Juan Anderson
My MECHANICAL ENGINEERING PROJECTS
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Custom Continuously Variable Transmission (CVT)
Blue Jay Racing SAE
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Background:
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CVT keeps the engine at peak power via the Primary that opens and closes sheaves through centrifugal force while the Secondary opens and closes sheaves through the load at the wheels
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CVT needs to shift quickly to allow the car to accelerate fast, but also climb steep hills
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CVT uses a rubber belt to transmit power. Power must be transferred efficiently to send max power to the wheels
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Knowledge and Skills Used:
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Solidworks
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Solidworks FEA
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ANSYS
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CES
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Result:
Previously, the team used an off-the-shelf CVT which was overbuilt for BAJA needs. The Primary (red-looking system), had a 40% weight reduction via using aluminum alloys such as 6061-T6 and 7075 T651 instead of steel alloys used in the off-the-shelf CVT. To minimize mass and maximize yield strength, a material index was created and plotted in CES, and aluminum was selected.
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The custom CVT also has unique flyweights. Flyweights in the primary dictate how much centrifugal force is turned into vertical clamping force to engage the CVT belt. As the flyweight rotates, it contacts a stationary roller. As the flyweight rotates, its CoG position changes, and therefore the centrifugal force changes. Also, as it rotates, the point of contact between the flyweight and the roller changes. All of these must be taken into account because it changes the FBD and loading of the flyweight.
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NASA JPL Europa Clipper Launch Vehicle Spring Preload GSE
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Background:
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Europa Clipper uses preloaded springs to separate the orbiter from the Falcon 9 launch vehicle
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Preload kickoff springs must have a pretension within +-0.75 lbs of the specified preload requirement
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Knowledge and Skills Used:
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NX
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GD&T
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Tolerance Stack Ups
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Storyboarding how to assemble and use a mechanical device
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Result:
Ground Support Equipment (GSE) was created to enclose the separation spring assembly, and accurately supply a specified preload. Afterward, the GSE with the spring assembly inside it would be put into a lathe, and the red Teflon bit on the spring assembly would be lathed down to the appropriate height. Additionally, an anti-rotation device was created to ensure that when the spring was preloaded through a bolt and nut, the spring would not rotate as well. Also, a spanner tool was created that held the spring assembly in place while the bolt connecting the assembly to the anti-rotation device was screwed into the assembly.
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BAJA SAE Continuously Variable Transmission (CVT) Case
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Objective:
Create a case for the CVT that is uses the least amount of material, requires less welding, easier to manufacture, and easier to remove than last year's design.
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Knowledge and Skills Used:
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SolidWorks assembly
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Proper mating - fully defined CAD
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Sheet metal bending
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Boss extrusion
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Extruded Cut
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Result:
I have gone through the first design and CAD phase. The CAD model for this first phase is shown below. This design uses latches instead of tabs which decreases the amount of welding our team has to do while also benefiting the component near the case - the CVT back plate. The latch design means no tabs for the back plate which decreases the weight of both the case and back plate. Currently, I am working on a second iteration of the case in CAD.
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Continuously Variable Transmission (CVT) Tuning
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Objective:
Tune the Gaged CVT to: quickly get shift output speed to max engine power RPM, increase power transfer efficiency, improve back shifting capabilities, keep engine on power curve, ensure CVT is close to ideal shift curve, CVT correct engagement speed
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Knowledge and Skills Used:
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Mechanical dissection process
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Mechanics
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Root Cause Analysis
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Mechanical Intuition
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Result:
There is no right or wrong way of tuning nor any manual to tell you step by step how to tune your specific CVT for your specific needs. In this environment, I have learned how to mechanically understand a problem through mechanical dissection, set goals for a project, quantify problems, and devise my next step to achieving my goals via mechanical reasoning and logic whether it be determining what spring to use in the primary or how weight to add to the primary's spider arm. Ultimately, this project has bolstered my "mechanical intuition."
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