You can use just the diameters, but using pitch diameters
is more accurate.
Free air if volumetric efficiency (%) and piston
displacement are known:
Free Air = piston displacement X eff. (%)
To find cubic feet of either compressed air or free air:
cu.ft. comp. air X (psig + 14.7) = cu.ft. free air X 14.7
- cu.ft. comp. air [ Cubic Feet of Compressed Air ]
- cu.ft. free air [ Cubic Feet of Free Air ]
To convert gallons (tank size) to cubic feet:
gallons X .134 =cu.ft.
Cubic Feet of free air required to raise a receiver from
some pressure to a greater pressure:
If you enter time in seconds, you will get CFM. If you enter CFM you will get
the time to pump up to the final pressure.
Air Cylinders:
Total force in lbs. of air cylinder = area of the cylinder
diameter (inē) x psi gauge pressure
CFM of Free Air req'd to Operate Air Cylinder (single acting)
= vol. of cyl. (in cu. ft.) x cycles per minute x (gauge psi + 14.7)/14.7
For double acting air cylinder multiple by 2
Compressor RPM:
motor pulley diameter x motor rpm
compressor pulley diameter
Motor Pulley Diameter:
compressor pulley diameter x compressor rpm
motor rpm
Compressor Pulley Diameter:
motor pulley diameter x motor rpm
compressor rpm
Motor RPM:
compressor pulley diameter x compressor rpm
motor pulley diameter
Required Piston Displacement:
free air
vol. eff.
Piston Displacement in Cu.Ft. Min.:
cyl. bor in in. x cyl. bore x stroke in in. x rpm
2200
Cu. Ft. Compressed Air:
cu. ft. free air x 14.7
(psig x 14.7)
Cu. Ft. Free Air:
cu. ft. compressed air x (psig + 14.7)
14.7
Gallons:
cyl. bor in in. x cyl. bore x stroke in in. x rpm
2200
Pump Up Time:
V (tank size in gallons) x (final tank press-initial tank press)
7.48 x atmos. press. (psia) x pump delivery (cfm)
Gallons:
cubic feet
.134