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Advanced Adhesion Model Effects of advance adhesion model Rate Topic: -----

#1 User is offline   Gehe 

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Posted 04 October 2015 - 04:45 AM

Hi All,


I started recently some trials with the advanced adhesion model and got some effects which I would like to share and discuss.

I used a diesel loco with about 1.220 kw. The algorithm in OR reduces this by 2 % so I have about 1.196 axle input force. With Standard Curtius-Kniffler Parameters (7.5 44 0.161 0.7) you get a maximal axle output power of about 1.090-1.100 kW, so about 10% of the input power are gone (related tractive forces between 30 to 50 kN). If you have a heavy train with such a loco it makes a difference having this 10% or not. Of course I could increase the input power by 10% but for smaller tractive forces like 15kN the difference between input and output force becomes smaller. In General I cannot imagine that the microslip necessary for larger tractive forces "consumes" that much energy. I think the model has to be adopted here.

One approach to overcome this in an easy way would be to "activate" the Curtius-Kniffler parameters also for the simple adhesion model. Because the standard set does not reflect the adhesion behaviour of modern locos.


Regards
Gehe

#2 User is offline   copperpen 

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Posted 04 October 2015 - 06:24 AM

I think that losing only 10% of power between the diesel engine and the rail is in fact a bonus for most classes of locomotive.

#3 User is offline   Gehe 

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Posted 04 October 2015 - 08:37 AM

The 10% is the difference between the axle input power and the axle output power shown in the F5 HUD. The efficiency of the entire power train: diesel - generator - traction inverters - motors is a different issue.
This is not adressed in OR and has to be covered by appropriate choice of tractive power resp. tractive force tables.

I guess these 10% are caused by the advanced adhesion model itself.


Regards
Gehe

#4 User is offline   Coolhand101 

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Posted 04 October 2015 - 09:45 AM

View PostGehe, on 04 October 2015 - 08:37 AM, said:

The 10% is the difference between the axle input power and the axle output power shown in the F5 HUD. The efficiency of the entire power train: diesel - generator - traction inverters - motors is a different issue.
This is not adressed in OR and has to be covered by appropriate choice of tractive power resp. tractive force tables.

I guess these 10% are caused by the advanced adhesion model itself.


Regards
Gehe


Yes i have notice the lower axle out force. Using real world tractive effort values, the axle output is lower as calculated by OR. I thought this was a real world effect?

I'm not complaining though. Mostly all my trainsets use the 'ORTSTractionCharacteristics' with real world tractive effort curves.
The performance still matches real world values. Using the above curve program, OR is reporting 2580hp at crankshaft and 2080hp at rail, around 20% loss, which is spot on.

In OR, my passenger class 47/4 with a 440 ton load, will balance at 44.5 mph on a 1 in 100 grade. This matches real world values( just under the second field divert ).
That figure was with ETH of around 66% ( around 250hp loss ).

Could it be that this axle out loss, is actually not lost and is just some sort of internal OR calculation ? I cannot see the OR team allowing a 10% loss unless this was prototypical?

Thanks

#5 User is offline   copperpen 

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Posted 05 October 2015 - 01:53 AM

The tractive force tables are something else entirely. If someone has no wish to use these tables, or cannot find usable data for them, then the program itself has to provide. The 10% difference between axle in and axle out is just that far as I can see. It is a catchall, because the early diesel and electric locomotives were nowhere near as efficient as the newer models and this is one area where MSTS has the advantage. The eng file power could be tuned to allow for all the variations without resorting to tables.

#6 User is offline   Coolhand101 

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Posted 05 October 2015 - 02:55 AM

View Postcopperpen, on 05 October 2015 - 01:53 AM, said:

The tractive force tables are something else entirely. If someone has no wish to use these tables, or cannot find usable data for them, then the program itself has to provide. The 10% difference between axle in and axle out is just that far as I can see. It is a catchall, because the early diesel and electric locomotives were nowhere near as efficient as the newer models and this is one area where MSTS has the advantage. The eng file power could be tuned to allow for all the variations without resorting to tables.



The axle out loss, still applies when using the tractive curves/tables.

Without the table, IIRC, the RHP appears to high from the forces HUD. You have to lower the publish HP at crankshalf in the ENG file for the correct RHP( as in MSTS ).
It's very rare for me to use any diesel or electric traction without the tables, so im unsure what else is greatly affected or applies.

Even if you don't have publish TE curves. The ORTSTractionCharacteristics table allows you to adjust the TE forces to match the publish RHP, which normally applies from 13 mph to 75/80 mph for most B.R diesels.
This inclusion of the tractive force tables, is like the holy grail, in finally getting my MSTS rolling stock to perform with 100% prototypical traction performance.

It's just the Brake Characteristics for certain trains that need updating.

Thanks

#7 User is offline   Gehe 

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Posted 05 October 2015 - 08:33 AM

It was not my intention to complain, OR physics is much better than MSTS and OR is developing from version to version.

I use the tables as well as the power to get realistic values, depending on the loco. The tables are the matter of choice if you want to get real throttle characteristics.
The only issue for me is that I have to tune the tables or the power value by 10% if I use the advanced adhesion model.

In general I would appreciate if the Curtius-Kniffler Parameter would also work with the simple adhesion model.
But it is clear that this is a nice-to-have feature with low priority.


Regards
Gehe

#8 User is offline   Coolhand101 

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Posted 05 October 2015 - 11:45 AM

View PostGehe, on 05 October 2015 - 08:33 AM, said:

The only issue for me is that I have to tune the tables or the power value by 10% if I use the advanced adhesion model.


So when not using the advanced adhesion model, theres no 10% deduction of force from the axle out?
It's been a while since i last uncheck this. I will test this myself with publish performance curves and publish rolling resistance.

Thanks

#9 User is offline   hroch 

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Posted 06 October 2015 - 02:31 AM

Hi
This is correct?

Attached thumbnail(s)

  • Attached Image: Open Rails 2015-10-06 10-35-31.jpg
  • Attached Image: Open Rails 2015-10-06 11-28-12.jpg
  • Attached Image: Open Rails 2015-10-06 11-30-34.jpg


#10 User is offline   copperpen 

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Posted 06 October 2015 - 05:25 AM

Steam does not handle the advanced adhesion model in the same way as diesel and electric. The code does not read maxpower etc, it generates its own from other data within the eng file.


Wagon ( GW_4959_or_adv )
Comment ( ***************** OR Parameters - Engine Section ************************)

Comment ( *** General *** )
ORTSSteamLocomotiveType ( Simple )
Type ( Steam )
WheelRadius ( 36.0in )
ORTSDriveWheelWeight ( 127700lb )

Comment ( *** Cylinders *** )
NumCylinders ( 2 )
CylinderStroke ( 30in )
CylinderDiameter ( 18.5in )

Comment ( *** Boiler *** )
ORTSSteamBoilerType ( Superheated )
BoilerVolume ( "448.5*(ft^3)" )
ORTSEvaporationArea ( "1737.5*(ft^2)" )
ORTSSuperheatArea ( "295.0*(ft^2)" )
MaxBoilerPressure ( 225psi )

Comment ( *** Fire *** )
ORTSFuelCalorific ( 13700btu/lb )
ORTSGrateArea ( "27.07*(ft^2)" )
SteamFiremanMaxPossibleFiringRate( 3000 )

is all that Open rails uses to generate the power for a steam locomotive. There are other lines that can be added to fine tune performance all of which are listed in the manual.

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