Talk:OpenTTDDevBlackBook/Simulation/Train Acceleration

From OpenTTD

Question/Suggestion on this formula: First of all, it says units used v= 1mph. Then i doubt whether the acceleration calculation is correct, as it uses m/s2 instead of miles. Or is it just me blind as hell missing the miles-to-meters-per-second calculation? And 1t denotes 1000kg?

I guess Fr stands for the total resistance on the moving body. (As F should be the total force moving the train). To get a realistic Fr, it should cover at least the air resistance from the train, which depends on size and aerodynamics, and the rolling resistance, which counts for the contact with the ground. (Like a sledge on snow will go smoother then a sledge on gravel, for example)

So we have Fr = Fr_air + Fr_roll.

According to Wikipedia the CRF of a train will is about 0.001 . Fr_roll = CRF * Nf. So, the normal force on one wheel is Nf = m * 9.81 / n, where n is the number of wheels.Then we have Fr_Roll = 0.001 * m * 9.81 / n. But this is for just one wheel, so we should multiply with n, reducing the formula to Fr_Roll = 0.001 * m * 9.81. For Fr_air, this is very hard to determine, as it greatly depends on shape of the vehicle. Looking up known values and comparing those to create nice values in between seems best to me. Hope this is addition is usefull. -- THW Mark on november 4th, 2006.

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I Thinks that every formula should be calculated in SI, then converted to the metrics selected.

Train accelaration should have as well de-acceleration... In snow, traind will brake slower than in "tropical regions"... i think... o.o