CR21 assembly line covering the differential.
Superseded by the Drivetrain Assembly grouping from CR22 onward. 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 differential and carrier pages. No car generation is attached to them. 1. Settle spool against Drexler on data. Compare lap times and corner exit speeds for the open differential and for the Drexler at several preload levels including fully locked. If the fully locked car is not noticeably slower, weigh the cost of keeping a spool and the team workload that comes with it. 2. Locate the carriers so the differential comes out easily, because preload tuning needs it out. Both frame tabs and engine pins through the carriers have been used. 3. Run FEA on the design against the acceleration and engine braking load cases below. 4. Judge the result on deflection, not stress alone: maximum deformation must stay within 0.0125 in of the front sprocket centre at peak load. 5. Validate against the car. Strain gauges on the differential carriers are named as the way to check the model.
From the Sphinx wiki differential and carrier pages: - Serviceability. The differential has to be easily removable so preload can be tuned. - No chain tensioner. The carriers were remade seven times in one year for want of one, and a tensioner is the fix the page asks for. - FEA convergence. Carrier simulations have a history of not converging, and finding out why is left as an open item. - Weight. No reduction target is set, because the loading and fatigue analysis that would justify one has not been done. The stated target is no weight increase.
FEA load cases from the Sphinx wiki differential and carrier pages. Spool: 8,533 lbf torque on the flower petal design, coming from chain loading. Fixed at the bearing supports on both bearing surfaces for the carriers. 7075-T6 aluminium, 73 ksi yield. Master carrier, 1.5 G acceleration: 3,024 lbf radial plus 26.76 lbf axial from the bearing holders. Master carrier, 0.4 G engine braking: 920 lbf radial plus the same 26.76 lbf axial. 6061-T6 aluminium, 39 ksi yield. Slave carrier, same material, yield and axial load: 632 lbf radial at 1.5 G acceleration and 189 lbf radial at 0.4 G engine braking. Boundary conditions on all four carrier cases: fixed hinge at the mounting points, roller or slider at the engine pin and frame contact areas. Acceptance is on deflection. Maximum deformation under peak load must be within 0.0125 in of the front sprocket centre, so that the assembly does not move off concentric and raise frictional losses.
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.
From the Sphinx wiki differential and carrier pages: - A chain tensioner. The carriers were remade seven times in one year without one. - Find and fix the cause of the carrier simulations that do not converge. - CV joints are named as the place to cut rotating mass. A code for it already exists; acting on the result would need a wire EDM sponsorship. - Strain gauges on the carriers, to validate the FEA against a real car. - Hold weight flat until the loading and fatigue analysis exists to justify a reduction target.
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. Differential (cost report) (mm): 94.62, 70.00, 244.48 CR25 Differential (as drawn): 34.00, 3.40, 87.00, 8.70, 233.99, 23.40, 6.500.65, 73.70, 7.37 Source: Cost report drawings: CR22/Powertrain/Design/X - Cost Report Drawings/Drivetrain Assembly/Differential (cost report).pdf; CR25/Powertrain/Design/Y - Cost Report Drawings/Drivetrain/CR25 Differential.PDF; CR26i/Powertrain - IC/Design/Y - Cost Report Drawings/Drivetrain/CR25 Differential.PDF; CR27i/.Powertrain/Design/Y - Cost Report Drawings/Drivetrain/Archive/CR25 Differential.PDF
Nothing in CrimsonStorage covers these yet.