Problem: Calculate SCFM

Force is 200 lbs. + 50 lbs. of spring = 250 lbs.

Area of 2” diameter cylinder is 3.14 sq. in.

Pressure: F=PA  250 / 3.14 = 79.6 PSI

Compression Ratio =
(79.6 + 14.7) =6.42 C. R.
       14.7

Cycles / Minute = 60 / 2 sec. = 30 cpm

Volume of cylinder = 3.14 Sq. in. x 6” = 18.84 in³

CIM = 18.84 x 30 cpm = 565.2 CIM

Volume of hose = .11 Sq. in. x 6” = .66 in³

Total volume = 565.2 + .66 = 565.86 CIM

CFM = 565.86 / 1728 = .327 CFM

SCFM = .327 x 6.42 C. R. = 2.09 SCFM

Note – A gravity retracted cylinder (without the spring) would be:

200 lbs. / 3.14 = 63.69 PSI

C. R. (63.69+ 14.7) = 5.33 C. R.
                 14.7

Volume of cylinder and hose @ 30 CPM = .327 CFM (from above)

SCFM = .327 x 5.33 C. R. = 1.74 SCFM instead of 2.09 SCFM

Spring return cylinders do not use energy to retract, but more to extend. No free energy.