Damper sensors usefulness

[DaveW]

The damper speed graphs are not wrong, though. I re-plotted them for you to see that higher speeds are reached but they still dont contributed much to the histogram...

Histograms can be quite misleading, especially if the vertical scale is linear. If the histogram is plotted log(occurrences) against (measurement)*abs(measurement), then the histogram becomes triangular when the disturbance has a "normal" (gaussian) distribution.

Some choose to use histograms to decide on rig test input levels, choosing (oddly) to neglect the extremities (large disturbances). I argue that small disturbances generally don't have a major impact on performance, whilst large disturbances frequently do, so it is more important to get the suspension set-up right for larger disturbances. Selecting out time histories from "critical" corners is an intelligent alternative, I believe, although histograms can look unconvincing in that case.

[speedsense]

Looking at it again.. that your dampers are working almost entirely at less than 2 in/s seems really odd.

Sorry, when I said that I had calibration issues I was referring to the track vs. post rig tests. What I question now its those graphs practical usefulness.

The damper speed graphs are not wrong, though. I re-plotted them for you to see that higher speeds are reached but they still dont contributed much to the histogram:



After continuing judging them, you should know more about the cars motion ratio, and maybe masses and rigidity, because remember they are damper and not wheel movement.

All the graphs are "full" lap graphs. This a problem when looking for shock trends and aero trends.

The FFT graph is for a braking + curve + beginning of acceleration (arround 8 seconds) for a single wheel.
The damper speed histogram is for a whole lap.
The DF level graph is only for a straight, I have re-plotted to graph erasing the first part as DaveW suggested and calculated the 2 front damper average displacement:

With Aero downforce, the same technique can be applied, with perticular speeds chosen for gates. It is best to analyze, with the car straight (no lateral, or braking long g) and keep the range within a few KM's for each target speed.
Without a pitot tube however, you could be spitting into the wind... (pun intended)

Right.

If you would, re-plot these (raw shock signal) with the fronts on top of each other, same for the rear, and include a lat g signal/steering overplot, throttle/ and either long G/brake pressure, along with it. If possible zoom to one right hand corner including (end of braking event, entry, apex, throttle on exit) then a similar one in a left hand corner.
In a more exact plotting, would be breaking each "element" up into three zooms, entry, apex, throttle on exit. Just to simply things a bit. This will help define, if it's a bleed problem, valving or in some cases pressure problems (cavitation? Hydraulic overpressure,some cases due to heat) with the rear shocks.
In comparisons of raw data vs a shock dyno or even a seven poster, the missing element is always the dyno "known" load input measurements, so assumptions have to be made in the reactions of the shocks. Though, when analyzing shock data, comparisons such as these can still extract vital info of how the shock transitions from low speed to high speed.
The "timing" of how quickly the shocks blow through the low speed (<48mm per sec) and enter high speed, as the car takes to a "static" set vs the input just before that supplied the velocity (steering, throttle etc.) It is necessary that you known the input that is causing the shock reaction and hence the need for driver info to be involved and slicing out the higher velocities of the bumps,curbs etc.

In my opinion, the rear shocks are spending so little time in low speed, and have frequent overshooting into high speed velocities, compared to the front low and high speeds. The rears appear to be under damped, especially in the low speed and even under damped, allowing almost twice the high speed velocities (can't tell as the graph is "clipped" at the high frequencies, though the number is almost twice) of the front (even considering the mass weight of the rear of the car)

IMHO

[Caito]

Hi hi. A bit OT:

Is it for argentina?
Which series?

Thanks!

[Belatti]

I have recalibrated the sensors to show wheel displacement (not damper displacement)

The results (front and rear) were averaged to show front and rear ride height.

I made the offset with the car standing still in the pits, includes the driver and fuel. So if you see a positive value we are in droop and negative in bump.

[Belatti]

@ J-Tom: motion ratio is not far away from 1 and you can see ride height doesnt go beyond 20mm

[DaveW]

Looks promising (except that I think you may have mis-quoted the sign convention). Do the derived aero values look more likely now?

[Belatti]

Ups, u r right Dave.
I have corrected what I wrote.

The derived aero values are still odd and I think that its not because the sensors or dampers but because the aero may not be working as expected.

(60Kg front and 20Kg at the back)

[speedsense]

Ups, u r right Dave.
I have corrected what I wrote.

The derived aero values are still odd and I think that its not because the sensors or dampers but because the aero may not be working as expected.

(60Kg front and 20Kg at the back)

The only place that the front and rear seem to come into unison, is at the throttle on, right at the exits of the corners. The last corner is the only place where momentarily the car's front and rear are at unison. (the on throttle run in a straight line the Front and rear are in unison, changing with speed back to forward rake.) The rest of the data looks like:
Rake induced differences front to rear either due to aero imbalance (more front aero) or higher percentage of spring stiffness (by appearances, the front) at one end. Generally speaking the rear is maintaining a higher rear height most of the time. To me this car would rotate on it's own in "off throttle instances" with lateral G applied.

In a purely basic point, there are two types of drivers in the world, one that likes the car to rotate for them and those that induce rotation into the car. Depending on which one you have is a completely opposite direction of setup.
By appearances, if the driver likes this car, he also likes to have the car rotate for him.

[Belatti]

By appearances, if the driver likes this car, he also likes to have the car rotate for him.

Definitively.

Wheel rates are arround 50Kg/cm for both ends. The problem is aero. ARB dont contribute much and are quite soft compared to spring rates.

[bill shoe]

The rest of the data looks like:
Rake induced differences front to rear either due to aero imbalance (more front aero) or higher percentage of spring stiffness (by appearances, the front) at one end. Generally speaking the rear is maintaining a higher rear height most of the time. To me this car would rotate on it's own in "off throttle instances" with lateral G applied.

speedsense, et al- I'm getting a lot out of reading this discussion.

speedsense- did you mean more spring stiffness at the REAR when you wrote "higher percentage of spring stiffness (by appearances, the front)"? I ask because I don't understand this point, to my eye the data looks opposite what you wrote.

[speedsense]

The rest of the data looks like:
Rake induced differences front to rear either due to aero imbalance (more front aero) or higher percentage of spring stiffness (by appearances, the front) at one end. Generally speaking the rear is maintaining a higher rear height most of the time. To me this car would rotate on it's own in "off throttle instances" with lateral G applied.

speedsense, et al- I'm getting a lot out of reading this discussion.

speedsense- did you mean more spring stiffness at the REAR when you wrote "higher percentage of spring stiffness (by appearances, the front)"? I ask because I don't understand this point, to my eye the data looks opposite what you wrote.

The movement is combined front and combined rear. The rear maintains a higher ride height especially in the corners, which implies less spring rate or less roll resistance. The accell squirts, if the car were stiffer in the rear wouldn't be below the straightway ride height of the front (with higher spring stiffness) they are. I'm assuming it is because of the springs being softer in the rear.

[Belatti]

To clarify all these, springs are the same at both ends, but motion ratio isn´t. That gives us a 10% softer wheel rate in the rear. As weight distribution is 57% rear, then the rear natural frec is way lower than at the front. That is what we have found it suits the different sizes (width) of front and rear tyres.

Its curious how, if front DF seems to be much more, in the last race a new driver (novice, not the one who likes the car to rotate for him) lost one of the front diffusers in an off track trip and he kept almost a similar peace for the next couple of laps.

Or this new kid likes less front DF or Im lost bigtime here.

[RH1300S]

His limit is in his head not the car............surely

[speedsense]

To clarify all these, springs are the same at both ends, but motion ratio isn´t. That gives us a 10% softer wheel rate in the rear. As weight distribution is 57% rear, then the rear natural frec is way lower than at the front. That is what we have found it suits the different sizes (width) of front and rear tyres.

Its curious how, if front DF seems to be much more, in the last race a new driver (novice, not the one who likes the car to rotate for him) lost one of the front diffusers in an off track trip and he kept almost a similar peace for the next couple of laps.

Or this new kid likes less front DF or Im lost bigtime here.

lost one of the front diffusers?????

Is this a sedan or open wheel car?

[Belatti]

Its the car from this thread (with some aero changes)

viewtopic.php?f=5&t=7895&start=0

Basic Rules: 670 Kg min with driver, 150HP measured to the wheel, 200Nm torque, static ride height 40mm and flat bottom between front and rear axes, 14" rims with 12" width tyres rear and 10" front.