EMD "Tunnel Motor" official thread (covers all variations)

[trainiac]

I just found an amazing video clip of an SP train battling a grade at about 15 mph with 13 EMD units for power. Seven units were at the head end and six were mid-train.

The head-end consist:
SD40T-2
SD40
SD45T-2
SD45T-2
SD45 (sounds to be running at reduced rpm)
SD40T-2
GP9

Mid-train consist:
SD40T-2
SD45T-2
SD45T-2
SD40T-2 (making black smoke--turbo problems)
SD40T-2
SD40T-2 (not running)

http://home.att.net/~cz17/Tanktrain-bealville.wmv

[MEC407]

Good stuff! Especially the mid-train helpers and the GP9.

[trainiac]

I love the GP9 too! I remember when the St. Lawrence & Atlantic had GP11's--wonderful sounds!

By the way, as the fourth (smoking) helper unit is passing, there's a metallic "clunking" sound. That's apparently due to the turbo trouble as well.

Assuming that the SD45 in the lead consist is running at reduced power and the last helper isn't running (which appears to be the case), this train would still have in excess of 36000 horsepower.

[MEC407]

I heard that weird sound as well, and was wondering what it was.

Sure is neat to see an EMD acting like an Alco.

[GOLDEN-ARM]

That "weird" sound, as you called it, is known as "turbo-bark", and it is the sudden de-celeration, then rapid acceleration of the turbo , due to coked bearings, damaged impellers, bent case, etc. ( it does not sound like a clunk, but more like a buzzing sound, that goes WWWWWHHHHHUUUUUMMMMPPPP!!!!) A quick drop in the RPM of the engine causes the turbo to suddenly "lag", and when it catches again, with the engine producing power, the turbo is suddenly accelerated to operating speed, with the "bark" being heard, at that moment. Often it is heard when making transition, when wheel slip occurs with a drop in engine speed, or when the air filters are clogged, and the engine is costantly running, then "choking" for air. It sounds cool for a while, but it quickly gets annoying, even though the plumes of black smoke are fun to watch. I will isolate a unit, that barks excessively, if it's in the lead position. Regards

[trainiac]

I found out earlier that it was called "barking" but couldn't figure out exactly what was involved. Thanks for the info!

[MEC407]

I found out earlier that it was called "barking" but couldn't figure out exactly what was involved. Thanks for the info!

I thought barking was something that only GEs (and big Alcos) did.

[CN_Hogger]

That "weird" sound, as you called it, is known as "turbo-bark", and it is the sudden de-celeration, then rapid acceleration of the turbo , due to coked bearings, damaged impellers, bent case, etc.

Thanks for the explenation Golden Arm.... I had an SD40-3 do that everytime I went from notch 8 to 7, had no idea what it was exactly. Although this unit didn't pour out the black smoke like that T-2....

[Tadman]

Excellent video - any idea if there are other similar ones around that come to mind?

And you've got to love the non-turbo geep... The stack talk from the local geeps and MP's at Chicago Heights and Blue Island makes the drive across town all worth it.

[trainiac]

There was one other video posted on the same site with a train in half-throttle on flatter track, with two SDP45's, three SD9's, a Kodachrome GP35 and a GP20 (what a consist!) The address is
http://home.att.net/~cz17/untitled_0067.wmv

The main page is http://home.att.net/~cz17/ Clark Bauman made this site, and the videos appear to be from the late 1970's or early 1980's.

I've got recordings myself (now on a new server-- http://trainiax.net/merecordings.htm), but I have no videos... yet. I do plan on taking videos within the next year at what it currently my favourite recording location--the crest of the 1% Waterville, QC, grade on the St. Lawrence & Atlantic, where 10 mph in run 8 is the norm and anything above 15 mph is the exception.

[U-Haul]

I have a SD40T-2 on my layout and was pondering whether it is feasible for a railroad to do this. In event of an incident swap out a -2 truck and repalce it with a Flexicoil truck. Would it matter whether the Flexicoil was on the rear or front? If this rear wire mesh* (lack of a better word) was removed and left off would the debris entering the opening do damage to the locomtive?
* http://www.drgw.net/drgw-info/roster/sd ... 80x960.jpg
I know it is a day late my computer was being RIP.)

1-28-1986 to 1-28-2006
OV-099 Space Shuttle Challenger

"We will never forget them, nor the last time we saw them, this morning, as they prepared for their journey and waved good-bye and slipped the surly bonds of Earth to touch the face of God.
Ronald Regan

[LongIslandRRTom]

Conrail's SD40-2 fleet all uses flexicoil trucks... None of them has the HTC trucks normally seen on SD40-2's. So it's plausible to use Flexicoils on Dash-2 engines yea.. Don't know about swapping out just 1 truck though.

[GOLDEN-ARM]

The "wire mesh" you refer to, is correct. It is a wire grill, pressed into a series of "V's", and it collects leaves, and trash that would otherwise be sucked into the radiators, clogging them. (think giant bugscreen, like on the grill of a car). The openings are larger, square footage wise, than a standard SD model, for improved air flow, and for more air volume. Of interest to note (if you find such things interesting) is the fact that since you cannot access the inside of the radiator compartment, with a tunnel motor (without using tools) that the firemans side catwalk, directly behind the end of the traction motor blower duct, (located under the letter "E", in Grande) contains two lift-up doors, that are used to store brake pipe hoses, hammers, pipe wrenches, etc., that are normally stored for use by the crews, inside the air compressor/radiator compartment. They are supposed to have drain holes, to allow rain water to drain, but everyone I have ever opened was filled with stinking brown water, and an assortment of rusted, useless tools. Nice picture, of that old gal, and I sure miss runnin' her......

[mxdata]

The Flexicoil three axle truck and the HTC three axle truck have the traction motor air boots in different positions and require different layouts of the high voltage cabling. The center plate arrangement is also different. The Conrail SD40-2 units that were built specifically to use Flexicoil trucks are not adaptable to HTC trucks without very major alterations.

[U-Haul]

Thank you for all your responses.

BLACK HISTORY MONTH