F1 Rules Clarification: What is the reference plane?

[marcush.]

as i read it ,you got reference plane and stepplane which is geometric -not the real surface .
all measurements are in reference to the ref plane .
and from this imaginary plane you got a +/-5mm leeway.depending on where you put your reference plane you can possibly get almost 10mm degree of freedom from 330 mm behind the front wheels till midaxle rear .
You could use this tolerance degree of freedom also to angle the stepplane ,as the same tolerance is allowed ther is no word requiring the surfaces of the car to be paralell ..there is only talk of the (imaginary) planes ...but of course its only 10mm total you got.

[747heavy]

agree, but you can´t angle the "step plane" (imaginary plane), what you can do is haveing said tolerances in the parts (floor) which have to be on this plane.
So you could angle the floor slightly
It will depend, on how they interpret the bold part in the rules- IMO:

3.12.6 To help overcome any possible manufacturing problems, and not to permit any design which may contravene any part of these regulations, dimensional tolerances are permitted on bodywork situated between a point lying 330mm behind the front wheel centre line and the rear wheel centre line.

[marcush.]

agree, but you can´t angle the "step plane" (imaginary plane), what you can do is haveing said tolerances in the parts (floor) which have to be on this plane.
So you could angle the floor slightly
It will depend, on how they interpret the bold part in the rules- IMO:

3.12.6 To help overcome any possible manufacturing problems, and not to permit any design which may contravene any part of these regulations, dimensional tolerances are permitted on bodywork situated between a point lying 330mm behind the front wheel centre line and the rear wheel centre line.

exactly ..her we got the fine line of what is a lack of precision or a design contravening the regs...From my side I´d think they have some crown in their bottom surfacehis will make for incredibly difficult measurement in the field.
I´m pretty sure the teams have duplicate measuring devices at home to meke sure they cannot get cought.

[Richard]

Thanks marcrush, you and n_smikle have mentioned tolerances before. It is a badly written tolerance rule, it allows cumulative tolerances so the step can range from 60 to 40.

They should use +10/-0 tolerance on the step itself to ensure that any manufacturing tolerance makes the step bigger, hence detrimental to performance.


Going back to my diagram, we can see there are several components. I have assumed a kink roughly 1000m behind the plank edge, and 1000 to the front wing (it is actually 1090)

1 - The first part (in black) exploits the tolerances to drop the front wing by 10mm, this pivots about the kink in the plank. The wing is now

2 - The second (in red) shows that adding rake will pivot about the leading edge of the plank.

3 - Add in 25 mm of wing deflection (not shown) based on aero load being 2.5 times test load reported by Ferrari at Spa, and the wing is only 25mm off the ground. Say that increases to 3.5 factor for a high downforce track gives 35mm, so the wing is 15mm above the ground.

4 - Add in 5mm of tray deflection to steepen the kink (not shown) assuming same as test load, then the wing is now 10 mm off the floor.

Items 1 to 3 are merely playing with tolerances and simple deflection under load. You would think all teams adopted these steps routinely. Item 4 requires something clever to make the tray to lift up when moving.



Edit to tidy up diagram and correct numbers

[747heavy]

I think this is why the rules say, the lowest point of the floor/part which holds the plank.
So if you lower your car, onto the "set up/scrutineering table" you may touch with your two lowest points (in longitudinal direction), this defines the reference plane for your car then, and all dimensions is relation to it, need to comply with the rules.
But I would agree, that the reference plane, due to the allowed tolerences you mention, from car to car can be slightly different to the ground plane.

ermmm.just can´t find this piece ..would you please give a reference?
looking up the regs again it seems al measurement is taken in relation to the reference plane so the lleway is not 20 but just 10mm ,youre not allowed to add up the tolerances there.Of course the rule says :for manufacturing inaccuracies...so you need precise imprecision there..

O.K. it does not say it in this words, but if you see how they measure in relatio to the reference plane (similar as in DTM), that is what it boils down to - IMHO.
And that not all parts of the floor are on the reference plane, I took from this paragraph in the rules.

3.13 Skid block :
3.13.1 Beneath the surface formed by all parts lying on the reference plane, a rectangular skid block, with a 50mm radius (+/-2mm) on each front corner, must be fitted. This skid block may comprise more than one piece but must...........

[marcush.]

cool graph .. thanks!
the tolerance is a very important thing here and in effect considerable degree of freedom between stepplane and reference plane by this as well as the mentioned possibility to build a "accidential hump/ badly manufactured part" in the 1000mm area to allow for the excessive lowering of the car front...its quite simple to think out and very very difficult to do in the season ..now with the homologated tubs.

[747heavy]

in regards to the measurement method..
If the lower the car onto the carbon set up plate ( and I think this is what they do)
the two or three (if we account for lateral plane)lowest points of the floor will form the "reference plane" which now is the set up plate surface, from which all the other measurements are taken.

Another possibility would be to project a plane via a rotating laser beam.
AFAIK, Champcar used such a system for their measurements

[Richard]

So if you lower your car, onto the "set up/scrutineering table" you may touch with your two lowest points (in longitudinal direction), this defines the reference plane for your car then, and all dimensions is relation to it, need to comply with the rules.

That is the sensible method, it would result in a position tolerance of +10/-0 for a manufacturing tolerance of +5/-5.

However, the rules don't say that, they only reference to an arbitrary datum. Your suggestion is that they reference to the as built bottom of the car.

[marcush.]

in regards to the measurement method..
If the lower the car onto the carbon set up plate ( and I think this is what they do)
the two or three (if we account for lateral plane)lowest points of the floor will form the "reference plane" which now is the set up plate surface, from which all the other measurements are taken.

Another possibility would be to project a plane via a rotating laser beam.
AFAIK, Champcar used such a system for their measurements

I used the champcar laser beam setup when working for the damper company .anything less than 1mm is pure guesswork.
I´d say you need a faro arm or equivalent to acquire useful data.there was a guy who did something with a landscape measuring tool that was also very precise ah and btw:

http://metrology.leica-geosystems.com/d ... tm?id=1035

sorry just german ..but they claim to have optised their tunnelwork with it as the thing can see all points of the undertray and car at speed and they have highest precision in adjusting rideheights etc without need to touch the car to
prove valid adjustments.

[scarbs]

may be this wil help....

http://scarbsf1.files.wordpress.com/201 ... litter.jpg

[747heavy]

Yeap, agree but it´s horses for courses.
The champcar system was/is good enough for a +/- 5 mm tolerance - IMHO, and we talk +10years ago.

Even the RBR report is from 2005, so most likely things have move forward in this area, and other teams probably use similar systems in the meantime.

On the other hand, if you see some of the FIA scrutineeing photos, they seem to measure with a tape measure as well. So +/- 0.5 mm at best.

[marcush.]

Yeap, agree but it´s horses for courses.
The champcar system was/is good enough for a +/- 5 mm tolerance - IMHO, and we talk +10years ago.

Even the RBR report is from 2005, so most likely things have move forward in this area, and other teams probably use similar systems in the meantime.

I´m sure they all do it was just to show what kind of precision they are able to measure = produce in a world that is content with +/-5mm ...thats two galaxies apart...

[Richard]

On the other hand, if you see some of the FIA scrutineeing photos, they seem to measure with a tape measure as well. So +/- 0.5 mm at best.

I saw a glimpse of the scrutineers on the TV coverage a few races ago. They use template cut outs to check compliance with the body work rules. The bit I saw was testing the side pods/cockpit. They had a goal post arrangement sat on the inspection table that had the cut outs of required profile. They then placed that over the car in front of the sidepods and dragged it back to the airbox. Wonderfully simple.

[747heavy]

yes, this is very likely, sounds sensible to me

DTM does (used to do, I left in 2004) the same - it´s quick and easy.

The last time I saw the F1 scrutineering bay/table (in 2002/Hungary) they also had an optical reference system in front and above the car.

I`m not 100% sure for what or how they use it, maybe just a laser plane which projects car centreline and outer extremities - dunno for sure

You can still see the system on the photos above, you see the three opening in the box on the frame above the plate, there is another similar bax behind the car.

[marcush.]

On the other hand, if you see some of the FIA scrutineeing photos, they seem to measure with a tape measure as well. So +/- 0.5 mm at best.

I saw a glimpse of the scrutineers on the TV coverage a few races ago. They use template cut outs to check compliance with the body work rules. The bit I saw was testing the side pods/cockpit. They had a goal post arrangement sat on the inspection table that had the cut outs of required profile. They then placed that over the car in front of the sidepods and dragged it back to the airbox. Wonderfully simple.

Yes at least the FIA is still in the good ol times...still ou need to find a ways to define the reference plane from where youdo all your measuring .its not like you could say that putting the tub flat on the rig would equal the reference plane -5mm the only reference point would be total height of the car wich is also regulated .
Infamously almost all measurements in the regs have no tolerance to them ...so wow can you go out with a tapemeasure ,when you ask for absolute precision? or isthere somewhere a standard tolerance of x mm written?