JD 4720 - Issue with hydraulic control for stump grinder

[TCowner]

I picked up a used Worksaver SG36 pto powered stump grinder this past weekend. The unit requires two sets of hydraulic couplers for operation. I have the 3rd valve (rear) that I used for the side to side control and my plan was to use the loader curl couplers for raising and lowering the grinder. I wanted to keep the loader on for a little extra front end weight as the stump grinder weighs around 900#.

I unhooked the two hoses for the loader curl operatin and plugged in the hoses to the grinder cylinder and can't get the cylinder to move more than a few inches. I thought there might be an issue with the cylinder so I hooked the hoses to the rear couplers and the I could lift and lower the grinder with ease so the cylinder is good.

I'm at a loss. Why isn't there enough hydraulic flow from the mid couplers to operate this cylinder? Is there something unique about the mid control hydraulic valve that affects the flow of oil? I thought about taking off the loader and try using the loader lift couplers to see if that made any difference but again, I would prefer to leave the loader on for some additional front end weight.

Someone suggested that the mid valve has a regeneration feature that might be the problem. Can someone explain how that would affect the operation of a remote cylinder?


Thanks.

Terry,

 

[jenkinsph]

Can't speak about the regeneration feature.

When you connected the hydraulic lines did you run them to the mid couplers independently or did you attach them to the curl cylinder lines on the front of the loader?

I ask this because some loaders are using a hydraulic self leveling feature that may be causing this. Just a shot in the dark. Also after plugging in to the rear coupler did you try the curl circuit again?


Steve

 

[kennyd]

The Regenerative function of the dump/curl circuit is causing your problem. There is a way to lock it out-but not sure how on your model.

Do a search for the term "regen", and read at least the first post in THIS thread to learn more about why it's causing issues for you.

 

[Dutch445]

is there a chance that the stump grinder was designed
for a closed center hydraulic system instead of open?

 

[GreatWhitehunter]

Isn't a power beyond type circuit needed for contstant flow?

Matt

 

[kennyd]

is there a chance that the stump grinder was designed
for a closed center hydraulic system instead of open?

I seriously doubt it. It's the regen that's the problem-guaranteed.

 

[kennyd]

Isn't a power beyond type circuit needed for contstant flow?

Matt

He stated it need's two remotes to operate-so it does NOT have it's own valve.

 

[GreatWhitehunter]

He stated it need's two remotes to operate-so it does NOT have it's own valve.

Actually he said nothing about remotes. He said two sets of couplings. For a constant flow hydralic motor have constant flow you need a power beyond setup. I think he assumed that he'd have constant hydralic flow at the curl circuit. I'm certainly no expert but from a common sense standpoint, it would make sense that to run the rotor at a constant speed you need to have constant flow. So oil coming and going back to the sump.


Matt

 

[kennyd]

Actually he said nothing about remotes. He said two sets of couplings. For a constant flow hydralic motor have constant flow you need a power beyond setup. I think he assumed that he'd have constant hydralic flow at the curl circuit. I'm certainly no expert but from a common sense standpoint, it would make sense that to run the rotor at a constant speed you need to have constant flow. So oil coming and going back to the sump.


Matt

I am not going to debate you Matt, the rotor is PTO powered and the two remotes are for the side-to-side motion and the up-down of the cutterhead.

 

[Jdman4x20]

The Regenerative function of the dump/curl circuit is causing your problem. There is a way to lock it out-but not sure how on your model.

Do a search for the term "regen", and read at least the first post in THIS thread to learn more about why it's causing issues for you.

The regen is causing the issue.
It can be locked out. The lever has a three position lock, the center position that has the picture of the manual will limit the lever movement.