www.engineeringnews.co.nz 23 “It soon became apparent that understanding the complex interactions between the positions and sizing of all of the components comprising the rear wheel suspension system and how they affected the strength and position of the rear wheel shock waves was not going to be an easy task,” says Ben Evans. “We therefore set about trying to simplify and parameterise the geometry at the rear of the car focussing on the variations that we felt were the critical ones: rear wheel track and the position of the delta leading edge. With help from MathWorks (providers of the MATLAB software package) we implemented a technique known as ‘Design of Experiments’ (DoE). This allows us to vary known parameters within the design space to find the optimum solutions - things like what combination of the parameters we were varying would give us the minimum rear car lift and drag.” Ultimately, the output from this DoE study prescribed the way that the rear of Bloodhound SSC looks today. “More importantly, it told us that we needed to minimise the rear wheel track width as far as possible (in our case, as far as we deemed it safe from a roll stability point of view),” says Mr Evans. “It also gave us the precise shape of the rear body of the car and the size and position of the crucial delta strut.” One thing both APU systems will require is cooling, using the water tanks on either side of the monocoque. However, as there is no need for a cooled air intake for the electric option, the system for the electric alternative could be much simpler. Incorporating an electric motor in the car still presents challenges, but ones which the team see as an exciting opportunity to explore the boundaries of what an electric motor can achieve. Not only will it have to perform in very extreme physical conditions, including high temperatures, intense vibrations and desert dust, but it will also have to deliver its power in around 20 seconds, which is in marked contrast to how it would be expected to perform in a road car. The one hour turn-around time will require either very rapid battery recharging or a highly efficient way to swap out the battery units. Experience with changing battery packs in F1 would indicate that considerable special design investigation is critical. “We’re convinced that the technology is now at a stage that will allow us to use an electric solution and we are keen to work with companies in this field to explore what’s available and how it can be integrated into Bloodhound SSC,” says Mr Chapman. The high speed runs at Hakskeen Pan in South Africa are very weather dependent. “We need the lakebed to flood every year,” says Mr Chapman. “But not in their winter - this can happen as early as November or as late as January (South African Southern Hemisphere summer) the lake then dries off by April/May and sometimes a few showers can mess things up. We need to clear the track by hand as just under the surface is a light layer of shale and beds of rock underneath that. If we used earthmoving equipment we would churn up the underlying shale and bring more stones to the surface. When we clear the top level by hand this gives us a great smooth-running surface.” Land speed records involve complex engineering solutions, but often the vagaries of the weather and the ability to produce a viable lakebed running surface by hand can scupper even the best laid plans. “ W E ’ R E C O N V I N C E D T H AT T H E T E C H N O L O G Y I S N O W AT A S TA G E T H AT W I L L A L L O W U S T O U S E A N E L E C T R I C S O L U T I O N "
EN-Feb18-eMag
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