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.

 

[Dutch445]

If it was a Regen problem, wouldn't that only interfere
with the cylinder going 1 way?
If the cylinder isn't going in either direction properly, maybe
the hoses aren't in the correct couplers for the curl
function?... possibly 1 is, and 1 isn't..

 

[TCowner]

Update: I took the loader off yestereday. I played with the control that is supposed to shut off the regeneration function and it made no difference. I hooked up to the set of couplers that controls the loader lift function and still nothing.

My hydraulic knowledge is rather limited so help me here. According to the John Deere build site "Note: All front hydraulic couplers are 3/8-in. All rear hydraulic couplers are 1/2-in."

So could this be the issue. The male ends will fit into the front couplers but don't work. When plugged into the rear couplers the cylinder works just fine. I also just realized that the male ends have the spring loaded round ball (I apologize for the terminology) instead of the spring loaded tapered tip that the loader male hoses use. I asked the service rep at the JD dealership and he said that shouldn't make any difference. If the rear couplers are larger than the front then perhaps the different style of male coupler is less significant. But when using the smaller front couplers is does make a difference.

I am going to replace the male couplers with the style that is identical to the male loader hose ends to see if that remedies the problem. I will post another update.

 

[kennyd]

Keep us updated TC

 

[TCowner]

UPDATE: Ladies and gentlemen, this is one of the most difficult things I've had to do. I'm embarassed and ashamed.

The source of the problem was discovered and it had nothing to do with the hydraulic hose tips. I have the third hydraulic valve on the back of the tractor. I also installed the Deere third function kit that couples the third function (rear) to the mid hydraulic manifold with a set of quick couplers. This is what I use to operate the loader mounted grapple. The two hydraulic hoses that extend to the manifold at the middle of the tractor are mounted at the top of the manifold, side by side. So I assumed, wrongly of course, that the loader curl hoses and loader lift hoses were side by side as well. They are not. The two are stacked one on top of the other. So I was only supplying oil to one side of the cylinder on the splitter with no way for the oil to return. I noticed that the loader curl cylinders were trying to move a little when I was trying to operate the stump grinder lift cylinder. I couldn't see how that was possible if the hoses were unhooked to the curl cylinder.

SO, after a few choice words I switched out the hoses and problem solved. I had the operators manual in the shed but no reading glasses close. So as best I could I found the section where it showed the hose hookup and it seemed to suggest that the solution was there all along, although I believe Deere could have a better picture with greater detail. The picture is rather dark.

So the excuse I am going to use to lessen the embarassment is the side by side location of the third function hoses and the top to bottom on the other two functions. It probably won't buy me much sympathy here but its all I have.

Thanks for the suggestions and the all of the effort by you folks. I think I will keep quiet for a little while. Does anyone know how I go about chaning my user name?

 

[kennyd]

I am glad it was a simple fix that was FREE

 

[jenkinsph]

TCowner, thats OK just don't do it again anytime soon, someone might bring up this thread. Glad it was a cheap fix for you.



Steve

 

[ddivinia]

OK - now show us a picture of that thing in action.

D.

 

[TCowner]

Darin, Here are a few pictures of the 4720 in action with the stump grinder. The grinder will use all of the 50 pto horsepower if I try to take too much stump at one time. Actually, its one of the few times I've made the tractor growl a little.

I picked this up on ebay for $3950. It cost me $250 to have it shipped from Kansas to Minnesota. I hadn't planned on purchasing a stump grinder but couldn't overcome the high prices all of the guys were getting here to grind stumps. I understand the need to charge a reasonable price to cover fuel, replacement parts, the cost of the equipment, and the operator's time but the best price I could get was just under $1200 for 40 stumps. I've ground 35 stumps so far in about 6 hours of time and used about 12 gallons of fuel.

I'm in the process of thinning a stand of scotch, norway and white pine and will have 40 to 50 stumps a year for the next five years. The grinder will get plenty of use and might try a little custom work with it.