Electronic Theses and Dissertations (Masters)

Permanent URI for this collectionhttps://hdl.handle.net/10539/37972

Browse

Now showing 1 - 2 of 2

Aerodynamic Force Variation on a Trailing MotoGP Motorcycle in a Corner
(University of the Witwatersrand, Johannesburg, 2024) Shaw, Craig Byrne; Boer, Michael
Motorcycle racing is a popular form of motor racing. The MotoGP category produces exciting and competitive races due to motorcycles following each other so closely. This has led to significant aerodynamic advancements being made in the MotoGP category over the past decade. Motorcycles and riders often race within the wake of a leading motorcycle as a result of this competitive racing. Racing in the wake provides an advantage on a straight due to the reduced drag force. This allows for greater acceleration and an opportunity to overtake the leading motorcycle. The effect of the wake on a trailing motorcycle in a corner has not been explored in depth. This research was focused on the aerodynamic force variation on a trailing motorcycle in the wake of leading motorcycle. The optimal position for the trailing motorcycle to gain an advantage over the leading motorcycle was determined subsequently. This was achieved using Computational Fluid Dynamics (CFD). The geometry of the motorcycle was obtained using 3D scans of a 1/18th scale model 2018 Repsol Honda RC213V. The geometry of the rider was drawn using CAD. Initial CFD models were created simulating the motorcycle and rider in a straight line to compare to existing published data for validation. The CFD cornering methodology was developed by Queens University in association with Siemens. The method makes use of rotating reference frames. This simulates the motorcycle and rider cornering at a constant velocity around a constant radius corner. Models were created for a singular motorcycle and rider at varying lean angles between 40 and 60 degrees with matched velocities and corner radii. The aerodynamic forces of drag, lift and side force were analysed on the motorcycle and rider for each case. The trends for these forces were determined relative to the changing lean angles. The drag on the motorcycle and rider increased non-linearly as the lean angle increased with the side force following a similar trend. The lift on the motorcycle and rider also increased non-linearly as the lean angle increased. These same CFD models were recreated with a second motorcycle and rider following a leading motorcycle to determine the effect the wake had on the aerodynamic forces. The second motorcycle and rider were positioned 1 characteristic length behind the leading pair on the same racing line. The drag on the trailing motorcycle and rider decreased as the lean angle increased. The lift on the trailing motorcycle and rider followed a similar trend to the leading pair with it increasing as the lean angle increased and the side force fluctuates as the lean angle increased. This resulted in the trailing motorcycle having a negative allowable change in forward acceleration relative to the leading motorcycle at lean angles lower than 60 degrees. The optimal position for a trailing motorcycle in a corner was determined by positioning the motorcycle and rider on various racing lines and following distances behind the leading motorcycle and rider. This created a grid pattern of the tested trailing positions. Two smaller racing line radii, three larger racing line radii and three different following distances were tested. The optimal trailing position at a 50 degree lean angle was found to be 1 characteristic length behind and on a racing line 1 characteristic width larger than the leading motorcycle. This position resulted in a positive allowable change in forward acceleration relative to the leading motorcycle around a corner radius of 125.86 m at 38.36 m/s. This iii position was tested around another two corner radii of 75 m and 150 m. This resulted in a negative allowable change in forward acceleration of around the 75 m radius corner and a greatly improved positive change in forward acceleration around the 150 m radius corner. From these results it was concluded that this optimal position is only viable around larger radius corners. It was approximated that this optimal position provides the trailing motorcycle an advantage around corner with radii larger than 86.8 m.
Metallic Equivalent of Aircraft Landing Gear Using Composite Materials
(University of the Witwatersrand, Johannesburg, 2024) Kotze, Marius Hugo; Boer, Michael
There are two types of Light Sport Aircraft landing gear configuration. The taildragger and tricycle arrangement where the difference is specified by the position of the main landing gear. Shipment delay of the current Aluminium 7075 T6 landing gear has caused further delays in the manufacturing of the BushCat Light Sport Aircraft. Thus, a composite alternative was required which could be manufactured locally. The objective was to determine which locally available material was best suited as an alternative to the current Aluminium 7075 T6 design. This included estimation of the correct design loads acting on the BushCat aircraft main landing gear and to specify a composite alternative that could withstand these calculated design application loads. The loads that were used would be obtained from the ASTM F2245-14 regulations and EASA CS-23 amendments. The loads were validated by means of Finite Element Analysis and analytical calculations. Drop tests were also conducted by the company and image processing was used to compare the calculated deformations to the FEA results. This was used to validate the load and constraint applications in Ansys 2023 R2 software. The composite materials used for analysis were unidirectional epoxy e-glass wet layup and prepregs fibres. A coupon study was conducted on Aluminium 7075 T6 alloy and [0/90/90/0], [0/45/45/0], [0/90/45/0] layered unidirectional epoxy e-glass wet layup and prepreg coupons loaded under tension, compression, bending and torsion. The FEA results were validated using analytical calculations obtained from the Classical Lamination Theory. It was concluded that the unidirectional epoxy e-glass prepreg coupons were best suited as an alternative as better results in withstanding the applied load applications were obtained. The prepreg fibres also contained a lower void content in comparison to the wet layup fibres, thus increasing the fatigue life of the composite laminate as well as reducing the moisture absorption. The final composite landing gear was analysed using the Puck-failure criterion and it was found that after analysis and modifications were conducted, the newly designed composite landing gear could withstand the applied loads during limit load and ultimate load conditions without any fibre or inter-fibre failure in the strut of the landing gear. It was found that, failure had occurred in one of the fibre plies near the bolted regions of the axle section during ultimate (emergency) landing conditions and was thus concluded that the composite landing gear should still be inspected when attempting emergency landing at higher load conditions at an aircraft maximum take-off weight of 600 kg. The final composite landing gear design after modifications was 4.613 kg heavier than the Aluminium 7075 T6 landing gear. With regards to manufacturing the final composite landing gear a vacuum bagging process should be followed where the final vacuum bagging assembly containing the composite layup of the landing gear should be placed inside an oven or autoclave to start the curing process. Once the composite landing gear is cured, it could be machined into its final shape were non-destructive techniques such as ultrasound of thermography should be used to inspect the final composite landing gear for any air of volatile compounds withing the laminate. Static and dynamic destructive testing should also be used to validate if the final composite landing gear can withstand all landing conditions aircraft maximum weight without any fibre failure or delamination occurring.