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The V4.7 SD series of physics updates are now uploaded. These include most DC models made by EMD from the SD7 to the SD70M. These will now be available in addition to the already released GP series from EMD and the GE 6 axle models. Please let me know if you find any errors in the files. As usual, these are released public domain, so you are free to use them any way you choose, and in free or payware either. I do appreciate the credit for the files in your work, however. Bob Boudoin plainsman
Bob,Thanks so much for your work on these files. I have been looking forward to them. I am currently hanging out with the parents for the holiday, so won't be home to play for some time, but now I can't wait to get back to my computer.Have a great holiday!Bryce
BobI noticed that the new 4.7 upgrade for the couplers did not have the two sections like the GP's did. I did a cut-and-paste for the couplers, so he SD's are upgraded.I had done some upgrading to your 4.5 values using FCqlc 2.0, but my firction values were different from the ones you listed in he 4.7 upgades. How do you determine the fontal area? Also, do yue a value of 1 for the drag and adjuct speed to the max the engine would run?
Hi Frank, The reason I did not use the double coupler section in the SD units, is that the only real benefit would be for switching action, and the SD models are much less likely to be used that way by most folks. If you use one in hump duty, feel free to use one of the similiar GP coupler sections instead. I usually use something between 13-13.4 square meters for frontal area. This is a little less than the calculated area (a SD50 would be about 14.75 sq. meters calculated), but most of these units will be run as 2 or 3 unit consists, and to use the full frontal area will too adversely add drag to the second and third units. If you run single unit head end power, you might increase this a bit to the calculated area. For close fitting B units (like f units) I drop the area even more, as testing shows they need even more reduction to behave like the real ones. I also use something between 0.92 and 0.98 for most freight units drag coefficient. I usually use max velocity plus 2-3 mph. Keep in mind, slight variation in these values is not critical, as the temperature variation would well span the variance of the magnitude of difference we are discussing. Glad you are finding the V4.7 files helpful! Bob
BobThanks for your insight into how you choose valus for FCalc. Makes very good sense and all of you mods making running MSTS seem much more realistic.Again, Thanks for all your work.