Lithonia Operator Let's say that you had two units up front, a mid train engine, and a tail end unit. 2 x 1 x 1 The lead unit suffers a failure, requiring the prime mover to be shut down. Can you still control the power from the lead unit?
Let's say that you had two units up front, a mid train engine, and a tail end unit. 2 x 1 x 1
The lead unit suffers a failure, requiring the prime mover to be shut down.
Can you still control the power from the lead unit?
Yes. Until the batteries die.
Lithonia Operator If the lead unit is totally shot, so much so that it can't be used as a "cab car," is the enginee allowed to run from the second unit? If so, would it be required that the conductor ride the dead lead unit, as a lookout?
If the lead unit is totally shot, so much so that it can't be used as a "cab car," is the enginee allowed to run from the second unit? If so, would it be required that the conductor ride the dead lead unit, as a lookout?
The rules may vary from railroad to railroad. In my area a member of the crew must be positioned on the leading end to view signals when approaching them, or in non-main track when visibility is restricted from the controlling unit.
Lithonia Operator And if the second unit must be the controller, will this mean someone must walk to the the DP units, to reset something telling them to heed a different master?
And if the second unit must be the controller, will this mean someone must walk to the the DP units, to reset something telling them to heed a different master?
Yes. And if your new "leader" is facing backwards, you will have to re-qualify the remotes again after you wye the lead unit later in the trip.
It's a bit simpler on a conventional train, and some EOT's can be armed and tested from the lead unit, others require an employee to go back there and push the button a few times.
Greetings from Alberta
-an Articulate Malcontent
Overmod Paul Milenkovic , all of the running locomotives supply brake line air pressure. You'll get a better picture if you think of each locomotive's air compressor charging that locomotive's main reservoir. As SD70dude notes, all the main reservoirs in an MUed consist are piped together to act as one with higher volume, and you can run multiple compressors to get larger volume into the reservoir system. This assists in charging the trainline in some respects, but not others; as noted, the trainline is charged only through the operating brake valve on each consist, NOT by all the compressor outputs delivering separately. So the added effect is through less pressure drop from the main reservoir(s), not larger mass flow in parallel to charge the pipe through larger delivery area.
Paul Milenkovic , all of the running locomotives supply brake line air pressure.
You'll get a better picture if you think of each locomotive's air compressor charging that locomotive's main reservoir. As SD70dude notes, all the main reservoirs in an MUed consist are piped together to act as one with higher volume, and you can run multiple compressors to get larger volume into the reservoir system.
This assists in charging the trainline in some respects, but not others; as noted, the trainline is charged only through the operating brake valve on each consist, NOT by all the compressor outputs delivering separately. So the added effect is through less pressure drop from the main reservoir(s), not larger mass flow in parallel to charge the pipe through larger delivery area.
Despite the combined air pumping and reservoir capacity of the combined locomotive consist - the limiting factor in charging up the air brake system on a train is the amount of air that can be handled through the trainline, which has a internal diameter of apporximately 2 inches - 2 inches to charge all the reservoirs, both service and emergency on all the cars in the train. The more cars, the more air must be pumped through that 2 inch diameter 'air highway'.
The difference between Main Reservoir Pressure (nominally 130-140 PSI) and train line Feed Valve setting (normally in the 90-110 PSI range) as well as the size of the Main Reservoirs when compared to car reservoirs is intended to keep a steady supply of air moving through the trainline when necessary.
Never too old to have a happy childhood!
Paul Milenkovic, all of the running locomotives supply brake line air pressure.
The lead locomotive and the controlling unit in the remote consist will have their automatic brakes valves cut in, and are the only units directly supplying air to the train.
Trailing units in each consist provide additional air to the lead unit through the main reservoir equalizing pipe (one of the three MU air hoses found on modern units). This helps maintain the lead unit's MR air supply if it's compressor cannot keep up.
According to a snarky remark in the last of the Kalmbach Diesel Spotter's Guides that I had seen, all of the running locomotives supply brake line air pressure.
Or at least the GE's do, until they shut themselves down.
If GM "killed the electric car", what am I doing standing next to an EV-1, a half a block from the WSOR tracks?
Here is a somewhat related question: Yesterday I saw a coal train from my favorite train watching spot. It appear to have about 120 to 160 cars. I lost count.
The train was led by two Dash-9 locomotives; two SD70 locomotives brought up the rear. Which locomotives provide the air pressure for the train?
rdamonNice video of a MU separation. https://youtu.be/6aF3LkCa2V0
https://youtu.be/6aF3LkCa2V0
There are shut off valves for each of the pneumatic hoses that are separating on each engine. Part of the routine in separating locomotives in addition to disconnecting the 27 pin MU cable that distributes electrical controls among all engines in the consist is to turn all the valves for each of the pneumatic control hoses to the closed position on each of the locomotives at the separation point.
Nice video of a MU separation.
BigJim BaltACD they are dependent on the designated Lead locomotive to defined direction of movement to the Trail units by the electrical and pneumatic control signals that are sent from Leader to Trail units via the MU and pneumatic connections. There are no pneumatic control signals between the locomotives that pertain to which direction the units are travelling.
BaltACD they are dependent on the designated Lead locomotive to defined direction of movement to the Trail units by the electrical and pneumatic control signals that are sent from Leader to Trail units via the MU and pneumatic connections.
There are no pneumatic control signals between the locomotives that pertain to which direction the units are travelling.
They pertain to the controlled ability to stop among all the units of the engine consist so coupled.
zugmannMR, actuating, apply & release.
OvermodMore precisely, the hose connections made when units are MUed pertain to 'control' over several functions of the air-brake system, including charging, main-reservoir equalization, and independent-brake connection between units. (These multiple connections were seen on electric locomotives like GG1s, not just diesel-electrics.)
MR, actuating, apply & release.
The opinions expressed here represent my own and not those of my employer, any other railroad, company, or person.
BigJimThere are no pneumatic control signals between the locomotives that pertain to which direction the units are travelling.
Naturally on locomotives with pneumatic throttles, there would be air connections. There are very few of these still operating. I don't know if there are two locomotives so equipped still running in MU ... perhaps on SMS?
The two control wires for forward and reverse are reveresed at the rear of the locomotive and in the MU cable, the are not reversed at the front of the locomotive.
BaltACDthey are dependent on the designated Lead locomotive to defined direction of movement to the Trail units by the electrical and pneumatic control signals that are sent from Leader to Trail units via the MU and pneumatic connections.
.
Lithonia OperatorBut how do the rear-facing units know that the lead unit's "Forward" is "Reverse" to them?
When set up in Trail - units have no idea what is ahead or back - they are dependent on the designated Lead locomotive to defined direction of movement to the Trail units by the electrical and pneumatic control signals that are sent from Leader to Trail units via the MU and pneumatic connections. When set in Trail, locomotives cede their 'mind' to the Leader.
In DPU each trailing consist has to be set for direction at the unit containing the radio receiver but the other locomotives in that consist are 'automatically' cable MUed.
Recently I reviewed the GE 29-notch MU on the PRR E44s when participating in the thread containing the 1966 DDR proposal. There the issue of 'handedness' was addressed by having MU receptacles both sides but keeping cables between units 'all to the same side'.
Lithonia Operator But how do the rear-facing units know that the lead unit's "Forward" is "Reverse" to them?
But how do the rear-facing units know that the lead unit's "Forward" is "Reverse" to them?
It is hardwired in.
I believe that the forward and reverse pins are in opposite places on the MU plugs at the front and rear of the locomotive.
When setting up DP the direction in relation to the lead consist must be entered manually, you can choose "same" or "opposite". If you get it wrong the remote will work against the lead consist (this has happened a few times over the years).
JPS1This is a related question. I think! Yesterday I saw three BNSF Dash-9s pulling a train past my next best train watching spot. The first locomotive was facing forward, but the two trailing locomotives were facing rearward. Or for the uninformed like me, the front locomotive was going forward and the two other locomotives were backing up. (Chuckles will be held to a minimum please.) When the locomotives are positioned like so, do the ones that appear to be backing up have to be set manually before the train departs or is the process automatically set from the lead locomotive?
Yesterday I saw three BNSF Dash-9s pulling a train past my next best train watching spot. The first locomotive was facing forward, but the two trailing locomotives were facing rearward. Or for the uninformed like me, the front locomotive was going forward and the two other locomotives were backing up. (Chuckles will be held to a minimum please.)
When the locomotives are positioned like so, do the ones that appear to be backing up have to be set manually before the train departs or is the process automatically set from the lead locomotive?
Trailing locomotives, no matter the direction their cabs are facing, are set up as 'trailing' locomotives. As such their electrical and power circuits are controlled by the control inputs that the designated 'lead' locomotive makes.
When the Engineer places the reverser in Forward and then advances the throttle to notch 4 - all locomotive that have been configured as 'TRAIL' will do the same. The 27 pin MU cable that is connected between the units transfer all the electrical controls, the 'small' air hoses on either side of the coupler when coupled between the units pass all the pneumatic contol inputs.
When you start talking DPU - Jeffhergert would be the local expert.
This is a related question. I think!
blue streak 1 If my memory is correct... The Atlanta and StAndrews Bay RR ( Bay line ) had an old Alcoa Road Switcher model unknown on display in Panama City, Fl. Opened the MU cable connector and it only had about 19 (?) pins. That was a surprize to me.
If my memory is correct... The Atlanta and StAndrews Bay RR ( Bay line ) had an old Alcoa Road Switcher model unknown on display in Panama City, Fl. Opened the MU cable connector and it only had about 19 (?) pins. That was a surprize to me.
I think this is an older style of GE multiple-unit control; units up to S4 had it, which I think is long past the time of air throttle control on 539 Alcos. I can't remember the date of adoption of AAR S-512, but I suspect the GE system (derived from electric practice, iirc) predates it.
I suspect the Alco was old enough to use an air throttle, thus needing fewer MU connections.
Darn duplicate postings.
JPS1 Yesterday I saw two Dash 9s and a SD40-2 pulling a freight train past my favorite train watching spot. What issues, if any, arise when locomotives from different manufacturers operate together?
Modern locomotives all use the same connections and are full interoperable. Some older units (pre-1960s) had slightly different MU cable pin arrangments and not all the features would work on trailing units when you had mixed consists (NDG stated on several occasions that EMD and FM units had different dynamic brake control systems, and the DB would not work on trailing units when the two were coupled together).
Air brakes are another story, some older units with 6 or 14 (and some 26) "one pipe" systems could not lead units with 24 (and most 26) "two pipe" systems, as there would be no way to bail off the trailing units. Someone eventually realized that in this situation you could connect one of the lead unit's MU sander air hoses to the bail off hose on the trailing unit, and then turn the applicable sander switch on whenever you wanted to bail off.
Most Baldwin diesels had a air-controlled throttle that was not compatible with units from other builders, though some were later retrofitted to make them compatible.
Specialized features like Distributed Power and Pacesetter (automatic slow speed control) still have their quirks and surprises. The latest versions of DP (since about 2015) seem to have resolved most of the compatibility issues, but I've seen a few cases where we couldn't get older units from different railroads to link to each other, and of course the older Locotrol I and II systems are not compatible with modern DP.
Pacesetter seems to have been standardized since about 2005 (GEVO and SD70M-2/ACe), but anything older than that can have any one of several systems, and not all of them will work together. With a mixed consist there was no way to know in advance exactly how each trailing unit would react to the leader. Some would trail properly behind units they could not lead, some would trail in straight throttle, others would rev up and not load, or not react at all.
zugmann BaltACD The volts and amps of each engine have no idea of the volts and amps of any of the other engines in the consist - each locomotive is working to its own maximum capability for the throttle notch that the engineer has selected. Don't some of the newer engines have that smart consisting or EM stuff, and do know what the other engines are doing? I know when I ran some of the GEVOs or ACes, I beleive they had displays that showed what other engines were doing, if they also had compatible software. It's been a few years since I've had that high tech stuff. Jeff?
BaltACD The volts and amps of each engine have no idea of the volts and amps of any of the other engines in the consist - each locomotive is working to its own maximum capability for the throttle notch that the engineer has selected.
Don't some of the newer engines have that smart consisting or EM stuff, and do know what the other engines are doing? I know when I ran some of the GEVOs or ACes, I beleive they had displays that showed what other engines were doing, if they also had compatible software. It's been a few years since I've had that high tech stuff.
Jeff?
Those engines equipped have a consist monitor. There's a limit to how many trailing units it will display, but all you see is tractive/brake effort. At least you know if the trailing units are working. I've had too many engines with smart start/stop that won't restart when needed and won't ring an alarm bell that there's a problem.
There was an EMS (Smart Consist) that showed what the trailing units (up to 2) were doing, but SC was deciding how each engine produced power. No one, except maybe bean counters who don't know much about how things really work in the real world, liked it. Even managers, except those who drowned in the kool-aid and thought they were destined to high management positions, who had to enforce it's use thought it was a big waste all the way around.
Jeff
SD70Dude zugmann Overmod My guess is that your actual control over much of that is limited by the interface in the first place, and by access permissions and 'not being distracted by electronics while maintaining vigilance (or some other mealymouthed excuse) should you try making informed use of the dataflow and controls. If you only knew at times... Here's an example. We used to be told to use Trip Optimizer as much as possible (CN doesn't use any of the other systems), and WiTronix would 'phone home' if we were not using it. When in Trip Op we are exempt from obeying throttle restrictions, as the program is supposed to be smart enough to calculate how to save the most fuel. Eventually someone figured out that if you opened the Trip Op screen and "intialized" it, no alarms would be generated. But you would still be free to manually control the throttle, without being hindered by those pesky throttle restrictions. Eventually the Company figured out what was going on, and now we are told not to use Trip Op, and obey the throttle restrictions religiously.
zugmann Overmod My guess is that your actual control over much of that is limited by the interface in the first place, and by access permissions and 'not being distracted by electronics while maintaining vigilance (or some other mealymouthed excuse) should you try making informed use of the dataflow and controls. If you only knew at times...
Overmod My guess is that your actual control over much of that is limited by the interface in the first place, and by access permissions and 'not being distracted by electronics while maintaining vigilance (or some other mealymouthed excuse) should you try making informed use of the dataflow and controls.
If you only knew at times...
Here's an example.
We used to be told to use Trip Optimizer as much as possible (CN doesn't use any of the other systems), and WiTronix would 'phone home' if we were not using it. When in Trip Op we are exempt from obeying throttle restrictions, as the program is supposed to be smart enough to calculate how to save the most fuel.
Eventually someone figured out that if you opened the Trip Op screen and "intialized" it, no alarms would be generated. But you would still be free to manually control the throttle, without being hindered by those pesky throttle restrictions.
Eventually the Company figured out what was going on, and now we are told not to use Trip Op, and obey the throttle restrictions religiously.
For us, they've always known if you used the EMS or not. Even if you logged in but ran manual, they knew it. It's why at the end of the trip you had to give feedback as to why you didn't use it when it was available.
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