[Lindsayts]

Just some thoughts after much playing around with OR and some eng files.

Steam loco's vary quite widely in effieciency, ie the amount steam taken to produce give amount of power. Some of things effecting the efficiency being slide valves V piston valves, type of valve gear, eg stevensons, Walscharts, poppet etc, size of piping leading to and from the cylinders and many others. To allow for this sort of thing MSTS used the parameter "CylinderEffectivity" OR appears to have dropped this without bringing in anything to replace it with. As a consequence one is stuck with a given cylinder effiecency. There is a number of ways to get around this by "cooking" the figures, but this goes against the way OR seems to work, that is OR requires the parameters to be as close to the real thing as possible.
Now the steam engine implementation in OR is quite good I find it somewhat (OK, real) annoying one cannot go this last step. Would the developers consider adding some kind of support for the old "CylinderEffectivity" parameter. This parameter was one of the REAL saving graces of MSTS allowing almost anything to be simulated in reasonable fashion.

While it is unlikely to be as simple as this what would be nice is being able to apply a "factor" in the range of 0.5 to say 2.5 to the amount of steam the cylinder uses in a given period of time, all other values such as Brake mean effective pressure, force on the piston etc going unaltered.


Lindsay

[captain_bazza]

I second that motion, Lindsay. I've been told by an engine driver that different locos of the same class each had their own steaming characteristics. Being able to tweak a loco's physics to add quirks would be very desirable.

Cheers Bazza

[D&RGW]

 captain_bazza, on 13 October 2012 - 03:33 PM, said:

I second that motion, Lindsay. I've been told by an engine driver that different locos of the same class each had their own steaming characteristics. Being able to tweak a loco's physics to add quirks would be very desirable.

Cheers Bazza

For sure! I'm acquainted with an engineer here on the Durango & Silverton who has described variations in operating and steaming characteristics even on locomotives of the same class. While some of these variations would be difficult to introduce into a simulator like OR, there are some variations I know of between locomotives that are probably significant enough for the virtual operator to notice in the simulator. For example, one of the K-28s here (478?) is rumored to have slightly larger valve cages than the other remaining locomotives of its class, which, from a mathematical perspective, if not a practical one, would have a significant affect on its maximum steam usage and efficiency at speed. However, other "quirks" and operating characteristics like a poorly timed valve gear or rough-riding suspension would be far to subtle for the virtual operator to even notice (at least, until someone out there builds one of those NASA-style full-size replica locomotive cabs that actually hydraulically rocks back and forth and responds to output from the simulator. And at that point, you're probably better off just buying your own shortline!) Still, it would be neat to be able to simulate to some degree these subtle variations in OpenRails as its physics model continues to be improved--although the physics model should be relatively finalized before those features be put in place, I guess, so as to avoid non-compatible or obsolete .wag or .eng files in the future.

Thanks,
Eliot

[Lindsayts]

I understand the replies (Note 1) but I am not talking about something that subtle. The variation in efficiency between different valve gears is significant as is the effect of differing steam piping and at this stage the appears to be no way to take this into account.

The current code produces slightly high steam consumption (around 10 to 20 percent) for superheated loco's with walscharts valve gear and there is no way one can alter it (Note 2), which I find annoying. Partly this is due to the code OR is using actual being quite good, one notices the smaller things.

Superheating also has a MAJOR effect (reducing water consumption by a factor of between 2 and 3 times) although I have not as yet done much testing on this in OR to see how effective the "SuperHeater" parameter is. I will correct that this evening.

Note 1: I lived for a number of years right next to the Puffing Billy Railway in Victoria on one of the railways 1 in 30 grades within a month or so I could tell you which of the 5 NA's the railway had was on the current service just by the sound, all the locos having a distinctively different sound inspite of them all being the same class and maintained very well.

Note 2: I should actual say there is no legal way to change it. I have found one can get what one wants by "cooking" some of the figures, but "cooking" the figures should not be part of the exercise.

One of the REALLY great things about posting a problem is one gives one self a much clearer view of the issue...............

Lindsay

[captain_bazza]

Quote

I guess, so as to avoid non-compatible or obsolete .wag or .eng files in the future.

I would regard that as a minor inconvenience and not a barrier, because the model is separate to the physics. All that is required would be a new WAG or ENG encompassing the new parameters, etc, not a new model. I also regard that as part of the process of developing the new sim.

Cheers Bazza