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Downloaded the BNSF Big Blow the other night, but when I tried to pull 50 US2FREIGHTREFRIGE cars east out of Whitefish my speed dropped to 3 mph in trottle 8. Looking in the .wag file I found this Friction ( 528N/m/s 0 1mph 2.89N/m/s 1.8 5.1N/rad/s 1 -1rad/s 0 1 )Notice the 528N/m/s. In other .wag file this entry is 100N/m/s. Which is closer to prototype???
CarToad Dave Wise Camas Prairie Route Track Lay at Orofine working on Second Sub.
The friction value of 528 is more accurate, but friction calclation is not just dependant on that number, but is measured on a curve basis. Note the correct line here vs. the default MSTS friction at the bottom. 528N/m/s 0 0.7mph 2.89N/m/s 1.8 5.1N/rad/s 1 -1rad/s 0 1100N/m/s 1 1mph 0 1 5.1N/rad/s 1 -1rad/s 0 1I'm not certain about this, but with the accurate friction compared to default MSTS friction, the car is much more difficult to start, but once moving, it rolls more freely, and thus takes less effort to keep moving. The top friction values are accurate, as similar values are used in Bob Boudoin's v4.5 physics. He should be able to explain these friction values in more detail. By the way, you said 50 reefers east out of whitefish? there is a steep grade just east of the yard, and 50 of those reefers wieghs 5200 tons. If you were using only one Big Blow, I would not be surprised at this. The Big Blow was very fast, but not the lugger you would expect for an 8500 hp unit. You don't really get much out of its great power at low speed, at which it would be out-pulled by a Dash 9 (although the Big Blow's performance will eclipse the Dash 9's at high speeds). Long story short, I think the grade is what's killing you, not the wagon friction. P.S. I use this friction model on all my cars, and I'm comfortable with it.
The original values in the post look like they are a derivative of Joe Realmutto's friction calculator which is very good for modern roller bearing cars.We have been experimenting with modifying the values for friction bearing trucks and so far have found the following modifications to the values.Original First Line:528N/m/s 0 0.7mph 2.89N/m/s 1.8Modified First Line for Friction Bearings581N/m/s -0.11 1m/s 2.89N/m/s 1.8Essentially what has been done is to increase the first value by 10% to allow for the reduced rollability of the friction bearings.The second value was originally experimented at -0.35 which simulated the slower start of a friction bearing truck very well, however this introduced an unforseen surging in the train when stopped and the value of -0.11 seems as far as this can go without producing side effects.The third value was changed on Joe's recommendation to 1m/sThe fourth and fifth values are the same.This project is ongoing in connection with getting more correct acceleration values for consist file and will be fully posted when the testing is complete.If you are using arch bar trucks and tallow lubrication, there will be additional modifications as there was minimal lubrication until the friction in the bearing melted the tallow.