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Do Bump Rubbers Work The Same In '69 As Other Mods?


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#31 MECH

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Posted Aug 03 2010 - 04:48 AM

View PostJohn Woods, on Aug 02 2010 - 10:38 PM, said:

But I'll just sit quietly and try to not get too far ahead. Except, I just noted the exclaimation sign after "head." As in, head motion figures into force acting on the chassis?!!! Or is that the unfinished part?

Well that got my attention  :huh:
So they have the data for the head movement but failed to implement that?

Pity  :duh:

Mental note: must figure out a bypass to get the wheel turning applied to the head movement :think:

#32 Phil

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Posted Aug 03 2010 - 06:06 AM

View PostJohn Woods, on Aug 02 2010 - 10:38 PM, said:

And it is difficult for me to believe Mosport, Kyalami, and Monza all have the same grip. I always thought the factorials of the variables offered a wide range of choice for track surface grip
All Papy tracks use Asphalt surface type (the most grippy) except the following corners, which use slippery Concrete:

Rouen: Nouveau Monde hairpin, Scierie corner and the straight towards Paradis
Nurburgring: Karussell and Mini Karussell.

The variation you feel is probably due to the amount of camber in the turns.

#33 Border Reiver - guest

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Posted Aug 03 2010 - 06:13 AM

View PostJohn Woods, on Aug 02 2010 - 10:38 PM, said:

Okay, I can be patient.

A vague memory involves reading about track builders setting grip or traction variables. Isn't there something about that in the GPLEA Guides? (Stefan just posted them, guess I could check). Or somewhere. And it is difficult for me to believe Mosport, Kyalami, and Monza all have the same grip. I always thought the factorials of the variables offered a wide range of choice for track surface grip, and matching a setup to a particular unknown grip recipe was part of the art of being fast.

But I'll just sit quietly and try to not get too far ahead. Except, I just noted the exclaimation sign after "head." As in, head motion figures into force acting on the chassis?!!! Or is that the unfinished part? And clutch?

Well?Posted Image I'm waiting. Quietly...

Track makers can choose from various surfaces which have different grip coefficients, e.g. asphalt, concrete, curbs etc. which does affect traction. As an example look at Rouen where the grip varies between the penultimate and last corners to be concrete not asphalt, changing the grip to a factor of 0.96 as opposed to 1.00.

However, the bigger grip variation comes about due to camber on the road whilst using the same surface. An uncambered track with asphalt grip actually feels very slippery and is surprisingly hard to drive on, but adding even a modest amount of camber makes the road much more appealing and fun to drive on. It is actually then all about choosing the correct line and entry speed if the road is cambered or not which makes the difference as in effect the camber is changing the effective radius of the turn. It seems that Papy tried to fudge the laptimes they got by using constant grip for all main track surfaces and then adjusting the road width and/or camber to give approximately the right lap time result, or if not, then to give something that was a pleasing/fun result to drive on.

Rob

#34 Lee200

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Posted Aug 03 2010 - 06:26 AM

View PostJohn Woods, on Aug 02 2010 - 10:38 PM, said:

Except, I just noted the exclaimation sign after "head." As in, head motion figures into force acting on the chassis?!!! Or is that the unfinished part? And clutch?

Yes.  The head's mass and any movement affect the chassis.

It is unfinished and the driver's head doesn't actually move.  But if you want to know how much Jackie Stewart's head weighed, it was about 1 thousandth of a pound.  Apparently, that was before he was knighted.   :lol:

The clutch code does work, but its rigid body is only allowed freedom to rotate about the longitudinal axis and put a torque on the chassis.  It causes the chassis to rock back and forth as you rev the engine.

Lee

#35 Lee200

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Posted Aug 03 2010 - 06:31 AM

View PostMECH, on Aug 03 2010 - 04:48 AM, said:

Well that got my attention  :huh:
So they have the data for the head movement but failed to implement that?

Pity  :duh:

Mental note: must figure out a bypass to get the wheel turning applied to the head movement :think:

Hi Martin,

Have no idea how to do that.  Nigel did, but he's long gone now.

In fact, just before he left he was working on adding another two rigid bodies; one hub for each of the rear wheels in order to correct a bug where they weren't tilted properly.

Lee

Edited by Lee200, Aug 03 2010 - 07:12 AM.


#36 Lee200

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Posted Aug 03 2010 - 07:04 AM

Back to the rigid body stuff, I was a little remiss in not mentioning how important linear and angular momentum are to GPL.  Momentum is mass times velocity so at any given moment (no pun intended), GPL knows the chassis momentum in each of the six degrees of freedom.

When a force is applied over time, that value is called impulse and when GPL applies impulse to the existing momentum, a new momentum is reached which is stored for the next calculation cycle.

Momentum is used not only to determine how much the chassis rigid body is accelerated, but also for collision reaction with objects such as other cars and hay bales.   :wave:

Lee

#37 John Woods

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Posted Aug 03 2010 - 07:42 AM

Hay bales again?

#38 Lee200

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Posted Aug 03 2010 - 09:48 AM

View PostJohn Woods, on Aug 03 2010 - 07:42 AM, said:

Hay bales again?

Yes, I'm an expert on hay bales.  Grass hay is much more forgiving than alfalfa so I usually look for those to hit.  It's also much better to run into the rectangular or cubed hay bales versus the large round ones as the round ones contain much more moisture and can rust the brake rotors.

Also after a particularly bad shunt, the grass hay is particularly tasty to chew on while waiting for the ambulance.   :hat-tip:

Lee

#39 John Woods

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Posted Aug 03 2010 - 12:56 PM

Now that's some information I can use.

Just going all crossthread and off-topic, wondering about GPLTime vs. real time and the validated see-saw laptime effect, is there any chance factors like momentum and inertia have some relation to these effects with unknown causes? For instance, might they have limits at which values are re-set to zero, or re-set every two laps?

Edited by John Woods, Aug 03 2010 - 01:02 PM.


#40 brr

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Posted Aug 03 2010 - 01:07 PM

View PostJohn Woods, on Aug 03 2010 - 12:56 PM, said:

Now that's some information I can use.

Just going all crossthread and off-topic, wondering about GPLTime vs. real time and the validated see-saw laptime effect, is there any chance factors like momentum and inertia have some relation to these effects with unknown causes? For instance, might they have limits at which values are re-set to zero, or re-set every two laps?

The laptime effect is supposed to be based on full rotations of the car. Spinning the car 360 degrees has the same effect as driving one full lap.

#41 John Woods

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Posted Aug 03 2010 - 02:14 PM

Caught me guessing again.

But now I understand. When I spin, every other time I go faster. Thanks.

Edited by John Woods, Aug 03 2010 - 04:40 PM.


#42 grego

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Posted Aug 03 2010 - 03:18 PM

.............and i have found a nice way of spending time by keeping a spinn going using the wheel and the accelerator.
i used to do it just for some smokin fun and can keep the spinn going for many rotations.
who would have guessed it would make me into a champion racer .........................;)

Edited by grego, Aug 03 2010 - 03:19 PM.


#43 Wozza_UK

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Posted May 10 2016 - 01:22 PM

Firstly, I apologise for bumping an old thread but this is GPL and old threads can still be new ones right? No sense in creating a new thread when all the relevant info is held in this one.

Anyway I was greatly interested in the graph posted on page 2 by Lee200 that shows the bump/rebound settings in GPL. I have been trying to develop a new setup over the last week and this graph completely changes my opinion on how to use the dampers in GPL.

From my research on the web I am led to believe that rebound should always be higher than bump because in a car the sprung mass (body) is always heavier than the unsprung mass (wheel) etc etc. This graph shows me that I have been doing it wrong. I have been dutifully using settings like 3 bump and 4 rebound thinking I was doing it correctly, when I should have been using 3 bump and 2 rebound. :really:

Anyway, now to my question. Maybe some of you setup gurus can answer this: in a car, which set of dampers generally speaking should be stiffer, front or rear?

Logic tells me the dampers at the rear of a rear-engined car should be stiffer because they would support the weight of the engine. But how about in a front engined car? Would it be reversed?

Or is it be based on some other parameters?

Any help appreciated. :rolleyes:

#44 M Needforspeed

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Posted May 10 2016 - 02:02 PM

View PostLee200, on Aug 03 2010 - 06:31 AM, said:

View PostMECH, on Aug 03 2010 - 04:48 AM, said:

Well that got my attention  :huh:
So they have the data for the head movement but failed to implement that?

Pity  :duh:

Mental note: must figure out a bypass to get the wheel turning applied to the head movement :think:

Hi Martin,

Have no idea how to do that.  Nigel did, but he's long gone now.

In fact, just before he left he was working on adding another two rigid bodies; one hub for each of the rear wheels in order to correct a bug where they weren't tilted properly.

Lee

thanks again Lee,

Five years after your post, you handled the work successfully and give us those great drivers heads movements . Or is it a shared work with Martin?

Edited by M Needforspeed, May 10 2016 - 02:04 PM.


#45 gregc

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Posted May 22 2016 - 06:47 AM

Wozza_UK - great thread, thanks for bumping.




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