Nissan 200SX driftiauto tagavedrustuse projekteerimine

Enamik projekti eesmärke said täideti etteseatud piirangute sees. Kinemaatika analüüs näitas, et vedrustuse kinemaatika tuli projekteerida täiesti erinevaks mõõdetust ja see andis ka vabaduse kasutada erinevaid ühendusi hoobade jaoks käänmiku pool, mis vähendas oluliselt vedrustamata massi. Uus käänmik ja õõtshoovad kaaluvad kokku 4,9kg, mis on märkimisväärne tulemus, kuna enne kaalusid need detailid kokku 9,8kg. Vedrustuse kinemaatikas vähendati põikikalde muutumust kere rullamise ja vertikaalliikumise suhtes, vähendati parasiitroolimist ja optimeeriti rullamiskeskme kõrgust. Uus vedrustuse kinemaatika muudab auto juhitavuse neutraalseks ja suurendab rehvi sidestust teekattega sellepärast, et kontakt pindala teekattega on nüüd suurem ja sirgema muutuskõveraga Parasiitroolimise nullimine 50mm vedrustuse kokkuliikumisel ja 40mm lahkuliikumisel aitab auto juhitavust stabiiliseerida. Anti-squat parameeter vähenes 0,8%, selle kõver on nüüd lineaarsem, mis tagab ka lineaarsema rehvide haardejõu. Pidurisüsteem käänmiku küljes tuleb asendada sama auto uuema mudeli (1994-1999 Nissan 200SX) omaga, et säiliks seisupidur, mis on driftiautole oluline lihtsustamaks külgsuunalise läbilibisemise alustamist ja juhtimist. Projekti eelarve läks küll lõhki 207 euroga, kuid seda ei olnud palju sellise eesmärgiga projekti puhul, mida lahendatakse esmakordselt. Kõige aeganõudvam osa projektist oli käänmiku disaini optimeerimine, kuid tulemused õigustavad investeeritud aega. Sarnast toodet on võimalik osta, kuid projekt oli kindlasti väärt ettevõtmist, kuna juurdeõpitud teadmiste hulk on suur, raha säästeti üle 1000 € võrreldes valmis asja ostmisega. Projekti võib minu arvates lugeda õnnestunuks.

In conclusion all the goals set for the project were achieved. The final design of the upright weighs less than three kilograms, the exact weight is 2.543 kg. The new upright does however require a bent upper control arm to clear the drive shaft, which increases its construction and design complexity. The chosen method for constructing the upright is welding together laser cut and CNC formed S355 sheetmetal. It is designed so that there is no need for a welding fixture, but can be bolted together with the suspension links’ bolts and proprietary offset spacers and pieces assembled with dovetail joints, which are integrated into their design. Double shear connections were used for mounting suspension arms and the shock absorber to the upright. The original upright uses a steel shaft pressed into the upright for mounting the shock absorber, which was also considered to be used when conceiving the design for the new upright. The double shear way of mounting the shock absorber was much easier to implement into the upright, more cost effective and lighter. The steel shaft would have been difficult to mount as the shock absorber is not mounted straight in any axis relative to the upright. The new kinematics resulted in a drastically reduced bumpsteer – the maximum toe in under suspension compression was reduced from 5,47 millimeters to 1,72. Bumpsteer is close to 0mm at 50mm suspension bump and 40mm droop. Cambergain was also reduced. The need for reducing camber gain was to increase traction and longitudinal acceleration by increasing the tyre contact patch area with the ground. This was achieved by optimising the height of lateral control arms. Roll center height was raised at the same time. Raising the rear roll center improved geometric weight transfer. A major change was changing the suspension linkage type from multilink (virtual upper a-arm, lower a-arm and toe link) to to double wishbone with a toe link. This resulted in a slightdecrease of anti-squat. The static value decreased from 25.8% to 25% and the curve is less steep resulting in more linear traction. Overall the project is a success, despite the budget increase of 207 €. A lot of new information was obtained through the process of this project. The most challenging part was the design optimisation of the new rear suspension upright, but the result is well worth the effort. Around 1000 € was saved on developing the new rear suspension instead of buying an aftermarket kit and results can be sure of as more detailed information is available for wheel aligment.