Test­ing tech­nol­ogy

F1 Racing - - INSIDER -

Dur­ing post-sea­son test­ing in Abu Dhabi, we saw many strange ap­pendages on the cars that we don’t see at race week­ends. What were they?

On a race week­end, we can run ex­tra in­stru­ments and sen­sors on the Fri­day, but they must keep within the reg­u­lated bounds of body­work height, width and over­hang. Th­ese re­stric­tions don’t ap­ply in test­ing and so we can use trans­duc­ers that would oth­er­wise be il­le­gal.

The most vis­i­ble bits of test­ing kit you see are the aero­dy­namic rakes, which are used to un­der­stand the airow as it sheds off the body­work and forms the com­plex wake struc­tures that sur­round the car. Th­ese de­vices con­sist of an ar­ray of sen­sors called Kiel tubes, which are at­tached in a ma­trix fash­ion to a large assem­bly mounted on the car. Th­ese mea­sure the to­tal pres­sure of the air that they en­counter. Mea­sure­ment of the to­tal pres­sure is a means of de­riv­ing the air­speed, and by un­der­stand­ing the speed and di­rec­tion of the air around the car, we can un­der­stand the con­torted vor­tices that are fun­da­men­tal to per­for­mance.

How pre­cise are th­ese mea­sure­ments?

The very act of mea­sur­ing any­thing ac­tu­ally changes the state of what­ever you are try­ing to mea­sure, some­thing known as ‘The Ob­server Ef­fect’. Th­ese sen­sors are no ex­cep­tion. Their pres­ence af­fects the airow be­cause the air has to deect around them. Hence we need to bal­ance the de­sire for ac­cu­racy with the need to have low in­ter­fer­ence, which is achieved by hav­ing a min­i­mum num­ber of sen­sors.

Surely this is what the wind­tun­nel is for?

Yes it is, and a large part of what we do is to cor­re­late the ow struc­tures be­tween the wind­tun­nel and com­pu­ta­tional uid dy­nam­ics (CFD) to mea­sure­ments made at the track. In the wind­tun­nel we will mount scale ver­sions of th­ese sen­sor ar­rays and see if we get sim­i­lar re­sults to those mea­sured on the car.

What other un­usual sen­sors are used?

At the end of 2014, we tested the 2015 tyres and, as well as as­sess­ing the driv­ers' sub­jec­tive view of the ef­fect of the tyres on han­dling, we need to un­der­stand the true op­er­at­ing shape of the tyres. We do this by run­ning a laser scan­ning de­vice mounted to the up­right, which shines a laser line across the tyre side­wall. A cam­era mounted along­side it lms the laser line over a lap so we can mea­sure the deected shape of the tyre side­wall un­der true loaded con­di­tions.

Why is the tyre shape so im­por­tant?

If we were able to seal the gap be­tween the tyre and the dif­fuser we could nd enor­mous per­for­mance. This is what the pre-2014 ex­haust-blown dif­fusers were about. We were try­ing to use the high-en­ergy ex­haust ow to pro­duce an air cur­tain that sep­a­rated the dirty air em­a­nat­ing from the side of the tyre from the clean dif­fuser ow. They say you can never un­in­vent some­thing, and we still spend a lot of time try­ing to un­der­stand the ow elds in this re­gion. Fun­da­men­tal to this un­der­stand­ing is the ever-chang­ing shape of the tyre side­wall. Laser scan­ning shows us how this shape changes and lets us choose var­i­ous shapes to sim­u­late in wind­tun­nel and CFD test­ing.

Does the sin­gle ECU com­pro­mise your tests?

It can do, in that it has a nite amount of sen­sor in­puts and mem­ory, but dur­ing test­ing we of­ten run with an ad­di­tional data log­ging de­vice that lets us record ad­di­tional in­puts and sam­ple them at much higher fre­quency.

Does run­ning all this ex­tra in­stru­men­ta­tion present any dan­ger?

No. While we may not be sub­jected to FIA scru­ti­neer­ing dur­ing test­ing, we are all re­spon­si­ble en­gi­neers and will use our best en­deav­ours to en­sure that any­thing we put on the car, no mat­ter how tem­po­rary, is safe.

So is all this in­stru­men­ta­tion about cor­re­la­tion? Cor­re­la­tion of on-track re­sults with ex­per­i­men­tal tech­niques is vi­tal. Test­ing gives us a rare chance to com­pare our re­sults with real life. Do th­ese de­vices re­place the flow-viz fluid and even the wool tufts of days gone by? Largely, but there is a dif­fer­ence in that rakes mea­sure and vi­su­alise the ow once it has sep­a­rated from the sur­face, whereas ow-viz paint lets us pic­ture the ow while it is at­tached. Both are nec­es­sary to un­der­stand the full pic­ture.

Is there any­thing you can’t mea­sure? The hard­est things to mea­sure are down­force and drag. We have no di­rect means of mea­sur­ing drag at all, so de­rive it from mea­sur­ing en­gine torque at con­stant speed while try­ing to ac­count for the non-aero­dy­namic re­sis­tances, or by let­ting the ve­hi­cle coast from a given speed and then try­ing to work out the con­tri­bu­tion of aero­dy­namic drag to the re­sul­tant de­cel­er­a­tion.

It is equally hard to mea­sure down­force. We have load cells in the push and pull­rods, but th­ese don’t just mea­sure the down­force, which con­stantly in­creases with speed; they also mea­sure the weight trans­fer as­so­ci­ated with cor­ner­ing, brak­ing and ac­cel­er­a­tion. We try to sep­a­rate th­ese but it is not easy. The other prob­lem of mea­sur­ing down­force via chas­sis­mounted sen­sors is that a large amount of our to­tal load is gen­er­ated by the mul­ti­ple winglets on the brake ducts. Th­ese pro­duce load di­rectly on the up­right and tyre and hence are not seen by a load cell mounted on the pushrod.

Newspapers in English

Newspapers from Australia

© PressReader. All rights reserved.