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Speed and ground contact

Forum Overview >> Farming Simulator 2011

CategoryFarming Simulator 2011
Created17.03.2011 12:22

Michel Dorge (Unknown) 17.03.2011 12:28
hello, i noticed that a tractor go faster when its 2 front wheels have no ground contact. in fact, the speed increase above the limit set by the gear ratio.
is it a normal behavior ? or something is "messing" with the "getWheelRpm" ???

Michel Dorge (Unknown) 17.03.2011 13:20
i think i got the culprit : it seems to be the "downforce"
in fact, the additional force (downforce parameter of the xml) is added perpendicular to the vehicle body. so, if the vehicle's "nose" is toward the sky ;) when you drive, some of this "downforce" is added to the "traction force" (the more you face the sky, the more of the force is added)
i think it will be better to add this force toward the earth's center (additional gravity for the vehicle) in a future version of LS

Michel Dorge (Unknown) 18.03.2011 08:27
i tried various configuration, and the donwforce can be neglicted (if not set too high like 100 or more)
the problem occurs anyway with a downforce of 0

i discovered the marvellous "debug console" (game.xml => development / controls / true) and the "gsVehicleToggleDebugRendering" command, and it's help a lot !

when the front wheels leave the ground, the computed "wheel rpm" change a lot (in accordance with the ratio between rear and front wheels => the larger the difference, the larger the "wheel rpm" change)
so, the problem do not exist if the 4 wheels have the same size (i tested it)

Michel Dorge (Unknown) 18.03.2011 08:40
i peek an eye into the "wheelsUtil.lua" from "" and especially at the "computeRpmFromWheels" function.
1. the "compute wheel rpm" take into account "non motorized" wheels ! ("requiredDriveMode" = 0)
2. on most "tractor" vehicle, the rear wheels are higher than the front ones. then, if we have a ratio of 3 between the rear and the front, the standart (no wheelies !) max rpm will be for example, 400rpm (front = 600rpm, rear = 200rpm), that is to say, 2300 motor rpm and 40km/h
but, if the front wheels leave the ground, only the rear wheels are taken into account, so the 400rpm become 200rpm and the motor rpm become 1150 rpm... (like we just engage the higher gear on a manual gearbox ;)) and the tractor can go 2 time faster (if the torque curve is sufficient to do so)
of course, with a smaller ratio between rear and front wheels size, the difference will be less significative.
so, i think this function "computeRpmFromWheels" need a little ajustement.

Michel Dorge (Unknown) 18.03.2011 11:24
here is a universal solution, which take into account the old rpm so that we do not have to check and modify all the torque of the genuine vehicle and modded ones :

wheel rpm coefficient = (1/r1 + 1/r2 + 1/r3 + 1/r4)/4 (when we have 4 wheels)
with 6 wheels, it's become : (1/r1 + 1/r2 + 1/r3 + 1/r4 + 1/r5 + 1/r6)/6

we consider only "motorized" wheel ("DriveMode >= 1")
this coefficient do not change whether the wheel are on the ground or not

pretty simple, huh ?

global wheel rpm = "wheel rpm coefficient" x AVG(wheel radius x wheel rpm)
this time, we consider only the motorized wheels with ground contact for the "AVG"

r1, r2, r3... = radius of the weels

it's work with any wheel size ;) and there is no need to modify the genuine torque with this modification.

please let me know if this modification could be done in a future patch for FS ?

thank you

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