[darwins]

It has been proposed in the Menu options thread that modellers should enter the Curtius Kniffler adhesion parameters for their motive power units.

Some help is needed here. How do we set this parameter?

Do we apply to all traction units steam locomotive, diesel (electric, hydraulic, mechanical) locomotive, electric locomotive, steam railcar, diesel or petrol (electric, hydraulic, mechanical) railcar, electric multiple unit?

Where do we find the real life information needed to correctly set this?

How do we change that information into OR entry?

What if we can not find relevant data? Will OR give a good estimate? Is there a way that we can estimate?

Which types of traction are likely to be most or least influenced by relying only on default values?

If it is concerned with 'adhesion' should we also adjust for carriages, wagons, tenders and driving trailers? Will at affect braking as well as tractive force?

[Weter]

And take in account, that different railroad "schools" use different adhesion calculating methods:
I have never heared about Kurtis-Kniffer formulas before I read ORTS manual.
We will need the methods of converting one units to another?
Why can't adhesion be derived from common parameters of *.eng-files as tractive mass, area of wheel-to rail contact (related to wheel diameter), coefficient of adhesion (related with wheel and rail material, corrected to track inclination, ambient temperature and humidity later) and current tractive effort, speed?
http://www.elvastowe...el-locomotives/
Related topic

[R H Steele]

I use Fcalc ( Joe Realmuto's utility ) to derive CK values for OR...which is not entirely correct...there are several CK formulas besides the Davis formula and using the formula suited to the rolling stock should be a consideration. Good place to start is here >>> CK Values (resistance)
It really is not that hard to construct a spreadsheet calculator for the CK numbers ... I believe there are one or two here in the library --- or attached in one of the threads.
FCalc2 can be downloaded here or at TS.

[Weter]

This means-I have forgotten.
At 2006 I used Fcalc just once.
It takes in account air resistance as well.

[darwins]

Sorry, I can't see anywhere on that page Curtiss-Kniffler adhesion parameters. The page is dealing with resistance - Davis A, Davis B and Davis C. How do I derive the CK parameters from the quadratic coefficients for rolling stock resistance?

[ErickC]

It seems to me that it would make sense have a graph of adhesion percent versus speed available, since this is the information actually available from manufacturers and publications. But adding parameters adds complexity, which is problematic in its own way, and those graphs are always going to be for the best-case scenario (which today means the wheelslip control system is maintaining wheel creep - which is often not the case in real life).

[R H Steele]

 darwins, on 25 July 2021 - 01:27 PM, said:

Sorry, I can't see anywhere on that page Curtiss-Kniffler adhesion parameters. The page is dealing with resistance - Davis A, Davis B and Davis C. How do I derive the CK parameters from the quadratic coefficients for rolling stock resistance?

Whoops, sorry.. it's Sunday & I've relaxed with too many http://www.elvastower.com/forums/public/style_emoticons/default/cheers3.gif I'm starting the mix up resistance & adhesion! Sorry
So to clarify -- some links for CK values
OR Manual-Physics
Traction Paper with CK formula
Paper with General Equations
GitHub Paper on OR Physics
The default CK values ( ORTSAdhesion ( ORTSCurtius_Kniffler ( 7.5 44 0.161 0.7 ) ) will work for everything up to the modern locomotives...AFAIK that's where calculating new values would be of benefit...rule of thumb ( so I've been told ) is anything newer than SD40-2s.
I've included CK values ( where applicable ) with version2 of the Std_Eng files...I used Joe Realmuto's Curtius_Kniffler calculator to obtain the numbers. A Public Domain utility to calculate these values would be useful to the community.

[ErickC]

 R H Steele, on 25 July 2021 - 02:24 PM, said:

rule of thumb ( so I've been told ) is anything newer than SD40-2s.

Remove the Dash-2 from that statement and it's good advice. The HT-C has significantly greater adhesion than the flexible SD truck*. Bear in mind, also, that most EMD units of yesteryear have been retrofitted with newer wheelslip control modules, so they get considerably better traction than they would have out of the factory. Many of them have the same or equivalent microprocessor wheelslip control modules as current locomotives (although they lack ground radar, meaning detection speed is lower and thus they are incapable of wheel creep).


*Since retconned with the name "Flexicoil," a term that doesn't appear in EMD materials until the 1980s

[R H Steele]

 ErickC, on 25 July 2021 - 03:36 PM, said:

Remove the Dash-2 from that statement and it's good advice. The HT-C has significantly greater adhesion than the flexible SD truck*. Bear in mind, also, that most EMD units of yesteryear have been retrofitted with newer wheelslip control modules, so they get considerably better traction than they would have out of the factory. Many of them have the same or equivalent microprocessor wheelslip control modules as current locomotives (although they lack ground radar, meaning detection speed is lower and thus they are incapable of wheel creep).


*Since retconned with the name "Flexicoil," a term that doesn't appear in EMD materials until the 1980s

Thanks Erick, of course, makes sense. I really don't know if OR will ever be able to code&implement all the variations, retrofits, and subtleties found in the real world. The idea of modeling ground radar is intriguing, is it not?

[engmod]

 R H Steele, on 25 July 2021 - 04:43 PM, said:

Thanks Erick, of course, makes sense. I really don't know if OR will ever be able to code&implement all the variations, retrofits, and subtleties found in the real world. The idea of modeling ground radar is intriguing, is it not?

I don't see a problem, we already have a variable for speed, we can use that as the radar generated speed.