JD 2520 pressureless return?

[gertjand]

Hi all,

Got a question. I have a John Deere 2520 with 4 hydraulic couplers for the FEL. Now I want to use a trailer with lifting cilinder. That one has only one hose and it drops by gravity. Are the Fell couples able to handle the retour? The Fell couplers are grouped in 2 x 2 for up and down and for loader up and down. If I connect one hose to FEL up. And I push FEL down does the fell up becomes pressureless so it drops by gravity?

 

[Tx Jim]

You could place boom control lever in float position to accomplish what you desire or stop engine from operating while lowering trailer bed

 

[CobyRupert]

I think float position would quickly drop the box. Perhaps in some cases, too quickly.
FEL hyd connector(s) will handle a dump trailer. Use FEL joystick to control rate of rise and fall of dump box just like you do the loader.

Yes, the box will lower by the force of gravity when the hyd oil in the one “push up” hose to the cylinder isn’t blocked from returning to the tractor. It’s this blockage that keeps the dump box in the elevated position. The oil is trapped as has no where to go, cylinder can’t move. Moving the FEL joystick in the “opposite of lift” direction opens a path in the FEL hyd valve for the oil to flow back through the valve as the hydraulic cylinder retracts due to gravity.

 

[kennyd]

Hi all,

Got a question. I have a John Deere 2520 with 4 hydraulic couplers for the FEL. Now I want to use a trailer with lifting cilinder. That one has only one hose and it drops by gravity. Are the Fell couples able to handle the retour? The Fell couplers are grouped in 2 x 2 for up and down and for loader up and down. If I connect one hose to FEL up. And I push FEL down does the fell up becomes pressureless so it drops by gravity?

Yes.

 

[gertjand]

Many thanks, will give it a try tomorrow and keep you posted. First get a matching coupler.

 

[npalen]

My first thought on lowering the trailer with a single acting cylinder connected to one of the two ports normally associated with a double acting cylinder is that the hydraulic system will have to go into "relief mode" since it is trying to force fluid out of the unused port. I don't think that would be a concern other than the temporary squeal of the fluid going over the relief valve.

I don't know if the Deere 2520 is an open center or closed center hydraulic system. I'm thinking that, on a closed center load sensing system, the relief valve wouldn't have to open as the system wouldn't see a demand for pressure. Is that correct?

 

[kennyd]

The 2520 CUT has an open center system. Yes, it will be in relief while the trailer is lowering, but that won't hurt anything.

 

[LD1]

Depending on the geometry of the dump trailer.....and cylinder.....gravity down can be slow. I personally wouldnt want to wait that long for it to lower while forcing oil over relief. Because as others said....it will go into relief due to the unused port.

Simply use either lift or lower to raise the trailer (which one really dont matter). Then just use float to lower it. Using loader float to lower it wont let the trailer lower any faster than forcing the unused port to open the pressure relief. Because in BOTH cases....the oil coming back from the trailer has a clear path back to tank. But using float mode also gives the pump flow a clear path back to tank as well instead of no where to go and forcing the relief open.

 

[KennyG]

In general these comments are correct, but don't worry about "float". When a single acting cylinder is attached to one port, you get backflow from gravity when you go into the opposite position. Float allows backflow through both ports, which you don't need.

I know this because the mower independent lift system on a John Deere is a single acting cylinder. No need to go into float to lower the deck.

 

[LD1]

In general these comments are correct, but don't worry about "float". When a single acting cylinder is attached to one port, you get backflow from gravity when you go into the opposite position. Float allows backflow through both ports, which you don't need.

I know this because the mower independent lift system on a John Deere is a single acting cylinder. No need to go into float to lower the deck.

Its not about allowing backflow through both ports. Its about not blocking the pump flow causing it do deadhead and go over the relief.

A few seconds of relief here and there isnt an issue. But gravity down trailers can take 30 seconds or more at a time to lower. And thats a long time to be deadheading your hydraulics at max pressure and putting it over the relief.

And seriously.....if you have loader raise for your dump trailer raise....and loader lower for dump trailer lower....rather than sit there and hold the lever how hard is it to simply click it into the float detent?