Fighting the sierra grade up to "Dog Soldier Pass" : An ongoing struggle.

[Snowman]

A WB lashup exits the Twin tunnels north track.

Ah...helpers moving back uphill maybe.

 

[Snowman]

Sorry but BEMF is quite a mystery for me.
What I know is that dynamic brakes sound is only activated when I press the dedicated
"button", there is no automatic activation.

It actually bothers me sometimes. When a train passes from upgrade to downgrade I progressively switch from notch 8 to dynamics, which is fantastic to do.
BUT if there is a rear helper consisted with the head end, ALL locos obey to the same order.
BUT again it is possible to do better.
1- I activate the dynamic brakes.
2- I rapidly open the rear helper control window to switch off the dynamics sound and activate notch 8.
It works ! So I have notch 8 on the rear helper and dynamics on the head end.
You gotta be fast though and be used to the app control.
When the helper reaches the top I again progressively switch from notch 8 to dynamics.
You understood that, even if it's possible, it would be complex to do with mid plus rear helpers. You would need an extraordinary sense of coordination !!!

Back Electro-Magnetic Force

 

[Snowman]

Sorry but BEMF is quite a mystery for me.
What I know is that dynamic brakes sound is only activated when I press the dedicated
"button", there is no automatic activation.

It actually bothers me sometimes. When a train passes from upgrade to downgrade I progressively switch from notch 8 to dynamics, which is fantastic to do.
BUT if there is a rear helper consisted with the head end, ALL locos obey to the same order.
BUT again it is possible to do better.
1- I activate the dynamic brakes.
2- I rapidly open the rear helper control window to switch off the dynamics sound and activate notch 8.
It works ! So I have notch 8 on the rear helper and dynamics on the head end.
You gotta be fast though and be used to the app control.
When the helper reaches the top I again progressively switch from notch 8 to dynamics.
You understood that, even if it's possible, it would be complex to do with mid plus rear helpers. You would need an extraordinary sense of coordination !!!

According to D&RGW operating rules, it's true the dynamics should only be used on the first 24 axles in front, so with a five unit consist (lashup) of tunnel motors, the fifth unit should be cut out.
But that's the Rio Grande, lessons won the hard way from experience (wrecks), and other road's rules might vary.
As far as those late sixties/mid-seventies EMD's go (with the original control stand (SD45's)), the correct procedure when cresting a grade was: Drop the throttle progressively down to idle by pulling back on the lever...wait ten seconds, move the lower lever from power to brake (and for the electronics to flip the relays), then move the lever forward again to ramp up the dynamics by raising the prime-mover RPM's back up again, but then bleeding off the excess (decending grade power into the traction motors) and into the toaster grids atop each side. The reason for raising the RPM's was to speed up the fans to draw the heat up and out the top. I read somewhere when EMD's went into dynamic mode, the RPM's jumped up to the equivalent of about RUN 4 (of 8). If the engineer leaned on them even more, and moved the lever further forward, the pitch went higher and higher.

But that system caused a couple of incidents, where the engineer was pulling up the hill, dropped to idle, but then FORGOT to move the lower lever from power mode into brake mode before raising the engine RPM's again. As you can imagine, it led to a couple of FAST downhill accelerations from the front end already pulling down over the crest...so EMD shifted to a Dash-2 control stand, where the power lever is dropped to idle...10s pause...and then the dynamic lever is brought in instead. Two separate levers, not one.

It may not be obvious, but the head end pulls the train over the crest and downhill again to keep the slack stretched, then gradually dropping to idle and then D-brake to bunch the slack...so the units would pull the train over the crest possibly still in RUN-whatever...and then kick in the dynamics a bit further down the hill. FWIW.

 

[Snowman]

Thank's, very interesting story Snowman.
I didn't know the nick name "Minnern", I suppose it stands for Minturn.

Minturn indeed, but RC...parenthesizes IIRC too...as "Minnurn." He was up there often enough talking with railroad men that I'm sure he got it right. But I wouldn't have guessed either.

 

[Snowman]

The coupler failure occured at Sullivan's curve a few cars behind a WB head locos.
The "peak" is just a gap marking the end of the second 3% "step" upgrade. Past the gap the track progressively change to a 2% downgrade at the east end of Sullivan's Curve.
The problem was that 1/4 of the train was already on the downgrade and 3/4 still moving upgrade. Plus all the power on the head end.
I also eased the track superelevation of the gap curve. The name is "Rattler Gap".
(Check my upper level plan).

And that's a real-world problem in train-handling right there. An engineer moving downhill has to bunch the slack, but the rear end is still stretched. And with real motive power you can do that, but it's more difficult with models. They just don't operate the same way.

 

[Snowman]

An observation as far as your unit only consists go. They can get up to speed quite quickly and will almost always move both upgrade and downhill both right at the speed limit <cough> of the territory or curve section.

But engineers are like motorists too, and they will often speed--as in "breaking the law" both ways without a train. Unless there is an accident or derailment, none of the higher ups are going to read the "speed tapes" (there is a recorder on one of the front axles), so they can get away with it.

The way I would handle this is post speed signs--all railroads have them--and then...because they apply to all trains, require (such as you do) that a train pass a sign at that given speed, or slower. But then be allowed to accelerate again until the next sign, at which point he should be slowed down again to the speed of that sign.

In the real world, an engineer would pass the sign, and then keep at or below the speed limit until the rear end of the train had also passed the sign...and then speed up again if the territory allowed for it.

Selective compression--our mainlines are just too short--tells me go to the speed sign, then ramp it up as soon as the head end passed the limit sign. In the model world, the train behind you won't care.

Of course, then you may ask "why the speed limits at all?" Curvature, grade, etc. dictate those and almost always running downhill, but with an unloaded set of units moving upgrade, the engineer could ramp them up to illegal speed quite easily too...if he thought he could get away with it.

Most US mainline railroads will have speed limits in different places, and it's usually not only expected...but even required of an engineer that he keep his train right on the limit if he can. This particularly applies to moving downgrade. In order to meet the schedule (even though most operated as extras).

Trains Magazine had an article years ago about "Beaumont Hill" coming out of Bakersfield and heading east. The engineer worked right on the edge to keep his train moving at the maximum allowable speed over the whole district. Twenty Five MPH, in that particular case.

The article read: If he overspeeds it and they catch him, he'll quite likely be fired. Out of work for a month or three until they rehire him again. But if he's overly cautious...twenty four when the speed limit allows twenty five, he won't be fired...but will probably be demoted to running a switcher in a yard for the rest of his career.

Until I read that article all those years ago now, I had no idea what engineers really had to deal with every day. A fine line and a narrow window.

This was all on the Southern Pacific too, and FWIW.

 

[Snowman]

Meeting at the Twin tunnels.

Love the twin tunnels and if I had to guess (correct me if I'm wrong...and based on the design of your twin portals) your tunnels are modeled on the twin tunnels at Kyune, UT, on the D&RGW's Soldier Pass grade.

Not a stretch if yours is known as "Dog Soldier Pass."