Hydraulics 101

(quoted from post at 08:38:16 04/24/20) Ford open center hydraulic system, single 2 way valve, thinking about adding a single acting hydraulic cylinder to my drum mower where gravity will accomplish the return function. Question is, when putting the valve in the unloading position, does the hyd fluid just drain back through the valve rather than being forced like would happen with a 2 way cylinder?

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(quoted from post at 12:35:26 04/24/20)
My Ford 3000 was a '68 model,5610 was '84 & 7600 is '80 on all just plug one hose & single acting cylinder operated just fine

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(quoted from post at 14:25:40 04/24/20) The hydraulic oil does deadhead at the unused coupler. It deadheads and the excess oil goes over relief. Creates a little heat and maybe some noise.
But that is why there is a relief valve.

Now a very few tractors did have a selectable function to change to single acting, which is great, but most are not that way.

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(quoted from post at 14:34:28 04/24/20) Mark, since you are posting this as ...Hydraulics
101...let us explore this in a little more depth. Now
some people don?t like a poster that adds this
disclaimer, but I don?t know anything about the
specific valve set up in that Ford. My answer will be
based off general knowledge that applies to open
center hydraulic systems. So, if JMOR is referring to
the fact that he knows the valve set up on your tractor
then the following applies. If you use it as described
by TxJim, when moving your control lever to the
position which would allow the cylinder to retract or I
assume lower the mower head you will be forcing full
hydraulic pressure against the unused remote outlet
of the pair connected to the control valve you are
using. This will pressurize the piping or hose to the
unused coupler and cause the hydraulic system
pressure relief valve to open. And in that position the remote your cylinder is plugged in will allow oil to flow back to the reservoir as if it were allowing oil to return from the unpressurized side of a double action cylinder. And doing this will work but it will put undue stress on
the hydraulic pump and drive, pressure piping, relief valve and
will heat the hydraulic fluid. The only way to operate a
single acting cylinder on a two way remote valve is to
add a hose plugged into the opposite remote outlet
that flows oil back to the reservoir as Deltared has
proposed. Now if your valve setup has a
...float...feature then this would allow you to use the
single action cylinder as well. A float position control
valve generally has fourth additional position beyond
the ...down... position JMOR describes that opens the
line of the remote outlet to the return reservoir
allowing the cylinder to float or move freely as the
implement encounters changes in terrain etc. Having
a float position would allow you to return oil back to
the reservoir or lower the machine without the
pressurization I spoke of earlier. The other way is to
have a switchable valve, some Farmalls had this
feature. Another option that in my knowledge
generally does not apply to factory equipped valves is
there is an internal plug to remove to switch the valve
from double to single action. This is generally found
on add on valves. Hope this helps.

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(quoted from post at 16:50:23 04/24/20)
I'm not denying when moving control valve to operate one way cylinders that a "relief valve briefly opens". All 3 of the tractors that I utilized for yrs in that fashion have shown no ill affects. So I guess I won't add an extra hose plumbed to sump on my tractor. YMMV

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