hydraulic cylinder sizing

i have a 12 wheel H & S "v" rake. has a 2" cylinder on it now and my john deere A wont lift it. i have 1000 psi at the power trol. so, stopped at my local bomgaars last night and they have a 3.5" and 4" cylinder, same stroke. they also have a 3". wondering on anyones thoughts as to which one i should get? the 3.5 and 4 have bigger pins in them so would have to modify my rake for them to work, but thats no big deal.
thanks
Gary

Pushing or pulling to raise the rake? If pushing the 3" ram will have 2.25 times more linear force than the 2"

pulls to raise the rake

Force is pressure x area of the piston. Area is 22/7....3.14...... (pi, ratio of the circumference of a circle to the square of the distance from the center to one side known as the radius) times the radius squared (radius x radius).

Since the radius is half the distance across the circle measured at the center and is squared, a small increase in diameter results in a big increase in area and the bigger the difference in dimensions the bigger difference in the result, hence force.

So as a quick comparison, a 4" dia cylinder (2" radius) would use 2x2 whereas a 6" (3" radius) would use 3x3. You increased the diameter 50% but got 225% increase in force as BD stated.

So, either know what your item weighs, or get the largest diameter you can afford and reasonably use.....course it has to exceed the weight of the load if you plan on doing any lifting.....or up your hyd popoff and increase your pressure...but that's a linear increase. 500# increase on your current 1000 only gets you a 50% improvement but could solve the problem when added to the new cylinder.

I have noting to do but blab today so I sorta drug this out... Happens sometimes to old pfarts. Sometimes things are just better passed over. Grin

Mark

(quoted from post at 13:35:39 06/25/13) pulls to raise the rake

Click to expand...

Assuming the hydraulic ram has a 1-1/4" rod and the A is making 1000psi but I'll wager less than 1000psi after several decades of wear.
A 2" ram will push 1920lbs
A 3" ram will push 5850lbs
A 3-1/2" ram will push 8400lbs
And a 4" ram will push 11350lbs.

A 3 inch will give over twice the force. The same as a 2 inch at 2100psi or so.