MUed diesels

A question I've always wondered about.
As you can see by this photo http://railpictures.net/viewphoto.php?id=142056&nseq=39 there are 4 diesels MUed together. The 3rd engine in the consist is facing backward. How does that engine know that for this trip the rear of unit is the front? What keeps the engine from trying to pull in the opposite direction when the engineer moves the consist forward or the other way if the engineer backs the consist up?

TL 8 and 9 are switched in the nose MU receptacle-

Thanks for the answer. But being a dumb armchair railfan could you tell me what a TL8 and TL9 are?
Again thanks for your answer.

Ok, here is another question relating to this.

With Modern Pushers being used on long coal trains, a single engine is pushing from the rear. How is it connected to the lead engines?

I do not believe it has a crew on board, I can't believe they string cables all the way back, so it must be radio controlled?

ricebrianrice wrote:Ok, here is another question relating to this.

With Modern Pushers being used on long coal trains, a single engine is pushing from the rear. How is it connected to the lead engines?

I do not believe it has a crew on board, I can't believe they string cables all the way back, so it must be radio controlled?

Pusher would be controlled from the lead unit by radio. This is not a brand
new technology, they were doing it in the 90's, I had trains of this nature
on Conrail before I retired in 1997.
Noel Weaver

They're not using that radio linkup anymore, Noel.

It's plain old-fashioned "human-interface" technology - there's a crew (in some districts, a solo engineer) in the "helper," the rear locomotive. They're in radio contact, advising the helper what the head-end is doing, whether it's cresting a hill, coming up on a bad signal, whatever.

The trainline air brake is cut out on the helper - the brake pipe is cut into the rest of the train, and as far as the brakes are concerned, the helper locomotive is just one more car. (Of course, the engineer of the helper has the independent locomotive brake to help control slack or effect braking as needed.)

Sounds like DP to me. We began this technology up in the Powder River coal fields on the BNSF in the mid-1990s. Worked like a charm after the bugs were worked out. Utilized the SD70MAC units followed later by GEs. Initially one unit was on the rear end of a coal train with two on the head end. Later BNSF put two and two which really worked great. The DP unit could be controlled in sequence with the lead units or operated independently from the head end.

In the 1970s BN used for a time what was referred to as Locotrol. Very complex technology that was finally discontinued after a horrific accident up on Crawford Hill in Nebraska. They never did get the bugs out of that system. Locotrol units were cut into the middle of the train instead of on the rear end.

So Noel and TB said it is controlled from the lead engines, and Conrail says there is a person in the pusher.

Maybe it is both ways?

DP is done electronically via radio. The signals are coded so as to avoid any interferance from other souces. Some DP units can be addded to the middle of the train as well as on the rear end.

Tunnels can offer problems, however and we were instructed to isolate the DP units just prior to entering tunnel number one west of Guernsey, WY.

ricebrianrice wrote:So Noel and TB said it is controlled from the lead engines, and Conrail says there is a person in the pusher.

Maybe it is both ways?

Yes sometimes its a ''manned helper'', the other option is radio controled DPU.

TL8 and TL9 are two TrainLined wires (aka FO and RE) that are switched in the front MU receptacle, or where the front MU wires come into the terminal board. These wires put each unit's reverser drum into the appropriate position.

Lets use F units as an example:

If you have two F units back to back, they SHOULD pull away from each other if both TL8 (forward) wires are energized. But the MU jumper has those wires (TL8 and TL9) switched between the ends, so the trailing unit runs in its own reverse.

Lets add a third F unit, coupled to the nose of the second, the lead unit's TL8 energizes the second unit's TL9, through the 'crossover' in the first MU cable. The second unit's reverser shifts into reverse, and that unit then runs in it's own respective reverse.

In the nose MU receptacle of the second unit, TL9 gets wired to the TL8 pin. The second MU cable crosses TL8 over to TL9, and vice versa. But the wiring in the third unit's nose MU receptacle switches TL8 and TL9 again, so the third unit's reverser gets shifted into forward.

It gets confusing, the wires crossing over, until you sketch it out. But there is nothing electrical that has to be set if the units are wired correctly.

There was a description of how MU works in an old issue of Trains that mentions a toggle switch that the hostler had to set when making up an MU consist, and that the first notch had to be taken carefully, to see that everything ran in the same direction. ("Lash 'Em Up" was the title, IIRC.)

I'm not sure where that misinformation came from. I have yet to see that toggle switch on any EMD, Alco, GE, or FM schematic I've ever studied, and I've pored over dozens of them; I have schematics from DL-109s to AC6000s in my personal collection.

WOW, thanks for that answer. You're right it was a bit confusing, it took a read or two but I get it.

ricebrianrice wrote:So Noel and TB said it is controlled from the lead engines, and Conrail says there is a person in the pusher.

Maybe it is both ways?

Depends on the railroad.

I understand the Western roads are still playing with various flavors of RC helpers; some cut into the center of the consist. On Conrail, those unmanned RC pushers came and went...and Conrail went before the idea was resurrected.

CSX, insofar as I know (and not in any territories near my runs) does not use unmanned radio-control pushers; and does not have regular pushers assigned anywhere in OH/NY/PA. Occasionally a coal train out of Columbus might need a shove up to Worthington, but they'll take a yard crew out of Parsons to do it (and begrudge the road crew every second of time used).

Manned helpers and DP are a totally different operation. Out in the Powder River Basin coal fields there were manned helper operations. Towards the end of my service in Wyoming on the BNSF there were three different helper jobs:
1.) Belle Ayr Helpers. Worked out of a helper track between West Belle Ayr Jct. and East Caballo Jct. Crew, engineer and brakeman, went on duty in Gillette and deadheaded out. Two jobs OD 06:30-14:30, 22:30 and 10:30, 18:30, 02:30. Power consist of each job was one SD70MAC. These jobs helped all coal trains from East Belle Ayr Jct. to MP 8.2.
2.) Campbell Helpers. Worked out of a helper track off the Eagle Butte Mine lead. Same crew and power consist as the jobs above. One job OD 06:30, 14:30, 22:30. Helped all coal trains on the Campbell Sub.
3.) Logan Helpers. Worked out of a helper track located near the bottom of Logan Hill. One job, same crew, OD time and power as the Campbell job. Helped any train calling for help up Logan Hill and sometimes beyond per dispatcher instructions.

DP, by contrast, stayed in train or on the rear end of the train terminal-to-terminal and many times through two or more terminals as operating conditions dictated, at least on the BNSF out of the coal fields in Wyoming.