CR22 front bellcrank at a 380 lb/in wheel rate.
CR22 goals for the bellcranks, from the Bellcranks Design Report: reduce manufacturing time by fifty percent by changing from one-piece to two-piece bellcranks so the profile can be waterjet; reduce weight by fifteen percent through the two-piece construction using less material; switch from bearings to bushings, which saves at least a pound on the car; and validate bellcrank deflection under load, which the report notes had been designed for in the past "without much thought or validation".
Use the given geometrical connection points. Use the pre-existing bellcrank chassis bung and nut. Reduce manufacturing time. Reduce weight. Use dry lube bushings rather than ball bearings. Rules: V.3.1.4 fasteners in the suspension system are Critical Fasteners under T.8.2. V.3.1.5 all spherical rod ends and spherical bearings on suspension and steering must be either mounted in double shear, or captured by a screw or bolt head or washer with an outside diameter larger than the spherical bearing housing inside diameter.
The greatest force the front bellcranks see is under maximum braking load. The FEA fixes the bung hole and applies pullrod and damper forces at their respective connection points. Because only one plate of the two-piece system is analysed, the forces are halved. The governing value is maximum displacement, which came out at about 0.0068 in. That is higher than previous bellcranks, which typically ran about 0.005 in, and the report justifies it explicitly on much lower system weight and decreased manufacturing time.
The first step is the waterjet: outer and inner profiles are cut and the connection holes roughed with about 0.1 in left to go. This is very fast because all front bellcranks come from one 0.19 in aluminium sheet and all rear bellcranks from 0.125 in sheet. The CNC mill then finishes the connection holes, varying the stock to leave in each hole until a snug fit is achieved in both the bolt holes and the bung hole for the bushing. Snug means no wobble or compliance when the bolt is inserted, but not impossible to insert. The bushing is press fit into the bellcrank.
Aluminium.
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.
CR22 two front bellcrank plates weigh 0.24 lb against the previous 0.366 lb. Two rear plates weigh 0.2 lb, slightly heavier than the previous rear design, with the bushing weight saving making up for it. Quantity per car, as costed: 2
Nothing in CrimsonStorage covers these yet.