The online racing simulator
VHPA v3.1.4 [updated 26/03/10]
(611 posts, started )
Finally the update Thanks.
#527 - Aid
nice update, live dumping graph is cool, i checked to-do-list and i'm really happy that you plan to add differential effect soon can't wait for that, beside that option i miss direct value imput a lot i'm not sure if i've seen it on your list though (maybe i've missed it somewhere) and other thing is i would enjoy in future releases is force display for 3 sections on tire contact patch LFS uses that would help a little to setup camber and pressures
great thing that u keep developing it, thanks!
Quote from Aid :nice update, live dumping graph is cool

The original damping graph was a mismash of the drop and live graphs, but when I fixed it to be just a drop, someone said the live part was actually useful, which is why I added it back in as a separate option. I'm glad others are finding it useful too.

Quote from Aid :i checked to-do-list and i'm really happy that you plan to add differential effect soon can't wait for that

At first it will only effect straight line acceleration, and thus only be noticeable for vehicles with a non laterally-central centre of mass, and will not work for viscous diffs (as they react to wheelspin, which simply isn't possible in VHPA). The effect on handling during cornering is much tougher to work out, so that will come at some later date.

Quote from Aid :beside that option i miss direct value imput a lot i'm not sure if i've seen it on your list though (maybe i've missed it somewhere)

It should be on my list. It's in my head as a feature to add, and has been requested in the past. One day...

Quote from Aid :and other thing is i would enjoy in future releases is force display for 3 sections on tire contact patch LFS uses that would help a little to setup camber and pressures

Camber effect on grip is currently not modelled, as it first needs the 2D kinematics of the suspension geometry to be modelled. I've got all that working in a spreadsheet, so that leaves 2 hurdles to overcome. 1) For geometry data to be exported from LFS, a feature request I've already put in to Scawen and 2) for the wheelbase and track widths to be dynamically changeable in VHPA (currently the mass is positioned relative to the wheels, rather than everything positioned relative to a fixed arbritrary point).
Quote from Bob Smith :The original damping graph was a mismash of the drop and live graphs, but when I fixed it to be just a drop, someone said the live part was actually useful, which is why I added it back in as a separate option. I'm glad others are finding it useful too.

Thanks for bringing back this feature keep up the great work.

Also optimized frequencies for level ride, depending on vehicle speed is really useful (it was for me anyway, now I deal with that mainly by damping espesialy if I don't want to alter greatly the spring frequencies). For a long time I did this calculations by hand. thank you thank you thank you . . . (the known flash)
BTW can anybody explain how the level ride stuff works?
Tried it some time ago on a FZR set with both axles at ~3 Hz (75;120), the level ride stuff says:

Front given rear: 2.42 Hz
Rear given front: 3.93 Hz

That's a split of 20 and 30% respectively. If I choose 'Stiffen' the rear spring end up at 205 N/mm with fronts still at 75.

So what am I missing here?
I don’t quite get how exactly stiffen and soften buttons work ether, except from the obvious.

As for the level ride optimized frequency differences between fron and rear, usually they are far from being ideal for handling especially if they are tuned for low speeds. (Try increasing the 108km/h or 30m/s vehicle speed from the “live settings” and recalculate the level ride frequencies.) But this level ride optimization might help you if you have to tune your setup in order to be as stable as possible hitting a bump in a certain-narrow speed range. (Also damping affects spring frequencies so you have to keep this in mind while tuning)
You always have to compromise things anyway.




Ok I'll try playing with it a bit. BTW is it correct to use the 'Remaining travel' figure when tuning the rake angle?
Quote from kaynd :I don’t quite get how exactly stiffen and soften buttons work ether, except from the obvious.

The rear level ride frequency is calculated based on the current front spring stiffness, and the front is based on the current rear. The stiffen option increases the stiffness of whichever end is less than the level ride frequency, so that ride is level. The soften option decreses the stiffness of whichever end is above the level ride frequency, while the third option tries to main the current overall stiffness (and thus, your roll stifness shouldn't change too much), which also giving level ride frequencies.
Yes this makes sense


Quote from NightShift : BTW is it correct to use the 'Remaining travel' figure when tuning the rake angle?

I don't realy understand what you mean by "rake angle".
But anyway I have seen that usualy the graphs showing the remaining suspention travel, reach the bottom a bit earlyer than what happens in LFS, espesialy if we talk about the remaining travel afected by roll angles. This might have to do with some suspention kinematics that as Bob has said, he hasn't modeld yet.
It's just the angle between the longitudinal axis of the car and a flat horizontal surface.

So if I wanted to have the car sitting perfectly horizontal, would I just adjust ride height until remaining travel is the same for both axles?
This depends on the suspension design of each car.
I used to aim for perfectly horizontal sitting cars, judging by the damping graphs but I found out this is meaningless if the suspension kinematics are not exactly the same in both front and rear axle.

Now I alter it mainly by feel or trying to approximately bring both front and rear roll centres to close levels.
Quote from kaynd :I used to aim for perfectly horizontal sitting cars,

Well AFAICT cars IRL are usually set up with some rake for several reasons, so having it flat is not what I'm looking forward to.

My point is if you can tell what ride height difference is equivalent to 0 rake given certain suspensions settings, then it'd be easy to find out the rake for whatever set you stumble upon.

That can be useful to compare completely different sets, especially when the axles are set up with different frequencies. The actual ride height value of course means nothing by itself, the ground clearance and thus rake depend on the actual spring stiffness and bump as well.

Quote from kaynd :Now I alter it mainly by feel or trying to approximately bring both front and rear roll centres to close levels.

What I find hard is to tell is how much oversteer/understeer is caused by rake alone, as it affects the amount of F/R weight transfer and also has aerodynamic effects especially at high speeds.

Sometimes even relatively small adjustments to ride height result in a remarkable change in handling.
Quote from NightShift :What I find hard is to tell is how much oversteer/understeer is caused by rake alone, as it affects the amount of F/R weight transfer and also has aerodynamic effects especially at high speeds.

Sometimes even relatively small adjustments to ride height result in a remarkable change in handling.

I know it's more semantics than anything else, but that's more due to shorter spring lenght etc. than rake angle really... Rake angle is just a result of your suspension settings, not the other way round - in itself it is pretty meaningless...
Maybe it would be better to have ground clearance for both axles, but I think VHPA can't calculate that
It hast to be class


Downloading....

I get that error :


Look at the pic below
Attached images
Error.jpg
cant use it because somethine .OCX isnt there
-
(ussbeethoven) DELETED by ussbeethoven
This tool is really something
A setup balanced according to VHPA handles in a very peculiar way. It's nor bad nor good, just different.

Is there some kind of tutorial on how to make best use of this tool?
I don't think anyone's made a detailed walkthrough for LFS cars, and I'm not knowledgeable enough to make one myself.

I use it mostly to find values quickly, usually I do something like this (let's say for XRG):
- pick front suspension natural frequency depending on track profile, between 2.2 and 2.5Hz for road cars
- select rear frequency a couple of tenths higher (I tend to aim for around 55% rear balance from springs)
- set dampers to between 65-100% critical rebound, to suit the track profile
- in live settings change values to maximum lateral suspension deflection at a speed common to the track I'm setting up for
- adjust ride height to as low as practical
- aim for about 1 deg/g roll angle with ARBs, so that the overall roll stiffness is 50/50, with around 2.7-3kN front stiffness
- in LFS, guesstimate pressures and camber; copy drivetrain, brakes, steering from some other set
- drive some laps and adjust rear ARB and dampers to fine tune handling
Though, for all I know I could be doing it very wrong
What's ARB?
Anti Roll Bar
Quote from spyxter :A setup balanced according to VHPA handles in a very peculiar way. It's nor bad nor good, just different.

People say that about my personality.

Quote from spyxter :Is there some kind of tutorial on how to make best use of this tool?

I am still intending to rewrite my setup guide to use this tool (I started over a year ago now, trying to do it on my lunch breaks, but I found an hour at a time was not enough to really get into it). Hopefully I'll finally find some time to get that up to scratch in the not too distant future.
Quote from spyxter :This tool is really something
A setup balanced according to VHPA handles in a very peculiar way. It's nor bad nor good, just different.

the only car I made an (almost) all green setup for, that actually works very good, is the XRR. It made a very predictable, even driftable setup, combined with a ~50% lock diff.

VHPA v3.1.4 [updated 26/03/10]
(611 posts, started )
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