</font><font color="blue" class="small">( Henro, et.al.,
I think it turns out that this might be a bit of a case of the fingers being faster than the brain /forums/images/graemlins/blush.gif.
You can get cavitation in the supply line if you have a flow restricter there, AND the cylinder is being driven by an external load (as would happen in lowering a loader with a load on it for example). In this case the fluid can exit the system faster than it can be supplied. It's hard to figure out how this situation would occur for a set of grapples though.
A similar situation can occur with hydraulic motors if they end up running as a pump due to an external load (e.g. flywheel loads, braking with wheel motors).
Managing the return flow addresses these issues. FWIW, I think of it as making the cylinder "look" like it's under a heavier load.
I found a number of references to "smoother" control with the "one way" type of valves in the return path. This would be consistent with the above information, where the system might work like it had "air" in it.
The "brain surgery" comment is well placed too. The "right" solution take a lot of factors into account. It'll be interesting to hear how the simple solution works out in practice.
I should also mention, that I haven't had the need (chance) to use any of these valves in the hydraulics that I've done to date (loader and backhoe), so I was just going from (recollected ... always hazardous /forums/images/graemlins/grin.gif) experience from others, and from my efforts to "figure out" hydraulics. I'm no expert, and sometimes having an engineering background can work against you /forums/images/graemlins/wink.gif.
HTH, and sorry for any mis-information. Andrew )</font>
I had you figured out on the first message, but I see you got back to it.
If the flow restrictor is on the high pressure supply side only, you sort of turn the cylinder into a one-way cylinder at times. Any time you allow the cylinder to move, oil can flow away from one side rapidly, while you are supplying oil very slowly to the other side. This will allow the cylinder to draw a vaccumn & fully extend if it has enough load on it, but will take a long time for the oil to build up on the other side of the cylinder.
It would indeed act like there is air in the system under certain conditions. One would have less positive control of the situation. You effectively have a 1/2 hose supplying oil to or from one side of the cylinfer, & a 1/16" hose supplying oil to or from the other side. That's unbalanced...
May not be important in a grapple.
And it would not cause damage, it just might, possibly, in some uses, cause a feeling that one isn't in control of what is happening all the time - extra slap or bounce on the controls.
As someone else said, this is brain surgery analysis, go ahead & hammer it together & have fun. /forums/images/graemlins/smile.gif
--->Paul
