I think you're thinking of recent designs from GE and EMD, which intake through the side and exhaust through the top.
Come to think of it, is there any North American built locomotive that was not arranged that way?
RWM
-Don (Random stuff, mostly about trains - what else? http://blerfblog.blogspot.com/)
Railway Man wrote:I think you're thinking of recent designs from GE and EMD, which intake through the side and exhaust through the top. Come to think of it, is there any North American built locomotive that was not arranged that way?
Early (1934 - 36?) EMD passenger locomotives and some of the SW series took in from the front.
"Side" would include "any side of the box", don't you think? Or is there something special about the front side as opposed to the side side? It certainly makes no difference on cooling performance that I can think of.
Railway Man wrote: "Side" would include "any side of the box", don't you think? Or is there something special about the front side as opposed to the side side? It certainly makes no difference on cooling performance that I can think of.
The fan in the front just made the drive arrangment cheap and easy - pulleys and belts off the front of the engine. Air flow was still "up".
Railway Man wrote:"Side" would include "any side of the box", don't you think? Or is there something special about the front side as opposed to the side side? It certainly makes no difference on cooling performance that I can think of.
I was being a bit nit-picky with the comment about drawing from the front, you're right in that the intake was from the front side. I was also intending to get across the point that the front intake was an unusual case.
On the early passenger trains (i.e the UP M1000 and CB&Q shovel nose Zephyrs), the front intake had teh advantage of using ram air pressure to aid cooling flow, similar to automotive practice (EMD was owned by GM). IIRC, this didn't help as much as expected and the area available for air-flow was limited compared to a side intake. (Added comment: Front intake would not worked for anything but the front unit, which would be a pretty darn good reason for any unit intended for MU operation to intake from the side. A notable exception are the SW's which have a generous front porch and are normally operated at low speeds.)
One other exception to the intake from the side and exhaust to the top rule was the Alco-GE-IR box cabs of the 1920's with the cooling coils on top with the "intake" air coming from the top. The phrase "the exception that proves the rule" comes to mind here.
on almost all locomotives..the exceptons are the switchs with the fans on the font and other types of swicher configerations... EMD...the fans pull air from the sides and pull it up past the radiators and out the top...on GE...air is pulled in from the sides and pushed up past the radiators and out the top... thats why you see the fans on top of the long hood in EMDs..and if you look on the long hood of GE..you will see the fan inside the carbody inside the air intakes on the rear of the carbody under the radiator section
csx engineer
J. Edgar wrote:leave us not forget the SP and there variuos "tunnle motors"......the SD-45T2. and others....with the rad. intakes low on the engine body to draw cooler air in tunnles......as stated heat rises and 4 or 5 or 6 units pounding up Donners Pass would overheat in the sheds and tunnles.....kinda the same but different as the idea behind the Cab-Forwards
There is no cooler air lower down in the tunnels and snowsheds. The tunnel motor option was a method of increasing the cooling rate (technically the "heat rejection rate", by placing the fans below the radiator cores instead of the standard location above the radiator cores, and increasing the air flow rate, so that the locomotives could cool down faster between tunnels and snowsheds not inside tunnels and snowsheds. Inside the tunnel and snowshed there is nothing you can do, it's a very small space with very little air volume to waste heat into.
Heat doesn't rise, it radiates equally in all directions, but hot air does because it is less dense than cold air. But it doesn't matter inside a tunnel. Stick five locomotives into a tunnel moving thousands of cfms of air through their engine, radiator, and traction motor/generator blower intake and exhaust, and in a matter of few seconds all the air is mixed up and the same temperature.
Railway Man wrote: J. Edgar wrote:leave us not forget the SP and there variuos "tunnle motors"......the SD-45T2. and others....with the rad. intakes low on the engine body to draw cooler air in tunnles......as stated heat rises and 4 or 5 or 6 units pounding up Donners Pass would overheat in the sheds and tunnles.....kinda the same but different as the idea behind the Cab-ForwardsThere is no cooler air lower down in the tunnels and snowsheds. The tunnel motor option was a method of increasing the cooling rate (technically the "heat rejection rate", by placing the fans below the radiator cores instead of the standard location above the radiator cores, and increasing the air flow rate, so that the locomotives could cool down faster between tunnels and snowsheds not inside tunnels and snowsheds. Inside the tunnel and snowshed there is nothing you can do, it's a very small space with very little air volume to waste heat into.Heat doesn't rise, it radiates equally in all directions, but hot air does because it is less dense than cold air. But it doesn't matter inside a tunnel. Stick five locomotives into a tunnel moving thousands of cfms of air through their engine, radiator, and traction motor/generator blower intake and exhaust, and in a matter of few seconds all the air is mixed up and the same temperature. RWM
im not trying to pick nits......nor doubting the logic expressed.....but quoting Model Railroader Cyclopedia Volume 2: Diesel Locomotives............'this SD-45T-2 tunnel motor draws cool air from near track level to improve engine performance in tunnels and snowsheds where the air near the top of the locomotive is too hot for effective cooling'.......im not a super scientist so i leave it to the fine folks at Kalmbach ....as it was my original post was ment only to bring the SD-45T-2 to the attention of those discussing engine cooling....railroading in Mi i didnt get to many T-2's in many of my consists.....the 2 i remember having both broke down enroute....or for that matter we didnt get to many tunnels here either
J. Edgar wrote: im not trying to pick nits......nor doubting the logic expressed.....but quoting Model Railroader Cyclopedia Volume 2: Diesel Locomotives............'this SD-45T-2 tunnel motor draws cool air from near track level to improve engine performance in tunnels and snowsheds where the air near the top of the locomotive is too hot for effective cooling'.......im not a super scientist so i leave it to the fine folks at Kalmbach ....as it was my original post was ment only to bring the SD-45T-2 to the attention of those discussing engine cooling....railroading in Mi i didnt get to many T-2's in many of my consists.....the 2 i remember having both broke down enroute....or for that matter we didnt get to many tunnels here either
So THAT'S where that story comes from. I always wondered! Anyway, all due respect to my good friends at Kalmbach, but this one is wrong. There was an "Ask Trains" question in Trains somewhere around 2002 or 2003 where EMD's Jack Wheelihan set the story straight.
Thanks for citing the source.
No, I guess you didn't see too many SD40T-2s or SD45T-2s in Michigan. We didn't see too many E-units in western Colorado, either!
and the story ends.....thx for the correction
Railway Man wrote:So THAT'S where that story comes from.
While I know Jack Wheelihan well and have a lot of respect for him, he is wrong on this one. I was a co-op engineering student in the EMD Engineering Dept. in 1970 when the tunnel cooling system was developed. I spent a few months working with Mansoor Ali, the EMD cooling system engineer, when he had just returned from a cooling system field test with a box full of chart recorder records from a tunnel test on the SP. It was my job to transcribe the chart records and graph the data to compare different test conditions. The test locomotive, an SD45, was tested in original configuration, with elephant ears, and with radiator water spray in repeated runs in the Cascades through a series of tunnels and snowsheds. The data clearly showed a significantly lower radiator air inlet temperature with the elephant ears, which was why the effort was spent to develop the SD45T-2 cooling system. If the only benefit was obtained with capacity, it would have been a lot easier to put an SD45-2 cooling system on an SD40-2, since the underframe length was available. There would have been no reason to put elephant ears on the SP GP40X units if there wasn't an expected benefit since they only add restriction to the cooling system, not enhance it's capacity. But the main reason the elephant ears were much less effective than the T-2 style cooling system is that the ends could not be closed off because of the need to keep the walkway clear.
FWIW, EMD created a design for a GP50T model, going so far as to assign a PLI number to it (each locomotive model at EMD was defined by it's PLI-Parts List Index) and would have built it if an order from the Rio Grande had been secured.
Dave
Wow, cool concept for a kitbash project, a DRGW GP50T. Other than the GP15, it would have been the only GP tunnel motor. Interestingly, DRGW bought SD50's and they did not come equipped as Tunnel Motors, anybody have any idea why? Were later EMD radiator sections more efficient, and thus did not need to be in a Tunnel configuration?
Jason Kuehn
bogie_engineer wrote: While I know Jack Wheelihan well and have a lot of respect for him, he is wrong on this one. I was a co-op engineering student in the EMD Engineering Dept. in 1970 when the tunnel cooling system was developed. I spent a few months working with Mansoor Ali, the EMD cooling system engineer, when he had just returned from a cooling system field test with a box full of chart recorder records from a tunnel test on the SP. It was my job to transcribe the chart records and graph the data to compare different test conditions. The test locomotive, an SD45, was tested in original configuration, with elephant ears, and with radiator water spray in repeated runs in the Cascades through a series of tunnels and snowsheds. The data clearly showed a significantly lower radiator air inlet temperature with the elephant ears, which was why the effort was spent to develop the SD45T-2 cooling system. If the only benefit was obtained with capacity, it would have been a lot easier to put an SD45-2 cooling system on an SD40-2, since the underframe length was available. There would have been no reason to put elephant ears on the SP GP40X units if there wasn't an expected benefit since they only add restriction to the cooling system, not enhance it's capacity. But the main reason the elephant ears were much less effective than the T-2 style cooling system is that the ends could not be closed off because of the need to keep the walkway clear.FWIW, EMD created a design for a GP50T model, going so far as to assign a PLI number to it (each locomotive model at EMD was defined by it's PLI-Parts List Index) and would have built it if an order from the Rio Grande had been secured.Dave
and the story continues......
RVM?.....comment?......
What, you want me to get in between two EMD men and take sides? No, I've been around the railroad too long for that!
For what it's worth, on my trips on mid-train helpers through tunnels in notch 8, I observed the exhaust "horizon" -- the dividing line between opacity and clear air -- would quickly form at about the level of the top of the locomotive and then slowly move downward. After about 1,000 feet of tunnel the horizon would have lowered to roughly walkway level and the engine, now sucking in a lot of exhaust, would be surging and running roughly, and after about 1,500 feet the entire tunnel would be opaque. I think that observation could square with both what Dave and Jack are saying -- depending upon the length of the tunnel.
The SD50s as I recall had higher capacity water pumps and larger radiator cores, in excess of the 500-horsepower increase, but since my EMD parts manuals are all in boxes, buried deeply, at home, I can't go dig them up. I do recall at least one Rio Grande mechanical officer saying he wished they had purchased them as SD50Ts, but I wouldn't take that one sentence and run with it very far.
well all things considered....id take the word of the man on the ground....no offence to the EMD engineers but numbers on paper dont always equal what happens in the field
would it be redunant to assume no SD-xxT-2 had winterization hatches???
Except all of these guys are field guys!
I don't think there's any such thing as a tunnel motor with a winterization hatch, at least not with its as-built cooling section.
Railway Man wrote:For what it's worth, on my trips on mid-train helpers through tunnels in notch 8, I observed the exhaust "horizon" -- the dividing line between opacity and clear air -- would quickly form at about the level of the top of the locomotive and then slowly move downward. After about 1,000 feet of tunnel the horizon would have lowered to roughly walkway level and the engine, now sucking in a lot of exhaust, would be surging and running roughly, and after about 1,500 feet the entire tunnel would be opaque. I think that observation could square with both what Dave and Jack are saying -- depending upon the length of the tunnel.
Question: Is the "exhaust horizon" due to the exhaust of the leading units or a combination of the leading units and mid-train helpers?
I can see how the passage of a train through a tunnel would do a good job of mixing the air - along with the action of cooling fans and exhaust of the mid-train units (it would be fun to see a computational fluid dynamics program model this without choking). I would also argue that having the cooling air intakes lower on the side would allow for more mixing of 'ambient' air with air heated from passing through the radiators.
While on the subject of tunnels, the tunnel's on the Espee must have had a bit more vertical clearance than on the UP based on the GS-4 and AC-12 having OAH of 16'6" as opposed to the Big Boy's OAH of 16'2".
erikem wrote:Question: Is the "exhaust horizon" due to the exhaust of the leading units or a combination of the leading units and mid-train helpers?
Presumably both -- I don't know where else the exhaust of the lead units would go.
Bogie Engineer's measurements would seem to agree with that.
Or a specific tunnel. I think we'd have to look at all the clearance diagrams to know anything. Much depends on when the tunnel was drilled and the condition of the rock (whether it was lined when built). Tunnels that were drilled in competent rock and self-supporting have tended to stay small, whereas tunnels that were lined tended to get bigger -- when the original timbers failed, the railroad figured while it was there it would enlarge the tunnel, and often when it pulled the timber sets and cribbing, the back and ribs were so rotten the tunnel pretty much self-enlarged.
The UP proper has very few tunnels compared to the SP and almost all of them are 100% lined. The LA&SL tunnels are all post-1900 and built to a modern standard; I don't believe there was much work required (if any) to permit them to clear high-cube double-stacks. The original CP tunnels, conversely, are notoriously tight. There's a big difference on Donner between the original CP tunnels and the Harriman-era 2nd track tunnels.
erikem wrote:the tunnel's on the Espee must have had a bit more vertical clearance than on the UP
timz wrote: erikem wrote:the tunnel's on the Espee must have had a bit more vertical clearance than on the UP The 1929 clearances book shows a bit more room on the UP main (which probably means thru Aspen Tunnel) than on the westward track over Donner.
I'll buy that...
The thought about clearances came up from reading Huddleston & Dixon's book on the Allegheny. The authors mentioned that the Allegheny was three inches taller than the Big Boy (16' 5.5" vs 16' 2.5") due in part to more generous clearances on the C&O lines. Thought it would be interesting checking the height of some of the SP power as some of the SP lines were known for tight clearances and was surprised to find that both the AC-12 and GS-4 were taller than the Big Boy.
Tunnel clearance is an issue with cooling of diesel locomotives as a higher tunnel means more volume of available cooling air.
During our engineer training in Roseville, Oakland and finally in Cerritos, the mechanical portion constantly emphasized the main feature of the T-2's, that cooler air was in fact drawn from nearer the ground, and many of the referenced documents were provided by EMD and SP's own Mechanical and Engineering Departments. The main point being driven home was that we could expect fewer hot engine unloads or deratings, especially on trailing units, in environments traditionally associated with such events, i.e., snowsheds and tunnels.
Photos of the test units, one of which was the 9156 if my memory doesn't let me down, and the SD45X's, which I believe were the SP's test beds for the tunnel motor project, were prominently displayed in the classrooms.
From personal experience, I can say that I have had many hot engine alarms in tough environments, especially in the Bay Area, over Altamont Hill, in Arizona east to Lordsburg and in the El Paso area. None, and I mean none were ever T-2's.
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