Best way of meassuring downforce at race car

[godlameroso]

You think laser will be more accurate option than strain guage or load cell?

If road has even small bump of 2mm, laser will think downforce is increased,isnt laser good option only for very flat road like race track is?

So you take time average. You do a lap, and plot average ride height, make aero adjustment, plot average ride height. If average ride height decreases over a lap, you can be confident you increased downforce.

Yes but track time is very expensive,so I must test aerodynamic modifaction at road first.
If road is not 100% flat or it has small stones on it ,laser will read wrong values..
Isnt it?

Then you pick a stretch of road, and take an average there. Find a nice 3km stretch of deserted road and test. I live in a crowded city, and I know if I wait for the right time and go to the right place, I can find a nice stretch of open road to test on.

[Uwe]

So you take time average. You do a lap, and plot average ride height, make aero adjustment, plot average ride height. If average ride height decreases over a lap, you can be confident you increased downforce.

Yes but track time is very expensive,so I must test aerodynamic modifaction at road first.
If road is not 100% flat or it has small stones on it ,laser will read wrong values..
Isnt it?

Then you pick a stretch of road, and take an average there. Find a nice 3km stretch of deserted road and test. I live in a crowded city, and I know if I wait for the right time and go to the right place, I can find a nice stretch of open road to test on.

Do you know reason why F1 dont use load cell or strain guages?

[godlameroso]

Yes but track time is very expensive,so I must test aerodynamic modifaction at road first.
If road is not 100% flat or it has small stones on it ,laser will read wrong values..
Isnt it?

Then you pick a stretch of road, and take an average there. Find a nice 3km stretch of deserted road and test. I live in a crowded city, and I know if I wait for the right time and go to the right place, I can find a nice stretch of open road to test on.

Do you know reason why F1 dont use load cell or strain guages?

They do, F1 can afford redundancies.

[Jolle]

Without collecting tons of data to cross reference or see a pattern it’s impossible to see changes of a few Nm. A bit if wind, turbulence, a kilometer faster, a bump, etc will all have more influence then what you can measure in a few runs.

The best way might be trail and error on track with a GPS measuring apex speed (and feel the balance as a driver).

[Greg Locock]

laser measures distance, load cell measures force, strain gage measures strain and hence stress and hence force. Laser is not measuring anything directly force related.

[Uwe]

Without collecting tons of data to cross reference or see a pattern it’s impossible to see changes of a few Nm. A bit if wind, turbulence, a kilometer faster, a bump, etc will all have more influence then what you can measure in a few runs.

The best way might be trail and error on track with a GPS measuring apex speed (and feel the balance as a driver).

yes this is big probelm when you dont have wind tunnel,for aero-modifications wind tunnel is much better option than real-test.

[Greg Locock]

But the results from different wind tunnels will give you different estimates , as will results from the road.

[Dr. Acula]

But the results from different wind tunnels will give you different estimates , as will results from the road.

Yes, that's why you try to stick with one windtunnel you know. Many F1 teams have their own Windtunnel or rent always the same so they get reliable and more importently repeatable results.

Btw. Doesn't matter what you use, a laser or a strain gauge, you have to declutter the signal anyway to get any useful information out of it. If you drive over a bumb, a strain gauge will also show a deflection. If the recording resolution is high enough, you might see the vibration the moving parts of the car cause.
The strain gauge has the advantage to be easy to zero in. Under the premise that the stretch of the part you install the gauge behaves linear to the force applied (which in most cases it will) you only need 2 refrencepoints to define the whole system. With a laser measuring basically the ground clearance, it won't be that simple because the relative geometry change of the moving suspension can cause a slithly none linear behaviour when it comes to ground clearance relative to applied downforce.

[Uwe]

But the results from different wind tunnels will give you different estimates , as will results from the road.

Yes, that's why you try to stick with one windtunnel you know. Many F1 teams have their own Windtunnel or rent always the same so they get reliable and more importently repeatable results.

Btw. Doesn't matter what you use, a laser or a strain gauge, you have to declutter the signal anyway to get any useful information out of it. If you drive over a bumb, a strain gauge will also show a deflection. If the recording resolution is high enough, you might see the vibration the moving parts of the car cause.

If laser is not pointed at wheel path,laser will read road imprefection,even car is not moving up or down, ,road is not flat,so in that sense it is the worst solution,

[Big Tea]

But the results from different wind tunnels will give you different estimates , as will results from the road.

Yes, that's why you try to stick with one windtunnel you know. Many F1 teams have their own Windtunnel or rent always the same so they get reliable and more importently repeatable results.

Btw. Doesn't matter what you use, a laser or a strain gauge, you have to declutter the signal anyway to get any useful information out of it. If you drive over a bumb, a strain gauge will also show a deflection. If the recording resolution is high enough, you might see the vibration the moving parts of the car cause.

If laser is not pointed at wheel path,laser will read road imprefection,even car is not moving up or down, ,road is not flat,so in that sense it is the worst solution,

If you are using plotting software remove out-layers more than say 1mm from the previous reading, depending on sampling rate. Downforce would (should) not act in steps but an arc or straight line.

( Although I freely admit I am as far from an expert it is possible to get and still be breathing)

[Dr. Acula]

If laser is not pointed at wheel path,laser will read road imprefection,even car is not moving up or down, ,road is not flat,so in that sense it is the worst solution,

If the car drives over the curbs what will a strain gauge show installed on the push/pull rod? That's what i mean with decluttering. Aerodynamic downforce does not suddenly change significantly from one second to another, at least as long as the car stays on the track. So you average out (signal dampening/Noise reduction) all the sudden changes you record, because you know they are false/not relevant. Really in that regard a laser and a strain gauge wouldn't be to different.
In case of the curbs, a laser would even deliver better results because it would be installed at the sprung mass of the car.