Shock Adjustments Slow or Fast?

Rfn Owner

When it comes to shocks in rFactor we have slow and fast bump, then slow and fast rebound. What if the particular vehicle being made as a mod doesn't really use slow and fast settings? I am working on some cars for rFactor that don't exactly use slow and fast. Chassis manufacturers and shock manufacturers just generally use the terms bump and rebound especially in guides on how to adjust for track conditions. If the particular type of vehicle only uses general bump and rebound adjustments what would that mean in rFactor.

I am at a loss on this subject, could it be considered just slow bump and rebound, or would both slow and fast be linked together so slow and fast bump would always be the same, or something entirely different.

Exapmle: If the car is loose on entry and the chassis builder suggests decreasing front compression to tighten the car.

In rFactor terms since the real car does not specifically use slow and fast compression as different settings would this in rFactor mean the car should use slow compression settings or fast compression settings or should both slow and fast change together? And if both should change together is there a way to link them together so slow and fast are always the same?
 
I guess there are different ways to do that. I think the easiest is to set same numbers on hdv file parameters:

For example:
SlowBumpRange=(3000, 200, 5)
SlowBumpSetting=3
FastBumpRange=(3000, 200, 5)
FastBumpSetting=3

But then you still must use same garage setting for both slow and fast dampers.

Other way:
Damper force depends on piston velocity. There is a threshold to define at which velocity start to apply fast damping. Threshold is set by 'BumpStage2' and 'ReboundStage2' parameters.
I guess that if you set very high threshold values then your piston will never reach the velocity required to apply fast parameters. Then you only should worry about slow settings, and ignore fast settings which very rarely would have an effect.
However, i didn't try it, i am not sure which collateral effects could be applied for high threshold values.
 
If the shocks(or dampers) only have a single setting rather than fast and slow, then you can set this in the .hdv file as follows under the suspension section:

[SUSPENSION]
ApplySlowToFastDampers=1
LimitFastDampers=1

Now the shocks will only have one setting for both fast and slow.

Early shocks typically found in the 1950's and 1960's would have been this way.
 
Just for information, one way adjustable dampers (bump and rebound adjusted together) were introduced in the late 50s. Two way adjustable (bump and rebound separately adjustable) dampers were introduced in the mid 60s though most F1 teams continued to use one way adjustable dampers.

The introduction of gas dampers (monotube) in the mid 60s set back user adjustability, and there were no user adjustable gas dampers until the 1980s. 2 way adjustable gas dampers were not introduced until 1983. 4 way adjustment was not introduced until around 1990.
 
I seem to be having another issue. Does anyone know at what speed rFactor measures shock pressures. After using real life data I had an issue where the car just wanted to bounce up and down because of the rebound being too high. The shock manufacturer I got tech data off of uses a speed of 2 inches per second, the fastest speed they use is 26 inches per second. I used the values from each speed and the values from 2 inches per second worked best, but their highest rebound valving is 7 and is rated at 185 pounds per inch of pressure.

185 pound/inch should equal about 32398.464475 Newton/Metre

This high of a rebound rate causes the car to bounce up and down almost slightly, but very quickly as if I am always running over washboard bumps when I am not. I took a look at cars provided by ISI in rFactor and none of them are using rates this high. For rFactor to use such low rates would they have been measured at a much lower speed and using a single unit, so instead of 2 in/sec possibly 1 cm/sec? I assumed it might be 1 cm/sec since rfactor uses metric and I believe centimeter would be closest to an inch.
 
rFactor dampers produce a force (in Newtons) rather than a pressure. The force is calculated by multiplying the damper value by the wheel's/damper's vertical velocity.

e.g.

SlowBumpRange=(3000, 200, 5)
SlowBumpSetting=3

the damper value would be 3000 + 3x200 = 3600

velocity is measured in meters/sec.
 
Technically the units for dampers are N/m/s, Force/Speed. Yes, the gas pressure in the canister has influence, but this is generally not the way you adjust a damper. The pressure is considered to be static, and optimum in rf. If you want to adjust pressure, you'll need to use upgrades to alter the value and stepping for the range parameter. You are better off not bothering.

Your conversion of pounds per inch is correct but you are missing something for it to be useful (units of pressure is pounds per square inch).

Which mfg/shock did you pull data from?
 
Thanks for the information. I was looking KONI Shocks, the cars I am working on use the 30 Series shocks from KONI. I've been trying to wrap my head around this for a while. The diagram I was looking at is on KONI's website at http://www.koniracing.com/images/File/30force.pdf

I do have each shock in the upgrades since the cars I am working on are only allowed to run these in real life.
Front
30-7325
30-7436
30-7647
Rear
30-9325
30-9436

The amount of force between each rebound setting changes and since rFactor is a static number between each step I did deviate slightly from their numbers. As an example here is one of the corners of the cars upgrade code that did not cause issues:

UpgradeLevel="KONI 30-7325"
{
Description="KONI 30-7325 shock bump valving 3 and rebound valving 2-5"

HDV=[FRONTLEFT]
HDV=BumpStage2=0.6604
HDV=ReboundStage2=-0.6604
HDV=SlowBumpRange=(3502.5367, 0.0, 1)
HDV=SlowBumpSetting=1
HDV=FastBumpRange=(3502.5367, 0.0, 1)
HDV=FastBumpSetting=1
HDV=SlowReboundRange=(11383.244275, 3502.5367, 4)
HDV=SlowReboundSetting=2
HDV=FastReboundRange=(11383.244275, 3502.5367, 4)
HDV=FastReboundSetting=2
}




The particular shock that is causing the issue is the 30-7647 front shocks. I have it setup like this:

UpgradeLevel="KONI 30-7647"
{
Description="KONI 30-7647 shock bump valving 6 and rebound valving 4-7"

HDV=[FRONTLEFT]
HDV=BumpStage2=0.6604
HDV=ReboundStage2=-0.6604
HDV=SlowBumpRange=(19263.95185, 0.0, 1)
HDV=SlowBumpSetting=1
HDV=FastBumpRange=(19263.95185, 0.0, 1)
HDV=FastBumpSetting=1
HDV=SlowReboundRange=(20139.586025, 4086.29281666666, 4)
HDV=SlowReboundSetting=2
HDV=FastReboundRange=(20139.586025, 4086.29281666666, 4)
HDV=FastReboundSetting=2
}
 
Your unit conversion is off.
For the 30-7325,
Bump, 60lbs/10.32"/s= 1018.18 N/m/s
Rebound Pos 0=4751.50328 N/m/s
Rebound Pos 1=5515.13774 N/m/s
Rebound Pos 2=6618.16529 N/m/s
Rebound Pos 3=8315.13074 N/m/s

For the 30-7647 my suggestion is to graph Force vs Speed. Your unit conversion still is off, AND it looks like the valving is such that there is falloff between slow and fast bump speeds. You are going to have to interpret the graph, pick the knee point speed, then fit your rate lines. On top of that, it is likely that your force chart has been converted from metric and rounded. The numbers are a bit too nice, so converting back and rounding again is likely going to introduce a large margin for error (which might not be such a bad thing, as it gives you more wiggle room to fit the line).
 
Thanks lordpantsington. I really messed up that conversion big time. I thought it used the same as units as springs. By doing that I essentially made the number more than 3 times higher than they should be. I guess that part of the learning process. I asked around a bit within the oval racing community as the mod I'm making are oval track cars and this topic was not very well known so this should give us some new stuff to implement. Once again thank you for taking the time to assist me with this information.
 
You're welcome. It was a learning process for all modders, once you get through the learning curve it'll become second nature. What you are doing with the various damper types in the upgrades is exactly what you would do for pressure variation. The difficulty is finding data of what happens exactly to the rates for each damper type. I doubt that is something you'll find, unless you've a dyno and those specific shocks at your disposal.
 
That pdf I had linked is the best info I could get and that is right from the shock manufacturer. The great thing for me is the particular series of cars that is for specifically states in their rule book they only allow those models for competition so It does help me narrow my research to only one brand and one series of shocks. I am trying to incorporate real life data as much as possible and having the rule book for the series does help, but as you said it's a learning process for all modders. I already did some work on the shocks now and conducted a quick test and the issues I was having seems to be resolved. I will continue to keep plugging away.
 
As Lordpantsingtson says, slow and fast bump rates seem to be very different in most of cases (for example for the '30 7325'). Then i would suggest to use lower value for FastBumpRange base parameter. Perhaps half of the SlowBumpRange base could help to fit real curve if you use the right speed threshold value.
 
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