SPEEDERS — Physics Design Validator

Free sanity check before you spend a dollar. Every number below is computed from real physics (rolling resistance, grade power, tip-over geometry, battery energy, lock loads). Drag the sliders to your real numbers — if a card goes red, that part of the design is fighting physics and needs rethinking before any prototype.

—Design score

Inputs — set your real targets

Rider weight 75 kg Battery 45 Wh Top speed (governed) 12 mph Wheel diameter 45 mm Motor power (each ×4) 45 W Wheel track width 70 mm Grade to climb 8 % Shoe weight (each) 1.1 kg

What this is: a first-order physics model — it catches designs that are fundamentally broken (can't climb, no range, tips instantly, motors too weak) for free. It is not a substitute for a real prototype: it can't judge ride feel, control-software safety, or manufacturing. Green here means "the physics works out" — the cheap next step is still a ~$300–600 bench/plank build to prove the lean-steering feels safe, before any paid engineering.

Model assumptions: rolling coeff 0.015 (PU on pavement), drivetrain efficiency 62%, usable battery 80% of rated, rider CG ≈ 1.0 m. Sources & full spec: MANUFACTURING-SPEC.md.