Aux hyd question

[adsmith72]

Can I run a single acting hyd. cylinder from the aux hyd.? So it would be a cylinder with only one hyd. line. Gravity would need to return cylinder down. This is a 773G . I would be controlling with the thumb switch. Im pretty sure I know the answer, but need to confirm.

 

[Tazza]

I don't think you can, depending on what you are trying to run, can you convert the cylinder into double acting?

 

[Lowe.Buuck]

I don't think you can, depending on what you are trying to run, can you convert the cylinder into double acting?

Maybe...
I have two single acting cylinders on a snowplow and it works fine. As one extends it forces the other to retract.
I see two issues you will have to consider.
1. When you want the cylinder to retract, the thumb switch will open the line to return to tank at the same time the other line will be pressurized and deadheaded. That pressurized line will open the pressure relief valve and over time will cause the hydraulic oil to heat.
2. The second issue is what is the residual pressure in the system on the return line when the pressurized side is deadheaded?
You could put a pressure gauge on a hydraulic coupler and check the pressure as you engage the auxiliary hydraulics. The pressure you read on the return line as the pressure line opens the pressure relief valve will determine how much pressure the hydraulic cylinder must overcome to enable it to retract.
Note the load you will have to overcome is the residual pressure multiplied by the area of the hydraulic cylinder piston.
For example, if the residual pressure was 100 psi and your cylinder piston is 1.5 square inches. You would have to have a bit over 150 lbs of load on the cylinder to get it to retract.
If you are using a 3 inch cylinder, the piston area is 7+ square inches. You would have to have over 700 lbs of load on the 3 inch cylinder to get it to retract.

 

[chopper]

Don't think so. the oil would need a place to return from the cylinder. It would be a very slow let down with only atmosheric pressure helping with the return What is on the other side of the piston being moved by the oil?

 

[Tazza]

Don't think so. the oil would need a place to return from the cylinder. It would be a very slow let down with only atmosheric pressure helping with the return What is on the other side of the piston being moved by the oil?

Thinking about it more, it depends on how the fluid normally returns from the cylinder, if it's spring return, no it will not work. If it has another cylinder to push it back, it will.
I have a backhoe attachment that uses what is essentially 2 single acting cylinders to move the arm. Fluid goes in one side to extend the cylinder and it compresses the other, reverse the direction by pumping fluid from the other side.

 

[830Scott]

Thinking about it more, it depends on how the fluid normally returns from the cylinder, if it's spring return, no it will not work. If it has another cylinder to push it back, it will.
I have a backhoe attachment that uses what is essentially 2 single acting cylinders to move the arm. Fluid goes in one side to extend the cylinder and it compresses the other, reverse the direction by pumping fluid from the other side.

I have a scissor lift that I want to run with my SSL, but it's single acting. Just got a Post Driver, it has a single acting cylinder, and a manual lever spool valve. You have to stand beside it and run the lever one way, it extends cylinder up. Throw it the other way and it dumps the fluid back into the machine and drops weight. So, I'll be doing some research on that and doping out how to do it with the size of lift.

 

[flyerdan]

I have a scissor lift that I want to run with my SSL, but it's single acting. Just got a Post Driver, it has a single acting cylinder, and a manual lever spool valve. You have to stand beside it and run the lever one way, it extends cylinder up. Throw it the other way and it dumps the fluid back into the machine and drops weight. So, I'll be doing some research on that and doping out how to do it with the size of lift.

In theory it should work. My forklift mast is single acting, it has power up and gravity down, and the next valve is the tilt which is double acting.
The problem is the aux circuit is a double acting valve, can't see a way around that short of stubbing in another aux hydraulic circuit for single acting.

 

[dieselarry]

In theory it should work. My forklift mast is single acting, it has power up and gravity down, and the next valve is the tilt which is double acting.
The problem is the aux circuit is a double acting valve, can't see a way around that short of stubbing in another aux hydraulic circuit for single acting.

Have a spring loaded post pounder with a single action cylinder with a return line. Could I screw the return line in to the fill hole on the resivour?

 

[laurencen]

does your machine have a case drain

 

[dieselarry]

Will have to check it out.