Vehicle Road-Load Force and Power

The calculation that sizes an engine or motor and drives EV range and fuel economy. F_total = 1/2 rho V^2 Cd A + Crr W + W sin(atan(grade%/100)), P = F_total V; the aero term uses the same drag routine, so the two never drift. A 3,500 lb car at 70 mph, 24 ft^2 frontal, Cd 0.30, Crr 0.012 on the level needs 132 lbf and 24.7 hp (aero 90 + rolling 42); put it on a 5% grade and the grade load alone is 175 lbf, so it jumps to 307 lbf and 57 hp - the climb, not the wind, now sets the power. Power at the wheels; divide by driveline efficiency for engine power and add the mass x acceleration term for launch. A planning estimate; the manufacturer coastdown data governs.

F_total = 1/2 rho V^2 Cd A + Crr W + W sin(atan(grade%/100)); P = F_total V; hp = F_total V / 550. Aero term from aerodynamic-drag-force.

The vehicle road-load equation (aerodynamic drag + rolling resistance + grade) and the tractive power (SAE J2263 / J1263 coastdown road-load), by name; the aero term is delegated to aerodynamic-drag-force.

The road-load equation is a standard published vehicle-dynamics result; the drag coefficient, frontal area, rolling coefficient, weight, and grade are the user's inputs.

Estimate. AHJ and licensed professional govern.

Field names used by the API: speed_mph, vehicle_weight_lb, frontal_area_ft2, drag_coefficient, rolling_coefficient, air_density_lb_ft3, total_force_lbf, road_load_power_hp

• Road load F_total = aero + Crr W + W sin(atan(grade%/100)); P = F_total VSAE J2263 / J1263
• Aero delegation aero term computed by aerodynamic-drag-force (no drift)cross-tile chain
• Scope steady speed at the wheels; acceleration, driveline efficiency, headwind are separatescope of this tile