Tunnel Motor Uniqueness

[Murphy Siding]

Other than the placement of the air intakes down low, were the tunnel motors built any differently than other locomotives?

[edbenton]

Longer also by a few feet.

[CSSHEGEWISCH]

The low intakes for radiator air are hardly unique to the tunnel motors. GE designs from the U25B onward (and possibly earlier in Universal line export designs) all have a similar arrangement. Alco Century and M-line radiator arrangements are similar. The rear end of the tunnel motors also look like they were borrowed from any number of EMD export locomotives.

[CSXrules4eva]

What I am currently trying to understand is the fact that if tunnel motors had "bottom" mounted air intakes, which happens to be more efficient than the regular style air intake in terms of overheating, why didn't locomotive manufacturs continue building air intakes on the bottom? There must be some logic behind this.

[mudchicken]

Sarah:

Until Randy Stahl surfaces and gives you an answer from experience, look at it this way:

(1) You are trying to place the largest unitized radiators with the largest surface area possible to cool the prime mover in all kinds of weather.

(2) The coolest air is down low, BUT so is the source of most of the dirty air and loose material that plugs-up the radiator core element.

(3) GRAVITY (putting cooling fluid through the system and keeping vapor at the top)

(4) Look at the EMD SD45 series locomotives that had radiator intakes vertical (SD45-2), slanted (SD45) and horizontal SD45T-2. The SD45 was notorious for having radiator problems. Randy saw them all at WC.

The struggle is to get all the elements to work together and in an optimal way.

EdBenton: Tunnel Motors shared a common frame with their straight SD40-2 and SD45-2 cousins, all that changed was the length of the hood.

[Anonymous]

Other than the air intakes, the tunnel motors are mechanically identical to the SD40-2 & SD45-2. They were developed specifically to counter overheating problems experienced by the SP in long tunnels.

[zardoz]

QUOTE: Originally posted by James_the_Mad

Other than the air intakes, the tunnel motors are mechanically identical to the SD40-2 & SD45-2. They were developed specifically to counter overheating problems experienced by the SP in long tunnels.

Exactly. The design is such that the "fresh" (cooler) air was pulled in from the ground instead of by the roof where the exhaust fumes would collect in the tunnels.

[Anonymous]

Here's a link to one of my favorite SP sites, to the tunnel motor page:

http://espee.railfan.net/tunnel_motors.html

The site also has an excellent collection of photos. The only drawback is you have to register to get to some of the stuff, like the Detail Breakdowns, and there is a fee involved. Someday I'm gonna have to break down and register.

[fuzzybroken]

QUOTE: Originally posted by mudchicken

EdBenton: Tunnel Motors shared a common frame with their straight SD40-2 and SD45-2 cousins, all that changed was the length of the hood.

That just didn't sound right to me, so I checked WikiPedia:
SD40-2 length: 68' 10"
SD40T-2 length: 70' 8"
Of course, my original point of knowledge on this subject was that Athearn's SD40-2 had a shorter frame than their SD40T-2!

[Anonymous]

According to The Contemporary Diesel Spotter's Guide, Wikipedia is out to lunch on this one.

The SD40-2 and SD40T-2 both have 68' 10" frames, and in the SD40 series, only the SD40A has the 70' 8" frame.

The only other units that share the 70' 8" frame are the SDP45 and the SD45X. The SD45-2 and the SD45T-2 shared the same 68' 10" frame.

Oops - just did some further checking, and this is incorrect. See my next post, about 4 posts down.

[Anonymous]

The tunnel motor design had nothing to do with the location of hot exhaust gasses while inside the tunnels.
It was all about their ability to cool down faster while between tunnels.

Former EMD guru Jack Wheelihan covered this in an earlier issue of trains magazine.

with the force of exhaust flow and the air turbulance caused by the trains movement inside the tunnel, the fact that 'heat rises" is not by itself sufficient to keep the heat stagnated near the top of the passageway.

[NscaleMike]

Here is a "Snoot" nosed version, lettered for the Cotton Belt...

Would the frame be the same length as a regular T-Motor?



Here is a standard version...

[Anonymous]

I noticed that amtraks genesis has a tunnel moter type radiator on it as well

[Murphy Siding]

QUOTE: Originally posted by CSSHEGEWISCH

The low intakes for radiator air are hardly unique to the tunnel motors. GE designs from the U25B onward (and possibly earlier in Universal line export designs) all have a similar arrangement. Alco Century and M-line radiator arrangements are similar. The rear end of the tunnel motors also look like they were borrowed from any number of EMD export locomotives.

I've always wondered if EMD's were the only ones that needed the modification for improved tunnel operation. Did the types listed above operate ok in the tunnels?

[Anonymous]

Ooookay, looks like The Contemporary Diesel Spotter's Guide got this one wrong, not Wikipedia. Turns out, the tunnel motors are approximately 2' longer:

http://www.trainweb.org/utahrails/drgw/locolength.html

So it looks like they used the longer SD40A frame after all.

Hmm, that just opened up a couple of possibilities. Since the frames are nearly identical, I wonder how hard it would be to cobble up an SDP45? [(-D]

[fuzzybroken]

QUOTE: Originally posted by NscaleMike

Here is a "Snoot" nosed version, lettered for the Cotton Belt...

Would the frame be the same length as a regular T-Motor?

Yep, snoot-vs.-regular nose the frames are the same.

QUOTE: Originally posted by James_the_Mad

Ooookay, looks like The Contemporary Diesel Spotter's Guide got this one wrong, not Wikipedia. Turns out, the tunnel motors are approximately 2' longer:

http://www.trainweb.org/utahrails/drgw/locolength.html

So it looks like they used the longer SD40A frame after all.

Hmm, that just opened up a couple of possibilities. Since the frames are nearly identical, I wonder how hard it would be to cobble up an SDP45? [(-D]

About the only limitation would be the Flexicoil vs. HTC truck, as well as truck/wheelbase spacing. Then again, if you can live with the differences (if any), then you're good to go!

Glad somebody confirmed what I knew! Figured somebody must've got bad information from somewhere... [#oops]

[Anonymous]

QUOTE: Originally posted by TheAntiGates

The tunnel motor design had nothing to do with the location of hot exhaust gasses while inside the tunnels.
It was all about their ability to cool down faster while between tunnels.

Former EMD guru Jack Wheelihan covered this in an earlier issue of trains magazine.

with the force of exhaust flow and the air turbulance caused by the trains movement inside the tunnel, the fact that 'heat rises" is not by itself sufficient to keep the heat stagnated near the top of the passageway.

if that is true then what is the design advantage of the tunnel motor configuration

[PBenham]

The tunnel motors are noticably longer, in part because the hood takes up a higher percentage of the frame's length. GE had their legal department and R&D look at the tunnel motors when some of their higher-ups smelled what they thought was patent infringement by EMD, but the EMD design was different enough that GE had no case! On the operational level ,they tend to be quieter, but vibrate more than regular SD40-2s. Any Engineers care to verify or debunk this?

[Anonymous]

There was a very long discussion on this a while back and I think AntiGates has it right from what I can remember. Something about it being more efficient to blow the cool air up through the radiator rather than to suck it through.

[Anonymous]

QUOTE: Originally posted by equinox


if that is true then what is the design advantage of the tunnel motor configuration

The reason the air intakes were moved down was because the fans themselves were moved to below the radiator cores themselves (instead of the usual location above)

By moving the fans below they were able to get a "venturi" effect by having the fans operate within a channel

Basically meaning more air was blowing through the radiator because the airflow was more efficient.....


Why don't they build them all that way? Try changing one of the fan motors one time, and you will be glad they are not all that way.

[Anonymous]

QUOTE: Originally posted by fuzzybroken
:About the only limitation would be the Flexicoil vs. HTC truck, as well as truck/wheelbase spacing. Then again, if you can live with the differences (if any), then you're good to go!

The frame is the same. The T2 is 8" longer over the coupler faces, probably because of the anticlimber, and I think I can live with a truck spacing difference of 5". As for the trucks, the Athearn SD45 has the right sideframes, so that can be corrected fairly easily.

And while the SP's SDP45's had been retired by my timeframe (1995-1998), there were 6 MK rebuilds of EL/CR units, listed as SD40M-2's. These units were built as freight units, using the longer frame for a larger fuel tank, and they never had boilers. But they still retain the look of the SDP45.

Hmm, that could be an interesting project. [(-D]

[cpbloom]

Ok I got an add-on question.

Are GP15-1s similar to tunnel motors or are they similar only in looks?

[Murphy Siding]

QUOTE: Originally posted by cpbloom

Ok I got an add-on question.

Are GP15-1s similar to tunnel motors or are they similar only in looks?

Are you saying similar, because the intakes for the radiators are down low?

[cpbloom]

QUOTE: Originally posted by Murphy Siding

QUOTE: Originally posted by cpbloom

Ok I got an add-on question.

Are GP15-1s similar to tunnel motors or are they similar only in looks?

Are you saying similar, because the intakes for the radiators are down low?

Yes.

[coborn35]

As far as I know, they just looked like that. Another locomotive has lower intakes, but I cant remember which....

[chad thomas]

What it boils down to is the 40-45 series locomotives cooling system was insufficient for the conditions in snowsheds and tunnels. The tunnel motors were a "band aid" for the insufficiency of those.

[trainfan1221]

If I recall, the frame was the same legnth as a contemporary SD40-2, it looked bigger because it actually filled the whole frame out. I could be wrong. It is very hard to judge once something is changed on a locomotive.

[Murphy Siding]

QUOTE: Originally posted by chad thomas

What it boils down to is the 40-45 series locomotives cooling system was insufficient for the conditions in snowsheds and tunnels. The tunnel motors were a "band aid" for the insufficiency of those.

Did others EMD units up untill then not have that problem?

[chad thomas]

QUOTE: Originally posted by Murphy Siding

QUOTE: Originally posted by chad thomas

What it boils down to is the 40-45 series locomotives cooling system was insufficient for the conditions in snowsheds and tunnels. The tunnel motors were a "band aid" for the insufficiency of those.

Did others EMD units up untill then not have that problem?

I don't know.

[Anonymous]

It became an issue with the SD40 & SD45 because of their higher horsepower. Cooling capacity wasn't an issue on lower horsepower units.