Last night my 20month old sun and I convinced the wife to let us go see some trains, and she actually wanted to come along. As a UP was waiting for the green light on the main, I was telling about he engines. We came across a UP SD40T-2, so I told her about the vents. She then brought up a good question–“If those vents were set low on that engine, then why isn’t all the new engines have them there?”
I didn’t know the answer until I just thought about it now. Am I right to say that they do have the vents set low on the newer engines?
Are not these lower vents on this AC4400 like the vents on the SD40T-2s?
The tunnel motors were not really about the intake vents. The 40/45 series locos had insufficient cooling systems for the tunnels / snowsheds. The Tunnel motors were designed with higher capacity cooling systems to handle these by being able to contend with longer heating & cooling cycles nessasary on routes with many tunnels and snowsheads. Subsequent models had sufficient cooling capabilities to handle these situations without special radiator sections. The height of the intake makes little difference for cooling due to the turbulances inside the tunnels.
Basicly the tunnel motors were a band aid fix for an insufficiant cooling system design.
The vents normally are set as high as practical so that dirt and dust intake is minimized.
However, in tunnel and snowshed territory, all those pesky hot exhaust gasses are up where the cooling air intakes are, and it doesn’t take long for a 645 serices engine to overheat in those circumstances. SP first tried “elephant ears” on SD-45’s and assigned them to pusher service over Donner and Willamette.
Power failures due to overheating went way, way, down; but the cooling temperatures didn’t go down far enough unless the “elephant ears” were fully enclosed to make air ducts out of them, pulling the cooling air in from hand rail level and below.
Well, that worked pretty well except, whe the helper crew had to attend to a trailing unit, the whole train had to come to a stop since you couldn’t get around the “elephant ducts”.
About this time, somebody in the SP’s motive power engineering department got the idea to put the intakes down to the running board, rebuild the radiators so that they didn’t tilt out, put the intake fans under the radiator so that more cooling air could be put through and exhausted out the top of the radiator with a smoother air flow pattern. EMD accomodated them with the Tunnel Motors – SD45T-2 and SD40T-2. SP bought both models and the DRGW bought the '40’s only.
That’s the WHY of the Tunnel Motor. But why aren’t current units sucking their air up in the same way?
Well, the T-2s, while intaking the air as low as they did also dragged that air around all the elelctrical gear, air pumps and stuff which didn’t help them keep clean from the dirt and they failed more often and needed filters (which also needed service). So GE, which uses a lower cooling air intake than EMD, still has theirs up about the middle of the hood with the air pump, blowers and stuff in a pressure sealed and filtered compartment. Lower maintainence costs. EMD made the radiators MUCH bigger and kept the air intakes as high as they co
Eric,
Once again I have to dissagree with you today. I’m not trying offend you I hope you know.[;)] I thought the position of the air intakes was to pull cooler air off the lower position. I was set straight by none other then our own Mark Hemphill. He pointed out that the turbulance inside a tunnel would mix the exhaust and cool air enough that intake height would make no differance. The tunnel motors bigest advantage was it’s recovery time once outside that tunnel. It could recover from any overheating much faster then a standard SD40-2 could.
I’m not going to argue with Mark (or you), but there is a lot more to it than air turbulance. I “was there” during all of this monkey business with the “elephant ears”, and for whatever reason(s), those modified SD-45’s ran much better with the “ears” than without. We never had an engine overheat after the modifications and the advent of the SD-45T-2’s except when there was a cooling system failure.
As I mentioned above, the proposal for the “T’s” included enlarged radiators - but I didn’t put it just those terms.
Eric, To tell you the truth I belive the intakes do help by drawing in lower, cooler air but I have had several qualified people (includeing Mark) tell me otherwise. I find what you say about the elephant ears on the SD45 interesting. Can you describe them? I am visualiseing an enclosed shroud extending down the body to the walkway. Is that right?
I am not a mechanical engineer. But I did have to go “rescue” some of those “stranded” trains (actually, part of the process, not part of the patch crew). Even though I am not an ME, I did ask a lot of questions of those (ME’s) involved with this process and therefore, did learn a lot. Like I said, there is a lot more to it than turbulance, and it is not as simple as just relocating the air intakes. There were a lot of “animated” conversations between the motive power people on just this very subject area!
And I do not hold anything against anyone when the may disagree with me. There is a phrase --“Everyone has a nose. Opinions are like noses - we all have them.” And there can be disagreements of fact with neither party being in error.
As to those “Elephant Ears” – you have the basic idea. There were several different designs, starting with a simple “upside-down elephant ear” -upside-down from the steam engine design and closed over at the top. This helped some, but was not a solution. So the trailing (or “B” end of the ear) was closed off to make a scoop, which worked better, but only when the unit was in forward motion, and it prevented a crewman from going between units. Then they closed off the front of the ear leaving an opening only from the handrail down and only on the side. This worked best but still had the problem of crew mobility. Putting doors in the front and back walls of the ear (now a duct) didn’t help much as they couldn’t keep them closed.
Esentially, these contraptions were a box welded to the locomotive s
I am not a mechanical engineer. But I did have to go “rescue” some of those “stranded” trains (actually, part of the process, not part of the patch crew). Even though I am not an ME, I did ask a lot of questions of those (ME’s) involved with this process and therefore, did learn a lot. Like I said, there is a lot more to it than turbulance, and it is not as simple as just relocating the air intakes. There were a lot of “animated” conversations between the motive power people on just this very subject area!
And I do not hold anything against anyone when the may disagree with me. There is a phrase --“Everyone has a nose. Opinions are like noses - we all have them.” And there can be disagreements of fact with neither party being in error.
As to those “Elephant Ears” – you have the basic idea. There were several different designs, starting with a simple “upside-down elephant ear” -upside-down from the steam engine design and closed over at the top. This helped some, but was not a solution. So the trailing (or “B” end of the ear) was closed off to make a scoop, which worked better, but only when the unit was in forward motion, and it prevented a crewman from going between units. Then they closed off the front of the ear leaving an opening only from the handrail down and only on the side. This worked best but still had the problem of crew mobility. Putting doors in the front and back walls of the ear (now a duct) didn’t help much as they couldn’t keep them closed.
Esentially, these contraptions were a box welded to the locomotive s
Interesting info. Thanks Eric. Do you by chance have any pictures or know where there are any of these shrouds? Or do we have to send Dale on a hunt. [swg]
Photos of the 12 Elephant Ear SD45s are here http://espee.railfan.net/spsd45t-1.html
This page is from Richard Percy’s tribute to the SP. Also three SD45Xs were equipped with the ears for testing purposes, SP9500-9501 and EMD 4201. Tunnel motors rock! [8D]
There was an article by Jack Wheelihan about the tunnel motors in CTC Board that explained why they were better at recovery between the tunnels than in the tunnels. Jack Wheelihan was an EMD test engineer IIRC.
The other big difference with the tunnel motors is that the fans are located below the radiators and pu***he air through the radiator, rather than drawing the hot air out of the radiator hatch.
If the tunnel motor’s main advantage was in the extra cooling capacity in the hot desert climates and tunnels that SP and DRGW encountered, is there any particular reason these models are still in use? (outside of the old SP map) That is, they are used by Wheeling & Lake Erie (ex-DRGW) and a variety of leasing companies, but I think it’s safe to say these spend time all over the map, or in areas where the extra cooling capicty goes to waste, so to speak. So many are not necessarily in the same demanding conditions they were designed for…would it be possible / economical to change back to the “original” or stock SD40 radiator layout? If after all the Tunnel motors are harder to work on, tend to pull dirt / sand across the other components, had more maintainance costs related to these extra parts, etc…
On a simlar note: What’s up with the “mini tunnel” GP15T / GP15-1? Was that little 8-cyl engine in the GP15T tough to cool, or was EMD trying to use up some old parts…?
Redrabbit the reason the tunnel motors are still in use basically they are 40 or 45-2’s under the hood and so everyone knows what to expect. I for one would not want to have one being ex-SP. In the early 90’s when they were getting all those rebuilt GP40’s they stated flat out in the contracts not a one could be ex SP SSW or Rio Grande. That tells you what SP mainatnce policy was like.
This is just a guess, but I think that it would take a lot of time to make the radiators on the T-2s into normal ones, and it probably does’t make that much of a difference anyways. The reason they bought them is probably because they’re SD40s, good working locmotives which are perfect for their lines.
I think the reason for this is that the shop union would scream bloody murder if they sent SP units to an outside shop (Morrison Knudsen in that case) to be rebuilt instead of giveing the work to SP employees. If the carcases to be rebuilt came from other railroads the union couldn’t consider there craft work to be outsourced as they would be considered new units (new to SP anyway).
And as for turning tunnel motors to reguler SDs, why fix it if it aint broke. So what if it’s more difficult to work on the fan motors. When it come to $$$ it’s hard to justify the expense of a new radiator section by saveing a little extra labor.
