Hydraulic leak on Flail Mower

[imarobot]

I recently bought a Del Morino Centurion Super 158 flail mower. I have noticed that with the mower lifted off the ground that after a few minutes the mower will start to tilt down. Would this be a leak in the rear remote valve or with the mower hydraulic cylinder? How can I tell which one it is?
Is this normal?

 

[Russell King]

There is a speed control valve that you can probably put into a lock position. Put it into that position and see if it falls. If it does that indicates the cylinder is leaking past its seal.

I would assume that the fall rate will be very slow in the lock position so would probably just use that to hold the flail mower up. But why are you holding it up for use?

 

[imarobot]

I don't think there is a speed control valve, although I would like to put one on for both levers. This thing is very jerky when swinging or tilting. Takes a lot of fine lever movement with two hands to control it smoothly.
I don't cut with it in the raised position, only when transporting, making sharp U-turns, backing up etc. and typically have to level it off again if lifted more than a few minutes. It even tilts down a little bit when on the ground due to a pivot in one of the lower 3 point links. I notice that when I lift it off the ground it is tilted a bit down.

 

[Russell King]

Oh sorry I thought you meant the THREE POINT HITCH, not a hydraulic cylinder on the mower or tractor.

You can do a couple of things like adding a dual pilot operated valve to the cylinder that locks it in place when not being adjusted. That eliminates “float“ on that cylinder if the valve is capable of float.

To slow down the rate of movement you can install a needle valve or a flow restrictor fitting into the hose or cylinder ports.

You can do the restriction and the pilot valve both In unison on one cylinder.

 

[JonM]

I recently bought a Del Morino Centurion Super 158 flail mower. I have noticed that with the mower lifted off the ground that after a few minutes the mower will start to tilt down. Would this be a leak in the rear remote valve or with the mower hydraulic cylinder? How can I tell which one it is?
Is this normal?

probably has air in the hydraulics. just need to rev up the tractor and cycle the hydraulics a few timea to work it out

common with new equipment. check ypur hydraulic levels anytime you add a new piece of equipment after a short bit of use

 

[Russell King]

And that leak down can be either a cylinder or a valve. Disconnect both lines (assuming they have a disconnect fitting on the hoses) and see if it locks in place (cylinder is NOT leaking, it is valve leaking).

 

[imarobot]

probably has air in the hydraulics. just need to rev up the tractor and cycle the hydraulics a few timea to work it out

common with new equipment. check ypur hydraulic levels anytime you add a new piece of equipment after a short bit of use

Good point, but I've run this thing for several hours now so I'm guessing it's not air.
I did check the fluid level and it is good.

 

[imarobot]

And that leak down can be either a cylinder or a valve. Disconnect both lines (assuming they have a disconnect fitting on the hoses) and see if it locks in place (cylinder is NOT leaking, it is valve leaking).

Gotta give this a try

 

[TheOldHokie]

Gotta give this a try

Dollars to donuts its the valve. New cylinders dont leak but valves all do.

Dan

 

[imarobot]

Dollars to donuts its the valve. New cylinders dont leak but valves all do.

Dan

And you are right, what would prefer dollars or donuts?
I disconnected the hydraulic hoses, and it didn't drop.
Didn't think of it at the time but I am going to connect the hoses to the other valve and see if that does the same thing.
Is this behavior to be expected?

 

[TheOldHokie]

And you are right, what would prefer dollars or donuts?
I disconnected the hydraulic hoses, and it didn't drop.
Didn't think of it at the time but I am going to connect the hoses to the other valve and see if that does the same thing.
Is this behavior to be expected?

Coffee rolls from Dunkin please.

That behavior is to be expected. Spool type control valves do not have shutoff seals. They rely on a very close (a few ten thousandths of an inch) cleaeance fit in the housing for the shutoff function. That clearance is both a pressure and fluid leakage path. Valves with tighter spool clearances and manufacturing tolerances cost more and leak less but they all leak. Pilot operated check valves (poppets) on the work circuits are commobly used to mitigate that leakage.

Dan

 

[imarobot]

Coffee rolls from Dunkin please.

That behavior is to be expected. Spool type control valves do not have shutoff seals. They rely on a very close (a few ten thousandths of an inch) cleaeance fit in the housing for the shutoff function. That clearance is both a pressure and fluid leakage path. Valves with tighter spool clearances and manufacturing tolerances cost more and leak less but they all leak. Pilot operated check valves (poppets) on the work circuits are commobly used to mitigate that leakage.

Dan

I'll do what I can, but coffee will be cold and donuts stale by the time they get there.
While you are waiting, could you please explain what you mean by "Pilot operated check valves"?

 

[TheOldHokie]

I'll do what I can, but coffee will be cold and donuts stale by the time they get there.
While you are waiting, could you please explain what you mean by "Pilot operated check valves"?

I am a very patient man

Pilot operated check valves are poppet type positive shutoff valves that are installed between the work portvand the cylinder. They are sometines called "lock valves" and prevent reverse flow from the cylinder. When pressure is applied to one side of the circuit it acts on the opposing check forcing it to open permitting return flow to the valve. When used in asirs on a double acting cylinder they are called dual pilot operated check valves (DPOCV). Hydraulic top links often come with a DPOCV mounted directly on the cylinder to prevent drift - see picture. You can buy them standalone abdcadd them to equipment as well.

 

[Russell King]

I'll do what I can, but coffee will be cold and donuts stale by the time they get there.
While you are waiting, could you please explain what you mean by "Pilot operated check valves"?

A simple way to think of these is that they let the “pilot” adjust the cylinder in either direction by using the control valve. Then they act as a check valve and hold the cylinder in place until the ”pilot” adjusts it again.

 

[imarobot]

A simple way to think of these is that they let the “pilot” adjust the cylinder in either direction by using the control valve. Then they act as a check valve and hold the cylinder in place until the ”pilot” adjusts it again.

Thanks. Coffee and donuts for you too?
I'll have to investigate these things. I never knew how complicated hydraulics could be!

 

[imarobot]

Found a of video which explain the operation of a pilot valve on YouTube from LunchBox Sessions. The video explains an issue with the valve being jerky when lowering the load as the pilot opens and closes with the pressure changes. With an orifice added this does not occur but the speed of lowering is much slower.
A follow up video explains the operation of a counterbalance valve which overcomes this.
In addition to eliminating the valve leak problem I would also like to slow down the movement of the cylinders so I'm thinking a pilot valve with the orifice may also accomplish that too.
Any thoughts?

 

[TheOldHokie]

Found a of video which explain the operation of a pilot valve on YouTube from LunchBox Sessions. The video explains an issue with the valve being jerky when lowering the load as the pilot opens and closes with the pressure changes. With an orifice added this does not occur but the speed of lowering is much slower.
A follow up video explains the operation of a counterbalance valve which overcomes this.
In addition to eliminating the valve leak problem I would also like to slow down the movement of the cylinders so I'm thinking a pilot valve with the orifice may also accomplish that too.
Any thoughts?

I have DPOCV on my remotes. They are a little noisy and "jerky' on opening but otherwise smooth. I would suggest adding one or more to your mower along with restrictors in the implement hoses to slow the cylinder(s) down. I am using these.

Double Pilot Operated Hydraulic Check Valve, #6 SAE Ports, 11 GPM

Double Pilot Operated Hydraulic Check Valve, #6 SAE Ports, 11 GPM Free Shipping

summit-hydraulics.com

Dan