Contents
1. Conversion of non-SI units
- Foot = 0.3048 m
- Mile = 1.61 km
- Pound, lbs, lb = 0.453 kg
- Ounce, oz = 28.35 g
- Lbs / sf = 4.88 kg/m2
- HP (horsepower) = 735.5 W
- 1 tesla [T] = 104 gauss [G]
2. Definitions
- m = mass [kg]
- n = revolutions per minute [rpm]
- v = velocity [m/s]
- ω = angular velocity [rad/s]
- e = back electromotive force [V]
- F = force [N]
- T = torque [Nm]
- P = power [W]
- E = energy [Ws]
- Tf = friction torque [Nm]
- r = radius [m]
- Cr = Rolling resistance [m]
- ρ = Air density [kg/m3]
- Cw = Drag coefficient [ ]
- A = Reference area [m2]
3. Physics
- 1 kg = 9.81 N
- 1 calorie = 4.1868 joule
- v [m/s] = [km/h] / 3.6
- ω = 2 * π * n / 60 = 0.105 * n
- ω = v / r = kmh / (1.8 * diameter)
- F = m * a
- P = E / t [W] or [Nm/s]
- E = 0.5 * m * v2
4. Required bicycle power
- Proll = Cr * m * g * v
- Pdrag = 0,5 * ρ * Cw * A * v3
- Pslope = m * g * v * slope[%] / 100
5. Bicycle speed calculation
- kmh = n * wheel circumference * 0.06
6. Motor torque and power
- P = T * ω [Nm/s]
7. The two linear relationships of an PM motor
- e = k * ω = 0.105 * n
- T = k * i
- Thus k = e / ω and also k = T / i [Nm/A]
