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Clutch pack preload?
(136 posts, started )
Quote from Ball Bearing Turbo :The colors are relative to the slip ratio, afaik.. At max green, the slip ratio is optimal and the tire is producing as much force as it can. Go beyond that, and the line decreases length, and turns red because you're past optimum longitudinal slip ratio.

Just checked in-game. Agree.

Quote from Ball Bearing Turbo :
If the weight is mostly on the outside wheel, and just a tiny bit of force is being applied to keep the car at steady speed, then the inside tire is probably slipping a bit and getting closer to it's optimal slip ratio which accounts for the colors/lines.

Looking at the raf data you are right that the inner slip ratio is higher than the outer. This would account for the colours but not for the length of the arrows. The way I understand the working of an open diff (equal torque to both wheels) the tyres should adjust their slip ratios to meet the equal torque requirement.

Quote from Bob Smith :
Or is that screenshot taken looking backwards?

Bingo.
Holy posting speed, Batman. Can't keep up.

Quote from Bob Smith :
Tyre scrub is still going to affect the total force on each tyre though, thus the length of the lines. The tyre supporting the majority of the weight will have the greater rolling resistance and tyre scrub resistance, so the lines should be shorter. I just don't know if that would accout for the different in forces, it's hard to say how many times larger the force on one tyre is than the other (the left line goes off the top of the image, and I think both lines start from the centre of the tyre, so the bottom of each line is obscured by the tyre itself).

So what you're saying is that in steady state cornering the torque on the drive shaft does not equal the force that is pushing the car forward but the force pushing the car forward + the force needed to deal with friction in the tyre itself?

That does sounds very reasonable but I'll have to give it some thought. :up:

The forces are LR: 388 (N?) to RR: 298 N according to f1perfview.
OK, thought about it. I think you're right! The arrows are probably tractive force - friction resistance. So tractive force can still be equal to drive shaft force. I guess only Scawen can clear us up on this.

Of course this makes it all the more difficult to learn anything about diff operation by looking at the forces view. Not impossible, you could still find out things like what it takes to get a preloaded diff to start slipping or at what point the preload stops having an effect, but I think I'll leave it for now.
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(Ball Bearing Turbo) DELETED by Ball Bearing Turbo : stupid post, and didn't edit it but made a new one.
Quote from J.B. :OK, thought about it. I think you're right! The arrows are probably tractive force - friction resistance. So tractive force can still be equal to drive shaft force. I guess only Scawen can clear us up on this.

Yes, it's the total net force I would imagine, otherwise the vector would be misleading.
if im not mistaken the colour of the rr forces indicate that the tyre is at its limit of overall traction (long+lat) so maybe it could be a problem in how lfs deals with force combining and how that interacts with the diffs

from a quick test with one wheel on the grass and the other one on tarmac it seems like the open diff works as expected on pure lat situations
Racecar Engineering had a great article covering LSDs. If you can find the old December 2004 issue, it would be good to read over it a couple times. The understeer/oversteer characteristics depends on your driving style. There isn't one universal best setting unfortunately. However, it's good to know what settings creat what end effect and be able to tune with it.
Aha, mvw2 from RSC IIRC?

/OT
Couldn't find it on the net but found it on my HD. And I can't remember ever reading it either.

EDIT: Hmm, can't upload it, probably because of my demo status.

EDIT2: Shame I have to go with rapidshare: http://rapidshare.com/files/27 ... mited_Slip_Diffs.pdf.html
@Bob: Actually, I'm pretty sure the yellow load lines start at the contact patch. It's been like that since the very early demo days.
Logically that makes sense, thinking about it.

+1 for semi-transparent tyres in forces view.
Quote from J.B. :EDIT: Hmm, can't upload it, probably because of my demo status.

Spend another 18€
Or he could upload it with his licensed account, then link to the attachment with having to post using that account. I think.
I have to say I thoroughly enjoy reading these technical threadies here, despite having nothing but spam and a five-star-rating to contribute.

What I really like is how these technical real-life theories and 'stuff' actually work inside the LFS simulation. Despite the sometimes buggy and unfinished physics, it's wonderful that adjusting sets actually makes the car feel and react like it should be.

Again... unfinished physics sometimes mix and mess things up, but I'm sure you understood what I'm babbling about.

Carry on!
Quote from Bob Smith :Or he could upload it with his licensed account, then link to the attachment with having to post using that account. I think.

http://www.lfsforum.net/attach ... id=29345&d=1177669474

Testing.

Nope. Link isn't valid. Probably needs to actually get posted before I can link to it.

Thx for the idea anyway, how could I not think of it myself? Next time I need to upload something I'll just add a post with my licensed name. Two other things I just noticed while using IE to log-in to my other account: the edit avatar and edit signature buttons sure are nice, *drool, and that IE is ridiculously fast compared to FF.
Both links work for me.
???
Quote from Bob Smith :Or he could upload it with his licensed account, then link to the attachment with having to post using that account. I think.

But that again would be less money for the devs
btw: at least the second link worked fine for me

edit: While the second one was there
Not sure if anyone mentioned this already as i haven't read the entire 5-6 pages of this thread. But Torque is displayed in 2 types of measurements, the first one being Foot-Pounds, and the second being Newton-Meters, which is what the Nm should stand for.

Mostly all FWD vehicles with standard Transmissions use a Transaxle, while RWD vehicles use a Transmission. The diference between the 2 is that FWD uses the Transaxle which Houses the Gear Box that includes the imput shaft, the output shaft while the smaller gears with less teeth drive the larger gears with more teeth, usually 2-4 times as much for better torque Multiplication.

RWD Vehicles use this combo of components in this exact order 99% of the time. The Cranks shaft is attached to the rear of the Engine, which has the flywheel or (Flexplate for auto trannys) mounted directly to it with a splined Hub. Then you have the Clutch which is mounted in front of the Pressure plate and basically between both the flywheel and the pressure plate.The clutch and pressure plate should be attached to the input shaft. When torque is being transfered to clutch housing, the clutch is squeezed together between the flywheel and pressure plate which causes all 3 to rotate together, and continue to gain more velocity.When the clutch pedal is released, the clutch assembly/pressure plate disconnect from the engine causing the power to be cut.But once released, power is once again cnnected to the inout shaft which then transfers the torque through the input shaft and into the Gear Box. From there on out, the torque travels through the first input gear which is in mesh with the bottom output gear, the output gear (4th gear) then tranfers the power through the output shaft until it reaches the set of gears in charge of 1st gear. In the meantime, the first and second gear synchronizer has connected first gear to the shaft so that it can rotate with the shaft at the same speed, the torque then leaves the gear box and is transfered to the Drive shaft which then changes the angle of power flow by 90 degrees through a Ring and pinion gear set which is in mesh with the rear Differental( AKA Final Drive Gear). The Diff then transfers the power to both rear axles and of course finally to the rear drive wheels.

But lastly, the outer wheels must travel faster and further then the inner wheels in order to have correct traction when cornering, and for safe turning. If this action doesn't take place, then the vehicle will lose traction easily and will create faster and more incorrect tire wear.

As for auto transaxles, the gearbox, clutch sets, differ, and drive axles are all included in the single transaxle housing for mostly all modern vehicles.

4WD used a transfer case which is usually positioned behind the front axles, or underneath the middle of the vehicle. The transfer case is in charge of getting power to the front drive wheels through a small drive shaft, and also to the rear wheels with a longer drive shaft. Drive Shafts use U-joints so that the rear wheels/suspension can travel when the vehicle changes vertical and horizontal angles while driving on bumpy roads, or any other object that may cause the vehicle to shift angles.

Now i was very tired when i wrote this, but i assure you all my facts are straight. I figured this small guide would be helpful to those not familiar with real life Manual Transmissions and Transaxles, along with other Drive Line/Drive Train Components.
Quote from Jimston :<snip>
Now i was very tired when i wrote this, but i assure you all my facts are straight.
<snip>

Whether your facts are right or not is irrelevent because your post is not particularly relevent to the thread.

The topic at hand is on differentials, or more specifically clutch pack differentials, and the effect of clutch preload in the differential on the differential's opperation.

I think I see what you're getting at by trying to explain a car's driveline to those who may not understand it, but I think most (if not all) here do.
Quote from J.B. :I was just going to have a look at diff/tyre forces using forces view and raf data. I went to the skidpad, started out with an open diff and adjusted my driver inputs until I was keeping to a more or less constant, steady state circle.

I was expecting the longitudal tyre forces to be identical for both rear tyres in this case (fully open diff) yet the result can be seen in the attached screenshot.
Does anyone have an explanation? Is the assumption that in steady state an open diff delivers the same amount of torque to each wheel wrong? I can't find any disagreement via google.

Been gone for a few weeks with work. Sorry for the late reply.

Indeed, in the case of an open diff with no preload they should be the same just as you thought. The rolling resistance and whatever other mysterious factors someone would interject into the picture that might be at play should effect the differential "just so" to produce equal forces at the tires as you expected (once the car is in a nice, steady state without blipping the throttle/brakes or shifting weight around with the steering wheel of course; those are transients and alter the picture a bit as discussed elsewhere briefly). The slip ratios would adjust themselves to equalize the forces. Good detective work

This is a fairly minor detail though and doesn't throw a big wrench into LFS physics by any means, so I'd hate to see folks run with this and say "the diff modelling isn't right and this is why this and that, etc., is wrong" ad infinitum. So what if the open diff might not be truly, totally open? Who really wants an open diff, anyway?

In a racing sim, you want a good LSD model, and LFS has that
it doesnt matter wat it is jus tyell ur wat the best setting wud be
Quote from [106]dan :it doesnt matter wat it is jus tyell ur wat the best setting wud be

20 % power, 30% coast and 50 Nm preload...

Clutch pack preload?
(136 posts, started )
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