The .tgm, and +ttool

[jtbo]

Edit: I made mistake, with nodes you do create outer layer of tire, surface that touches ground, so I did edited misinformation to barely readable to avoid confusion which has gotten me more than once with this aspect. But black writing is how things are in real world, still don't know how much of it applies to rF2 but we test, we learn.
One thing about nodes that has not been probably mentioned, idea is to model inner liner of tire, all layers are being put on top of that (or more of bottom, but nodes make inner layer of tire).

So with those nodes you don't make shoulder of tire, it is just something which you lay up plies and belts, so with thickness of thread you create shoulder of tire and shoulder of tire should in theory have quite bit of say how much steering 'talks' about road, at least that is so with real street tires.

So sharp shoulder is something that average drivers consider horrible to drive as it is quite sensitive to road conditions and tells lot about road, average driver considers good to drive to be completely lifeless dead steering and suspension that eliminates every bump so that you don't feel anything about road even from seat, total opposite of what those more active drivers like to have.

To what extent this works in rF2, I have no idea at the moment, but I try to test and see if I get any impressions about it.

[jtbo]

Year 1948 data from Rayon (material used in older bias ply tires)
http://naca.central.cranfield.ac.uk/...ca-tn-2084.pdf

That is aircraft tires of course, but material probably is similar, mixture might then vary, but there is different mixtures listed in data so it should give some guidelines to work with.

There are things like TR-direction, RT-direction and modulus is in psi, but I guess it is possible to work out those to right units and find explanations, I have just laid quick glance to that information, but 50's information when making 50's tires surely should have correct era materials represent, stuff they use these days is not same they used to use, even during the years materials probably changed so that data from correct era is one that gives best idea about material.


I managed to make menu disappear from ttool as it did do calculations, I know of ctrl+D that is what I used to make image go away, but when I can back I can't get floating toolbar to appear, several black screens and then screens with tire graphics are only ones I can see, there is no small square at near bottom which usually contains hidden menu, so I don't know what stage my tire calculation is at the moment. Well I wait for few hours, it should be close to end and I should see from fps when calculation is finished :P

edit: Oh yes, I have now one bias ply tire in my possession, it is very old one, Continental made, 6.45-13 4PR, 2 plies Rayon, load rating 970LBS and max pressure 32PSI, older euro cars did run those I believe.

[patryksok.]

Anyone have problem with ttool? When I run automated test, pause, save file, and then you want to load this file I have this error:

[jtbo]

Anyone have problem with ttool? When I run automated test, pause, save file, and then you want to load this file I have this error:

I don't need to even save file, it at least used to render tire files useless in computing process, well at least in previous version, so I usually make copy to another location before I load tire to ttool, then I never save tire to same name etc.

However I have not seen such error message before, usually it just shuts down or freezes completely.

Oh and I always end up for tool getting infinite loop, but I can get away from that by reducing quasi rotation from 244.xxx while it computes, which probably will make something terrible to lookup table, but then again I doubt that I reach 244 rads/sec rotation.

Problem probably lies in my tire construction thinking as I always seem to meet this problem.

There was few times problem with test that tests 0 pressure and has 400 load to tire, it got to infinite loop there, maybe adding pressure would of make it move again, but I really don't think I should change anything during the tests.

Next I try to do that bias ply tire with rayon and see if I get same result of infinite loop, but that has to wait until I can sit again, back decided to broke and it might take a while until it gets better so I'm stuck in bed.

[patryksok.]

Ok, I solved the problem.

[jtbo]

Ok, I solved the problem.

What was it, how did you solved it?

[patryksok.]

Read TGM tutorial carefuly I cant load initial file, but I can load quasi static partial result tgm and load it and run test from where I paused it.

[krivjur]

Hmm, I'm now wondering about these two, what might be best way to choose correct values for these?
TemporaryBristleSpring=(24000, 14800, 31500) // Lat/Vert/Long
TemporaryBristleDamper=(0.55, 0.3, 0.55)

Tutorial says this:
TemporaryBristleSpring = Bristle spring rate for (Lat, Vert, Long). Temporary until contact patch model finalised. Once a TGM is generated through the run automated tests, this effects the stiffness of the bristles in the real time model (which are in contact with the road). This should be adjusted so that the real time model approximates the stiffness as seen in the QSA model. For the vertical component this can be done relatively simply by adjusting this value until the load for a given deflection in the real time section matches that obtained in the QSA section. Keep in mind at present, the tyre should be softer in real time than QSA, due to computational reasons. In other words, you may see it fit to use the bristle spring rate as a compensation for this effect.

My QSA Model section says Y stiffness being 3090021.xxxxx so do I really set Vert tempbristlespring to that high value? It seems rather high to me, especially as it originally is so much less, should this level of spring be something in range or is it out of the whack meaning there is major issue with my built tire?

With my earlier made tires value is over 2 million also and with those only thing changed is tire size (changed nodes) and thread depth, rest is same as original rTrainer tires, well optimal tire pressure was also set to 200 instead of 150, but other than that those earlier ones should be almost like rTrainer tires.

But if rTrainer uses values of only 14800 for Vert(y-axis) I become very skeptical about my readings, it is huge difference. What kind of values others have got and what kind of values have you put to tempbristlespring?

Then also come question of tempbristledamper, should original ratio between spring and damper be maintained or is there any better way determining appropriate damper values?

I will just lay down what I understood the tutorial meant on the vertical component for TemporaryBristleSpring. I think you use those params as trial and error tweaker, you don't get those values directly from ttool. I only briefly looked on to it, so I may be wrong, but this can possibly give you some ideas.

MICHELIN S8B 24-65-18.TGM (Megane2009 Rear tire (Dry))

TemporaryBristleSpring=(68000, 28250, 83000) // Lat, Vert, Long



on ttool:

Let ttool calculate QSA results with the seleted Surface height.

QSA
Peak radius = 0.324008 (calculated with no deflection)
Surface height = -0.321008
Deflection = peak radius - |surface height| = 0.003000

Result: ground Force Y = Load = 1007.6397

Not sure what speed and rotation you should use in realtime, this is with both 0, so forces don't fluctuate.

Realtime
Long Vel (m/s) = 0
Rotation = 0
Nominal Radius = 0.324
Deflection 0.0030 (from QSA surface height used)
Gauge Pressure = 150

Result: Vertical Force = 640.73

------

TemporaryBristleSpring=(68000, 26250, 83000)

Realtime
Long Vel (m/s) = 0
Rotation = 0
Nominal Radius = 0.324
Deflection 0.0030
Gauge Pressure = 150

Result: Vertical Force = 599.46


TemporaryBristleSpring=(68000, 30250, 83000)

Realtime
Long Vel (m/s) = 0
Rotation = 0
Nominal Radius = 0.324
Deflection 0.0030
Gauge Pressure = 150

Result: Vertical Force = 681.43


TemporaryBristleSpring=(68000, 60250, 83000)

Realtime
Long Vel (m/s) = 0
Rotation = 0
Nominal Radius = 0.324
Deflection 0.0030
Gauge Pressure = 150

Result: Vertical Force = 1231.86

--
I don't know if the realtime result values are right to be comparing with the QSA result, but the TemporaryBristleSpring definitely has effect. Other stuff may be full of holes as well, but at least the conditions are same between tests.

[Tim Bennett]

I went though and found most of the relative links here and edited the original post, along with some of the more important info like changing DT Multiplier and how little the TBC controls now.

Hopefully this will help keep down any duplicate posts, thanks for all of the info guys!

[jtbo]

--
I don't know if the realtime result values are right to be comparing with the QSA result, but the TemporaryBristleSpring definitely has effect. Other stuff may be full of holes as well, but at least the conditions are same between tests.

Thank you krivjur, for me that what you describe sounds very possible and probable way to get those values. I'm under impression that those values become obsolete at some point, but for now it is good to have them right.
So it is more or less of load rating of tire + some other stiffness stuff.

There might be possibility to gain value also from spring formula, if we take max load of tire and deflection of tire it should be possible to work out spring rate as it is possible to work out deflection from spring rate and deflection, that might give also something to compare to, but I have not yet put enough time on finding proper formulas to put into excel.

It will be great information when we manage to open up every aspect and parameter so that one don't need to be engineer to learn how to put tire info from real tire to tgm.

[dv8r]

Anyone concluded further info on tyre wear yet?

I know the wear is limited, but i have not yet been able to generate a tyre that appears to wear in a controlled manner.

I have tried some very extreme values in the TemporaryAbrasion with little or no effect, if there was an effect im not sure if it was a placebo.

[dv8r]

4 lines from the QSA that are uncommented in the quick start guide. I have not seen them used in the beta cars ive checked.

VolumeLoad=0
LoadCamber=0
LoadInclination=0
LoadDeflection=0

Some info please,
what are they?
can we add multiple tests for these?
what units or values should we expect here?

[KSP]

Question for ISI tyre model developers:
For example MICHELIN S8B 24-65-18.TGM (Megane2009 Rear tire (Dry)) have string
TemporaryBristleSpring=(68000, 28250, 83000) // Lat, Vert, Long
I try to tweak this values and it has big influence for tyres stiffness and behaviour. Question is: which real world stiffness (N/mm) is stay behind this values in this example? And if I want to apply Lat, Vert, Long stiffness like 200, 300, 500 N/mm accordingly so which values I should use in TemporaryBristleSpring for this tyres?

[Kev]

Idea for ISI programmers: allow run multiple instances of TyreTool to run test of different tyres simultaneously.
Currently i have 4 different tyres (front/rear for dry/wet track) and hardly can sit seen my CPU 13% loaded running automated tests of first tyres... It will work about 4 hours, then 3 times more by 4 hours. Totally 16 hours! Oh my...

[jtbo]

Year 1948 data from Rayon (material used in older bias ply tires)
http://naca.central.cranfield.ac.uk/...ca-tn-2084.pdf

edit: Oh yes, I have now one bias ply tire in my possession, it is very old one, Continental made, 6.45-13 4PR, 2 plies Rayon, load rating 970LBS and max pressure 32PSI, older euro cars did run those I believe.

I have not much more that a day, but I thought that I try to make tires based on those old ones.

So they have 2 plies of rayon at sidewalls and 2 plies of rayon on top of those at thread area.

For Rayon, I have this chart.


Then I have information about density:
http://www.engineeringtoolbox.com/de...ity-d_290.html

Apparent specific gravity for rayon is according to that pdf 0.038 of some unit, but I don't have information of volume, it is said that two mats were 30 and 45 pounds per 3000 square feet and test piece size are also told, but thickness of material is missing to get volume that I could convert it to SI units I believe. Or then I'm again missing out something obvious.

There are two poisson's ratios, several modulus of elasticity and I have no idea about young's modulus, so I'm bit stuck before I could start.

Is it even possible to convert those rayon material numbers to rfactor form, is there critical bit missing?

Bit troublesome, but cleverly spying what ISI has done with 60's open wheelers reveals this kind of values, I guess that those are values for Rayon as it was common material in tires back then:

[Node] // 18
Geometry=(-0.051,-0.29246,0.0105)
BulkMaterial=(273.15,930,16500000,0.46,-1,1250,0.63)
BulkMaterial=(373.15,904,12400000,0.46,-1,1290,0.58)
AnisoCarcassConductivityMult=(1.2,1,2)
TreadDepth=0.0055
TreadMaterial=(273.15,837,8000000,0.47,-1,1900,0.188)
TreadMaterial=(373.15,814,5900000,0.47,-1,2200,0.18)
RingAndRim=(1,0)
PlyParams=(25.3,0.000692,3)
PlyMaterial=(273.15,1295,1850000000,0.34,-1,1680,0.26)
PlyMaterial=(373.15,1275,1400000000,0.34,-1,1700,0.246)
PlyParams=(154.7,0.000692,3)
PlyMaterial=(273.15,1295,1850000000,0.34,-1,1680,0.26)
PlyMaterial=(373.15,1275,1400000000,0.34,-1,1700,0.246)
PlyParams=(25.3,0.00052,3)
PlyMaterial=(273.15,1295,1850000000,0.34,-1,1680,0.26)
PlyMaterial=(373.15,1275,1400000000,0.34,-1,1700,0.246)
PlyParams=(154.7,0.00052,3)
PlyMaterial=(273.15,1295,1850000000,0.34,-1,1680,0.26)
PlyMaterial=(373.15,1275,1400000000,0.34,-1,1700,0.246)

When comparing to this rTrainer tire that has steel and nylon6+6, there is difference in materials, not large, but difference and of course steel is missing from 60's tires, so I guess that I settle with ISI 60's material for now as my head is too old today to figure out how to get rayon numbers converted to these units.

[Node] // 18
Geometry=(-0.06,-0.324,0.011)
BulkMaterial=(273.15,925,26500000,0.46,-1,1250,4.6)
BulkMaterial=(373.15,903,20500000,0.46,-1,1290,4.4)
AnisoCarcassConductivityMult=(1.2,1,2)
TreadDepth=0.0055
TreadMaterial=(273.15,925,9500000,0.47,-1,2000,0.172)
TreadMaterial=(373.15,903,7300000,0.47,-1,2200,0.165)
RingAndRim=(1,0)
PlyParams=(80,0.0004,3)
PlyMaterial=(273.15,1305,2100000000,0.3,-1,1695,0.25)
PlyMaterial=(373.15,1285,1700000000,0.3,-1,1715,0.24)
PlyParams=(100,0.0004,3)
PlyMaterial=(273.15,1305,2100000000,0.3,-1,1695,0.25)
PlyMaterial=(373.15,1285,1700000000,0.3,-1,1715,0.24)
PlyParams=(0,0.0009,3)
PlyMaterial=(273.15,7907,201500000000,0.3,-1,450,52)
PlyMaterial=(373.15,7879,195500000000,0.3,-1,485,50)

edit: I feel more stupid today than an average day, I did found earlier Young's modulus for rayon, but I forgot about it, here is link:
http://acswebcontent.acs.org/landmar...rbon/car4.html

The process resulted in a ten-fold increase in Young’s modulus — a major step on the way to duplicating the properties of Bacon’s graphite whiskers.

Union Carbide developed a series of high modulus yarns based on the hot-stretching process, beginning in late 1965 with “Thornel 25.” The trade name was derived from Thor, the Norse god for strength, and the Young’s modulus of the fibers — 25 million pounds per square inch (psi), which is equivalent to about 172 GPa.

So before that time rayon had certainly 10 times smaller modulus, which might be useful to know at some point, but is that used in tires ever is another questionmark, but maybe it helps to guess bit closer.

[Tuttle]

Hey, I'm searching for Rayon infos as you (I've 3 rayon for sidewalls and other 2 for tread) and I get this paper about Rayon performances (for tires);

http://www.cordenka.com/pdf/Profile_...nforcement.pdf

[jtbo]

Hey, I'm searching for Rayon infos as you (I've 3 rayon for sidewalls and other 2 for tread) and I get this paper about Rayon performances (for tires);

http://www.cordenka.com/pdf/Profile_...nforcement.pdf

Thank you from sharing Tuttle, there one can pick up densities easily

I try to make first different size tire from ISI material definitions, starting small first, then move on to more challenging parts, there is so much to learn with these tires that I feel rather lost at the times.

Anyway, I did manage to calculate rim volume of 14" Volvo alloy wheel, I came up with 3.8 litres, 0.0038 for TGM, surprisingly small amount, but shape is such that there is one deeper section bit side from center line and it is rather narrow, rest is not much lower than rim edge, so air is mostly in tire and not much at rim. 5 1/2J x 14 x 20, Volvo part 1229539, made in Germany 1982. 240 Volvo alloy wheel. Of course there can be errors made in measuring, it is more of estimate with precision measurement tool, calculating volumes of complicated form toruses is not easiest thing to do, so I estimated two toruses from main shapes and calculated those, then combined results to get volume.

[Tuttle]

Anyway, I did manage to calculate rim volume of 14" Volvo alloy wheel, I came up with 3.8 litres, 0.0038 for TGM, surprisingly small amount, but shape is such that there is one deeper section bit side from center line and it is rather narrow, rest is not much lower than rim edge, so air is mostly in tire and not much at rim. 5 1/2J x 14 x 20, Volvo part 1229539, made in Germany 1982. 240 Volvo alloy wheel. Of course there can be errors made in measuring, it is more of estimate with precision measurement tool, calculating volumes of complicated form toruses is not easiest thing to do, so I estimated two toruses from main shapes and calculated those, then combined results to get volume.

Hmmm..sounds pretty weird. How did you calculate the rim shape volume? I'm just using an average method with a basic cylinder (Eg: 13"x9.5" - rim flange height) and it gets more realistic results than using volume mesh calculations into 3D softwares (there're a lot of traps in a mesh volume calculation as edges faces, normals, closed/open parts, extrusions etc...), so I prefer to go for averages than fake realistics.. I know rims are not cylinders but the only area we're interested for is the inner part that usually is a sort of cylinder, especially for racing cars...

The very little value you get could be the internal volume of the rim shape (the volume between external surfaces)

[jtbo]

Hmmm..sounds pretty weird. How did you calculate the rim shape volume? I'm just using an average method with a basic cylinder (Eg: 13"x9.5" - rim flange height) and it gets more realistic results than using volume mesh calculations into 3D softwares (there're a lot of traps in a mesh volume calculation as edges faces, normals, closed/open parts, extrusions etc...), so I prefer to go for averages than fake realistics.. I know rims are not cylinders but the only area we're interested for is the inner part that usually is a sort of cylinder, especially for racing cars...

The very little value you get could be the internal volume of the rim shape (the volume between external surfaces)

It is amount of air in wheel area, tire has then much more.

I try to draw it .... done, not much of drawing, but you get idea of shape of wheel, tire bead rests against those higher areas and against rim edges, so there is really small area, 3.6x3.6cm of that actual cylinder, but I did include area to top of rim edges also as it is also part of rim, but it is also part of tire when tire is installed.


rTrainer has volume of 14 litres (again from my memory) and it's wheel is wider, imo, was it even taller too, can't remember that.

There can always be errors, comma errors, rounding errors, conversion errors and calculation errors, I did my best to measure and try to calculate space as good as possible but my meter seems not always to be same as everyone other's :P

[Tuttle]

Hmmm...Maybe I'm wrong but for what I see with other ISI tires seems they're using an average cylinder as well (V=pi*rsquared*h)

Some eg:

18"x9" (370z) get a cyl volume of 0.039615 and the TGM use 0.03724 (0,002 difference)
18"x10" (370z) get a cyl volume of 0.0417 and the TGM use 0.0392 ( 0,002 difference)
13"x13.7" (F1 ISI) get a cyl volume of 0.029799 and the TGM use 0.02712 (0,002 diff.)
13"x12" (F1 ISI) get a cyl volume of 0.026101 and the TGM use 0.02375 (0,002 diff.)