Locate the front wheel relative to the chassis and carry the resulting loads back into the frame.
Upper and lower A-arms, each two tubes running from two chassis pickup points to a single spherical bearing holder at the outboard end. Because they are effectively two-force members, tube sizing is a buckling problem before it is a yield problem. Design Philosophies and Processes: Sized in the in-house tube calculator, which sweeps outside and inside diameter against critical buckling force, critical buckling stress and actual stress, returning both buckling and yielding factors of safety plus estimated weight. Target buckling FoS is above 1.8.
Kinematics fixes the geometry points. Clearance to the wheel, upright, tie rod and actuation rod through full travel. Frame tab positions, which measurably deviate from nominal and are measured with a FARO arm after welding.
Sample calculation for the upper front fore arm: 1088.73 lb load, 8.69 in length, 70,000 psi material yield, 29,700 ksi modulus, 4130 steel. CR26I front upper tube 0.375 in OD / 0.305 in ID gives minimum FoS 1.946 with 0.25 in tab thickness. Front lower tube 0.625 / 0.527 gives minimum FoS 2.49. Deflection under cornering, front left: upper fore -67.253 lb giving -0.00053 in, upper aft -983.120 lb giving -0.00608 in, lower fore -805.743 lb giving -0.00412 in, lower aft -308.531 lb giving -0.00140 in. Resulting geometry change: caster 8.086 to 8.114 deg (+0.028), kingpin 6.326 to 6.339 deg (+0.013).
Welded in a lower and upper A-arm jigging assembly. Time tracking for CR26I upper A-arms: design and CAD assembly 5 hours, CAM 6.5 hours, manufacturing of bearing holders and rod inserts 30 hours, welding and assembly 8 hours, roughly 50 hours total against 100+ hours on CR25.
AISI 4130 steel tube with threaded inserts and welded spherical bearing holders. FK WSSX4TV wide series alloy grooved spherical bearings at the uppers, Aurora HAB-5TG high-misalignment Grumman groove bearings at the lowers.
Fault Vault, CR26I, Manufacturing, Potential Failure. The upper arms' ball joints became loose within the housing and had vertical compliance. No fix was settled; the working theory is that the bearings are being staked with too much force. The recorded want is a pressure gauge on the pneumatic press so the actual staking force is known rather than guessed. CR25 had a separate spherical bearing retention problem caused by an improperly designed chamfer in the bearing holder.
Upper bearing holders machined complete on the mill with soft jaws rather than welding the actuation rod tabs in a jig, which cut A-arm build time from over 100 hours on CR25 to about 50 hours on CR26I. A pressure gauge on the pneumatic press is the proposed control for the ball joint staking force.
CR26I front upper 0.39 lb against CR25's 0.40 lb. Fore tube 0.750 x 0.856 in at 9.14 in, aft tube 0.750 x 0.856 in at 7.31 in, 2 in rod insert length, design FoS 2. Lower fore 0.527 x 0.625 in at 13.48 in (FoS 2.16), lower aft 0.527 x 0.625 in at 11.97 in (FoS 2.62). 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. CR22 FL (as drawn): 25.30, 3x 0.79, 1.59, 43.26 IA Mount Plate (as drawn): 0.16, 6.67, 4.64 Source: Cost report drawings: CR22/Suspension/Design/01_Cost_Report/Cost Report Drawings/Suspension & Shocks/Front A-Arms/CR22 FL.pdf; CR22/Suspension/Design/01_Cost_Report/Cost Report Drawings/Suspension & Shocks/Front A-Arms/IA Mount Plate.pdf
Nothing in CrimsonStorage covers these yet.