U25toU36

General Electric "U-boats", U25 through U36

On another page of this article, it was mentioned that numerous submodels of the FDL-16 were built, and are referred to in the maintenance manuals by drawing number, but reference is made in the U30 sales brochure to an actual subletter on the FDL-16 nomenclature. This is reflected elsewhere as well. The E9900, E9900A and E9900B reflect modifications in the 2500 HP for traction (2750 gross HP) engine of the U25. The drawing E-13461 (seen on the U30 page) applies to both the U28 and U30, and also apparently to the U33 before about 1969. E-16188 is found in 1969 and appears to apply to all units of type U23, U30, U33 and U36 produced after some unspecified time which likely corresponds to introduction of either the U23 or U36, which would be either 1968 or 1969.

E9900A

E-16188

Controls

The three-lever control stand familiar to many was, of course, originally inverted from the usual position and mounted on the forward cab bulkhead in the few high-nose U25 units built. The normal arrangement was used in all production low-nose U25 units, and in all units of type U28. Units of type U30 used the old three-lever stand partway into 1968, at which time they changed over to the new two-lever stand. This two-lever stand was used in all U23, U30, U33 and U36 units until the AAR approved controller was employed beginning about 1972 (except for the few units built with the EMD controller which was essentially that used in everything from late GP-9 units up through the AAR controller in that make as well.) The two-lever stand was converted to 8-notch throttle in 1969.

At right, the "two lever" GE control stand. GE officials had noted numerous complaints about the original controller and its throttle, noting that in order to ensure that proper operation was obtained and that enginemen not "hang up between notches," that the original design included "some easy notches and some hard ones." The new controller was designed to have the same feel in all notches, and obviously has a shorter and easier to manipulate throttle handle (11, the lighter colored handle) which is also more beside the engineer than in front of him. In addition, GE had also, to quote, "rounded off the notches" electrically. The new transistorized excitation system included a rate control circuit that limited rate of increase of excitation level, whether by throttle operation or by load regulator operation. This continued on later models, and was later supplemented in about 1970 by the pressure-bias load control and fuel limiter device, which essentially limited fuel injection based upon intake manifold pressure. This was yet another way to prevent smoking, and increased engine wear as a result of excessive fuel injection for the available boost.

The "1966 locomotives" had introduced the engine air filtration system seen at left, which included six oil bath air filters, onto the front of each of which was mounted a single unitized GE air cleaner. Dirty air was removed via an exhauster mounted in the diesel engine exhaust stack, known as an aspirator. (This was supplemented at low engine load by pressurized air tapped from the sealed off space of the underframe, normally used for cooling of equipment, and a valve in the system prevented mixing or backpressuring between the air system and the diesel exhaust.) Yet another change was made with the first test U33 units, and adopted when the U33 went into production in 1967. The GE air cleaners were then mounted in side doors, in a new plenum arrangement, with the oil bath filters still on the bulkhead. Later, paper air filters were made available, replacing the oil bath filters. The diagram of the first U33 test units (note flowing roofline from hood to radiator section) shows the change in engine air filtration.

In 1963, ALCO introduced its Century series of improved locomotives. Included in this line was a locomotive which included all of the most modern features, available with all of the options, but which was rated at only 2000 HP instead of the industry standard 2400 HP or 2500 HP. This was the C-420, intended for sale to roads which did not require, or could not use, the high horsepower per axle, or did not want the high purchase price or maintenance cost of higher power units. The C-420 sold better than predicted in some quarters, and when EMD introduced its "1966 Line" of units powered by its new 645 series engine, both a new 2000 HP B-B and matching C-C were included. (ALCO had cataloged a C-620, but none were ever built.) Following these developments, and an intial takeoff in sales for the EMD GP-38, General Electric decided that there was enough market demand in this segment to enter it.

General Electric had already been producing for export a 12-cylinder engine, known as the FDL-12, and simply placed it in the contemporary U30 body. At first, only direct current transmission was available, using the tried and proven GT-581 for the B-B units and the GT-586 for C-C units. Later, an alternator-rectifier transmission was made available. General Electric, in order to both enter this market and have an advantage in it, decided to rate its 12-cylinder engine at 2250 HP for traction. This resulted in U23B and U23C models, and essentially forced EMD into developing a directly competitive turbocharged 12-cylinder GP-39 and SD-39 rated 2300 HP for equality of competition and operating characteristics.

Original DC transmission U23B at right. Note extension shaft from generator gear case to equipment blower, necessary since the 12-cylinder engine was much shorter, but had its accessory end located at the same place as a U30's FDL-16.

At left, and very obviously not shown to scale, the U23C. This design did not sell extremely well, selling mostly for heavy ore service or else hump yard service.

Left, 1967 advertisement for the U33.
Right, 1970 advertisement for the U36.

Both advertisements point out the capacity of the units in terms of haulage at speed per ton of locomotive weight, in which category GE had the lead. However, adhesion problems apparently continued to plague the high horsepower four axle units, even with advanced Automatic Power Matching systems which had been developed essentially for the U33, and were applied to U30/U33/U36 locomotives as standard in four axles, and optionally in six.

We hope you've enjoyed this little journey through some of the less often seen technical details about GE road locomotives built during their "first generation," which as we all know actually helped to trigger the "second generation" locomotive designs of EMD and ALCO -- a period of time which ALCO, as a locomotive builder, would not survive. It is obvious from both the transcripts of the annual meetings of the Railway Fuel and Operating Officers' Association, and from the GE manuals, that GE tirelessly tried its best to improve the locomotives, and to respond to wishes and complaints from the railroads, right down to the enginemen. It is certain that GE's position in the field today reflects this unending commitment to improvement.

In addition to the RF&OOA transcripts, 1959 through 1972, and the U30 sales brochure dated 1967, the following actual GE manuals from our collection were used in writing this article. (The original article ran 10 pages, was later deleted, and now some content reappears here with some new content added as well.)

GEJ-3812C, Diesel Engine Mechanical Service Manual, Model U25B Diesel-Electric Locomotive, 4/63
GEJ-3813A, Electrical and Air Equipment Service Manual, Model U25B Diesel-Electric Locomotive, 3/62
GEJ-3815B, Educational Manual, Model U25 Diesel-Electric Locomotive, 6/66
GEJ-3816, Operating Instructions, Model U25B Diesel-Electric Locomotive, 3/62
GEJ-3816B, Operating Manual, Model U25 Diesel-Electric Locomotive, 1/64
GEJ-3834, Operating Manual, Model U28 Diesel-Electric Locomotive, 1/66
GEJ-3837, Operating Manual, Model U28 Diesel-Electric Locomotive, 5/66
GEJ-3847, Diesel Engine Mechanical Service Manual, Diesel-Electric Locomotive, 3/67
GEJ-3848, Electrical and Air Equipment Service Manual, Diesel-Electric Locomotive, 6/68
GEJ-3849, Educational Manual, Model U30 Diesel-Electric Locomotive, 4/67
GEJ-3849A, Educational Manual, Model U30 Diesel-Electric Locomotive, 7/68
GEJ-3856B, Operating Manual, Diesel-Electric Locomotives, 6/72
GEJ-3866, Educational Manual, Model U33 Diesel-Electric Locomotive, 1/71
GEJ-3869, Diesel Engine Mechanical Service Manual, Diesel-Electric Locomotives, 5/70

Other manuals are in the family collection, and were not specifically used as they are duplicative or not directly contributory. The RF&OOA transcripts are from the Dave Davis Collection. GEJ-3816, GEJ-3834 from Matt Newshutz Collection. All other manuals and U30 brochure from Will Davis Collection.

The information and pictures on this site come from original non-copyrighted materials; they are employed solely for the information and entertainment of enthusiasts, but also serve as a tribute to the often unspoken many thousands of man-hours put into the development and testing of this line of locomotives, and those who performed this work.

Air system

Further developments

to see the various engine diagrams together.