Converts column rotation into lateral tie rod movement, at the steering ratio the kinematics package needs.
A purchased rack and pinion unit. Rack travel and ratio set the relationship between steering wheel angle and wheel angle, which combined with the tie rod mount position on the upright sets Ackermann.
Purchased rather than designed. Steering rack options were compared before selection. From the design reports and one-pagers: The CR25 steering one-pager states the problem plainly: the Mark Williams aluminium rack was several years old, the teeth were worn out and it allowed steering compliance. The NARRco 11.4 in rack was proposed at $600 with clevises included, against a new Kaz rack at $735, and was chosen from a decision matrix agreed with suspension kinematics. The CR22 predecessor decision is the cautionary tale. CR22A switched from the Mark Williams to a Kaz Technologies rack, mainly to fix rack and pinion compliance. The comparison recorded was: Kaz at 3 lb with 3.25 in maximum rack travel for $735, against Mark Williams at 1.74 lb with 6 in travel for $407. What was missed is that the Kaz had a starting ratio of 4.71 in per revolution against the Mark Williams' measured 2.67 in per revolution, which left the steering wheel with only 90 degrees of total movement, 45 degrees each way.
Rack mounts are milled from 6061 aluminium, with the CAM in Fusion. The report carries one specific warning: do not over torque the mounts, because over torquing causes excessive friction in the system. NARRco rack mounts were sold out at the time of writing, so in-house mounts were estimated at 5 hours of mill time.
Purchased unit.
Fault Vault, CR26I, Manufacturing, Potential Failure. The team did not know that all NARRCO racks have a different alignment of the output shaft when the rack is centred. A new rack was going to be swapped in before CR26I's competition, which forced column tubes to be remanufactured at the last minute to align the wheel. It was not done properly and the wheel ended up slightly off-centre. Corrective action recorded: take more care aligning the wheel when drilling the last set of column holes. A 3D printed jig to mount a level to the wheel was proposed. A guaranteed manufacturing method for perfect alignment from the spline to the rack is still an open item.
A 3D printed jig to mount a level to the steering wheel was proposed so the wheel can be aligned properly when the last set of column holes is drilled. A guaranteed method for perfect alignment from the spline to the rack is still open.
Claimed value from the one-pager: decreases weight by more than half against the previous design, and reduces steering compliance. Long-term wear performance was recorded as to be determined. Quantity per car, as costed: 1
Nothing in CrimsonStorage covers these yet.