Mount the differential to the chassis and hold the rear sprocket in plane with the front sprocket.
Keeping the sprockets in plane is what prevents excessive chain and sprocket wear or failure. A non-adjustable, fixed pin design reduces assembly complexity and points of failure; integrating the mounting with the engine pins reduced manufacturing effort to a single setup on the mill, removed the need for weld-on carrier mounts on the frame, and removed the need for tension adjustment at the carrier to maintain allowable chain slack.
No part-specific design process is documented. The DriveTrain subsystem design process applies: 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 CR22B Drivetrain Design Report: the system must fit and be serviceable within the rear subframe of the chassis; the half shafts must stay within their working range through the entire travel of the suspension to avoid pullout; the system must withstand the maximum engine torque of the previous car (about 35.3 lb-ft) with a 25% factor of safety to cover increases (about 44.1 lb-ft); and it must be manufactured or sourced within the intended manufacturing cycle.
Acceleration case at 39 lb-ft engine torque with a 2.0 shock loading factor, 6,040 lbf bearing load: peak von Mises 32.949 ksi, minimum FoS 1.211. Without the shock factor: 16.434 ksi, average axial deflection of the bearing bore 0.013 in. Deceleration at -11 lb-ft, 859.6 lbf: peak von Mises 5.42 ksi. Boundary conditions: 'on cylindrical faces' constraint on engine pin bores constrained radially only, roller/slider on surfaces that interact with the engine, bearing load applied in the chain force direction on half the bearing surface. Standard mesh, 0.045 in global size, 0.002 in tolerance. From the design reports and one-pagers: CR22 ANSYS/SolidWorks static analysis: hinge fixtures on the inside diameter of both pin holes; a 3,024.07 lb force applied in the acceleration direction defined by the acceleration coordinate system in the CAD; a 26.76 lb sideways force on the back of the carrier split across the six bolt holes. Mesh quality: over 90% of elements with aspect ratio under 5, over 90% with Jacobian ratio under 10 and all under 40. Result: maximum stress 23.628 ksi against a 39.885 ksi yield for 6061-T6, minimum factor of safety 1.688, maximum displacement 0.04624 in. See the CR26I entry above for the later analysis with the 2.0 shock loading factor.
Single setup on the CNC mill. From the design reports and one-pagers: No workholding required. Clamp the stock to the table on top of an aluminium plate and follow the CAM. CAM programs live in Fusion 360.
6061 Aluminium-T6.
The carriers had to be remade seven times in one previous year. Simulations that do not converge were called out in knowledge transfer as an unresolved analysis problem.
Nothing in CrimsonStorage covers these yet.