House the front upper ball joint, separately from the upright.
Keeping the upper ball joint in its own part means the upright does not have to be machined to reach it, which cuts machining time on the larger and more complex part.
Material chosen for low cost and stock availability. Optimised for manufacturing: straight tabs decrease machining time. From the design reports and one-pagers: The top mount exists because the offset angle at which the upper A-arm connects to the upright is not feasible to machine into the upright itself. It is an angled offset, and it is also the camber adjustment: steel camber shims go between the top mount and the upright. Design considerations: packaging and mounting within the upright design, with the top mount geometry aligning exactly with the designated geometry point; strength, since the top mount should be as fixed as possible relative to the upright to minimise total assembly deflection; and camber change capability.
Reaction load applied as a remote force from the upper ball joint pivot location to the bolt faces. The bolted connection to the upright has a radial reaction; the upright mating face cannot separate but can slide against the opposite face. Analysed in both cornering and braking. From the design reports and one-pagers: The load case is simple. The mounting wall of the top mount is a roller/slider fixture, the two bolt holes are elastic supports with the spring rate of the steel bolts, and the force is applied at the centre of the tab as three separate vectors along each axis. The input forces are the coordinate-direction loads for the upper A-arm to upright connection, which the geometry designer issues once geometry is finalised.
Machined on the CNC mill. Machining time decreased by 63% (1.5 hours) against CR22. From the design reports and one-pagers: This is a part with angles that are not multiples of 90 degrees, so the manufacturing route has to be considered during design. The CR22 iteration required 5 setups and 2 workholdings, and took roughly 25 man hours of troubleshooting before all four top mounts were produced in 10 hours. The report is blunt that it should not have taken nearly that long, and that the process was not kept in mind during design; reducing top mount manufacturing time was set as an explicit goal for the following year. CR26I achieved a 63% reduction by using straight tabs.
Al 6061-T6. From the design reports and one-pagers: Keep the top mount material the same as the upright, because the upright and top mount assembly is treated as one solid object in analysis and that assumption only holds if the materials match. From the cost report drawings and CAD: From the cost report drawings: Al-6061T6 (CR25_SUS_TopMountFront).
None recorded. This part has no entry in Knowledge_Transfer/Issue Logging/Fault Vault.xlsx, in either Issue Log.xlsx, in CR22/Issue Tracking/Shakedown 7-15-23.xlsx, or in any design review issue list found in CrimsonStorage or Box.
Improved reliability and workability against CR22.
Weighed mass: 37.9 g (0.084 lb) (recorded as: FL Top Mount). Weighed mass: 37.6 g (0.083 lb) (recorded as: FR Top Mount). Measured mass, as built: CR25 37.9 g (0.084 lb) (weighed as: FL Top Mount). Measured mass, as built: CR25 37.6 g (0.083 lb) (weighed as: FR Top Mount). Dimensions called out on the cost report drawings. These are the figures printed on the drawing, not a labelled specification; open the drawing itself for what each one refers to. CR25_SUS_TopMountFront (as drawn): 21.97, 2.20, 12.70, R1.27, 25.40, 2.54, 57.15, 5.72, 42.42, 4.24 Source: Subteam weight books: CR25/Suspension/Validation/Component Weight.xlsx | CR26e Weight Tracker.xlsx, Final IRL Weights (weighed, not CAD) | Cost report drawings: CR25/Suspension/Management-Comp/Cost Report/Drawings/Sus Shocks - Front Upright Assembly/CR25_SUS_TopMountFront.pdf Quantity per car, as costed: 2
Nothing in CrimsonStorage covers these yet.