Crimson Racing Wiki

Barrel Nuts

Subteam: SuspensionSubsystem: BrakesAssembly: Balance BarCars: CR21, CR22, CR25, CR26I

Purpose

Terminate the balance bar in the clevises.

Function

Suspension hardware is standardised across every point on the car: NAS-620x National Aerospace Standard bolts, MS21042-x Military Standard jet nuts, and FK alloy steel rod ends. Bolt size at every joint is determined against shear yield and axial yield with a minimum factor of safety of 1.8, and minimum torque is calculated from the required clamping force rather than taken from a table.

Design Process

No part-specific design process is documented. The Brakes subsystem design process applies: 1. Set tire loads at the maximum airspeed seen (90 mph): rear 291.60 lbf at max acceleration, front 454.21 lbf under braking, 427.97 lbf cornering. 2. Sweep master cylinder bore combinations against required pedal force and achievable deceleration, then select. 3. Run a transient thermal simulation of the rotor for a single braking event (2.4 s, 260 C initial, 90 W/m^2-K film coefficient, 0.8 emissivity, 25,375 W heat flux front) and import that thermal load into a static structural run (1.84 g deceleration, 12 MPa pad pressure, 707 N-m moment) with cylindrical and frictionless supports. 4. Compare candidate materials on peak and low temperature and on minimum factor of safety. 4340 gave 741.2 C high, 344.5 C low and FoS 3.6438, against Class 40 cast iron at 490.5 C, 256.5 C and FoS 2.1622. 5. Validate with brake rotor temperature sensors on all four corners and compare measured against calculated.

Manufacturing Process

Purchased to specification.

Full Material List

Steel.

Reoccuring issues

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.

Still to document

Nothing in CrimsonStorage covers these yet.