, though unlike a lot of the engines there, it was just stored until work could be done on it. Photo Credit: FresnoSubber

By far the most well known of the gensets, the 3GS21B was the quintessential choice for railroads both big and small, with 206 units ordered in total. The first phase of units had a flat long hood that stored everything but did not allow for dynamics, whilst the second phase allowed for dynamics via a raised long hood.

But yet while it seemed that these gensets meant business at first, just like Railpower, NRE’s Gensets were prone to failures on Class Is. All but KCS and CN got them, and all of them experienced at least one failure from these in the yards they served. They simply weren’t as exceptional at switching compared to the more durable engines that they replaced.

This is why no Class Is still have these. In fact, much of the 3GS21Bs have now become bait for Knoxville Locomotive Works rebuilds, such as for their NZE15Bs.

Despite this, these Gensets can still be seen on shortlines and even some passenger railroads, where the trains are less intensive.

Technical Specifications

General Info	-
Prime Mover	Cummins QSK19C x3
Horsepower	2100
Truck Type	Blomberg B (1)
Axles	4
Traction Motors	4
Minimum Weight	238,000 lbs (1)
Maximum Weight	275,000 lbs (1)
Model Base Speed	65 MPH (1)
Top Speed	55, 65, 71, 77, 83, or 89 (1)

Electrical System	-
Generator Max Current	855 Amps (Marathon 572RDL) ⚠️ (2)(3)
Max TM Current	1500 Amps
Max Continuous TM Current	900 Amps
Traction Motor Type	DC
Adhesion	25%
Transition Mode	Automatic with no Selector
Transition Groups	2,2,1,1 (1)
Transition Shunts	1,0.75,1,0.75 (1)
Generator Transition	Yes
Traction Control	ETC
Dynamic Braking Mode	Electronic Blowers
DB Max Current	700 Amps
DB Max Continuous Current	700 Amps
Blended Braking	No

Miscellaneous	-
Head-End Power (HEP)	нет
HEP Power Consumption	N/A
HEP Standby/Run Mode	N/A
Load Ramp Speed	5 Amps/Tick ⚠️
TM Overload Protection	No
Start Mode	Fully Automatic Start
Air Brake Schedule	26-L
Compressor CFM	159 (Atlas GAR37 @ 2750 RPM) (2)
Main Air Reservoir	35 Cubic Feet (1) ⚠️

Notes:

(1): Depends on the core unit (Basis for these specs was the GP9).

(2): Multiply these values by 3 to represent the 3 engines.

(3): Rating taken from the 572RSL. Also the generator’s 3 phase but like, toast or whoever made the page on the sd70ace pretty much explained that multiplying the values by three is not how it works but whatever. Do what you want.