[P Escue]

I’ve been trying to run the SP Cab Forward on 3D Train Stuff’s Donner Pass, and they appear to have problems with Open Rails. An example of the problem is in the activity “Last Run Of The Cab Forwards.” you have an AC-11 No. 4274 1.6 miles from Colfax, where you need to take on water. As soon as the activity starts, you are going up a 1.3 grade at 35 mph with a string of passenger cars. Both brake systems are off. In MSTS, when you start out, the regulator is set to 0, and the reverser is set to 15 percent, the sander is on, and cylinder cocks are open. In Open Rails, the regulator and reverser are set to 25 percent, and the sander and cylinder cocks are both closed. Now for the problem: in Open Rails, it shows that you are having wheel slippage before you start. As soon as you un-pause the activity and look at the locomotive from outside, the first set of drivers appears to be working (no slippage), but the second set of drivers is spinning madly. In MSTS, both sets of drivers are working, and if you bring the regulator and reverser up to 25 percent, they are still working normally (of course, the sander is on). In Open Rails, the sander doesn’t stop the wheel slippage in the second set of drivers. Adjusting the regulator and reverser in Open Rails (with the sander on) will prevent wheel slippage and bring the train to a stop (not enough power to go up the grade).

I know that the articulated locomotive is in two parts, with the commands from the first part replicated in the second, much like the steam locomotive helper setup. It appears that the sander command is not working for the second set of drivers in Open Rails but is in MSTS.

Any suggestions?

[R H Steele]

I remember a thread about the Cab forwards and their problems in OR...it was here at Elvas, cannot find it at the moment. I believe there was a solution found. This was sometime ago. I'll search, if I find the time, you should poke around and see what you can find.

Start here >>> Cab Forward Slippage --- there are other threads, this is not the one I remember, but it may provide some help.

[P Escue]

Hello Gerry,

Thank you for your response. I looked at the .eng files on the link you provided and went through the rear .eng files that they had for 4279 and found that first the AntiSlip variable in the 3D Train Stuff’s on the one I had was set to AntiSlip ( ) where they had AntiSlip ( 1 ). Tried that and it didn’t fix the problem. Continue looking at their file and found that the section EngineControllers was in them .eng file but not in the one from 3D Train Stuff’s. Included all of it and tried it. Brought up it and the rear drivers are still slipping when the front drivers are ok.

I cannot seem to find anything else to change. Let me know if you find another link that is about the problem. I will continue to look as well.

Thank you,

Phil

[R H Steele]

Phil, check Peter Newell's web site >>> Coals to Newcastle and see if there is any information about OR parameters for wheel slip under steam physics.

[copperpen]

The weight on the slipping drivers is too low. Make the mass of each section 125 t and you should be fine.

[P Escue]

Hello Gerry and Copperpen,

First, thank you for both of your help. I just found the discussion over at trainsim on the 3dts cab forward wheel slippage:

Trainsim forum wheelslip

Now I know that the articulated locomotives in Open Rails are usually in two parts, front and rear. I don’t know how Open Rails handles a locomotive’s physics in two parts. I would assume that it would handle the physics as two separate locomotives, say a primary with a helper attached to the rear. If this is the case 3dts has the mass incorrect for both front and rear. They put 242 tons for the front and 10 tons for the rear. It is like the rear was an afterthought, giving it enough mass to work (in MSTS). Now over at trainsim it was suggested to use 150 tons for each the front and the rear, which gives a total of 300 tons. The actual weight of the AC 11 is given as 298.42 tons. However, that 242 tons that 3DTS is using is close to the adhesive weight for the AC 11 (241.18 tons). I noted that Peter says “the Adhesive force is determined by combining the weight on the drive wheels and the adhesion of the wheels to the track” and I take it that the weight on the drive wheels is the adhesion weight. So Copperpen suggestion of 125 tons per front and rear is really close. I would like to ask if the adhesion weight should be used.

I will give this a try tomorrow and post here if it works. Again, thank you for the help.

Phil

[Weter]

Hello, Phil.
FYI, Peter's WIP is about locomotives with multiple steam engines, particularly boosters, but duplex too.
So, You can try it, using Unstable versions of ORTS.

[P Escue]

Well, I took the original .eng files and changed the mass to 125t in both. That appears to have been the problem. I will now fix it in all .eng cab forward files. I'm assuming that the tons in .eng are metric and not US.

I have not had time yet to look at the code in Open Rails to see how it handles articulated locomotives, it's on the to do list.

Again, thank you for all of you, for your help.

Phil

[Weter]

Indeed metric. (untill You specify the units of mass measure as U.S. tons: t-us)
Peter recommends to always specify all known units - for putting real(prototipical) parameters from available technical documents into *.eng/*.wag-files.
See Manual's appendix for how to specify units, and which of them are acceptable for ORTS.