Here are the entries pertaining to inertia: {HDV} [GENERAL] Inertia= [DRIVELINE] ClutchInertia= ["Corner"] // EX:[FRONTLEFT] SpinInertia= BrakeDiscInertia= {PM} [BODY] // EX:Spindles, Wheels,Body (not used), Fuel tank (not used), Driver Head (Detached from physics calculations) inertia= {ENGINE.INI} EngineInertia= Questions: Is the Inertia= entry in the HDV for the entire car? What is SpinInertia? (What should be included in SpinInertia)
Inertia was whole inertia without fuel from my memory, but I can be mistaken too. Bit too little is worse than bit too much, correct numbers of course better, but I have so far found only for 1967 Camaro factory's inertia numbers for two axis and even those for base model. Can't remember what SpinInertia was, but ISI ZR car had this: SpinInertia= // inertia in pitch direction including any axle but not brake disc
http://www.eng.auburn.edu/~dmbevly/mech4420/vehicle_params.pdf Measured inertia data for some vehicles.
[GENERAL] Inertia= This one is for entire car (including a driver) but without fuel inertia. ["Corner"] // EX:[FRONTLEFT] SpinInertia= BrakeDiscInertia= SpinInertia is inertia of a wheel and disc bell, excluding brakediscinertia (but also including inertia for drivetrain parts, if applicable) BrakeDiscInertia is for brake disc (excluding disc bell) [PM] [BODY] // EX:Spindles, Wheels, Fuel tank (although not used), Driver Head inertia= This one is not used. rFactor takes inertia from GENERAL section and substracts (after calculations) wheels/spindles inertias (from unsprung masses) to get inertia for sprung mass.
sae1999-01-1336.pdf has been my reference some six years. http://www.nhtsa.gov/DOT/NHTSA/NRD/Multimedia/PDFs/VRTC/ca/capubs/sae1999-01-1336.pdf Those are measured values of course, not factory data, also I find none of cars from there that I'm making, quite few similar either, but it gives better starting point than nothing.
Forgot to add [HDV] [DRIVELINE] ClutchInertia= *edited first post What is not used? I found this in the 370z: So the mass is the total mass of things that rotate. The commented inertia=(1.8... is more of an expected value for the combined rotational inertia of a wheel+tire. Brakes obviously have their own entry. If you piece it together the axle/hub components, and component from drivetrain are missing. 370x spin for reference: That value is awfully small if it includes wheels. Why wouldn't the rotational inertia of the wheel get pulled from the PM entry?/Why is it included in SpinI...? Is there a particular reason why you've moved the bell from BrakeDiscInertia to SpinInertia? If the entries in the PM are not used, why bother having them?/why bother having different values for front and rear? Seems to me the values would be similar to the placeholders for Fuel tank and Driver head if not actually used.
This is the only one not used in the PM: [BODY] name=body mass=(0.0) inertia=(0.0,0.0,0.0) pos=(0.0,0.0,0.0) ori=(0.0,0.0,0.0) The rest of the pm file is very important. In the hdv file you specify the total mass and inertia of all parts combined, and the pm file gives mass and inertia of the unsprung parts. To find the mass and inertia of the sprung chassis you take the total minus the sum of the unsprung (PM) parts: m_chassis=m_hdv-SUM[m_unsprung] Ix_chassis=Ix_hdv-SUM[ Ix_unsprung+m_unsprung*(y_pos^2+z_pos^2) ] Iy_chassis=Iy_hdv-SUM[ Iy_unsprung+m_unsprung*(x_pos^2+z_pos^2) ] Iz_chassis=Iz_hdv-SUM[ Iz_unsprung+m_unsprung*(x_pos-^2+y_pos^2) ] If you're not careful the chassis inertia or mass can become negative which is disaster! (Just try to change the fl_spindle and fr_spindle mass of the BMW_F1.07 to 51 kg and see what happens) I havent tested yet but I think if you add inertia to wheel Ix or the "spininertia" it should have the same effect
Ahhh I see what was meant. Added Body as examples to first post. [BODY] as I was using it was a bit of a sub-section header, like [DRIVELINE] in the HDV. Found EngineInertia= in the engine INI (used in the ZR upgrade to reduce the mass of flywheel). *edited first post Is EngineInertia specifically Flywheel Inertia, or does it include the entire drivetrain? Judging from the number used 370z, It is all of the drivetrain. Which leads me back to what is SpinInertia?
That is rotational inertia from components of engine, my guess is that it is pistons, connecting rods, crank, flywheel and what ever pulleys, belts, chains there is as well as water pump, alternator, anything really that resists rpm change because of it's rotating with engine, but nothing that is behind of clutch. At least that is how I have understood it. I guess that propeller shaft would go to clutch, or has it own place? Can't remember, but transmission, where do you put that, clutch again? Some versions of Bristow's documents, latest improvements were probably lost again when new RSC pulled the plug? http://www.bozracing.com/forums/viewforum.php?f=79
Well I tell you what you can't do, run with very small SpinInertia numbers. FPS dropped to 1! I have the inertia of the drivetrain from a dyno (It is very close to the 370z Engine #), I just don't know what to do with it. The clutch has its own inertia value. If Engine is engine including flywheel, and clutch has its own, then it would makes sense that SpinInertia is from clutch to wheels?
Not wheels, from differential to wheels section is defined for live axles in rear axle statement, maybe for a-arms in spininertia section? Also to add confusion that old Bristow's document has mention of clutchinertia being parts between transmission and clutch, but I think that it should be driveline between diff and clutch, but that is just my imagination of things. As I don't know any other place to put transmission and propshaft inertias. Then again, I don't have means to calculate even engine inertia, always so reliable blip the throttle and adjust rise / decrease to match footage... FPS get big hit always when some value is out of range, with rF1 and vehicles weighting over 8000kg that was quite normal situation
Because as you noted (in bold), it is about inertia for sprung mass (excluding fuel tank and driver head). The full section of it is this: But this is not the only one that is not used. Also, driver head is not used from pm (as it has dedicated physics in separate file) and fuel tank (rF uses parameters from hdv file). EDIT: EngineInertia is about total inertia of all engine parts, like guys already said, but I'd also add to that inertia from gearbox when in neutral... if you have such precise data. Because if you want to just try to match videos from the internet, then there is a chance most of them are recorded in neutral without engaged clutch (so, inertia from gearbox in N is already there). As for drivetrain inertia distribution (in the current rF2 version), I see it like this: - ClutchInertia: clutch itself + [main shaft from engine to gearbox, if applicable] + gearbox (when in gear - I'd take something like an average from inertia values from 3 to last gear and use it), - SpinInertia (for driven wheels): [main shaft from gearbox to diff, if applicable] + (differential inertia/2) + halfaxle + wheel + disc bell - SpinInertia (for non-driven wheels): wheel + disc bell - ClutchFriction: clutch itself (very small though) + gearbox friction (when in gear - I'd take something like an average from friction values from 3 to last gear and use it), - FrictionTorque (for driven wheels): (<gearbox friction when in N> / 2) + (<diff friction> / 2) + ball bearing friction (loaded) - FrictionTorque (for non-driven wheels): just ball bearing friction (loaded)
You are correct to point out that the specific [Body] element with name=body is not used. Guess I had gotten so used to ignoring it I completely glossed over it for the hierarchy. It is added to post#1 now. Thanks for clarifying what exactly you meant. I still don't understand why you are including wheels in SpinInertia. If they are in SpinInertia, why also in the PM? Isn't that going to end up adding twice the actual wheel inertia? It is easier to understand that you are separating the bell from the disc, removing it from BrakeInertia and adding to SpinInertia. I suppose you've separated them because the disc bit gets multiplied by the thickness, and then adds to rotational. By keeping the bell off to the side, the multiplication gives a more accurate result. What are you defining as "All engine parts"? Everything grouped in front of the clutch/flywheel barrier?
No, nothing adds. Both are used and my guess is, they are just used in different calculations, for different things (I will try to get a definitive answer on that and will let you know). Yes, exactly. And when Knut Omdal Tveito mentioned about that, he reminded me I have to do some cleanup in my DiscInertia calculations, as I already have disc bell included in SpinInertia and Wheel Inertia but didn't take it off from DiscInertia (it was there as a part of my previous, more simple way to calculate that stuff) Yes
Great information, looking forward what can be found out about wheel inertia. Just to clarify, this engine inertia and all parts at front of clutch, we are talking about parts inside the engine that are moving parts, not block, head etc, right? I had understood clutch friction completely different, friction of disc, how it bites when you lift up clutch pedal.
Yes, we are talking about what makes your engine revving up slower/faster than you would want ;-) Block, head (literally, the whole engine) can be taken into account when you calculate inertia for the whole car. For this one, you have ClutchTorque parameter - how much torque can be transfered through clutch without slip.
