I would expect it to close slower, yes. Curling the bucket is accomplished by extending the cylinder. There is more volume on that side of the piston, so it takes longer to fill. More area, too, so it has more force when curling.
This is where my formal training would send me to a calculator not a stop watch.I just tested mine and it's about a 2 to 1 ratio.
It takes approx. 6 seconds to close and 3.5'ish seconds to open.
Interestingly enough, rpm did not seem to have a significant effect on opening and closing times, but remember I was do the "Scientific" One Mississippi, Two Mississippi method.
The WSM says i.d. 2.17" (55 mm), rod o.d. is 1.38" (35 mm) and stroke is 17.8" (451 mm). In the interest of accuracy, please recalc.This is where my formal training would send me to a calculator not a stop watch.
SCIENTIFIC
Its a fixed displacement pump so opening and closing times will vary linearly with pump RPM. Double the pump RPM and you double the cylinder speed in both directions.
For a double acting cylinder the ratio of retract and extend speed is determined by the oil capacities (volumes) of the two ends. Lets do a little middle school (???) solid geometry.
Let:
Rp = radius of the piston
Rr = radius of the rod
L = overall stroke of the cylinder
Then:
Volume of base end = Vb = PI x Rp**2 x L
Volume of rod end = Vr = Vb - (PI x Rr**2 x L)
Ratio of speeds - Vb/Vr
EXAMPLE
What is the retract/extend speed ration of a DA cylinder with 2" bore, 1" rod, and 20" stroke?
Rp = 1
Rr = .5
L= 20
Vb = 3.14 x (1**2) x 20 = 62.8
Vr = 62.8 - (3.14 x (.5**2) x L)) = 62.8 - 15.7 = 47.1
Retract/extend speed ratio = Vb/Vr = 62.8/47.1 = 1.333
I am pretty confident of the geometry but you might want to double check my arithmetic
Dan
Just looking at the two diameters rod is much bigger relative to bore so we know its going to be faster than the example.The WSM says i.d. 2.17" (55 mm), rod o.d. is 1.38" (35 mm) and stroke is 17.8" (451 mm). In the interest of accuracy, please recalc.
