Carry the rear sprocket on the differential and transmit torque into it.
A machined mount splined or bolted to the differential, with the sprocket bolted to it.
Maximum deformation of the differential must be less than or equal to 0.0125 in from the centre of the front sprocket at peak loading, so movement away from concentricity does not raise frictional losses.
Acceleration at 39 lb-ft with a 2.0 shock factor, 1,308 lb bearing load on each of six bolt holes: peak von Mises 42.019 ksi, minimum FoS 1.743. Without shock factor: 21.010 ksi, maximum resultant deflection 0.003 in. Boundary conditions: 'on cylindrical faces' on the splined bore constrained radially and rotationally, roller/slider on the circlip interface surface, bearing loads applied tangentially at each bolt hole.
Milled on the CNC.
7075-T6 aluminium. From the cost report drawings and CAD: From the cost report drawings: 7075 Aluminum (Rear Sprocket Mount Drawing).
Fault Vault, 2026-07-12, CR26I: chain-to-sprocket fit failure at the track, traced to milling stock or centre-to-centre analysis. Sprocket fit is now checked in the shop before testing.
CR20's sprocket mount was reused on CR25, saving the $371.25 cost of the stock. From the cost report drawings and CAD: 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. Rear Sprocket Mount Drawing (as drawn): 27.00, 2.70, 7.62, 0.76, 65.01, R6.50, 7.940.79, 17.441.74, 55.56, 5.56 Source: Cost report drawings: CR25/Powertrain/Design/Y - Cost Report Drawings/Drivetrain/Rear Sprocket Mount Drawing.pdf; CR26i/Powertrain - IC/Design/Y - Cost Report Drawings/Drivetrain/Rear Sprocket Mount Drawing.pdf; CR27i/.Powertrain/Design/Y - Cost Report Drawings/Drivetrain/Archive/Rear Sprocket Mount Drawing.pdf Quantity per car, as costed: 1
Nothing in CrimsonStorage covers these yet.