Crimson Racing Wiki

Bell Crank - 200 lb/in Wheel Rate

Subteam: SuspensionSubsystem: BellcranksAssembly: Rear Indirect Actuation AssemblyCars: CR25, CR26I

Purpose

Translate rear pushrod motion into damper and spring displacement at the motion ratio that gives a 200 lb/in wheel rate.

Function

Same architecture as the front crank plus a fourth connection point for the rear ARB drop link.

Design Process

Moved from 6061 to 7075-T6 because aerodynamic loads rose. Achieved both the deflection goal and the allowable stress.

Analysis

Single plate FEA at 0.19 in thickness: FoS 3.54. Rear motion ratio 1.000 designed; FARO measurement found 0.989 rear left and 0.987 rear right. Maximum wheel rate change at Ks = 200 lb/in, r = 1.929 in/in, giving Kw = 53.554 lb/in.

Full Material List

Al 7075-T6, 0.19 in plate.

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.

Properties

CR26I rear bellcrank 177 g both plates against CR25's 182 g. Total bellcrank weight change across the car -10 g (0.02 lb), -3.9%. Quantity per car, as costed: 2

Still to document

Nothing in CrimsonStorage covers these yet.