All F1 cars are forced up to a minimum weight (mass) by the regulations. In 2012 the minimum weight of the complete car without fuel but “…with the driver wearing his complete racing apparel…” had to be no less than 640kg (already heaver than some years before). For 2015 that number is 702 kg mainly to make it possible for the smaller teams to fit the energy recovery systems the cars run as part of the new powertrains – and still be on or close to minimum weight. That difference in starting mass makes the cars about 1.7 seconds a lap slower around an “average” Formula 1 race track. Not that interesting in itself, but what are the main mechanisms at play?
All that mass has to be accelerated by the powertrain – so the cars accelerate more slowly once there is enough grip to put the power that’s available on the ground. Engineers will often talk of “power to weight ratio” – because in the early phase of having enough grip this determines acceleration. As the acceleration is slower with a heavier car of the same power, you have to accelerate for longer (more time) to cover the same distance so you use more fuel. F1 (and Sports) cars are limited in how much fuel you can use so you have a double negative (you have to reduce power a bit or you’ll use too much fuel compared to having a lighter car). Top speed will only be a little down on the longest straights because at high speed the drag, effectively, becomes dominant.
Braking power is, to all intents and purposes, unlimited and, in fact, a heavier ERS car will recover more kinetic energy than a light one in the ERS braking phase – because it has more kinetic energy.
None the less, some time is lost in braking a heavier race car (we’ll come to that soon).
Probably the biggest single loss of time though is in the corners (depends on the layout of the racetrack). Two main mechanisms work together here to disadvantage the heavier car. Firstly and most importantly is the aerodynamics of the car. A race car creates downforce from the air it passes through which pulls (mainly as most of the force is created under the car) and pushes the car onto the ground. Once higher speeds are reached this starts to have a significant effect. If we add 640 kg of downforce to a 640 kg car then the tyres will see exactly 2 times the weight of the car at that speed. If the car weight is changed to 702 kg then the ratio is 1.9. That is the main mechanism that makes a light car with downforce faster around a corner than a heavy car. It is only the mass (of the car) that has to be “accelerated” – not the load created by downforce.
This picture is not a Formula 1 car but the concept is the same – it applies to any car with downforce.
The tyres too have their role in making a heavier car slower around a race track. It’s worth stating that tyres (written as “tires” in some parts of the English speaking world) have improved dramatically for passenger cars over the last 50 years. However for both road cars and race cars there are some common trends. Rubber effectively becomes harder as it is put under more load. This also translates to less grip (all other things being equal such as tyre temperature and condition etc).
I don’t own this picture and I don’t know who does – if it’s you, THANKS - let me know.
So in case you’re still thinking about why braking distances are longer for a heavier car it is simply because the tyre friction is slightly lower because the load is heavier (assuming the same tyres).
In racing categories, normally, a minimum weight is imposed for reasons of safety and equality. Reducing weight is so beneficial that teams would – and used to – take big risks with structural integrity and component stiffness to achieve lower weight. Even with minimum weights imposed also materials we can use are limited. For example we cannot use materials with more than a certain specific stiffness (these materials tend to cost mega money and also can be brittle). We can’t use depleted uranium for ballast (denser than Tungsten but tends to have some residual radioactivity which is not good – especially for the driver).
A trend can be seen on road cars of the last 40 years where, for reasons of safety, cars have tended to become stronger and more crashworthy but also significantly heavier. For example, “From 1980 to 2004 … the attributes of a Honda Accord have changed significantly. Weight has increased by over 50 percent, while horsepower has nearly tripled.” Between 1999 and 2005 the Accord’s NHTSA Safety Rating also increased from four-star to five-star. Despite this tyre development has resulted in improved grip and cornering speeds / braking distances. However that is a development story for someone else to tell.
While we’re talking tyres I think it is appropriate to mention…. Wider tyres on road cars work (and the difference is not huge) because the load per unit area (road contact area) is reduced so the grip is slightly higher due to the properties of rubber. That applies in the dry and it applies in the wet as well from all the studies I’ve seen – but only up to the point of aquaplaning. Aquaplaning happens when the tyres are no longer able to cut through water on the road to make contact with the road itself. On ice, narrower tyres are better, Modern winter tyres seem to have made the “problem” of wide tyres on ice less severe but it is still true. With homologated tyre sizes you can’t do too much about it these days with road cars but it used to be possible and very beneficial.
After years of optimisation for weight, the F1 teams have developed incredibly light-weight but effective safety structures including a protective monocoque and light energy-absorbing structures, which are needed to pass various crash tests. Of course, given the extreme nature of the sport, safety is also being evolved generally in F1, in the drive to keep human beings as safe as possible. The sport is of course inherently dangerous, but is constantly evolving to make it better. Safety structures is one area where racing can be contributing to normal passenger cars.
This is reblogged from Willem's LinkedIn account with his permission: https://www.linkedin.com/pulse/what-did-i-do-formula-1-willem-toet?trk=mp-reader-card
For UK followers of the blog the following opportunities exist for anyone interested in Willem's work...
2 Dec 18:30 to 20:30 plus Oxford - Free public lecture - F1 Performance, Design and (maily) Aerodynamics see toet.eventbrite.co.uk There will be some entertaining stories and time for questions. Free, book early. This is the one to aim for if you work as it starts at 6:30 pm for 7 pm talk start point. Organised by the IMechE. Some refreshments available from 6:30 pm. Questions and discussion due to finish at 20:30 but I'm happy to discuss any questions you may have for a bit longer. I will bring additional material so we have the potential to illustrate answers to questions.
4 Dec - 13:00 - 17:00 approx. Southampton University (Building 45 room 0045 which should be on the ground floor and is a large lecture theater - see site map here https://www.southampton.ac.uk/assets/sharepoint/groupsite/Administration/SitePublisher-document-store/Documents/About/visit/highfield_accessible_routes.pdf). Guests welcome and free. First lecture is similar to the one on the 2nd - Formula 1 performance, design, & aerodynamics. This does not require specialist knowledge. Would be suitable for higher school pupils, motorsport enthusiasts, engineering students and engineers. After the first lecture we then focus more on the use of CFD to develop a race car (aimed at university students but anyone using CFD may find it interesting) and how new aerodynamic testing restrictions (in the FiA regulations) are changing the approach F1 teams are taking to aerodynamic development. There will also be discussions with the Formula Student team which are probably not open to all.
Magari ya F1 yanapaswa kuwa na uzito wa chini zaidi ya kiwango cha kawaida. Kwa mfano, uzito wa gari kamili bila mafuta, lakini na dereva amevaa mavazi yake kamili ya mashindano, haipaswi kuwa chini ya kilo 640 (yaani, ni nzito kuliko miaka kadhaa iliyopita). Kwa mwaka 2015, idadi hiyo ni 702 kg, hasa ili kuwezesha timu ndogo za kuingiza mifumo ya kurudisha nishati ambayo magari yanaendesha kama sehemu ya mashine mpya za kuendesha gari na bado kuwa kwenye au karibu na uzito wa chini. Tofauti hiyo katika uzito wa kuanzia hufanya magari kuwa polepole kwa sekunde 1.7 kwa mzunguko kuzunguka uwanja wa mbio wa "wastani" wa Fomula 1. Si kwamba ya kuvutia yenyewe, lakini ni nini utaratibu kuu katika kucheza? Wingi huo wote lazima uharakishwe na gari la kuendesha gari <unk> kwa hivyo magari huongeza kasi polepole mara tu kuna kukamata vya kutosha kuweka nguvu inayopatikana ardhini. Wahandisi mara nyingi huzungumza juu ya "uwezo kwa uwiano wa uzito" kwa sababu katika awamu ya mapema ya kuwa na kukamata vya kutosha hii huamua kasi. Kwa sababu gari lenye nguvu nyingi na nguvu nyingi linashambulia polepole, ni lazima uendelee kuharakisha kwa muda mrefu ili kukamilisha umbali uleule, na hivyo kutumia mafuta mengi. F1 (na michezo) magari ni mdogo katika kiasi cha mafuta unaweza kutumia hivyo una mara mbili hasi (unahitaji kupunguza nguvu kidogo au wewe kutumia mafuta mengi sana ikilinganishwa na kuwa na gari nyepesi). Kasi ya juu itakuwa tu kidogo chini juu ya straights mrefu kwa sababu katika kasi ya juu kukandamiza, kwa ufanisi, inakuwa kutawala. Kwa kweli, gari nzito zaidi la ERS litapata nishati zaidi ya kinetic kuliko moja nyepesi katika awamu ya kusimamisha ya ERS kwa sababu ina nishati zaidi ya kinetic. Hata hivyo, muda fulani hupotezwa katika kuzima gari zito zaidi la mashindano (tutakuja hapo karibuni). Labda hasara kubwa ya wakati ingawa ni katika pembe (inategemea mpangilio wa racetrack). Utaratibu kuu mbili hufanya kazi pamoja hapa ili kudhuru gari nzito zaidi. Kwanza na muhimu zaidi ni aerodynamics ya gari. Gari la mbio huunda downforce kutoka hewa inayopita ambayo huvuta (haswa kama nguvu nyingi huundwa chini ya gari) na kushinikiza gari kwenye ardhi. Mara baada ya kasi ya juu ni kufikiwa hii huanza kuwa na athari kubwa. Ikiwa unashikilia gari lenye uzito wa kilo 640 kwa nguvu ya chini, basi magurudumu ya gari yako yatakuwa na uzito mara mbili ya uzito wa gari kwa kasi hiyo. Ikiwa uzito wa gari umebadilishwa kuwa 702 kg, basi uwiano ni 1.9. Hiyo ndiyo utaratibu kuu unaofanya gari nyepesi lenye nguvu ya chini liwe na mwendo wa haraka zaidi kuzunguka kona kuliko gari nzito. Ni tu wingi (wa gari) kwamba ina kuwa <unk>accelerated<unk> <unk> si mzigo kuundwa na downforce. Picha hii si gari la Formula 1 lakini dhana ni sawa <unk> inatumika kwa gari lolote na downforce. Magurudumu pia yana fungu lake katika kufanya gari zito liwe la polepole zaidi kwenye uwanja wa mashindano. Ni thamani ya kusema kwamba tairi (kuandikwa kama <unk> tairi<unk> katika sehemu fulani za ulimwengu wa kuzungumza Kiingereza) wameboresha sana kwa ajili ya magari ya abiria zaidi ya miaka 50 iliyopita. Hata hivyo kwa ajili ya magari ya barabara na magari ya mashindano kuna baadhi ya mwenendo wa kawaida. Kwa kweli, mpira huwa mgumu zaidi unapokuwa chini ya mzigo mkubwa zaidi. Hii pia hutafsiriwa kwa grip chini (vitu vingine vyote kuwa sawa kama vile joto tairi na hali nk). Mimi si mmiliki wa picha hii na sijui ni nani <unk> kama ni wewe, asante - nijulishe. Kwa hivyo ikiwa bado unafikiria kwa nini umbali wa breki ni mrefu kwa gari nzito ni kwa sababu tu msuguano wa tairi ni mdogo kidogo kwa sababu mzigo ni mzito (kufikiria tairi sawa). Katika makundi ya mashindano, kwa kawaida, uzito wa chini huwekwa kwa sababu za usalama na usawa. Kupunguza uzito ni manufaa sana kwamba timu ingekuwa <unk> na kutumika <unk> kuchukua hatari kubwa na uadilifu wa muundo na sehemu rigidity kufikia uzito wa chini. Hata kwa uzito wa chini uliowekwa pia vifaa tunavyoweza kutumia ni vichache. Kwa mfano, hatuwezi kutumia vifaa vyenye ugumu zaidi ya kiwango fulani (vitu hivi huwa na gharama kubwa na pia vinaweza kuwa dhaifu). Hatuwezi kutumia uranium iliyopunguzwa kwa ballast (ngumu kuliko Tungsten lakini huwa na baadhi ya radioactivity mabaki ambayo si nzuri <unk> hasa kwa dereva). Mwelekeo unaweza kuonekana kwenye magari ya barabara ya miaka 40 iliyopita ambapo, kwa sababu za usalama, magari yamekuwa na nguvu zaidi na zaidi ya kugonga lakini pia nzito zaidi. Kwa mfano, <unk>Kutoka 1980 hadi 2004... sifa za Honda Accord zimebadilika kwa kiasi kikubwa. Kwa mfano, wakati wa mwaka wa 1999 hadi 2005, kiwango cha usalama cha Accord kiliongezeka kutoka nyota nne hadi tano. Pamoja na maendeleo haya ya tairi imesababisha kuboresha kukamata na kuruka kasi braking umbali. Hata hivyo hiyo ni hadithi ya maendeleo kwa mtu mwingine kueleza. Wakati sisi ni kuzungumza tairi nadhani ni sahihi kutaja.... Kwa sababu ya kupanuka kwa taya, tofauti ya ukubwa wa gari na gari la barabarani ni kubwa, kwa sababu mzigo kwa eneo la kitengo (eneo la mawasiliano ya barabara) hupunguzwa, kwa hivyo kukamata ni juu kidogo kwa sababu ya mali ya mpira. Hiyo inatumika katika kavu na inatumika katika mvua pia kutoka kwa masomo yote nimeona <unk> lakini tu hadi hatua ya aquaplaning. Aquaplaning hutokea wakati tairi hazina uwezo wa kukata maji kwenye barabara ili kuwasiliana na barabara yenyewe. Kwenye barafu, tairi nyembamba ni bora, tairi za kisasa za majira ya baridi kali zinaonekana kuwa zimefanya "tatizo" la tairi pana kwenye barafu kuwa kali zaidi lakini bado ni kweli. Pamoja na ukubwa homologated tairi huwezi kufanya sana kuhusu hilo siku hizi na magari ya barabara lakini kutumika kuwa inawezekana na manufaa sana. Baada ya miaka ya kuboresha uzito, timu za F1 zimetengeneza miundo ya usalama yenye uzito mdogo lakini yenye ufanisi, ikiwa ni pamoja na monocoque ya kinga na miundo nyepesi ya kunyonya nishati, ambayo inahitajika kupitisha vipimo mbalimbali vya ajali. "Kwa kweli, kwa kuzingatia asili ya michezo ya nje, usalama pia unabadilika kwa ujumla katika F1, katika juhudi za kuweka wanadamu salama iwezekanavyo. """ Bila shaka, mchezo huo ni hatari, lakini unabadilika-badilika daima ili uwe bora zaidi. Miundo ya usalama ni eneo moja ambapo mashindano yanaweza kuchangia magari ya abiria ya kawaida. "Kama ilivyoelezwa katika makala ya wiki hii, ""Mfano wa Utafiti wa Utafiti wa Utafiti wa Utafiti wa Utafiti wa Utafiti wa Utafiti wa Utafiti wa Utafiti wa Utafiti wa Utafiti wa Utafiti wa Utafiti wa Utafiti wa Utafiti wa Utafiti wa Utafiti wa Utafiti wa Utafiti wa Utafiti wa Utafiti wa Utafiti wa Utafiti wa Utafiti wa Utafiti wa Utafiti wa Utafiti wa Utafiti wa Utafiti wa Utafiti wa Utafiti.""" Bure, kitabu mapema. Hii ni moja ya lengo kwa ajili ya kama wewe kazi kama huanza saa 6:30 jioni kwa 7 jioni kuzungumza hatua ya kuanza. Imeandaliwa na IMechE. Vyakula vya kupumzika vinapatikana kuanzia saa 6:30 jioni. Maswali na majadiliano yanapaswa kumaliza saa 20:30 lakini ninafurahi kujadili maswali yoyote ambayo unaweza kuwa nayo kwa muda mrefu. Nitawaletea vifaa vya ziada ili tuwe na uwezo wa kuelezea majibu ya maswali. 4 Dec - 13:00 - 17:00 karibu Chuo Kikuu cha Southampton (Jengo 45 chumba 0045 ambayo inapaswa kuwa kwenye ghorofa ya chini na ni ukumbi mkubwa wa hotuba - angalia ramani ya tovuti hapa https: www.southampton.ac.uk assetssharepoint.groupsite.admin.site.documentstore.documents.about.visithighfield.accessible.routes.pdf). Wageni wanakaribishwa na ni bure. Mkutano wa kwanza ni sawa na moja juu ya 2 - Formula 1 utendaji, kubuni, na aerodynamics. Hilo halihitaji ujuzi wa pekee. Ingekuwa inafaa kwa wanafunzi wa shule ya juu, enthusiasts motorsport, wanafunzi wa uhandisi na wahandisi. Baada ya hotuba ya kwanza, tutazungumzia zaidi juu ya matumizi ya CFD kuendeleza gari la mbio (iliyoelekezwa kwa wanafunzi wa chuo kikuu lakini mtu yeyote anayetumia CFD anaweza kuiona kuwa ya kuvutia) na jinsi vikwazo vipya vya majaribio ya aerodynamic (katika kanuni za FIA) vinabadilisha mbinu timu za F1 zinachukua kwa maendeleo ya aerodynamic. Pia kutakuwa na majadiliano na timu ya Formula Mwanafunzi ambayo pengine si wazi kwa wote.