from what i understand any movement of a guibo (flex disc) is usually a result of the bolts twisting in their holes.

here is a picture of a worn flex disc. you can see the cracks around the bolt holes.

http://www.alfagtv6.com/bb/files/1_237.jpg

i haven't found any hard figures on just how far the driveshaft can rotate indepdent of the transmission output flange, but as an estimate, if the guibo had a diameter of 10cm at the bolt centers, and the bolt heads could flex by 5mm side to side, the driveshaft would have about 5.7 degrees of freedom.

i think it can be assumed that when the bolts are twisted they compress the rubber, and it's like a spring being compressed. the energy will be released eventually (less any converted to heat in the process), either through the tranny (if the wheels retain traction) or back to the wheels if they lose traction. this might contribute to wheel hop under certain conditions?

Quote from JTbo :

Just to note that not all cars have guibo.

Don't know if these help, but here is pic and it came from this page


Material is bit similar to some engine mounts, it can flex, but it is used mainly to remove small vibrations, it is not flexing anything significant amount as you can see by looking photo.

I have a LOT of flex in my bmw drivetrain, I'm in the process of replacing all the bushings with polymer ones instead of this crappy, over-flexible rubber. It's a giant arse ache.

The flex matters a lot - the reason I'm swapping them out is because I raced someone elses with this already done and it was brilliant, really responsive dynamics.

You can even buy aluminium ones for racing, things like diff mounts especially.

My differential rocks enough just flicking it into first gear to make a clunk from it rocking in its carrier and the bushings, if you dump the gass and take it off again you can really feel the whole lot elasticate the application of torque to the wheels.

Quote from Bob Smith :

I'm sure Dennis mentioned somethime about axle twist due to inboard brakes on the dp1. Sadly I cannot find in emails/his site where this was mentioned, and I remember the exact figure. I remember it being higher than I thought, over 20 degrees I think (under full braking, that's 1.6gs or so).

They way I understand a flex disk is constructed I'd expect it to be able to flex upto about 30 degrees mechanicaly given enough forces at play. In reality there is probably a large safty margine before the metal components clash so a resonable guess would be what Bob said Also engine mounts can allow several degrees of movement, so it all adds upto quite abit.

Quote from evilgeek :

from what i understand any movement of a guibo (flex disc) is usually a result of the bolts twisting in their holes.

If that's how they work they wouldn't last 5 minutes

I'm pretty sure you will find that they all have six bolts, three attatch to a plate connected to the driveshaft, the other alternating three attatch to another plate that connects to the diff in most cases, this is all encased in rubber. The bolts are spaced 60 degrees apart. Looking at the pic JTBO post above you can see this fairly clearly. You can see by the shape of the connecting plate it would give 10 to 20 degrees of rotation easily.

So the effective (simulated sping) would need to take into account the mass of rubber acting between the two surfaces. (i.e. mass of rubber between two bolts times six) I guess just like tyres there would be varying characteristics between manufacturers etc and would assume road cars would have softer ones compared to race preped cars? So that might help the situation with the XFG.

Quote from Scawen :

Please try to answer the question I've asked. [...] I need to know which cars (if any) suffer more clutch overheating than others, on road or rallycross tracks, so I can hopefully start to see a pattern.

I've tried a "burn clutch" test on different cars, I hope it can help you in seeing a pattern.

The tests were done on Kyoto Oval with these steps
1) Wait for the green lights to start the race
2) Shift-up to the highest gear without touching throttle (using autoclutch)
3) Floor down the throttle
4) Drive around the oval keeping max throttle until the clutch burns out or until it becomes stable orange
5) Watch the replays and note down how many seconds it takes to make the clutch red / how many seconds it takes to completely burn the clutch.

It is obviously an "unrealistic" test since no-one would start the car in highest gear but I hope it helps in showing the differences between the cars.
Results:
Note 1: all cars were using their "default/hard track" setup
Note 2: some cars reached "red" temperature and then cooled down
Note 3: I did 2 tests on XFR, one with 5th gear, one with 6th

Cars which fully burnt the clutch: XFG, UFR, XFR, XRG, FBM
Cars where clutch became red but didn't burn out: FXO, LX4, LX6, FZR
Cars which run fine: UF1, RB4, XRT, XRR
Untested cars: RAC, FZ5, FXR, MRT, FOX, FO8, BF1

But wouldn't the gear ratios be different? Surely that would affect the auto-clutch?

Engine does rotate easily that 10 degrees, so there can be as much as 60 degrees of flex (street cars) when we put these together, it is of course different effect which side of gearbox flex resides, but it is quite surprisingly lot and that of course has lot of effect to driving feel and behaviour.

If you have leaf springs, rear axle also tends to rotate quite a lot at acceleration, also depending how axle is supported it tends to pull to side too so tail kind of steps out even it does not slide.

Thank you very much for your stories, comments and test results!

I think you will find the new X36 an improved version. Clutch heating is back to X33 levels but six of the cars have a stronger clutch. The stronger clutch was worked out purely by engine inertia. So clutch strength is now the larger value of that required for engine torque, and that required to deal with the engine rotational inertia.

I loaded all the cars and found that these ones were changed : UF1 / XFG / XRG / LX4 / LX6 / FZ5

You planning on getting any sleep tonight?

Yes, very soon, after you've tested my patch

Great stuff This sounds like a good way of going about clutch simulation for the while, letting you get on with finishing touches for Y.

I posted about the clutch earlier saying that my car had slip when virtually flat shifting right in my peak torque area, well i found out that subaru do it delibaratly with a clutch engaugement damper. Guys who drag race them dont have the damper and just sidestep the clutch and let the transmission flex and tyre slip do all the work, they dont get clutch wear or overheating. (busted gearboxes mainly)

Hope this helps

Simon

I haven't been able to test it myself since I'm at work, but the AI on Blackwood RallyX are faring okay using the XRG in patch X36 now. I ran 8 cars for 8 laps and they all finished with barely any heat in the clutch.

Huge improvement.

They certainly like to put on a show entering the pits though, sliding sideways and plowing into each other.

Quote from evilgeek :

from what i understand any movement of a guibo (flex disc) is usually a result of the bolts twisting in their holes.

here is a picture of a worn flex disc. you can see the cracks around the bolt holes.

http://www.alfagtv6.com/bb/files/1_237.jpg

i haven't found any hard figures on just how far the driveshaft can rotate indepdent of the transmission output flange, but as an estimate, if the guibo had a diameter of 10cm at the bolt centers, and the bolt heads could flex by 5mm side to side, the driveshaft would have about 5.7 degrees of freedom.

i think it can be assumed that when the bolts are twisted they compress the rubber, and it's like a spring being compressed. the energy will be released eventually (less any converted to heat in the process), either through the tranny (if the wheels retain traction) or back to the wheels if they lose traction. this might contribute to wheel hop under certain conditions?

thinking about this a little more, my estimate should have been double what it was, as there are two sets of bolts, one attached to the driveshaft, and one to the tranny, and each will twist in the flex disc.

so roughly 10* for motor mounts, 10-15* for flex disc, 10* for diff mounts, plus some flex in the chassis and other metal bits, and it starts to add up to quite a lot.

however the engine inertia vs clutch size change sounds like it will do the trick for now.

Quote from Cue-Ball :

They certainly like to put on a show entering the pits though, sliding sideways and plowing into each other.

I've noticed that too, the AI don't enter the pits on BL2 smoothly, instead they kinda spin around then go in. Maybe the racing line is undefined at some point...

Quote from Glenn67 :

If that's how they work they wouldn't last 5 minutes

got to disagree mate.

when at rest, the bolts will be parrallel to the driveshaft, but since they are a "single shear" connection (force is only applied to one end of the bolt), they will definitely twist from side to side within the rubber disc, and doing so will require a lot less deformation of the rubber (mostly concentrated near the edges) than moving in any other direction. the first few degrees of bolt twisting will hardly compress any of the rubber at all, but the further they twist, the more rubber becomes involved, with the load spread over a larger area. and if you think about it, this is actually needed to relieve stress on the bolts, and makes the connection more rubust, not less. if the bolts were not able to twist within the disc, they would be subject to much higher point loads, and more likely to fail.

and if you are thinking, "if that's true then why don't the wheel lugs fail?", the answer is that they have less inertia to cope with.

wheel: 4-5 lugs for 1 wheel + 1 tire

guibo: 3 bolts for 2 wheels + 2 tires + 2 axles + diff internals + driveshaft

Any chance of someone posting the patch zip? I don't have connection at home right now and I can't make LFS download the patch from here (work).

x36 is a good patch, but visually, the analog speed gauges are a little funny looking. For the TBO class, LX6, FZ5, the gauges just dont have enough numbers. Compared to the cars with much less power, the displays just don't look right.

Quote from evilgeek :

got to disagree mate.

The flex disk has metal sleves which the blots pass through they are done up tight (to a torque setting) metal to metal no flex involved there yes there would be load on the bolt near the plates but bolts of that size can take many tonnes of force. If there was any movement between the bolt and metal end plate they would certainly fail very quickly.

I did test now x36, report follows.

XFG in BL2 defineatly works now well, if I flatshift it is not likely to make 5 laps, If I shift properly and lift a bit at jumps it can last forever.

XRG I can flatshift to unknown future now and keep throttle floored on jumps, barely clutch temp.

Situation is better now I think, but original intention to reduce amount of flat shifting is not gained with XRG.

With LX6 flatshifting is not possible and if not flatshifted clutch seem to be cool and nice.

Other cars I did not test, also not much testing with XFG and XRG on tarmac me very tired, 4 am was long time ago

Edit:
I think that current situation is pretty qood as it is possible to race and learners car has clutch that will teach proper shifting, but that is of course your choice what level you are satisfied. My thoughts are that XFG from x36 and other cars from x30 might be pretty good, but that is just my thoughts :P

Just a little question... Don´t know if it´s the right place.
Can you change "Window while connecting" to save to NO, it´s just a little thing, but every time a person update the version of Live for Speed the "Window while connecting" come back to YES...
Thanks! As I said before, it´s just a little thing...
And sorry about my poor english.

Quote from Lodib :

Just a little question... Don´t know if it´s the right place.
Can you change "Window while connecting" to save to NO, it´s just a little thing, but every time a person update the version of Live for Speed the "Window while connecting" come back to YES...
Thanks! As I said before, it´s just a little thing...
And sorry about my poor english.

I admit that I find this annoying too. However there is a very good reason to have it this way. With new patches sometimes come new connection issues (new application needs permission to connect through a firewall etc). So, the program automatically defaults to Windowed mode, so you will see if your firewall has an issue

It's a minor annoyance, but for a very good reason

Absolutely Exellent

Quote from Lodib :

Just a little question... Don´t know if it´s the right place.
Can you change "Window while connecting" to save to NO, it´s just a little thing, but every time a person update the version of Live for Speed the "Window while connecting" come back to YES...
Thanks! As I said before, it´s just a little thing...
And sorry about my poor english.

YES!!!! I hate it when I forget that its in wondowed it also disconnets me from servers sometimes when its windowed because it has to go back to full screen..

Quote from Scawen :

I think you will find the new X36 an improved version. Clutch heating is back to X33 levels but six of the cars have a stronger clutch. The stronger clutch was worked out purely by engine inertia. So clutch strength is now the larger value of that required for engine torque, and that required to deal with the engine rotational inertia.

That sounds like a good solution to me also, as on thinking some more about the issue, FWD cars which were the most problematic have naturally alot less flex in the drive train than there RWD cousins so introducing more flex wouldn't have been realistic for that particular problem

Irl a car like the gti would most likely have had a heavy duty clutch installed if it was used in rallycross or serious racing. Trackday cars would probably have a clutch somewhere inbetween. The difference in leg strain would have been noticable between them too can't simulate that in LFS yet From what I've read from performance engineering sites about FWD cars standard to medium clutches dont take alot of abuse irl, so I think it would be pretty realistic now.

I have a problem with X36, after I installed the patch, LFS returns from S2 back to DEMO, but I cant find any button to unlock it again?