Design and optimize your pneumatic launcher with real physics calculations
| Type | Diameter | Mass | Cd |
|---|---|---|---|
| Golf Ball | 42.67 mm | 45.93 g | 0.24 |
| Tennis Ball | 66 mm | 57 g | 0.50 |
| Ping Pong | 40 mm | 2.7 g | 0.50 |
| Nerf Dart | 13 mm | 1.0 g | 0.40 |
| Valve Type | Size | Cv | Open Time |
|---|---|---|---|
| QEV | 1/4" | 0.10 | <5 ms |
| QEV | 3/8" | 0.80 | <5 ms |
| QEV | 1/2" | 3.25 | <5 ms |
| QEV | 3/4" | 5.50 | <5 ms |
| QEV | 1" | 8.00 | <5 ms |
| Sprinkler (mod) | 3/4" | 2.00* | ~20 ms |
| Sprinkler (mod) | 1" | 3.50* | ~20 ms |
* Sprinkler Cv values are effective values accounting for internal flow restrictions
Adjusts barrel length so the expanding air reaches atmospheric pressure exactly when the ball exits. Longer barrel = more time for air to expand = lower exit pressure.
Adjusts chamber volume to match your barrel. Larger chamber = more air = more energy, but requires finding the right balance for zero exit pressure.
Flow rate comparison at different pressure differentials. QEVs provide significantly faster flow due to larger effective orifice and minimal internal restrictions.
Velocity increases roughly with square root of pressure. Current operating point shown in red.
| Nominal Size | OD (in) | ID (in) | Wall (in) | Pressure (psi) | Projectile Fit |
|---|
Exit Pressure:
Pexit = P0 × Vch / (Vch + Vbar)
Muzzle Velocity:
v = √(2E / m)
Where:
P0 = initial pressure (psi)
Vch = chamber volume
Vbar = barrel volume
E = muzzle energy (J)
m = projectile mass (kg)
Lift Force:
FL = ½ × CL × ρ × A × v²
Spin Factor:
S = ω × r / v
Where:
CL = lift coefficient ≈ 0.5 × S
ρ = air density (1.225 kg/m³)
A = cross-sectional area
ω = angular velocity (rad/s)
r = ball radius (m)
Volume Flow Rate (SCFM):
Q = Cv × √(ΔP × P2 / (T × SG))
Where:
Cv = flow coefficient
ΔP = pressure differential (psi)
P2 = downstream pressure
T = temperature (°R)
SG = specific gravity (1.0 for air)
Drag Force:
FD = ½ × Cd × ρ × A × v²
Where:
Cd = drag coefficient
ρ = air density (1.225 kg/m³)
A = cross-sectional area (m²)
v = velocity (m/s)
Optimal angle: 30-40° with drag
Gap Ratio:
rgap = (Abar - Aproj) / Aproj
Base Efficiency:
ηbase = e-2.0 × rgap
Dynamic Penalty:
tf = √(100 / P)
ηdyn = e-3.0 × rgap × (tf - 1)
Where:
Abar = barrel cross-section
Aproj = projectile cross-section
P = operating pressure (psi)
η = ηbase × ηdyn (total)
Average Pressure:
Pavg = (P0 + Pexit) / 2
Muzzle Energy:
E = Pavg × Aproj × L × η
Where:
Pavg = average pressure (Pa)
Aproj = projectile area (m²)
L = barrel length (m)
η = seal efficiency (0-1)