CR21 assembly line covering the sprockets and mount.
Superseded by the Drivetrain Assembly grouping. Design Philosophies and Processes: Inherited from the DriveTrain subsystem design process: 1. Set gearing from the tractive force diagram, top speed and the event speeds actually seen (autocross top speed 69 mph, endurance 72 mph, gear-limited top speed 82 mph). 2. Design the carriers non-adjustable with a fixed pin, integrated with the engine pins, to reduce assembly complexity and failure points and remove the need for weld-on carrier mounts on the frame. 3. Analyse the carriers at acceleration and deceleration load cases with a 2.0 shock loading factor. CR26I LH carrier at 39 lb-ft with shock: 32.949 ksi peak von Mises, minimum FoS 1.211, 0.013 in average axial bearing bore deflection. RH carrier: 9.432 ksi, FoS 4.229, 0.001 in. 4. Set the half shaft length with a custom measuring jig so the tripod travel range cannot be exceeded, then groove for retaining rings. 5. Validate on track and by inspection of the wear surfaces after testing.
From the Sphinx wiki sprocket page. No car generation is attached to it. 1. Take the peak load case from engine torque through the chain. 2. Apply it tooth by tooth as bearing loads rather than as a single resultant. 3. Run FEA in 7075-T6 aluminium with the washer bolt holes fixed and a hinge along the inside of the flower petals. 4. Judge on deflection against the concentricity limit, not on stress alone. 5. Validate. Attaching strain gauges to the differential carriers is named as a way to check this family of parts against the model.
From the Sphinx wiki sprocket page: - Concentricity is the governing requirement. Deformation under peak loading must stay within 0.0125 in of the front sprocket centre, because movement off concentric raises frictional losses in the drivetrain. - The load case is set by peak engine torque arriving through the chain, so the sprocket cannot be sized independently of the gearing.
Sprocket FEA from the Sphinx wiki sprocket page. Bearing loads along the teeth, left to right: 1,246.13, 987.82, 482.71, 142.54 and 25.99 lbf. Fixed at the washer bolt holes, with a hinge along the inside of the flower petals. 7075-T6 aluminium, 73 ksi yield. The acceptance criterion is deflection rather than stress: maximum deformation must stay within 0.0125 in of the front sprocket centre at peak load.
From the cost report drawings: Alloy Steel (11T Front Sprocket Drawing); Steel (Front Sprocket).
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.
CAD mass, CR26I master assembly: 0.102 lb (0.046 kg). CG at X 77.06 in, Y -4.84 in, Z 10.77 in in vehicle coordinates. (CAD component: Sprocket) CAD mass, CR25 master assembly: 0.102 lb (0.046 kg). CG at X 77.06 in, Y -4.84 in, Z 10.77 in in vehicle coordinates. (CAD component: Sprocket) CAD mass, CR22 master assembly: 0.102 lb (0.046 kg). CG at X 77.06 in, Y -4.84 in, Z 10.77 in in vehicle coordinates. (CAD component: Sprocket) 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. 11T Front Sprocket Drawing (as drawn): 33.25R3.32, 25.40, 2.54, 65.38, 6.54, 13.39, 1.34, 5.77, 0.58 11T Front Sprocket (mm): 13.39, 66.05 Front Sprocket (as drawn): 20.32, 2.0333.25, R3.32, 13.39, 1.34, 5.77, 0.58 Source: SolidWorks mass model exports: CR22 (5 May 2024), CR25 (4 Jul 2025), CR26I (30 Jul 2025), CR26E (22 Mar 2026) | Cost report drawings: CR22/Powertrain/Design/X - Cost Report Drawings/Drivetrain Assembly/11T Front Sprocket Drawing.pdf; CR22/Powertrain/Design/X - Cost Report Drawings/Drivetrain Assembly/11T Front Sprocket.pdf; CR25/Powertrain/Design/Y - Cost Report Drawings/Drivetrain/Front Sprocket.pdf; CR26i/Powertrain - IC/Design/Y - Cost Report Drawings/Drivetrain/Front Sprocket.pdf and 1 more
Nothing in CrimsonStorage covers these yet.