Tunnel Motors

[JimValle]

Well, the other respondants have covered the technical side of tunnel motors pretty well. From a recognition standpoint, they seemed to be longer than standard units. The back end of the long hood was just a huge void space with louvers down low on either side. Standing on the gangway, you could look in and see nothing. a dim lightbulb lit up this space in darkness, at least on the one I saw. This one was one that Conrail inheireted from one of it's predecessors but I don't know which one.

[Anonymous]

Thanks to everyone for all the info...

[sd75t]

Whatever the reason is for sure (my thermodynamics class was 30 years ago), the lower intakes definitely had an effect because the SD40T-2 used only two fans versus three on the SD40-2 and SD45T-2.

The air temperature is probably lower as you go lower in the tunnel but not significantly. But the proximity of the high radiator intakes to the exhaust stacks probably did relate to some potential temperature difference because there wasn't much time to mix the new hot exhaust gases with the ambient air prior to the fans sucking it through the radiators.

The other item to remember is that with those big grills lower on the body, my suspicion is that there was more efficient airflow through the cooling system along with probably a much greater volume of air at the same time.

It isn't hard to imagine that the high-mounted radiators didn't have the best airflow circulation through them with those small grills. As I recall, the GE's only had one fan in them (albeit a much larger fan than what EMD used), and the GE's did not have to make special provisions for cooling in snowsheds. Ever since the 50 Series was introduced, the main difference in the radiators is not the length of the radiator section, but the grills are significantly deeper than on the 40 series, which would allow better airflow.

[Anonymous]

The hot air inside those Donner tunnels is nothing compared with what you get in some of these posts 8^)

[ericsp]

QUOTE: Originally posted by mudchicken

Most of these folks on here have not experienced working in a tunnel with a diesel engine (as opposed to a gasoline engine which would be fatally stupid, co2 vs. co)...Your view out the end of the tunnel has the horizon falling to the ground as exhaust above the spring line in the tunnel slowly heads downward.

That clears things up (pun intended). From the article on the SD45s in the June 2005 Trains, it sounds like Mullins Pass is on of, if not, the worst.

[Anonymous]

QUOTE: Originally posted by Mark_W._Hemphill

It does this by putting the fans on the cool side of the radiators (beneath them in this case) instead of on the hot side (above them), which makes transfer of heat between radiator and atmosphere occur at a faster rate than otherwise. You could have accomplished pretty much the same thing by reversing the fans on a standard SD40/45, but then you'd be blasting hot air out the sides, which would be a significant hazard to anyone on the walkway and possibly damage things next to the track. Better to take the hot air straight up, away from people and things.

Blowing "down" would also force the fans to overcome "stack effect" instead of taking advantage if it (as in the case with updraft), wouldn't it?.

I also think you get some advantage placing the fans on the cooler side because the air there will be more dense, and each fan blade stroke will force along incrementally more air (than it would if located on the less dense "hot" side) , as the result.

[Anonymous]

QUOTE: Originally posted by SSW9389

Right you are. The author was Jack Wheelihan, an EMD field rep. Look in CTC Board a couple of years ago.

[8D]

He heh, pretty bad when a n00b like me can call people "out" on technical matters and end up being right.

Just goes to show what an excellant and informative mag Trains magazine is... [:)]

[SSW9389]

COTTON BELT owned 94 Tunnel Motors (84 biguns and 10 little uns) and didn't have any tunnels. My point again being is that COTTON BELT was a cash cow for Southern Pacific.

[SSW9389]

Right you are. The author was Jack Wheelihan, an EMD field rep. Look in CTC Board a couple of years ago.

[8D]

QUOTE: Originally posted by TheAntiGates
[

I could SWEAR I read an explanation in trains magazine about 3 years ago that said the design had very little to do with "in tunnel" breathing, and more to do with the ability of the radiator to cool down quickly "between" tunnels (ie, after exiting the last one, and before entering the next one)

[mudchicken]

Most of these folks on here have not experienced working in a tunnel with a diesel engine (as opposed to a gasoline engine which would be fatally stupid, co2 vs. co)...Your view out the end of the tunnel has the horizon falling to the ground as exhaust above the spring line in the tunnel slowly heads downward.

[Anonymous]

QUOTE: Originally posted by chad thomas

Thanks for the explaination Mark. I was wrong guys. Sorry.

Not a prob,....it was however quite stressfull knowing I was right amd wondering if I should just bite my lip and let you be wrong, just to avoid a confrontation....

[broncoman]

Don't GE's radiator fans suck in air below the radiators and blow it up?

If so, given the same radiator area would that make them a little better at heat rejection, and if so did SP ever look at C30-7s since they did own U36s.

There may be jumps in logic there so somebody stop me if I am a little off.

Dave

[chad thomas]

Thanks for the explaination Mark. I was wrong guys. Sorry.

[chad thomas]

I think the tunnel motors do have more cooling water capacity but I didn't mention it because I don't have the facts in front of me.

[ericsp]

QUOTE: Originally posted by TheAntiGates

QUOTE: Originally posted by chad thomas

The tunnel motor design is all about pulling in cooler air while inside the tunnels and snowsheads. But naturally they will cool down in between tunnels. Also remember this is mostly for the trailing units. SP liked to run monster drags when it could and Donner is no exception. So you would have these monster consists of up to 8-9 units on the point. When you are grinding uphill at little more than a walking pace behind 8 other units doing the same, thing can get pretty hot in those tunnels. If the cooling system can't keep up the engines overheat and will unload to protect themselves.

Well, not to argue,...but I really do think that the issue I'm thinking of stated that the belief that tunnel motor design is an "in tunnel" benefit was a widely held misconception, because the benefit b eing designed for was actually how rapid the motors could be cooled in between tunnels.

The only reason why I even remember it was because it seemed like such a surprise at the time.

Little foggy on the following, but I seem to remember the source as being EMD's *** Dillworth, and MAYBE the issue was the one that had the "Greatest/ worst" loco's of all time featured as a special article.

You may have read it in "Tunnel Motors!" in the September 2004 issue of Railfan & Railroad. However, the author does not give a source. I have no doubt that part of the theory behind this is lowering the temperature of the engine outside of the tunnels. However, it can probably transfer more heat from the cooling water while in the tunnel than the SD40-2/SD45-2 can. I do not have the diagrams, so I do not know if there is any reason to move the radiator air intakes low other than the gases in the tunnel are more likely to be cooler down there.

[chad thomas]

The tunnel motors were most certainly designed to avoid the problem of overheating inside the tunnels and were very successfull. The SP aquired more than 500 of them over many years in the 40 and 45 series.I think you got some bad info or something. Think about it... Why would the radiator intake position make a difference outside of a tunnel or shed?

And I hope the SD40T-2s were in the greatest catagory as they are truly a top notch loco in my humble opinion.
[8D]

[Anonymous]

QUOTE: Originally posted by chad thomas

The tunnel motor design is all about pulling in cooler air while inside the tunnels and snowsheads. But naturally they will cool down in between tunnels. Also remember this is mostly for the trailing units. SP liked to run monster drags when it could and Donner is no exception. So you would have these monster consists of up to 8-9 units on the point. When you are grinding uphill at little more than a walking pace behind 8 other units doing the same, thing can get pretty hot in those tunnels. If the cooling system can't keep up the engines overheat and will unload to protect themselves.

Well, not to argue,...but I really do think that the issue I'm thinking of stated that the belief that tunnel motor design is an "in tunnel" benefit was a widely held misconception, because the benefit b eing designed for was actually how rapid the motors could be cooled in between tunnels.

The only reason why I even remember it was because it seemed like such a surprise at the time.

Little foggy on the following, but I seem to remember the source as being EMD's *** Dillworth, and MAYBE the issue was the one that had the "Greatest/ worst" loco's of all time featured as a special article.

[chad thomas]

The tunnel motor design is all about pulling in cooler air while inside the tunnels and snowsheads. But naturally they will cool down in between tunnels. Also remember this is mostly for the trailing units. SP liked to run monster drags when it could and Donner is no exception. So you would have these monster consists of up to 8-9 units on the point. When you are grinding uphill at little more than a walking pace behind 8 other units doing the same, thing can get pretty hot in those tunnels. If the cooling system can't keep up the engines overheat and will unload to protect themselves.

[Anonymous]

QUOTE: Originally posted by gabe

QUOTE: Originally posted by WilRogJr

Why do they call them "tunnel" motors?

Oh my goodness, a technical question to which I actually know the answer. Move over Randy Stall (joking).

They call them tunnel motors because the locomotives were designed to operate more effectively in tunnels. Some railroads, especially the SP, had a considerable amount of long tunnels on their system. The problem with long tunnels is the exhaust from the diesles would reflect in the tunnel and cause temperatures to rise and sometime cause the engine to shut down. This is also the reason the SP developed cab first steam locomotives.

Tunnel motors have the intakes closer to the ground where the air is cooler (heat rises) and the intake of cooler air allows them to operate in tunnels for longer periods without over heating. When you see an SD-40-2T look toward the back of the locomotive close to the walkway.

On a related aside--the story of UP's 4-8-4 and 4-6-6-4 having a diesle haul them through a tunnel on their way to a steam convention and the diesle overheating is a classic. The two steamers had to steam up in the tunnel and it got so hot the crews nearly melted and all of the smoke alarms in the passenger cars went off. Although, I bet the tunnels got a nice steam cleaning from all of that diesel soot on them.

Gabe

I could SWEAR I read an explanation in trains magazine about 3 years ago that said the design had very little to do with "in tunnel" breathing, and more to do with the ability of the radiator to cool down quickly "between" tunnels (ie, after exiting the last one, and before entering the next one)

[chad thomas]

Guys it's all about the radiators. The radiators don't care how much oxygen is in the air.

[Anonymous]

Exhaust fumes are heavier than the surrounding air as they cool down, so I don't think there will be a significant difference between the oxygen levels in the upper half or in the lower half of the tunnel.

[gabe]

QUOTE: Originally posted by CopCarSS

QUOTE: Originally posted by gabe
Now, if I can only figure out how to reduce the vibration damage caused by the 645 in an SD-50, I will be able to leave the school and go out in the world to combat the evils of middle/upper management.

Gabe

Gabe, I'm shocked! Didn't you read the propaganda in the last Trains?

Chris
Snowy Denver, CO

Actually, yes I did and that article is what prompted my comment. However, the article did not tell me how to accompli***he feet of a proper rebuilding and that is what I was referring to as the gold standard.

Gabe

[ericsp]

QUOTE: Originally posted by Hugh Jampton

I heard a rumour that the intakes were lowered because that's where the oxygen is,, the top space of the tunnel fills with exhaust, which has no (or very little) oxygen in it, I would have thought that trailing units were particularily succeptable to oxygen starvation, especially if the tunnel is on a rising gradient and the units are have to work a bit.

If there is more oxygen lower, it would be because the hot exhaust gases rise to the top, so it is really the same reason.

[Hugh Jampton]

I heard a rumour that the intakes were lowered because that's where the oxygen is,, the top space of the tunnel fills with exhaust, which has no (or very little) oxygen in it, I would have thought that trailing units were particularily succeptable to oxygen starvation, especially if the tunnel is on a rising gradient and the units are have to work a bit.

[CopCarSS]

QUOTE: Originally posted by gabe
Now, if I can only figure out how to reduce the vibration damage caused by the 645 in an SD-50, I will be able to leave the school and go out in the world to combat the evils of middle/upper management.

Gabe

Gabe, I'm shocked! Didn't you read the propaganda in the last Trains?

Chris
Snowy Denver, CO

[adrianspeeder]

Yep you got it, kinda like a reverse snorkle to get better air thats down low.

Adrianspeeder

[gabe]

Mid-to-upper management just took a collective sigh of relief. I am not yet ready for them.

Gabe

[Randy Stahl]

QUOTE: Originally posted by gabe

QUOTE: Originally posted by Randy Stahl

QUOTE: Originally posted by gabe

QUOTE: Originally posted by WilRogJr

Why do they call them "tunnel" motors?

Oh my goodness, a technical question to which I actually know the answer. Move over Randy Stall (joking).

They call them tunnel motors because the locomotives were designed to operate more effectively in tunnels. Some railroads, especially the SP, had a considerable amount of long tunnels on their system. The problem with long tunnels is the exhaust from the diesles would reflect in the tunnel and cause temperatures to rise and sometime cause the engine to shut down. This is also the reason the SP developed cab first steam locomotives.

Tunnel motors have the intakes closer to the ground where the air is cooler (heat rises) and the intake of cooler air allows them to operate in tunnels for longer periods without over heating. When you see an SD-40-2T look toward the back of the locomotive close to the walkway.

On a related aside--the story of UP's 4-8-4 and 4-6-6-4 having a diesle haul them through a tunnel on their way to a steam convention and the diesle overheating is a classic. The two steamers had to steam up in the tunnel and it got so hot the crews nearly melted and all of the smoke alarms in the passenger cars went off. Although, I bet the tunnels got a nice steam cleaning from all of that diesel soot on them.

Gabe

Fine job grasshopper.

Thank you master.

Now, if I can only figure out how to reduce the vibration damage caused by the 645 in an SD-50, I will be able to leave the school and go out in the world to combat the evils of middle/upper management.

Gabe

SD 50 vibration problems, don't worry, it's going to catch fire soon anyhow or have some other impossible electrical problem.
Randy

[gabe]

QUOTE: Originally posted by Randy Stahl

QUOTE: Originally posted by gabe

QUOTE: Originally posted by WilRogJr

Why do they call them "tunnel" motors?

Oh my goodness, a technical question to which I actually know the answer. Move over Randy Stall (joking).

They call them tunnel motors because the locomotives were designed to operate more effectively in tunnels. Some railroads, especially the SP, had a considerable amount of long tunnels on their system. The problem with long tunnels is the exhaust from the diesles would reflect in the tunnel and cause temperatures to rise and sometime cause the engine to shut down. This is also the reason the SP developed cab first steam locomotives.

Tunnel motors have the intakes closer to the ground where the air is cooler (heat rises) and the intake of cooler air allows them to operate in tunnels for longer periods without over heating. When you see an SD-40-2T look toward the back of the locomotive close to the walkway.

On a related aside--the story of UP's 4-8-4 and 4-6-6-4 having a diesle haul them through a tunnel on their way to a steam convention and the diesle overheating is a classic. The two steamers had to steam up in the tunnel and it got so hot the crews nearly melted and all of the smoke alarms in the passenger cars went off. Although, I bet the tunnels got a nice steam cleaning from all of that diesel soot on them.

Gabe

Fine job grasshopper.

Thank you master.

Now, if I can only figure out how to reduce the vibration damage caused by the 645 in an SD-50, I will be able to leave the school and go out in the world to combat the evils of middle/upper management.

Gabe