Penny-Loaded Ramp-Race Rolling Assembly

Design a rolling assembly for a physics ramp-race project, symmetric about its central axis. CORE ROD (central component, spans the full width and connects both wheels directly): - Solid cylindrical rod, outer diameter 22 mm, length 330 mm, centered on the main rotation axis - A cylindrical bore, diameter 19.05 mm, depth 15.2 mm, drilled radially inward from the rod's outer surface at the exact midpoint of its length (at 165mm from each end), to hold a stack of 10 US pennies (each 19.05 mm diameter, 1.52 mm thick) - Rod material: dense metal (copper, or lead/bismuth as a denser alternative) — model as a separate non-printed part - Both ends of the rod press-fit into the wheel hub bores below WHEELS (×2, identical, mirrored, mounted at each end of the core rod): - Thin rim: outer diameter 340 mm, radial thickness 1.2 mm, axial width 4 mm - 5 straight spokes per wheel, evenly spaced 72° apart, rectangular cross-section 1.5 mm x 3 mm, connecting rim to hub boss - Hub boss: outer diameter 32 mm, bore diameter 22 mm (press-fit onto the core rod), thickness 10 mm - Wheels are rigidly fixed to the rod ends, coaxial with it — no bearings, no relative motion between any parts CONSTRAINTS: - Overall height (wheel diameter) ≤ 350 mm - Overall width (rod + both wheel widths) ≤ 350 mm - Fully symmetric about the center (front-back and left-right) so center of mass falls within 10 mm of geometric center - Entire assembly is one rigid body — no moving parts MATERIALS: - Wheels (rims, spokes, hub bosses): 3D-printed PLA, 100% infill - Core rod: dense metal, modeled as a separate solid cylindrical part with the penny bore feature Generate as a parametric assembly: wheel as one part (patterned/mirrored to both ends), core rod as a separate part, so dimensions and the penny bore position can be adjusted later.

Parameters

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