dave wrote:

looking to buy a used hyd cylinder on ebay (or some similar source) for
use in a home-brewed tilt trailer. have a couple amateur hydraulic
questions:

if there's no label or tag on a given cylinder, how do you tell by
looking at the cylinder if it's SINGLE acting or DOUBLE acting? also

Hose fittings. Single hose fitting=single acting, two, double acting.
You can put vents on many double acting cylinders to use as single acting.

"all other things being equal", how does one tell what weight, say, a
given cylider can LIFT, straight up? for sake of discussion let's assume
load to be lifted has perfect "zero friction" bearings guiding it. I
assume the answer has a lot to do with size of the cylinder *piston*,
and amount of pressure pump puts out "to" the cylinder ? but what's
the formula?

Roughly. Use diameter and pressure rating to calculate force
available. (hint-use the diameter to calculate the area acted upon by
the pressure) Make sure to reduce the area by the size of the piston, if
there is one on that side.
Most guys check the column in the catalog that says "force available"
or similar.

also, can -ALL- hydraulic cylinders be operated 'in any orientation'?
eg: with cyl body horizontal, vertical, or at any angle anywhere between
the two?
Mostly. If the seals are working.

for application in a tiltbed trailer, I assume a cylinder that's bigger
and with a LONGER stroke mounted, say, closer to the hitch, would be
-vastly- better than having a shorter cylinder with an even bigger bore
mounted closer to the axle (so it had a shorter stroke). that be
correct, then?

Depends on the load and the design of the tailer. Best is a design
choice. Bigger and longer means more fluid to pack around.

in same appplication, bubba here also guesses designing a tilt-trailer
to employ very nearly the FULL stroke of the cyl is better that making
it use, say, only half the stroke, correct?

You can only get the trailer so empty, then you run out of work to do.
The location of the cylinder, and the location of structure suitable for
the cylinder to act on, determine the location more often than the
stroke of a cylinder does, in my experience. The cylinder does not care
if it is run to full stroke or not.



and is there a way for a guy to some sort of 'intermediate throttle
body' or something so that a single-acting cylinder can be made to
perform 'double-acting functions'?

No. If it's built as a single acting cylinder, that's what it is.

thanks for educating me, guys :-)

You really need to get hold of some catalogs.

Farm implement places and "surplus" places usually deal in Hydraulics
stuff. It is well covered in their catalogs. Do a little chinese
blueprinting. Look at what has been done, There are reasons for everyone
using a similar layout and parts. They work.

toolie

Cheers
Trevor Jones