Thanks again, KG.....shouldn't it be the tender that's the issue instead of the loco ?
Jim as Ann said the tender only specifies the fuel and water queues and indicates the products held in those special queues. A product asset does specify a mass density and for the the fuel and water held in the tender this is used to determine the total weight of the tender. In past versions of Trainz however, based on testing, this mass density of the fuel product is ignored by the game engine and a hard coded value of 0.86 kg/ltr is used instead for transferring any fuel from the tender to the firebox regardless of what is specified in the product config. 0.86 kg/ltr is the mass density of the coal product used by Auran/N3V for steam loco fuel. I don't know if this has been corrected in newer versions as I haven't checked for it in a number of years.
There are 2 required properties of fuel that are not specified in the fuel product asset. They are specified with the following tags in the espec:
1)fuel-energy
2)fuel-specific-heat-capacity
These specify the heat energy released by the fuel as it is burned and the energy required to heat it to a specific temperature in the firebox.
The espec also sets the minimum and maximum temperature of the fire. A characteristic that is dependent on the fuel burned and are specified with the following tags in the espec:
1)min-fire-temperature
2)max-fire-temperature
The espec also sets the size of the grate indirectly by specifying the amount of fuel it can hold at optimum and maximum capacity, this is also dependant on type of fuel used, with the following tags:
1)ideal-coal-mass
2)max-coal-mass
So an espec developed for a coal burning firebox would have different fuel energy, temperature and capacity values from a wood burning or an oil burning firebox. The fuel characteristics for these fuels are considerably different from each other. Actually different grades of coal should have slightly different values in the espec as would different fuel oils and different species of wood.
One might think that you could specify a different fuel to be carried in the tender and it would affect the locos performance but it doesn't. The properties that affect loco performance are specified in the espec and not in the config of the fuel product asset. If you change the fuel used you have to make several changes in the espec if you want to simulate realistic performance.
The amount of fuel added to the grate per shovel is also specified in the espec with the shovel-coal-mass tag. In past versions (IIRC TS 12 was the last version I checked) as noted the games always uses 0.86 kg/ltr as the value to convert the mass per shovel to liters of fuel removed from the tender. The actual value specified in the fuel product's config is not used. I'll also mention that truncated integer values are used by the game in the calculations involving the product queues. A bit picky I know but it could have been handled better at least IMO. With a large amount of product transferred at one time, the truncation to an integer value is a reasonable procedure but when hundreds of small values, as per shovel, are transfered the conversion error gets magnified and it will be more than just a few kgs out of a tender's total capacity. Yea, I know picky.
Bob Pearson
PS. There are a number of other tags in the espec that affect how the fuel is burned plus a number of efficiency tags that affect the total amount of useful energy converted into work to move the loco. Maximum steam flow tag and cylinder sizes determine steam consumption per stroke. But the animdist tag in the steam driver bogey actually determines steam consumption per unit time - actually distance traveled per rev in conjunction with the loco's speed. So while the espec is the major part of this it isn't the only one involved in simulating realistic performance.
We don't have much if any control on the actual draft produce thru the boiler either - that should be addressed at some point by N3V. We've been waiting for a dozen years or so for this "new feature" to appear - some of us less patiently than others I suspect.