[copperpen]

I am a great believer in using the correct data. Using your suggested method, and data I have on the classes I am working with, I get a fairly close approximation of the real life performance of the locomotive. The existing steamengine.cs could do with some tweaking in places, cylinder steam usage in particular, but that aside, it is fairly accurate. Next item to investigate is the evaporative surface figure.

[Lindsayts]

copperpen, on 04 September 2013 - 12:39 PM, said:

I am a great believer in using the correct data. Using your suggested method, and data I have on the classes I am working with, I get a fairly close approximation of the real life performance of the locomotive. The existing steamengine.cs could do with some tweaking in places, cylinder steam usage in particular, but that aside, it is fairly accurate. Next item to investigate is the evaporative surface figure.

This is correct the problem really is the way it is being done. The two data errors mentioned and included in the code post, ForceFactor2 and CylinderPressure drop almost cancel one another out, ie currently there is very litle pressure drop in the steam piping to the cylinders, the cylinders do not generate the extra force though as they calculate the motive force to low. A side effect of this is the high steam consumption as this is being calculated using the Cylinders actual input pressure which is to high.

The actual pressure lost in the steam piping at high steam flows according to Chapelon is at least 3 to 4 atmospheres (45 to 60 lbs/sqinch), Note this does not take into account the further pressure loss through the valves into the cylinder, this from calculations done using real performance data is significant.

To correct these two errors would be a (I hope) relatively easy step forward for OR. This what my code snippet is meant to do.

Lindsay

[Lindsayts]

A thought just occured to me, as these two errors (ForceFactor2 and CylinderPressure drop) almost axactly cancel out its quite likely that who ever did the data for the original table did no know that data they were working from included the pressure drop from the boiler to the cylinders (Note 1). All I have done is to seperate the steam piping pressure drop.

Note 1: It appears few manufacturers on steam locomotives understood the amount of pressure lost either, it appears Chapelon was one of, or even probably the first person to fully instrument a steamer to see actually what was happening, rather making sweeping assumptions.

Lindsay

[copperpen]

It looks like the steam chest pressure is being displayed using the throttle setting as a divisor of the boiler pressure. I am wondering therefore, if this is using a simple single port regulator instead of a twin port unit. I know that Kuju failed miserably in their attempt at it.

[captain_bazza]

Quote

The problem is that these require one to know the grate area to base the calculations on. This is available for a number of locomotives, but does take a bit of ferreting out at times.

It can be worked out if you have a good general plan library over several, or many, publications. You can extrepolate specifications over a range of a similar locomotive class, and also range them up and down a range of classes. No doubt it would be possible to build up a range table to help.

Cheers Bazza