Question about flow controlling side link "tilt" cylinders

[rfc143]

Adding two channels of rear hydraulics on my Kubota 5240. I've read that, depending on the tractor/top'n'tilt system, some restriction or flow control may be needed to slow down the adjustments.

My background is more industrial hydraulic related, and we've often "metered out" such systems, putting the restriction on the "out" port (Not contemplating using back to back flows here...just an orifice.

So the question is, if the rod of the cylinder is down (as I believe most side link cylinders are), would the most appropriate location for the restrictor to be placed, be at the loaded, lower end of the cylinder?

 

[oldnslo]

Since the load will typically be trying to extend this cylinder you must restrict the rod end flow to prevent the cylinder from running away

 

[ruffdog]

I ended up installing an orifice on my grapple's 2" cylinder.

 

[MtnViewRanch]

Adding two channels of rear hydraulics on my Kubota 5240. I've read that, depending on the tractor/top'n'tilt system, some restriction or flow control may be needed to slow down the adjustments.

My background is more industrial hydraulic related, and we've often "metered out" such systems, putting the restriction on the "out" port (Not contemplating using back to back flows here...just an orifice.

So the question is, if the rod of the cylinder is down (as I believe most side link cylinders are), would the most appropriate location for the restrictor to be placed, be at the loaded, lower end of the cylinder?

I don't want to get into any discussions as far as why, just giving you real world experiences gathered from many customers.

You "should" be able to restrict the flow on the rod end port (no matter what direction the cylinder is positioned) and have things work properly slowing the rod movement down.

But I have found for whatever reason that it seems to work better to have both ports restricted.

 

[RickB]

Only one port needs to be restricted if you are using a simple office that restricts flow both ways. If you put an office in the base end hose and it restricts too much, put it in the rod end side to speed things up a little.

 

[/pine]

FWIW...Most places that make custom hoses can use restricted orifice fittings which eliminate the extra connector and makes a neater installation...!

 

[rfc143]

I don't want to get into any discussions as far as why, just giving you real world experiences gathered from many customers.

You "should" be able to restrict the flow on the rod end port (no matter what direction the cylinder is positioned) and have things work properly slowing the rod movement down.

But I have found for whatever reason that it seems to work better to have both ports restricted.

Do the orifces typically used in this application work in both directions?
Using your advice, would both ports use the same size, or would the rod end use a slightly smaller orifice, to account for the differential volume of the rod end of the cylinder?

 

[ruffdog]

Only one port needs to be restricted if you are using a simple office that restricts flow both ways. If you put an office in the base end hose and it restricts too much, put it in the rod end side to speed things up a little.

Correct! For every inch of cylinder piston movement, each side of the cylinder will move a given amount of oil. Being that the rod end holds less oil, that side "moves" less oil. That is why the same sized orifice on that end has less affect on slowing the cylinder.

 

[ruffdog]

Do the orifces typically used in this application work in both directions?
Using your advice, would both ports use the same size, or would the rod end use a slightly smaller orifice, to account for the differential volume of the rod end of the cylinder?

If you would install the same sized orifice on both ends of the cylinder, only the one with the job of metering the most oil volume would be restricting cylinder speed. That would be the one on the rod-less end. Think of it this way, you must empty a closet full of people and a gymnasium full of people, through a small door, in the same amount of time. It would be the door for the highest volume of people (gym) that restricts speed.

 

[rfc143]

Correct! For every inch of cylinder piston movement, each side of the cylinder will move a given amount of oil. Being that the rod end holds less oil, that side "moves" less oil. That is why the same sized orifice on that end has less affect on slowing the cylinder.

Got it. So, since stroke is the constant, the orifice diameter would be proportional to the net area of each side of the piston, correct? So, for example, a 3" bore with a 1" rod has 89% of the area on the rod size, so the restrictor on that side would also be 89% of the restrictor on the piston side?