Description of Power Computations
- Robert LeMassena's Power Computation: Robert LeMassena's original suggestion that locomotive power could be compared by multiplying the grate area x boiler pressure:
- Doesn't account for oil-burning locomotives.
- Doesn't account for low-calorie, large-grate fireboxes such as the Wootten used in camelbacks.
- Doesn't say anything about the rest of the locomotive's ability to convert the resulting heat into steam .
- Same as above plus superheater percentage: First mod: factor in superheater percentage (multiply the LeMassenaR number by 1 + the percentage derived by dividing SHS into Combined Heating Surface)
- Same as above plus superheater percentage: Second mod: same formula as immediately above, but substitute firebox area for grate area (LOCOBASE.BLRPRESS * LOCOBASE.FBOXAREA * (1 + SHSPCT)
- PowerLl: Third mod that I also call the SPR for Super Power Rating:
If(number of low pressure cylinders > 0, (boiler pressure * CHSFactor * driver diameter) / (low pressure cylinder volume * 100), (boiler pressure * CHSFactor * driver diameter) / (cylinder volume * 100))
(Note the variable CHSFactor. Its formula is:
If(firebox area > 0 and LOCOBASE.CHS > 0, (((LOCOBASE.EHS - firebox area) / 6) + firebox area + (LOCOBASE.SHS * 1.5)), ''))
Translation: Take the boiler pressure, multiply by the CHS factor. This is a calculation that takes the Evaporative Heating Surface and subtracts the firebox heating surface from it. The formula then divides the remainder by 6, adds the firebox heating surface area and 1 ½ times the superheater area. Then multiply that number by the driver diameter.
Then take the product and divide by the cylinder volume x 100 (the multiplication is to reduce the number of zeros or digits in the answer -- it has no other significance).
My goal is to create a number that expresses the boiler's capacity to supply steam to the cylinders at speed. I give bonus points for a high ratio of firebox to evaporative heating surface and for higher superheat. Also, the taller the drivers, the fewer times per mile at a given speed will the cylinders require steam. So either the same amount of steam allows a higher speed or a given speed demands less steam.
It is not a replacement for LeMassena's number because I haven't quite figured out how to take the quality of the coal or the grate into account.
- PowerMT: Take the SPR and divided it by the average axle loading in metric tons.
Any questions on the above data should be directed to Steve Llanso of Sweat House Media.