• U25B in U28B clothing?

  • Discussion of General Electric locomotive technology. Current official information can be found here: www.getransportation.com.
Discussion of General Electric locomotive technology. Current official information can be found here: www.getransportation.com.

Moderators: AMTK84, MEC407

  by Allen Hazen
The Rock Island acquired a very large number (42: about 1/15 of their total locomotive fleet!) of U28B units in 1966. One or two were explicitly replacements for wrecked U25B units (this, or one of these, being the last U28B built with a U25B-style carbody).

I assume -- but don't know for a certainty -- that these would have re-used major components from the wreck victim(s). ???

If it (they) did re-use engines from the U25B units, were the engines modified to give 2800 hp(*), or were these 2500 hp U28B?

(Question inspired by recent query about FT to GP-9 trade-ins or rebuilds on the EMD forum.)


(*) As I understand it, the engines in "stock" U28B had a different exhaust manifold -- designed to get better turbocharging results -- from those in U25B, so you couldn't turn a U25B engine into a U28B engine just by re-setting the fuel racks. So, another question: what were the engines in the late U25B (for New York Central and SLSF) that had a 2750 hp rating like?
  by Typewriters
All of the important modifications found in the U28's 7FDL-16C engine could be backfitted to the 7FDL-16A engine, although in some cases machining of the block was required to fit the new cylinder units. The major changes other than fuel rate were the new steel cylinder head inserts / new cylinder assemblies and the single-pipe exhaust manifold. The electric transmission of the two units was the same in major essentials. (The design of the cylinder liner also changed.) So, my point is that even if they did re-use the engines it would not have precluded the units from being rated 2800 HP.

In addition, I have no clue where the "2750 HP" rating for pre-production U28 units interspersed with production U25 units came from. All official GE data from that time period shows 2800 HP for traction / 3050 HP gross for the C-series engine in either pre-production U28 or production U28 units. (In fact, there's no distinction ever made.)

To make that a little more clear: Nowhere in any of the fuel rack setting / load testing data for all models is there reference to a 2750 HP domestic locomotive with 16 cylinder engine. Whatever the case, you can be sure that these were simply pre-production "C" engines.

There is reference in one GE Annual Report I have here, printed before introduction of the U28 (no mention of it in fact, with production of U25 in full swing) that mentions road testing of a new design engine cylinder assembly in some units. This is only of interest in the following aspect: That report doesn't mention a higher power rating, just the testing of that new design cylinder unit (which we can probably safely assume to be the steel cylinder head insert design change.) The implication here is that the steel head units eventually adopted for the 2800 HP "C" engine might have spent time running around in 2500 HP "A" engines running up test data before any 2800 HP pre-production units were built by GE interspersed with U25 units. This is deeply speculative, and obscure and probably pointless to consider. However it does make sense to me from an engineering and testing standpoint and cannot be precluded. I will have to dig out the accordion file that report is in and get the year it's reporting on.

How is THAT for focusing on the obscure? Rivet-counting at its finest... even this many years later.

-Will Davis

See here for engine changes from the U25/U50 to the U28. http://railroadlocomotives.blogspot.com ... -no-2.html