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Clutch In Gpl Setups

GPL clutch

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#1 FJBH10

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Posted Nov 27 2017 - 06:18 AM

Hello all,

I've recently been on a mission to learn how to properly set up a car, I'm using GPL and Assetto Corsa as my main platforms. I have been making some good progress but one aspect of the car setup that I have never came across before and cannot find any proper resources for is the clutch. I'm guessing that the GPL setting relates to the clutch plates but I don't know what effect it has on the car, would more clutch plates give better acceleration but less reliability due to friction? I would be thankful if someone with a bit more knowledge than me could enlighten me on the subject.

#2 Millennium

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Posted Nov 27 2017 - 06:59 AM

More clutches means tighter diff, less clutches means looser. It should also be adjusted to the weight/amount of torque of a car.

I recently made a video about it, although it just covers the basics and is not very in depth.
https://youtu.be/awLhSsy5IqY?t=3m1s

Here's an excellent guide by Charlie Williscroft:
http://srmz.net/inde...?showtopic=1140

Edited by Millennium, Nov 27 2017 - 07:04 AM.


#3 mcmirande

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Posted Nov 27 2017 - 07:12 AM

They're clutches of the differential. Nothing to do with gearbox.

The more clutches (in combination with slower angles), the hard differential.

Cheers, Marcos.

#4 Cookie

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Posted Nov 27 2017 - 07:40 AM

My way to handle the differential is to look at Lee's Setup Manager wich displays the locking percentage,
so you get an absolute value of the differential locking ;)

#5 John Woods

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Posted Nov 27 2017 - 09:31 AM

There's a t-t-t-ton of info about this.

One idiot's theory:
There are only two differential conditions.
1. Power on accelerating, (99.9 percent of the time).
2. Coasting with power off, (momentary condition only to set sprung weight on rear of car for acceleration thru a turn).

Also note, as I understand, springs and anti-roll bars define the extent of sprung weight travel. Shocks and the diff effect the speed of travel.

The standard operating condition is power on accelerating.
The only time and reason to lift throttle and go into coast is to rotate the rear of the car to set it up for acceleration thru a turn.

So the diff setup priority is dependent on driver style and technique as well as the car's capability.

Refer to gpllinks tech section for some links to diff technology.

Here's one that is simple and easy enough to apply to GPL setups: Vari-loc

Plus this link to some setup secrets:http://srmz.net/inde.... skid fun&st=0

And a great place to test setups and effect of changes: Skid Fun

:D

Edited by John Woods, Nov 27 2017 - 09:43 AM.


#6 FJBH10

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Posted Nov 27 2017 - 10:05 AM

Thanks guys, a great example of the fantastic community we have here! I never thought that it could be referring to the diff... good job me! Gonna read through all the links and watch Millenium's videos and hopefully I can get an understanding of how to set up a diff. Thanks again... in less than 4 hours you guys gave me more info than I expected I would have after a fortnight. (Also Millenium you are a god to be able to drive at all with a pad, never mind as competently as you do!)

Edited by FJBH10, Nov 27 2017 - 10:11 AM.


#7 Stefan Roess

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Posted Nov 27 2017 - 10:28 AM

GPL Setup Sheets (Setup Basics) [English]

http://www.gplworld....ps-replays.html


Posted Image

Posted Image

#8 FJBH10

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Posted Nov 27 2017 - 10:41 AM

Thanks a ton Stefan, those are really useful.

#9 Michkov

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Posted Nov 28 2017 - 09:11 AM

It's clutches in the differential. GPL cars have a limited slip diff which is between solid axle and an open diff. The clutches are the locking parts in this case, with more clutches offering more area to grip hence a harsher locking.
The ramp angles control how much of force the accleration of the tyres/driveshaft puts on the clutchs. With the power angle(first value) in use when the engine is driving the wheels and the coast angle for the other case.

#10 JonnyA

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Posted Nov 28 2017 - 01:33 PM

My rule of thumb is, if the car feels otherwise balanced but reluctant to turn (not just because of understeer), I add clutches. And if too twitchy, take some out. Other than that, I never touch the diff settings.

Not rocket science (but then I'm only an average driver) but it works for me.

#11 Millennium

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Posted Nov 28 2017 - 02:34 PM

It's interesting to see the different approaches here on determining the amount of clutches. I am by no means an expert on this subject, personally I just start with the default settings to find out how that drives.

1. If I want more rotation under power, I lower the first ramp angle number. (power)

2. If I want more rotation while braking/steering into a corner, I raise the second ramp angle number. (coast)  

3. Based on how loose or tight the diff feels with the ramp angles I've chosen, I raise or lower the amount of clutches.

In that way I sort of use the amount of clutches as a way to fine tune my diff settings, not as a base to build up from. I don't know if that's the right way to look at it, but it works for me.

#12 leon_90

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Posted Nov 28 2017 - 02:44 PM

View PostJonnyA, on Nov 28 2017 - 01:33 PM, said:

My rule of thumb is, if the car feels otherwise balanced but reluctant to turn (not just because of understeer), I add clutches. And if too twitchy, take some out.

Its the exact opposite

#13 JonnyA

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Posted Nov 29 2017 - 12:41 AM

View Postleon_90, on Nov 28 2017 - 02:44 PM, said:

View PostJonnyA, on Nov 28 2017 - 01:33 PM, said:

My rule of thumb is, if the car feels otherwise balanced but reluctant to turn (not just because of understeer), I add clutches. And if too twitchy, take some out.

Its the exact opposite

Well it works for me!

#14 John Woods

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Posted Nov 29 2017 - 10:12 AM

View PostJonnyA, on Nov 29 2017 - 12:41 AM, said:

View Postleon_90, on Nov 28 2017 - 02:44 PM, said:

View PostJonnyA, on Nov 28 2017 - 01:33 PM, said:

My rule of thumb is, if the car feels otherwise balanced but reluctant to turn (not just because of understeer), I add clutches. And if too twitchy, take some out.

Its the exact opposite

Well it works for me!

:)

Say...what?

Small part of what Vari-loc says about tuning ramp angles:
"Differential locking action creates drag between the tires that in turn produces push. In general, the greater the locking action, the more push that is created."
"Corner entry and exit are controlled by the ramp angles, and neutral throttle by preloading the clutch pack."
"Locking rate of both sides of the ramp can be lowered by reducing preload, or by rearranging the clutches to reduce the number of active surfaces."

Pretty certainly, more locking causes more push. So Leon is correct in noting that increasing clutches will not correct push but actually does the opposite.

Maybe JonnyA is also correct, when steering car using throttle, as the effect of stiffer diff could be an advantage in precisely turning (rotating) the car?

Just a guess...plus if a typical morning post probably exactly wrong somewhere.


:D

Edited by John Woods, Nov 29 2017 - 10:40 AM.


#15 JonnyA

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Posted Nov 29 2017 - 03:41 PM

John, your guess is right. It's nothing to do with correcting understeer, it's about how the car rotates into the corner as I come off the brakes and onto the power.

#16 FJBH10

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Posted Nov 29 2017 - 04:07 PM

I found I'm fastest and happiest with 30/85, I got my best ever qualifying result with that (But blew up in the race) and it feels so much better than the stock setup. I like having the car really twitchy normally and was struggling to get that in GPL, especially in the '65 cars with their low power but thanks to you guys I am now about a second quicker on most of the tracks I've tried so far.

#17 John Woods

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Posted Nov 30 2017 - 09:29 AM

View PostJonnyA, on Nov 29 2017 - 03:41 PM, said:

it's about how the car rotates into the corner as I come off the brakes and onto the power.

Have been wondering a long time about how to deal with "not right in the middle" because there is no setup adjustment for pre-load, (as Vari-loc guide recommends).

Now see it must be clutches alone that tune how the car behaves in transition.
(Takes awhile).
Also, another guess based on experience of really having no idea, it also depends some on load balance, brake bias, and rear camber?

So, x-ing everything else out, for a given setup:

1. Tune coast ramp for entry.
2. Tune power ramp for exit.
3. Adjust clutches to tune for the middle?

Or, as some with no respect for reality might want to try, just set it for the quickest possible digital effect and run 15/85 and adjust clutches to maybe work best for a particular track?

More clutches > big tracks, long straights, fast sweepers?
Less clutches > twisty circuits?

:)

#18 Pete Gaimari

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Posted Nov 30 2017 - 09:51 AM

Use the ramp adjustments to set how you want to balance the car. Use clutches to set how hard and fast you want those ramp settings to lock.

#19 Michkov

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Posted Nov 30 2017 - 04:46 PM

Posted Image
This here diagram should help illustrate what the ramps do. The yellow peg transmits power from the engine towards the driveshafts to the left and right of the white block. If you stomp gas the peg moves forward and puts pressure on the block pushing it apart. Depending on the peg/block angle (this is your ramp angle) a certain amount of the peg force is transferred from the forward peg motion to sideways motion pushing the block apart.
Same goes for the deceleration case where the block is moving into the "stationary" peg which then pushes the block apart.
As you can see the closer the ramps are to 90° the less force is produced to push the block apart.

Now for where are the clutches? They sit at the end of the blocks. They function like a clutch you find on a gearbox, just in reverse. IE they're natural state is disengaged, allowing the shafts to rotate independently. The force pushing apart the blocks engages the clutch, locking the axle, or at least stick it together a bit more.

What adding more clutches does, is decrease the force necessary to achieve locking. Because there is more friction surface to work with. Below is an exploded LSD, clutches are the dark grey parts.
Posted Image

The TLDR:
Increasing clutch count has the same effect as decreasing ramp angle.
They effect both coast and power side equally
Consult the sheet mentioned above for on how big the effect is but my usual guideline is ramps for rough balance and clutches for fine tuning. So similar to the Springs/ARB to damper relationship.

View PostJohn Woods, on Nov 30 2017 - 09:29 AM, said:

View PostJonnyA, on Nov 29 2017 - 03:41 PM, said:

it's about how the car rotates into the corner as I come off the brakes and onto the power.
So, x-ing everything else out, for a given setup:

1. Tune coast ramp for entry.
2. Tune power ramp for exit.
3. Adjust clutches to tune for the middle?

Or, as some with no respect for reality might want to try, just set it for the quickest possible digital effect and run 15/85 and adjust clutches to maybe work best for a particular track?

More clutches > big tracks, long straights, fast sweepers?
Less clutches > twisty circuits?

:)

I use coast for braking stability after everything else doesn't work
Power for cornering, as I'm steering with the throttle more than the wheel if I have my car set up to my liking
Clutches for fine tuning.
There isn't really a steady state variable to tune, I'm not sure what GPL does in that case. Intuition says you got an open if no there is no preload build into the mechanism to force the clutches together at least a little bit. But I am not in the know how exactly GPL diffs are set up internally.

#20 Pete Gaimari

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Posted Dec 01 2017 - 12:47 PM

The problem is.......just like the suspension settings. The real car settings don't transfer to GPL like we'd like them to. I think that holds true for the diff too.




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