Steam Locomotive Adhesion
#11
Posted 22 December 2022 - 04:56 PM
I have read over your stuff but not sure how to figure out the ORTSDavis_A, ORTSDavis_B and ORTSDavis_C for specific locomotives. I would like to figure it out for my Milwaukee Road 261 model that is a big 4-8-4 Northern type over here in the States. I have everything else dialed in to a T with physics so getting that dialed in as well would be great.
I am just curious if that is what makes it slip more or less or is it something else in the physics that I am missing? The FofA for the real locomotive is 4.18 and it should still slip when at full throttle and regulator but does not slip at all in dry conditions no matter what type of load I put behind it.
Brandon
#12
Posted 22 December 2022 - 05:49 PM
Hobo, on 22 December 2022 - 04:26 PM, said:
Geared locomotives (such as the Shay) are treated like diesels as they have constant force for the full revolution of the wheel. Other locomotives that you have described will be treated the same as a steam locomotive, ie has a crank on the wheel, and therefore an unequal amount of force is produced around the full wheel rotation.
ATSF3751, on 22 December 2022 - 04:56 PM, said:
Have a look at this section of the CTN website as there is an excel spreadsheet to assist with determining the values of the Curtius-Kniffler equation. There is very little information available in regard to the adhesion values for steam locomotives.
ATSF3751, on 22 December 2022 - 04:56 PM, said:
As indicated above the Curtius-Kniffler equation is a major impact on the slipperiness of the locomotive.
Setting these values impacts on all track condition, ie dry, wet and snow, so care must be taken if adjusting them. Perhaps you could use the adhesion parameter from my ENG file as a starting guide, and this reduces the OR CoF from 0.33 to 0.3.
#13
Posted 30 December 2022 - 02:42 AM
i) Steam Cylinder Cocks - currently OR has "synchronised" steam emissions from the steam cylinders. This is typically incorrect as the cylinders operate at different times. For example in a 2 cylinder locomotive the first cylinder leads the second by 90 deg, hence the steam emissions should be at different times. To allow this to happen now 8 additional effects have been added in the form "CylindersABFX". The numbers AB indicate the cylinder number, and the stroke, ie forward or backward. So 11 would be the first cylinder forward stroke.
ii) Steam Cylinder Exhaust - the steam from the cylinder is typically exhausted out of the stack of the locomotive. To try and model this up to 4 cylinders can be modeled using a parameter "CylinderSteamExhaustAFX" where A represents the cylinder number.
iii) Steam Crank Angle variation - The crank angles for multiple cylinder locomotives can vary, for example a 2 cylinder locomotive has a 90 deg separation whereas a 3 cylinder locomotive has a 120 deg variation. OR will default to a "common" value for the number of cylinders defined, but the user can override this with "ORTSWheelCrankAngleDifference ( A B C D )", where A, B, C and D are the separations for up to a 4 cylinder locomotive. For example, a 4 cylinder locomotive can have a separation of 90 deg for each cylinder or sometimes it has two of the cranks separated by 45 deg instead. These values can either be in Rad (default) or Deg.
iv) Braking on Drive Wheels - On some steam locomotives brakes were only fitted to the drive wheels, whereas others had braking fitted to all wheels. For appearance sake non braked wheels should continue to rotate if the braked wheels are locked and skidding. This parameter "ORTSLocomotiveDriveWheelOnlyBraking ( x )" allows a distinction between the different wheels. x = 1, braking on drive wheels only, whereas if the statement is left out, or x = 0 the braking is on all wheels.
#14
Posted 30 December 2022 - 05:13 AM
Thanks so much for your efforts.
So we should have (4) “CylinderSteamExhaustAFX” pointing out the stack - so similar position and angle as the StackFX - and this should add the chuff effect to the stack we normally see in the RW?
Would it be possible to bind the Steam Cylinder Cock effect to a separate rail car - so we can get Articulated Steam Locomotives performing normally?
I’m not in front of my computer until next week to test any of this.
Regards,
Scott
#15
Posted 30 December 2022 - 08:42 AM
EDIT: I tried implementing the FX parameters after downloading the newest unstable (U2022.12.29-2236) but saw no change in cylinders or smoke. Was this added to the official version or am I doing it wrong?
#16
Posted 30 December 2022 - 10:51 AM
My question relates to point iv). How does the OR distinguish between driven and free running wheels? By numbering or by animation? I read in an old description that driven wheels have to be animated by the modeler, free running wheels do not. The existence of animation is a choice. OR doesn't seem to make a distinction between the two. But it could be that the model design taken as a sample is wrong in this respect.
Sincerely Laci 1959
#17
Posted 30 December 2022 - 01:14 PM
Jonatan, on 30 December 2022 - 08:42 AM, said:
EDIT: I tried implementing the FX parameters after downloading the newest unstable (U2022.12.29-2236) but saw no change in cylinders or smoke. Was this added to the official version or am I doing it wrong?
Did you try with a three cylinder loco? It should not make any difference for a 2-cylinder loco!! (or indeed for most 4-cylinder locos.)
It should be an improvement for three cylinder locos and any four cylinder locos like the Lord Nelson with 45 degree crank angles and eight beats per revolution.
#18
Posted 30 December 2022 - 01:42 PM
darwins, on 30 December 2022 - 01:14 PM, said:
It should be an improvement for three cylinder locos and any four cylinder locos like the Lord Nelson with 45 degree crank angles and eight beats per revolution.
I don't know how you interpreted this line:
Quote
What I asumed these new features were, was the addition of puffing smoke and steam tied to the wheel revolutions, which is what I've been hoping to see implemented for some time. Even with the normal smokeFX removed there were no puffs visible. The new cylinder cock parameters also did not make any visual difference.
This is how I implemented Peters new paremeters based on the description he gave on its use, although no proper example was provided how to use it so I might have implemented it incorrectly.
CylinderSteamExhaust1FX ( 0 6.4 3.778 0 1 0 0.4 ) CylinderSteamExhaust2FX ( 0 6.4 3.778 0 1 0 0.4 )
So this is why I asked wether or not it had been added to the latest availible unstable release.
#19
Posted 30 December 2022 - 02:04 PM
I think Peter mentioned updating his NYC Atlantic with the new params.
https://www.coalston...k/#nyc_atlantic
Regards,
Scott
#20
Posted 30 December 2022 - 05:22 PM
Jonatan, on 30 December 2022 - 01:42 PM, said:
This is the model I use to test the code before releasing it, so I can also use it to fault find any issues, and it also acts as a guide for users when setting up their own units. So any issues should be referenced to this model.
I would recommend downloading this and testing the features first to see how they operate, and then move them across to your own model.
Jonatan, on 30 December 2022 - 01:42 PM, said:
Again see the test model for an example.
Jonatan, on 30 December 2022 - 01:42 PM, said:
This is all in the latest unstable version.
Laci1959, on 30 December 2022 - 10:51 AM, said:
I think that the modeler needs to distinguish between driven wheels and non-driven wheels. (Perhaps a modeler can add a comment in regard to this.)
Certainly the physics of the wheels is handled in the ENG file, either in the engine section or wagon section of the file.
scottb613, on 30 December 2022 - 05:13 AM, said:
scottb613, on 30 December 2022 - 05:13 AM, said:
Articulate locomotives are not well defined at the moment in OR.