Elvas Tower: Maximum Speeds and Consists - Elvas Tower

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Maximum Speeds and Consists Thoughts about setting the Maximum Speed for a Train Rate Topic: -----

#31 User is offline   Csantucci 

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Posted 07 May 2020 - 11:58 PM

View Poststeamer_ctn, on 07 May 2020 - 11:27 PM, said:

...
Does anybody know whether the TCS system can "cut power" above certain speeds? If so, in the BASIC configuration, I would like to change the OR code so that above the MaxVelocity (design speed) the TF ramps down, rather then going straight to zero. The TCS could override this as a monitoring safety measure.

Thoughts?

Hi Peter,
the TCS system can cut power above certain speeds, but they would be not the max speed of the trainset, but the minimum between such max speed and the max allowable speed in that route point, if configured so; this can be done also with the built-in, MSTS-like, TCS.
I think this is different from eventual provisions that the locomotive may have to avoid to run above its own max speed; I would assume that such provisions might be absent from old locomotives, and might be of different types in more modern locomotives, but I'm not an expert.
What I wouldn't modify is how the maximum allowed speed is computed now in OR (except provisions for inserting a max speed paramenter in the .wag file are introduced), because this can change the behaviour of existing activities, but I think it's not your aim.

#32 User is offline   atsf37l 

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Posted 08 May 2020 - 12:06 AM

I said, "With the MaxVelocity in the .eng file set at 70MPH the loco will top out around 69.8 regardless of the 90 MPH track speed."

View Poststeamer_ctn, on 07 May 2020 - 11:27 PM, said:

Thanks for confirming my suspicions.



Whoa, Nelly! That is in Autopilot, as reflected in the last statements of the paragraph just above. In manual control the locomotive can certainly go past 70 MPH to what ever the errant engineer might run it up to, but in Autopilot the loco will roll along at a sedate 69.8. In otherwords, MaxVelocity sets the operating speed for any AI train - of which a Player train in Autopilot is one.

Then you said, "So the question is, again in real locomotives, what speed does MaxVelocity equate to? Is it the "maximum design speed"? Secondly what happens when this speed is reached, does TF go to zero, does it decay, or are the traction motors and gearing transmissions destroyed because of over speed?"

MaxVelocity equates to the speed at which the railroad allows the locomotive to attain on the road. It could be the maximum design speed, or timetable restrictions for a given locomotive on a given piece of track.

But it doesn't cut off the tractive force when reached, but merely maintains the maximum speed restriction. And, as I said above, in manual control the locomotive can blow right past the stated MaxVelocity. It has no effect in manual control but to change the green bars in the F4 display to yellow and red. It also affects the speed limit shown in the F4 display, being the max speed the loco is allowed vs the speed limits on the route.

#33 User is offline   atsf37l 

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Posted 08 May 2020 - 01:06 AM

And, when I say "allowed" that is not to say "allowed" by the simulator but "allowed" by the mechanical department of the railroad in question.

#34 User is offline   cr-stagg 

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Posted 08 May 2020 - 05:10 AM

View Postatsf37l, on 07 May 2020 - 10:12 PM, said:

Charles I'm a little confused about the way you say ConBuilder builds a consist file. I just created a consist file for a lite 60 Class D&RG 2-8-0 a couple of days ago, accepting the default values. Here's how it reads:

SIMISA@@@@@@@@@@JINX0D0t______

Train (
TrainCfg ( D&RG203Lite
Name ( "D&RG 60 Class 203 Lite" )
Serial ( 1 )
MaxVelocity ( 0.00000 0 )
NextWagonUID ( 3 )
Durability ( 1 )
Engine (
UiD ( 1 )
EngineData ( 60_class_d&rg_203 60_Class_D&RG_203 )
)
Wagon (
WagonData ( 60_Class_D&RG_203_tender-OR 60_Class_D&RG_203_tender )
UiD ( 2 )
)
)
)

MaxVelocity ( 0.00000 0 ).

Maximum speed for this loco either for "overspeed" indicators or Autopilot running is the 17 MPH specified in the MaxVelocity statement in the .eng file.

Conbuilder 6.1.2. So I don't understand what you're saying about the calculations involved with the default save??? :huh: :bigboss:

?? I just created a light consist with version 6.2.3 using an ENG and a WAG from my Trainset as I do not have that ENG you used.
Here is the MaxVelocity line created.
MaxVelocity ( 29.055 1.00000 )

Two thoughts as to why 6.1.2 created:
MaxVelocity ( 0.00000 0 ):
One there was a bug in 6.1.2 so you need to upgrade to the current version.
Or
Two you are using Include files in your Trainset and ConBuilder cannot find the data to calculate with. Do you use Include files? If not attach the ENG file to a reply.

View Postatsf37l, on 07 May 2020 - 10:12 PM, said:

........ So I don't understand what you're saying about the calculations involved with the default save??? :huh: :bigboss:


When I said default values in my post I meant MaxVelocity ( 40.00000 1.0 ). That is what the Freeware versions of ConBuilder wrote to CON files, UNLESS the user manually entered their own calculated values. I forget how it was done. I think it was only available through the menu item "Misc"

#35 User is offline   cr-stagg 

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Posted 08 May 2020 - 05:22 AM

View Postatsf37l, on 07 May 2020 - 10:32 PM, said:

Continuing, and I hate to stir it up but I just went into ConBuilder and built a light consist for 203's sister, 226. I elected not to accept the default just to see where it would take me and I noticed this is for a "durability factor:"

Leading you to a parameters selection screen:

Having nothing to do with MaxVelocity at all?????

And what, exactly, is a "durability factor?" :curiousPC:


It set the value of this line:
Durability ( 1 )
It is used by ACT files in deterring how well the engineer did in handling the cargo. I doubt any ACT creator uses the field. I seem to remember that some of the ACTs from the MSTS CDs gave evaluations with reports of leaving the station stop with a jerk or stopping too fast.

#36 User is offline   R H Steele 

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Posted 08 May 2020 - 07:26 AM

View Poststeamer_ctn, on 07 May 2020 - 11:27 PM, said:

....So the question is, again in real locomotives, what speed does MaxVelocity equate to? Is it the "maximum design speed"? Secondly what happens when this speed is reached, does TF go to zero, does it decay, or are the traction motors and gearing transmissions destroyed because of over speed?


View Postatsf37l, on 08 May 2020 - 12:06 AM, said:

But it doesn't cut off the tractive force when reached, but merely maintains the maximum speed restriction. And, as I said above, in manual control the locomotive can blow right past the stated MaxVelocity.

From all my current studies, trying to learn this stuff, I thought that in diesel performance, the tractive motors provided some sort of electrical/mechanical limit as to how fast the diesel locomotive could go. At some point current through the traction motors could not be sustained and the motors would blow out, or safety features would cause current to the motors to be cut off and tractive effort would not be applied to the railhead. At that point the energy that had been absorbed by the train ( consist ) would either dissipate over time, or not depending upon the current road grade and condition of brake system.

From reading this discussion, I think I'm missing something?

#37 User is offline   longiron 

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Posted 08 May 2020 - 08:05 AM

You can get a wealth of education on this topic from the EMD F7 Operating Manual: http://users.fini.ne...lais/EMD-F7.pdf

#38 User is offline   Aldarion 

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Posted 08 May 2020 - 08:54 AM

View Postdarwins, on 07 May 2020 - 10:11 AM, said:


locomotives when running light engine are often required to run at lower speeds when they would when pulling a train - usually I believe for reasons of fuel economy.


Light engines usually run at lower speeds due to stability issues.

#39 User is offline   darwins 

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Posted 08 May 2020 - 09:21 AM

Quote

From all my current studies, trying to learn this stuff, I thought that in diesel performance, the tractive motors provided some sort of electrical/mechanical limit as to how fast the diesel locomotive could go. At some point current through the traction motors could not be sustained and the motors would blow out, or safety features would cause current to the motors to be cut off and tractive effort would not be applied to the railhead. At that point the energy that had been absorbed by the train ( consist ) would either dissipate over time, or not depending upon the current road grade and condition of brake system.

From reading this discussion, I think I'm missing something?


Have a look at this model:
https://i.imgur.com/kfYw2Ga.jpg

Something I am learning about now from a diesel driver, and discussing with Peter. The above is for a diesel electric loco with dc traction motors. Things are a bit different with ac traction motors. They are somewhat different with hydraulic transmission.

Too much current is the danger at starting from rest - when the traction motors have very low resistance.

As speed increases the electrical resistance of the traction motors effectively increases - due to back EMF - making it harder and harder for the generator to push current through them. Eventually the back emf becomes so large the generator can no longer overcome it and the power that the traction motors can provide starts to fall. This is the "unloading point" Some locos have the unloading point greater than or equal to the designed maximum speed, most have it somewhere below maximum speed. Some have the mph of it vary quite a lot with rpm others not much at all.



As an example I gave to Peter, I had an interesting journey about two or three years ago with a 45 year old diesel electric loco on a short passenger train. The loco concerned has a designed maximum speed of 90 mph. The panel on the side of the cab (giving the max it is allowed to run at) said Maximum Speed: 80 mph. The train arrived very late and we thought we would be held for a 125 mph electric train due to follow in a few minutes time. Pleasant surprise to get a green light. 20 miles to the next station, mostly level apart from about a mile uphill at the start. We covered about 15 out of the 20 miles at 100 mph. (The fastest journey I have ever logged with that class of loco!)

#40 User is offline   atsf37l 

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Posted 08 May 2020 - 01:52 PM

Charles: I will stick with 6.1.2 because, for the most part, my operations rely on 0.00000 0 for a default setting in Consists. I prefer to be governed by the assigned locomotive's MaxVelocity, which I can and do set for specific activities. It does take a bit of balancing when you intend to use the Autopilot function while you go out and railfan the trip taking pictures and enjoying the scenery. :lol: One thing about AI's and Autopiloted Player trains is that the AI/Autopilot function WILL NOT STALL. You can put twice the tonnage and more behind a given locomotive combination and AI/Autopilot will run the train at MaxVelocity's speed setting.

IE, I just took four ( 3DTrains ) Santa Fe F7's, rated for 3200 Tons from Cajon to Summit on the Cajon Pass Route, and hung 6414 tons of loaded boxcars on the rear coupler. I started at Cajon, released the brakes, stepped the throttle up to Run 8 and the Consist began a backward slide towards San Bernardino. I clicked on Alt/A to engage Autopilot and the backward slide ended, the speed picked up and the train marched up the hill at 28.7 MPH.

Which brings up another issue with the concept of MaxVelocity vs. Route Speed Limits. MaxVelocity on these units is set at 65 MPH - the functional max speed for the EMD F-7 with 62:15 gearing - set by 3DTrains. Since the route speed limit for this portion of Cajon Pass is 30 MPH, this lower limit governs the maximum speed for the track and supercedes the locomotives maximum speed.

So any lower speed restriction, like the route speed limit or, say, the 40 MPH MaxVelocity of a 2-10-2 helper assigned to the train would hold the F7's to that lower speed and the MaxVelocity of the units would not come into play until the speed limit on the route changes to above 65 MPH or the helper is cut out or both.

IMHO, most of the correspondents here in this thread tend to look at things as game-imposed limitations or enhancements. The railroaders and model railroaders in the discussion, like your humble servant, tend to look at things like speed restrictions and mechanical functions in terms of prototypical operations of that which we model and operate. Sometimes I think that because of this we seem to speak in different languages, beyond the limitations of the languages represented by our national flags! I hope that discussions of this nature will continue to help us understand each other better and come to agreements in functionality.

Personally, I have already begun to step back from the Constant "improvement" of things, adopting, as I mentioned before, Conbuilder 6.1.2 rather than the latest upgrade because 6.1.2 best suits my operational needs. I have also settled in on Open Rails version X1.3.1-41-g54663ad6 for the same reason and particularly because of recent "enhancements" for vacuum brakes interfere with the prototypical operation of the non-self-lapping brakes of the American steam era.

I continue to monitor the progress of ORTS and download new versions for testing but I keep going back to X1.3.1-41. This software at this point is doing everything I wish it to do.

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