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LOCOTROL

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LOCOTROL
Posted by VGN Jess on Tuesday, February 28, 2017 4:42 AM

Wikipedia says: "Most systems use lead and middle of train locomotives, but up to four consists can be controlled from the lead unit. My questions are: 1) does that mean only four (4) locomotives connected together (either mid train or end of train) can be controlled from the lead engine? or 2) could I have, say, six (6) mid train and four (4) end of train locomotives controlled by the lead? I guess I am confused by the word "consists"; is each locomotive a "consist"? I have seen pictures of 5-6 locomotives as a mid train DPU and didn't know (because there more than four (4) whether there were LOCOTROLLED or had a crew. Thanks.

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Posted by beaulieu on Tuesday, February 28, 2017 6:00 AM

A locomotive "consist" can be any number of locomotives up to the maximum number that can be reliably controlled via the MU cable. What the statement of 4 locomotive consists means is four sets of locomotives. Only 4 additional locomotives can be controlled via Locotrol (current version is now referred to as Distributed Power). Each of the up to 4 locomotives controlled via Locotrol(DP), can control further locomotives via MU cables. 

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Posted by VGN Jess on Tuesday, February 28, 2017 7:32 AM

Thank you. So when I saw 5 locomotives as a midtrain DPU, there had to have been an Engineer and Conductor in the 1st of the 5?

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Posted by BigJim on Tuesday, February 28, 2017 7:44 AM

Nobody is on the DPU units.

.

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Posted by oltmannd on Tuesday, February 28, 2017 7:44 AM

VGN Jess

Thank you. So when I saw 5 locomotives as a midtrain DPU, there had to have been an Engineer and Conductor in the 1st of the 5?

 

Mid train locomotives wouldn't have anybody on them.  Train would have engineer and conductor on head-end only.

 

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Posted by PNWRMNM on Tuesday, February 28, 2017 8:36 AM

beaulieu

A locomotive "consist" can be any number of locomotives up to the maximum number that can be reliably controlled via the MU cable.

The portion of this statement "that can be reliably controlled via the MU cable." is incorrect.

The thing that limits locomotive consist size is some combination of drawbar (knuckle really) strength and Track Train Dynamics.

Grade C knuckles are rated for 240,000# of draft (pull or tension). Grade E is 360,000#. Given either limit, and given the ruling grade, and given maximum low speed TE of the consist, it is fairly simple math to figure out consist limits. In fact they are usually published in subdivision special instructions.

The Train Track Dynamics issues are more complicated mathmatically but the limit here is usually buff or compressive forces. The basic idea here is that under high buff loading it is possible to shove a wheel flange over the rail or roll the rail over. Again restrictions will be published in the special instructions.

The most power I ever saw on one train was the SP "oil cans" from Bakersfield area to the LA area on the loop at Walong. They had 4 SD 40 units on the point, 6 more cut in, and two more on the rear to climb to Tehachapi. I suspect the rear helper cut off at Tehachapi and the swing helper went through for dynamic braking on the 2.2% descents.

Each unit would have been rated for about 1100 tons on the 2.52% equavalent ruling grade (2.2% UNcompensated) so train could have been 11,000 tons or 83.6 cars given that power. My recollection is that the train actually operated with 80 cars.

SP SD 40's generated 90,000# of TE, so 4 of them were 360,000#, so we can safely assume grade E draft gear and knuckles.

It is all physics!

Mac 

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Posted by BaltACD on Tuesday, February 28, 2017 8:54 AM

Fictional Train -

Lead Locomotive Consist (4 units in MU with T&E Crew on lead engine)
80 cars
DPU Locomotive Consist (3 units)
80 cars
DPU Locomotive Consist (3 units)
80 cars
DPU Locomotive Consist (5 units)

The DPU consists are controlled by the crew on the lead locmotive.

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Posted by jeffhergert on Tuesday, February 28, 2017 12:56 PM

Just because you see multiple engines in a DP consist doesn't mean all may be working.  One of our manifest trains normally runs with 4 engines in the mid-train consist.  It normally sets out the entire DP set and cars behind it at an intermediate terminal.  Often only two, sometimes one, in the DP consist are working.  The rest are shut down/idling (depends on weather) for fuel conservation.  It all depends on the train tonnage for how many engnes are actually running (producing power) on any train.

Jeff

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Posted by RME on Tuesday, February 28, 2017 1:30 PM

A locomotive 'consist' is the "preferred" word for what DPM and generations of railfans termed a 'lashup' -- a set of MUed locomotives responding to the control signals from its 'leader'.  Locotrol has four separate controls, each of which can then control the leader of a set of locomotives, and of course the logical place for additional sets of locomotives is where DP puts them, distributed in the train (the cars are, confusingly enough, also often referred to as the 'consist' but that's a different consist!)

The number of locomotives in a MODERN consist is usually limited by rule (which in turn is written partly with an understanding of maximum number of powered axles, load on part of the train, etc. as just observed).  BUT, as noted, the MU control can technically control a larger number of individual locomotives.  Back in the bad old days of 1750hp maximum single-engine size, if I remember correctly, UP used to run as many as 15 units 'in multiple'.  How many of those were isolated during part of the trip, or being moved to balance power, I don't know; I was not there.  But Don Strack or someone like him will know.

So the answer is different depending on whether you're considering the maximum locomotive-consist size as being determined by operating conditions, or by the technical capability of the MU and DP systems.  You'll get different answers, but the one limited by train and handling characteristics is probably a better one.

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Posted by BaltACD on Tuesday, February 28, 2017 2:13 PM

CSX Rules limit the maximum number of engines in a engine consist to 12 engines.  Working, isolated or dead - the maximum is 12.  You will see these kinds of engine consists on trains destined major locomotive shops - the trains wil normally have only one or two engines operating - the rest are out of service for various reasons headed to the shop for repair.  You may see a large number of engines on trains originating at the location of a major locomotive shop, those engines will normally be set off at terminals along the route of the train.

Maximum allowed train tonnage, under CSX Rules, was the tonnage that was rated for 2 GE AC's + 1 Dash-8 over the ruling grade for the train.  Train was permitted to have a maximum of 27 powered axles. (AC's counted as 9 axles)

When you get into territory where Helpers (or Distributed Power) is required then you begin to get into 'trailing tonnage' restrictions that dictate where the additional power is placed in the train. 

Fun with engines!

 

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Posted by VGN Jess on Tuesday, February 28, 2017 6:42 PM

Then I'm still confused. If only UP TO FOUR (4) consecutive locomotives can be controlled via LOCTROL, then how could a train have five (5) in the midtrain DPU w/o a crew? How were these 5 locomotives operating?

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Posted by VGN Jess on Tuesday, February 28, 2017 6:50 PM

BaltACD:  Beaulieu told me that: "Each of the up to 4 locomotives controlled via Locotrol(DP), can control further locomotives via MU cables."  From your example this train has three (3) DPU consists plus one (1) lead. If my understanding is correct, how many locomotives are maximum LOCOTROLLED within each of those three? I see two (2) consists with just three (3) locomotives (ie..< 4) but the end of train consist has five (5) which is > four (4)?

All i'm really trying to get an answer to is: What are the maximum number of consectutive locomotives, in DPU mode, that can be controlled by the lead? I think the answer is: no > four locomotives in no > four consists behind the lead; is that correct?

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Posted by VGN Jess on Tuesday, February 28, 2017 7:00 PM

Jeff: Are there only 4 engines in the mid-train consist, because of: A) company or operational policy or B) because four (4) is the maximum number controlled by LOCOTROL?

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Posted by RME on Tuesday, February 28, 2017 7:12 PM

VGN Jess
If only UP TO FOUR (4) consecutive locomotives can be controlled via LOCOTROL, then how could a train have five (5) in the midtrain DPU w/o a crew? How were these 5 locomotives operating?

You're still looking at the 'consecutive' wrong -- in the fictional train, there are 80 cars between 'each' of those 'consecutive' locomotives.

The 'five midtrain units' represent ONE Locotrol-controlled unit, MUed to four followers with conventional cables.  (It's only a coincidence that there are four units MUed to the Locotrol-equipped one).

Now, in Balt's example, go back 80 more cars.  There are some more locomotives.  ONE of them is another of the four Locotrol-controlled units, and again, the rest of the locomotives at that position in the train are connected in conventional MU.

Is that clearer?  If not I'll try to explain it in different language -- PM me.

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Posted by BaltACD on Tuesday, February 28, 2017 7:17 PM

VGN Jess
BaltACD:  Beaulieu told me that: "Each of the up to 4 locomotives controlled via Locotrol(DP), can control further locomotives via MU cables."  From your example this train has three (3) DPU consists plus one (1) lead. If my understanding is correct, how many locomotives are maximum LOCOTROLLED within each of those three? I see two (2) consists with just three (3) locomotives (ie..< 4) but the end of train consist has five (5) which is > four (4)?

All i'm really trying to get an answer to is: What are the maximum number of consectutive locomotives, in DPU mode, that can be controlled by the lead? I think the answer is: no > four locomotives in no > four consists behind the lead; is that correct?

Maximums are set by rules.  Theory says that a unlimited number of engines can be operated by MU control.

My understanding is that DPU permits 4 additional engine consists to be controled from the lead engine consist.  As with my previous statement, in theory a unlimited number of engines could be operated as a part of each DPU engine consist. 

All carriers have rules that govern the operation of engine consists and DPU engine consist.  Those rules may vary a little from carrier to carrier.

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Posted by VGN Jess on Tuesday, February 28, 2017 8:23 PM

RME: Thanks. I think your 2nd paragraph answers my original question, ie...if I have one (1) midtrain DPU, I could have as many as 5 or 6 locomotives controlled by the lead engine. In reading about LOCOTROL, it sounded to me like only up to four (4) locomotives in the entire train consist could be controlled via LOCOTROL but I think I understand now that the four (4) max referenced refers to up to four (4) separate DPUs in a train consist, each which could conceivably have > 4 locomotives each.

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Posted by blue streak 1 on Tuesday, February 28, 2017 8:27 PM

Wouldn't it be interesting to be an engineer operating a train with 4 single locos eveenlly spaced in a train.  Wonder what handling characteristics would be observed ?   Why this configuration ?  Suppose several locals picked up cars and combined the train to some destination and then split at another main yard ?. 

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Posted by BaltACD on Tuesday, February 28, 2017 8:36 PM

UP 18000+ foot test train from Texas to Long Beach - 2 mid train DPU's and a rear end DPU

 

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Posted by VGN Jess on Tuesday, February 28, 2017 8:52 PM

Wow! Any idea what the avg. track speed was and the avg. consist speed?

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Posted by BaltACD on Tuesday, February 28, 2017 9:39 PM

VGN Jess
Wow! Any idea what the avg. track speed was and the avg. consist speed?

A old thread devoted to it

http://cs.trains.com/trn/f/111/t/166689.aspx

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Posted by VGN Jess on Tuesday, February 28, 2017 9:54 PM

BaltACD: Thank you.

To all: Thank you for your many responses. My original query was (and I failed to mention it) primarily focused on the period 1969-1979 when the HP range was 2,000 to 3,000 and more locomotives were needed (particularly on the western roads, eg...Cajon, Soldier Summit, Marias Pass, Donnor Pass, etc...) than in todays time. I had seen SP on Tennessee Pass and DRGW over Soldier Summit using up to six-7 (6-7) locomotives mid train. So when I read that LOCOTROL was good for up to four (4) locomotives...well you can imagine my neophyte confusion. THanks again to all who took their time to help me understand!!

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Posted by coopers on Tuesday, February 28, 2017 11:26 PM

How far back did LOCOTROL go? I didn't think DP was super common before the 90's. Could some of those SP trains back in the 70's have been manned helpers? I know BN used manned helpers back in the day in my state. They'd hook up at Balmer Yard in Seattle to push a train over Stevens Pass (Scenic Subdivision). MRL and BNSF still use manned helpers. 

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Posted by VGN Jess on Tuesday, February 28, 2017 11:53 PM

I believe it was available from 1967 on. Weren't manned helpers usually used at the rear of the train, not mid train?

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Posted by YoHo1975 on Wednesday, March 01, 2017 12:13 AM

coopers

How far back did LOCOTROL go? I didn't think DP was super common before the 90's. Could some of those SP trains back in the 70's have been manned helpers? I know BN used manned helpers back in the day in my state. They'd hook up at Balmer Yard in Seattle to push a train over Stevens Pass (Scenic Subdivision). MRL and BNSF still use manned helpers. 

 

 

There are other threads here that talk about this, but the super brief history is that it started out in the 1960s and was typically installed in an unpowered Locotrol car connected to the Engines.

 

It was then placed in Locomotives, most famously the 1970s era "Snoot nose" SD40(T)-2 series of ATSF, SP, UP. Basically the 123" nose contained the locotrol equipment.

 

What changed in the late 90s is that GETS (GE Transportation) bought Harris Controls which owned Locotrol at the time.

 

DPU is a genericized name. Locotrol is a brand name.  

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Posted by coopers on Wednesday, March 01, 2017 12:16 AM
BN sometimes cut in the middle of the consist on Scenic Sub. MRL does middle generally at Mullen Pass and rear end helpers at Bozeman. BNSF does rear helpers on Crawford Hill. Rear helpers have a nice fancy system that allows them to detach on the go so the train doesn't have to stop.
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Posted by coopers on Wednesday, March 01, 2017 12:16 AM

YoHo1975

 

 
coopers

How far back did LOCOTROL go? I didn't think DP was super common before the 90's. Could some of those SP trains back in the 70's have been manned helpers? I know BN used manned helpers back in the day in my state. They'd hook up at Balmer Yard in Seattle to push a train over Stevens Pass (Scenic Subdivision). MRL and BNSF still use manned helpers. 

 

 

 

 

There are other threads here that talk about this, but the super brief history is that it started out in the 1960s and was typically installed in an unpowered Locotrol car connected to the Engines.

 

It was then placed in Locomotives, most famously the 1970s era "Snoot nose" SD40(T)-2 series of ATSF, SP, UP. Basically the 123" nose contained the locotrol equipment.

 

What changed in the late 90s is that GETS (GE Transportation) bought Harris Controls which owned Locotrol at the time.

 

DPU is a genericized name. Locotrol is a brand name.  

 

 

Ah okay thanks! Forgot it went back that far. 

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Posted by cx500 on Wednesday, March 01, 2017 2:30 PM

CPR tested and then embraced Locotrol for unit coal trains in the west in the late 1960s.  Over time as electronics improved Locotrol underwent several generations of improvement and was expanded to other bulk trains and eventually intermodal and manifest trains.  I believe the original Locotrol could only handle one DPU set (CPR called them slaves at the time) but have no idea which new version enabled the additional DPUs.  I now see some trains with a mid-train DPU, others with a tail end DPU, and others with both mid and tail end DPU, of either one or two ACs.

I think CPR was the most loyal user of Locotrol, devising how to work around the continuity problems of the initial versions.  A number of US roads did try the early versions of Locotrol with varying degrees of success.  I don't know if any kept using it continuously throughout the decades of its development.  Of course today everybody has adopted it.

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Posted by PNWRMNM on Wednesday, March 01, 2017 4:39 PM

VGN Jess

I believe it was available from 1967 on. Weren't manned helpers usually used at the rear of the train, not mid train?

Each road had/has its typical practices, which may not hold even system wide.

The advantage of cut in is that you can safely cut in more power than you can safely put on the rear end and especially behind the caboose.

The advantage of rear end is that helper is easier to add/remove.

The GN over the Cascades, now BNSF Scenic Sub, in the early 1960's ran two pair of trains daily with F/GP 7 and 9 units. Grade C draft gear, 240,000 limit. Figure each unit just under 60,000# TE. Ran four on the point 240K TE and six cut in behind 60% of the tonnage, or 3,900 tons. With full tonnage train in normal state climbing the hill the lead units pulled 2600 tons, the cut in shoved 1300 tons and pulled 2600 tons, all with a 100 ton rounding error. With radio it took about 30 minutes to cut helpers in and about the same to cut out.

GN wanted helpers, then two units would probably have been the limit behind the caboose.

The B&O on Cranberry Grade coal trains with SD-35/40 units favored two unit rear helpers that cut of from the occupied caboose on the fly. Comming from Wenatchee WA, I was so astounded at the rear helpers behind the occupied caboose that I do not recall whether or not they had mid train helpers. I suspect they did since such units were good for only about 1200 tons each on the grade.

The point is that it depends on the territory.

Mac

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Posted by oltmannd on Wednesday, March 01, 2017 4:48 PM

The Southern used to run what the called "radio" trains from the 70s into the 80s (or 90s?)

https://goo.gl/photos/9Hf52pPKn6EtMfyU7

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Posted by BaltACD on Wednesday, March 01, 2017 6:08 PM

Pennsylvania had a law that no more than 3500 HP could shove against an occupied caboose.  The fix was to have the rear end train crew ride the helper power, therefore the caboose wasn't occupied.  I don't know if the law is still in effect, cabooses no longer exist on through freights.

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