On Mon, 15 Dec 2003 08:57:02 -0500, Glenn Ashmore
wrote:

The Vettus system is a double acting "balanced" cylinder. Balanced
cylinders have the rod going all the way through so the pressure is the
same in both directions. In that case you can divide by 2.

No. But your previous answer was good, so I am puzzled!

Brian W

Keep in mind though that if you use two cylinders you need to double the
capacity of the pump to get the same number of hard over turns.

garry crothers wrote:

"Glenn Ashmore" wrote in message
news:rJiDb.4799$JD6.1854@lakeread04...

If the cylinders are single action each needs to take the full load. If
double acting it gets more complicated both in calculation and
installing. The pulling force is reduced by the area of the rod.



Excuse my ignorance, but how can I tell if the cylinder is double action or
single. I've just looked at the Vetus catalogue and cant see any reference
to single or double?


For

example a 2" cylinder with a 1" rod will have a pull force about 75% of
the push so you can't quite divide by 2.


I kinda thought that it would just be as simple as divide by 2...



thanks again
garry

Brian Whatcott wrote:

On Mon, 15 Dec 2003 08:57:02 -0500, Glenn Ashmore
wrote:


The Vettus system is a double acting "balanced" cylinder. Balanced
cylinders have the rod going all the way through so the pressure is the
same in both directions. In that case you can divide by 2.


No. But your previous answer was good, so I am puzzled!

My original post assumed a standard double acting cylinder. These have
the rod attached to one side of the piston. In these, the displacement
on the rod side is reduced by the volume of the rod and the pressure
face of the piston is reduced by the cross sectional area of the piston.
That means you get less force on the pull stroke than on the push for
the same fluid pressure. Also you get more movement for the same volume
of fluid. That makes them hard to use for steering unless they are used
in opposing pairs like on heavy earth moving equipment.

A balanced or "steering" cylinder has the rod continue through the
piston and out the other end of the cylinder. This end of the rod
usually carries no force but makes the displacement and pressure face
the same on the two sides so the force is the same in both directions.

The down side is that you have two sets of seals that will leak someday
rather than just one.


--
Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at: http://www.rutuonline.com
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