• P42 cooling

  • 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 scannergeek
I just recently saw a picture showing the roof of an Amtrak P42, and there's only ONE fan on the roof! That one fan is probably for the dynamics. But when I've seen freight locomotives, there are 3-4 fans up there.

The P42 barely has any vents on the side either.

So how does the diesel engine receive air to cool itself?

  by Justin B
All GE locomotives from the Uboats up to the Dash-9s (GEVOs too I think) have only used one LARGE fan to cover cooling, as opposed to EMD that uses 2 or 3 smaller fans depending on the model.

  by EDM5970
Almost- Alco and GE typically used one large fan, engine driven and through a right angle drive and eddy current clutch. (Note the use of the word typically.) The U-25 family used two smaller fans, again engine driven. Some of the latest GEs use a large three phase electrically driven fan. On the 6000s it even reverses periodically to blow leaves and other debris out of the radiators.

EMD had a different approach, at least on later E and F units, and on the Geeps and SDs. They used several smaller three phase electrical fans, getting their power from an alternator built on the engine end of the main generator; this alternator also powers the traction motor blowers.

EMD "pups" had belts to the fan, as did the FT and I believe the passenger units up through at least the E-6. I just looked at a schematic and the F-3 had electric fans.

Again, the word 'typically' is important; I know UP switchers have been rebuilt with electric fans, etc., etc., The word 'all' can get you in trouble-

  by DutchRailnut
On the Genesis the fan is electric driven

  by timz
"this alternator also powers the traction motor blowers."

On older EMDs (up through the 40 series, at least) the TM blower was direct-connected to the engine.

  by DutchRailnut
maybe model 40 but every GP unit or F unit and E unit EMD had electric traction motor blowers , but lets get back to GE as thats what this forum is about.

  by Kevin B.
I really hope I'm not getting too far away from the topic on this post, but where exactly is the fan on the Dash series locos? It is not visible from the top like the EMD fans are.
  by Allen Hazen
Kevin B--
You're question reminds me of the days when I was first becoming a railfan, hanging over the railings of bridges over tracks in Pittsburgh, seeing LOTS of locomotives from above!
GE puts its (one, large) fan beneath the radiator, whereas EMD puts its (numerous, individually motored) fans above the radiator where they can be seen easily from above. The radiators themselves are at the rear (away from cab) end of the long hood, so looking down you see a large rectangular grill (wider than the hood itself on Dash-7 and later units: the "wingspan" on these GE units is the radiator housing. The fan is below this.
The radiator and fan arrangement is similar on a GE "Genesis" passenger locomotive, except that the radiator grill is in a cut-out toward the back (but not at the extreme back) of the passenger unit's full-width roof.
EMD copied the GE arrangement, putting the fans below the radiators, on their SD45T2, SD40T2 and GP15-1 units of the mid to late 1970s.
Since the two locomotive builders have pretty much stuck with their different schemes for several decades, it seems that there isn't much of an advantage to be gained from arrangement over the other.
  by Allen Hazen
While we're listing...
EMD used the "tunnel motor" style, fan under radiator, on the MP15AC too. (And I ***think*** had traction motor blowers driven mechanically by extension shafts from the engine on early-- SD-7, SD-9 -- SD units.)
GE used two fans on the original (1984 to 1986) Dash-8 units before reverting to a single fan for later Dash-8 and Dash-9.
GEVO units have the usual big GE radiator fan (I assume), but ***may*** have a second fan (somewhere in the "humpback" area at the front end of the radiator wingspan) for their air intercooler. I don't know.
GE went for mechanically driven radiator fans on the U25B for simplicity: it was part of their boast that the U25B had only four (?) rotating electrical machines above the deck. And simplicity was supposed to yield maintainability. Having the fan run by a separate electric motor, as on Dash-8 and later, allows more precise control, and so contributes to fuel efficiency (run the fan ONLY when needed!). The change reflects, I suppose, larger changes in the economic/social/corporate environments in which the locomotive builders' railroad customers operate.

  by Joe
In this picture: http://www.railpictures.net/viewphoto.php?id=79778 of an old B23-7 being ripped apart, you can see the one large fan under the flared radiator up top. If you ripped up a P42, it would look similar. :-D
  by Allen Hazen
Sort of a sad picture.... (Sniffle.)
If you go to the "General Electric" section of George Elwood's marvelous "Fallen Flags" rail photo (etc) site,
you can see some GE advertising artwork showing a U25B with the hood removed: basic arrangement is recognizable despite the 18 or so years between the early U25B and the Conrail B23-7 shown being scrapped in Joe's link.
Question I've asked before with no response: in U30 and U33 built in early 1968 there is a triangular fillet connecting the front of the radiator "wingspan" with the normal-width hood in front of it. Was this purely decorative, or did some of the piping for the radiators go through it? I think I've seen a photo of a U33 being scrapped showing a circular hole in the front sheet of the wingspan that would have been covered by the fillet in an early U33.
  by ATK
If you ripped up a P42, it would look similar.
The only thing the cooling systems of a P42DC and a B23-7 have in common is: they have set of radiators, and there is a single rad fan. Other than that, the manner in which the fan and radiators is configured in the carbody and the cooling system strategy is completely different.

The cooling system on the P40/P42DC is unique and not like that of any other GE locomotive. The standard cooling system setup on all GE locomotives (to the best of my knowledge) U, D7, D8, D9, AC including the P32ACDM, consists of the following: a rad fan (or fans) driven by either a motor or shaft driven off the free end of the engine via the right angle drive; a set of radiators directly on top of the rad fan. Air is drawn in the vertical side screens or angled screens (if the locomotive has "wings"), through the fan which blows the air through the radiators, and is exhausted out the top of the locomotive. The system strategy is a wet/dry system, in which water is not always in the radiators. A flow valve or diverter valve which is regulated by water temperature, opens at the designated temperature allowing water to flow to the radiators for cooling. On the U-series and Dash 7's, the speed of the rad fan depends on the speed of the diesel engine. On everything else with a motor driven fan, there are three fan speeds, 1/4 speed, 1/2 speed and full speed. IIRC, full speed is 3000 RPM's. The speed of the rad fan motor is regulated by a panel with a series of thyristors and is powered by the alternator. All rad fans that are motor driven have the capability to be run in reverse to blow out the air intake screens (this is done during normal maintenance cycles).

The P40/P42DC cooling system has what as known as a wet system, whereas water is always in the radiators. If you looked at a cross section cut-away of a P42DC, you would see from bottom to top, the radiators, a set of shutters, and the rad fan sitting on the very top. During cooling, the rad fan must draw air through the vertical V-screens, through the radiators, through the open shutters, through the fan and exhausted out the top. My understanding for why this type of system was originally installed in the P40 was that the GE engineers, during the design stage complained that they could not install a standard wet/dry cooling system into the Genesis style carbody. The wet system was developed as a result. (Ironic that only 2 years later, the P32ACDM would be released with a standard wet/dry system, however to support a smaller engine, 12 cylinders versus 16.) The shutters are needed to retain heat when the engine is warming up or is very cold and opens when the fan turns on. The speed of the fan is driven by engine water temperature. One of the original problems with the P40's during the winter time (especially on trains like the Empire Builder) was that the radiator compartment was constantly getting filled up with snow coming in through the vertical V-screens. Shop personnel would literally have to shovel out the back of the locomotive before any work could be done in the rad cab. One of GE's modifications to the fleet was to add a second set of shutters, just inside the vertical V-screens (air intake). These shutters would open at the same time as the horizontal shutters on top of the radiators.

The only locomotives that I know of that had twin rad fans are the U25B, C39-8 and the AC6000. Everything else had a single fan. GE originally advertised the mechanical driven fan as better, as in not driven by a motor that could fail. The classic Dash 8's were the first locomotives to have motor driven fans. In my opinion, the motor driven fan is a far superior design.
  by ATK
Allen - to answer your other question, I would have no idea, and I doubt that anyone from GE even remembers those locomotives. Your best bet would be to find someone who has (or has had) physical contact with either a U30 or U33. I think IRM has an ex-BN U30C, but I'm not sure if it has the "fillet" you mention. What's the LS&I running these days? A contact with those folks might answer your question.
  by Allen Hazen
Thanks, ATK (for the longer, very informative, discussion as well as for suggestions about my fillet problem)!
Come to think of it, the first, 1968, U23 -- U23B for D&H and, I think, U23C for LS&I -- also had the fillet, and I think one of the LS&I units may have been saved by a museum.
  by ATK
Yes, you are correct that the first U23B's built for the D&H had the so called fillets. Not quite sure, but I think all the D&H U23B's have been cut, with the exception of the 2309 on the Quebec Central(???).