Since this EMD product uses a 4 stroke prime mover (vs previous EMD 2 strokes), does radiator cooling air get drawn in from the walkway and forced up thru the radiators (as all GE 4 strokes do, ie..tunnel motor like)? Or does air still get drawn from the top of the locomotive down thru the radiators (as previous 2 stroke EMDs do)?
The ambient air is pulled through the shutters and the radiator cores by the fans, which discharge the warm air above the roof. This has been the standard design for EMD domestic road units since the beginning of time.
The exceptions are units such as the SD-40T-2,45T-2, MP15AC,MP15T and the GP15, in which the fan(s) push the ambient air through the radiator cores, where it is discharged through the roof.
The type of diesel engine (two stroke or four) is not relevant.
CPM500
Thanks. I always understood that EMDs fans pushed air from the fans atop the locomotive, down thru the radiators and out on the side vents. I understood that the purpose of the tunnel motor EMDs was to prevent hot air being drawn from the top of the locomotive in tunnels where the diesel exhaust would rise to the top of the tunnel and thus be drawn in from the radiators fans down thru the radiators.
If all EMDs exhausted air thru the top, how could the fans on top draw fresh air in from the top and exhaust it back out of the top?
VGN JessIf all EMDs exhausted air thru the top, how could the fans on top draw fresh air in from the top and exhaust it back out of the top?
I don't understand your question.
You said: "The ambient air is pulled through the shutters and the radiator cores by the fans, which discharge the warm air above the roof." Are you saying that EMD fans never pulled air from the top DOWN thru the radiators and out thru the hood vents? That is how it was explained to me several years ago on the forum, with the GE's doing the opposite (ie..pulling air thru the lower shutters and blowing UP thru the radiaters and exhausting thru the top).
EMDs have always pulled in air from the side grilles and exhausted it out the rooftop radiator fans. That's why F-units continuously had side upgrades; the later Farr air grilles allowed less dirt/dust to be yanked into the unit than the earlier screens.
GEs are similar, but the fans are located below the radiator cores, not above them like all EMDs but the tunnel motors.
The difference between the tunnel motors and standard models was that the radiator side grilles were located lower, so that the air that was sucked into them was cooler than the air higher in the tunnel near the top of the unit. They also had the fans below the radiator cores like GEs.
Now I understand (I hope); both EMD and GE pulled air thru the side grills and the fans sucked it up thru the radiaters and exhausted thru the top. The only difference is that with EMDs you can see the fan blades but you can't on a GE; right?
As I understand it, yes.
Thank you to all for "getting me straight" on a decades long misconception of mine. So the SD70ACe-T4 will maintain the EMD higher hood grates.
Can anyone provide some possible reasons why EMD prime movers don't draw cooling air lower on the hood, as GE does? It seems a no brainer to me that would provide cooler air in all situations without adding adding any additional cost.???
The current GE ET44 series locomotives draw cooling air in via those two large grills at the rear of the radiator assembly. This air is forced up through the radiators for the engine cooling system. The intakes forward are to draw air into the manifold & intercoolers.
The louvers further down at the rear are for the air compressor IIRC...
Drawing the intake air low like on the tunnel motors and early GE U-Boats draws in more dirt(and requires more filtration). Once EMD was able to cool the locomotive without the tunnel motor rear end(starting with the 50 line), the tunnel motor rear end option faded away. Note that GE also raised their intakes shortly following EMD. I suspect better/high capacity radiator cores were the solution...
Modeling BNSF and Milwaukee Road in SW Wisconsin
VGN Jess Thank you to all for "getting me straight" on a decades long misconception of mine. So the SD70ACe-T4 will maintain the EMD higher hood grates. Can anyone provide some possible reasons why EMD prime movers don't draw cooling air lower on the hood, as GE does? It seems a no brainer to me that would provide cooler air in all situations without adding adding any additional cost.???
Thank you all very much; I hope to never have ask a radiator cooling fan question again! :)
These days, the fact that engine cooling is managed by the locomotive control computer...and cooling fan(s) speed has been decoupled from engine speed enables enables unformity in the physical arrangement of the cooling system.
Almost, but not quite. Both EMD and GE pull air from the side grills. But on the GE the side grill is down by the walkway, so the fan pulls the air in from the side grill then "pushes" it through the radiator and out the top of the locomotive. There are no fans on the roof. This is the same way the EMD tunnel-motors and similar (MP15AC, GP15) work. ""Pusher" fans pulling from a low mounted air intake. The standard EMD uses roof mounted fans. In this case the air is "pulled" by the fans through the top mounted radiators from the intake grills mounted high up on the hood. For this to work, the radiator cores are mounted in a v-shape. On GE's and tunnel motors the radiators on the top of the hood are mounted horizontal.
Hope this helps.
Tom
VGN JessNow I understand (I hope); both EMD and GE pulled air thru the side grills and the fans sucked it up thru the radiaters and exhausted thru the top. The only difference is that with EMDs you can see the fan blades but you can't on a GE; right?
NOW, I understand. thanks again. I wonder how many rail fans are/were as misinformed as I was? Maybe I'm just in a minority of those who questions or wonder about these type things.
NorthWest VGN Jess If all EMDs exhausted air thru the top, how could the fans on top draw fresh air in from the top and exhaust it back out of the top? EMDs have always pulled in air from the side grilles and exhausted it out the rooftop radiator fans. That's why F-units continuously had side upgrades; the later Farr air grilles allowed less dirt/dust to be yanked into the unit than the earlier screens. GEs are similar, but the fans are located below the radiator cores, not above them like all EMDs but the tunnel motors. The difference between the tunnel motors and standard models was that the radiator side grilles were located lower, so that the air that was sucked into them was cooler than the air higher in the tunnel near the top of the unit. They also had the fans below the radiator cores like GEs.
VGN Jess If all EMDs exhausted air thru the top, how could the fans on top draw fresh air in from the top and exhaust it back out of the top?
Going through tunnels a train will cause surrounding air to warm up fairly quickly. The air is no longer cool at any level inside the tunnel. The grilles on the TM's were located at the walkway due to size, and configuration. Not for cool air as none would be present. TM's still had overheating issues just not as often as non TM equipped Dash-2's. The whole point of the setup was to rapidly cool off the rads before entering another tunnel.
It's a mis-conception that the reason for the tunnel cooling system on EMD's was that it would cool down faster between tunnels. The reason was the air temp is lower, the lower you measure in the tunnel. I was a co-op engineering student working at EMD in Dec. 1970 (or '71?) and was assigned to graph the temperature data taken during a test in the Cascades and at Donner comparing a standard SD45 with and without the elephant ears. I don't remember the exact temperatures, but the reason the T2 models got the green light for production was that the air was cooler at walkway level than higher up. As I remember, some of the snowsheds were open in the lower part where the temperature stratification was greater.
There's been a couple of cases where the elephant ears were used to improve the tunnel performance of more recent EMD units. If there was no temperature stratification, they wouldn't do any good, although their end result on tunnel performance is not huge.
I don't want to disparage anyone, but an EMD person once wrote an answer to a reader's question in Trains magazine re the faster cooldown so this mis-information is regularly repeated.
Dave
bogie_engineer It's a mis-conception that the reason for the tunnel cooling system on EMD's was that it would cool down faster between tunnels. The reason was the air temp is lower, the lower you measure in the tunnel. I was a co-op engineering student working at EMD in Dec. 1970 (or '71?) and was assigned to graph the temperature data taken during a test in the Cascades and at Donner comparing a standard SD45 with and without the elephant ears. I don't remember the exact temperatures, but the reason the T2 models got the green light for production was that the air was cooler at walkway level than higher up. As I remember, some of the snowsheds were open in the lower part where the temperature stratification was greater. There's been a couple of cases where the elephant ears were used to improve the tunnel performance of more recent EMD units. If there was no temperature stratification, they wouldn't do any good, although their end result on tunnel performance is not huge. I don't want to disparage anyone, but an EMD person once wrote an answer to a reader's question in Trains magazine re the faster cooldown so this mis-information is regularly repeated. Dave
Thanks for the correction, and I'll take your word for it.. In Nov 2002 Trains ask trains section. Jack Wheelihan stated in part of his explanation that the concept was developed for faster cool down not drawing in cooler air.
SD60MAC9500In Nov 2002 Trains ask trains section. Jack Wheelihan stated in part of his explanation that the concept was developed for faster cool down not drawing in cooler air.
Jack, bless his heart, knows more about steam than thermal engineering.
As I recall, the issue was directly related to stratification that turbulence didn't quickly overcome: the exhaust being vented into the tunnel does get 'turbulently mixed' in a comparatively short time, but not the time it takes radiators of a following unit to enter the 'exhaust plume' of a preceding unit. At that point the air 'down at running-board level' is still demonstrably cooler (as Mr. Goding's data no doubt substantiates) and intake air 'as low down as possible' will give better cooling air intake for fan effectiveness and radiator heat exchange, at least for the first units in a consist.
It would be interesting to see data from midtrain units, or helpers, on a consist in a long tunnel where the heat from exhausts and radiators has had a chance to equalize inside the tunnel volume -- there may still be some stratification, however, as the train's motion pulls cool air in as well as stirs the initial heated-air mass. Modeling this would be nearly pointless deterministically, so empirical data would be significant. I do suspect, however, that there would still be some thermal segregation vertically that would make low-mounted intakes/fans advantageous.
Naturally, in the "space between tunnels", any 'advantage' to stack effect through the radiators would be demonstrated -- again, I'd trust Mr. Goding's recorded information to indicate this. However, I'd also expect that within a couple of hundred feet from the end of a tunnel, fully cooled air would be present at 'equal' intake area whether high or low, and the effect of heat transfer to air mass would be comparable for either arrangement -- so there would be little additional 'recovery gain' from low intakes over conventional.
What was more interesting was that the 'elephant ear' methods to presumably 'duct' the cooler air up to conventional higher intakes were reckoned such failures. Investigating why that is so (I suspected it would have something to do with fan effectiveness in a hotter environment) would likely help establish why the low intakes were a better answer in practice ...
Overmod SD60MAC9500 In Nov 2002 Trains ask trains section. Jack Wheelihan stated in part of his explanation that the concept was developed for faster cool down not drawing in cooler air. What was more interesting was that the 'elephant ear' methods to presumably 'duct' the cooler air up to conventional higher intakes were reckoned such failures. Investigating why that is so (I suspected it would have something to do with fan effectiveness in a hotter environment) would likely help establish why the low intakes were a better answer in practice ...
SD60MAC9500 In Nov 2002 Trains ask trains section. Jack Wheelihan stated in part of his explanation that the concept was developed for faster cool down not drawing in cooler air.
There must have been a benefit from the elephant ear experiments 40+ years ago. Look at this Ferrosur ACe. Mind you this is from a 2015 order for 30 units?.. Which begs to ask. Did Progress Rail carry this option over for the T4's? If a customer were to request it.
Interesting, except that I can't figure out why Ferrosur would order locomotives with elephant ears when I consider their operating locale.
CSSHEGEWISCH Interesting, except that I can't figure out why Ferrosur would order locomotives with elephant ears when I consider their operating locale.
Ferrosur's (Ferromex) linea S operates through many tunnels in southern Mexico's Sierra Madre Orientals. Trains ran an article many years ago on Mexican Railroads.
Overmod SD60MAC9500 In Nov 2002 Trains ask trains section. Jack Wheelihan stated in part of his explanation that the concept was developed for faster cool down not drawing in cooler air. Jack, bless his heart, knows more about steam than thermal engineering. As I recall, the issue was directly related to stratification that turbulence didn't quickly overcome: the exhaust being vented into the tunnel does get 'turbulently mixed' in a comparatively short time, but not the time it takes radiators of a following unit to enter the 'exhaust plume' of a preceding unit. At that point the air 'down at running-board level' is still demonstrably cooler (as Mr. Goding's data no doubt substantiates) and intake air 'as low down as possible' will give better cooling air intake for fan effectiveness and radiator heat exchange, at least for the first units in a consist. It would be interesting to see data from midtrain units, or helpers, on a consist in a long tunnel where the heat from exhausts and radiators has had a chance to equalize inside the tunnel volume -- there may still be some stratification, however, as the train's motion pulls cool air in as well as stirs the initial heated-air mass. Modeling this would be nearly pointless deterministically, so empirical data would be significant. I do suspect, however, that there would still be some thermal segregation vertically that would make low-mounted intakes/fans advantageous. Naturally, in the "space between tunnels", any 'advantage' to stack effect through the radiators would be demonstrated -- again, I'd trust Mr. Goding's recorded information to indicate this. However, I'd also expect that within a couple of hundred feet from the end of a tunnel, fully cooled air would be present at 'equal' intake area whether high or low, and the effect of heat transfer to air mass would be comparable for either arrangement -- so there would be little additional 'recovery gain' from low intakes over conventional. What was more interesting was that the 'elephant ear' methods to presumably 'duct' the cooler air up to conventional higher intakes were reckoned such failures. Investigating why that is so (I suspected it would have something to do with fan effectiveness in a hotter environment) would likely help establish why the low intakes were a better answer in practice ...
Yes, I wondered about the benefit of the Cab Forward steam locomotives when to make the run in elevation leading to Donner Pass, they had as many as four locomotives throughout the train.
I guess with the Cab Forward arrangement, the crew is not getting hot, carbon monoxide fumes from a stack in right in front of them, but what about the mid-train and end-train helper locomotive crews?
If GM "killed the electric car", what am I doing standing next to an EV-1, a half a block from the WSOR tracks?
That was described in the Classic Trains issue some years ago on Southern Pacific's AC's on what crews of mid-train and trailing helpers had to do.
As I recall, the story told that the crew would have sheet metal cone connected to a air hose leading to a valve and a connection to the engine's air reservoir. They'd soak cotton waste in water to serve as a filter, stick it in the cone, open the valve, and strap it on to serve as an air respirator.
Unless the SD70ACe's and the partial collapse of Mullan Tunnel (And subsequent daylighting of one end) have changed things dramatically, the situation isn't much different today for Montana Rail Link helper crews on Mullan Pass. They have air tanks and breathing apparatus attached to the rear cab wall of their helper power. Crews have to wear these pressurized hoods in helper duty through the tunnel.
And there's a great story in Trains circa 2000 of the 3985 and 844 on Donner Pass. It's told by the fireman on the trailing locomotive (I think the Challenger). The plan was to coast through the tunnels to avoid steam cleaning all the diesel soot on the tunnel and snowshed roofs and dirtying up the power and passenger cars, but the accompanying diesel trailing the steamers failed half a mile into the climb through the two mile long Tunnel 41.
The crews all had air masks connected to portable air supplies, so breathing wasn't an issue as I recall when the steamers had to take over. But the air temperature in the cab of the trailing steamer was estimated to have reached 200 degrees and visibility was almost 0. As I remember, the article even said that the smoke alarms in every passenger car went off. Certainly one of the more memorable stories in the 80 year history of Trains Magazine.
Overmod What was more interesting was that the 'elephant ear' methods to presumably 'duct' the cooler air up to conventional higher intakes were reckoned such failures. Investigating why that is so (I suspected it would have something to do with fan effectiveness in a hotter environment) would likely help establish why the low intakes were a better answer in practice ...
I think it's two-fold why they don't work as well. The ends being open allows air higher up to bypass the area below the handrail and doors were not deemed practical. Also, the hot side fans are working with less dense air so their mass flow is lower. The reason the SD40-T2 worked well with two fans while the standard SD40-2 needed three was that the fans pumped lower temperature air prior to entering the radiators so could move a higher mass of air, it's mass flow not cfm that does the cooling. Since they did pump more mass, those T2 fans each operated at a high HP draw than the rooftop fans. Another factor was the placement of the fans further from the radiator cores and the large open inlet area made for lower system resistance. It wasn't until the 50 series with the taller inlet shutters that the airflow path was improved.
EMD has built many export locos with cold side fans but that was typically done because the lower clearance diagrams forced the radiators lower and to be able to have the radiators at the right height relative to the engine top deck; I think the criteria was the bottom of the radiators had to be no lower than 11" above the top deck.
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