# Research Report: Tri-Star Wheel Optimization (180mm Riser)

## 📋 Research Executive Summary
For a hand-powered vehicle weighing 75kg to clear an 18cm step, the Tri-Star cluster must maintain a specific "Stepping Ratio" to avoid the chassis bottoming out.

## 📐 Optimal Geometry
- **Arm Length (Center to Axle):** 185mm.
- **Small Wheel Diameter:** 250mm (10-inch).
- **Inscribed Circle Diameter:** 370mm.
- **Circumscribed Circle Diameter:** 620mm.

## ⚖️ Stability & COG
To prevent tipping backward during a stair-climb:
- The **Self-Leveling Seat** must lead the pitch by at least **15 degrees** during the "Step Up" phase.
- Center of Gravity (COG) must remain within the "Stability Triangle" of the three points of contact on the stairs.

## 🛠 Material Recommendation
- **Cluster Plates:** 6mm 6061 Aluminum Plate.
- **Axles:** 15mm Stainless Steel Hollow Shaft.
- **Tires:** High-durability Polyurethane (Puncture proof).