Grapple problems

[130ROY]

I would look into the problem cylinder to see why the extra holding pressure is bypassing the piston

 

[Jim.ME]

The point of saying “grapples” was that I have operated many of them and never seen this behavior. I’ve torn lines, rebuilt cylinders, and never seen anything like this. Usually a couple strokes and it’s in business. This one has been cycled hundreds of times and still has totally random misbehavior.

The plumbing is about as simple as can be..a line from the QD to a T then to the bottom of each cylinder, and another from the QD to a T to the glad-end of each cylinder.

I understand you have used other grapples on other machines. Have you used this particular grapple on skid steers? Not have you used other grapples on skid steers, but this one. I am trying to see if this grapple has operated properly on a different machine. Simply trying to see if the problem follows this grapple, as a starting point.

Then, have you operated any other attachment using the third function on this tractor. Can you find a manufactured grapple to try on your tractor to see how it acts?

It is sounding like the grapple you built has two separate grapple arms, not connected together, operated independently by two cylinders which are plumbed together. Again, to me a couple pictures would help. Did you maintain the same size hoses and fittings to both sides of both cylinders between the valve and cylinders? Is the third function valve a diverter valve that uses the bucket function to move the third function cylinders or is it a separate direct valve for the third function. If it is direct electric valve, the flow to the cylinders may well be all or nothing, no feathering as using the bucket control would allow. This could cause more violent action if the loading was uneven. (I am not ruling out you may need some flow restriction and recommend using adjustable flow controls, if that is what is needed.)

Two cylinders mounted separately, plumbed to the same source but acting on separate components, can operate/travel differently as they see different pressures required to move if the load against them is uneven. You mentioning them going out of sync is a sign this maybe happening. More check valves and interlock arrangements in the plumbing can be required to get such arrangements to move evenly. As well as air in the system, something binding, either in a cylinder or the grapple, then releasing when it builds up pressure enough to force it free could cause erratic action where the cylinder can move separately. If the two arms of the grapple are separate, as a test, can you tie them solidly together temporarily and see if the action is different?

 

[BarnyardEngineering]

So after reading all 20-odd messages, it appears that *THIS* *SPECIFIC* grapple is NOT new.

The only logical conclusion here is one or both of the cylinders are bypassing internally. It's the only way the grapples can move in opposite directions if the ports on the cylinders are not somehow cross-connected.

Intermittent is not unheard of. You've never known fun until the steering cylinder on your dual rake hitch starts bypassing, and your 2nd rake randomly swings 6' to one side or the other. Hard to do a neat job.

 

[Nc995]

I understand you have used other grapples on other machines. Have you used this particular grapple on skid steers? Not have you used other grapples on skid steers, but this one. I am trying to see if this grapple has operated properly on a different machine. Simply trying to see if the problem follows this grapple, as a starting point.

Then, have you operated any other attachment using the third function on this tractor. Can you find a manufactured grapple to try on your tractor to see how it acts?

It is sounding like the grapple you built has two separate grapple arms, not connected together, operated independently by two cylinders which are plumbed together. Again, to me a couple pictures would help. Did you maintain the same size hoses and fittings to both sides of both cylinders between the valve and cylinders? Is the third function valve a diverter valve that uses the bucket function to move the third function cylinders or is it a separate direct valve for the third function. If it is direct electric valve, the flow to the cylinders may well be all or nothing, no feathering as using the bucket control would allow. This could cause more violent action if the loading was uneven. (I am not ruling out you may need some flow restriction and recommend using adjustable flow controls, if that is what is needed.)

Two cylinders mounted separately, plumbed to the same source but acting on separate components, can operate/travel differently as they see different pressures required to move if the load against them is uneven. You mentioning them going out of sync is a sign this maybe happening. More check valves and interlock arrangements in the plumbing can be required to get such arrangements to move evenly. As well as air in the system, something binding, either in a cylinder or the grapple, then releasing when it builds up pressure enough to force it free could cause erratic action where the cylinder can move separately. If the two arms of the grapple are separate, as a test, can you tie them solidly together temporarily and see if the action is different?

Jim - I have already stated that I have used this particular grapple.

You seem more focused on finding fault in posts than anything

 

[Nc995]

The only logical conclusion here is one or both of the cylinders are bypassing internally….Intermittent is not unheard of.

Thank you! I hadn’t seen intermittent bypassing like this before and it’s good to know it happens on occasion!

 

[flying belgian]

So after reading all 20-odd messages, it appears that *THIS* *SPECIFIC* grapple is NOT new.

The only logical conclusion here is one or both of the cylinders are bypassing internally. It's the only way the grapples can move in opposite directions if the ports on the cylinders are not somehow cross-connected.

Intermittent is not unheard of. You've never known fun until the steering cylinder on your dual rake hitch starts bypassing, and your 2nd rake randomly swings 6' to one side or the other. Hard to do a neat job.

I don't know. He makes it sound like it goes so fast and violently that it seems like there must be pressure to it. So I'm going back to tractor valve.

 

[BarnyardEngineering]

I don't know. He makes it sound like it goes so fast and violently that it seems like there must be pressure to it. So I'm going back to tractor valve.

Well there is pressure to it. It only does it when he is running the valve.

The only way I can think of it possibly being the valving on the tractor is if the return is not opening up. Pressure from the return oil on one claw would gush across to the other claw, if the one claw had a grip on something and the other one didn't. Because of the larger surface area on the extend side of the piston, it would overcome the retract side and push the claw open. The oil from the retract side of that piston would gush across to closing clamp, making it close even more, pushing more oil back across to the extend side...

I'm not even sure if that could happen.... I may be missing something in that little thought exercise.

It's more likely and logical that the cylinder is bypassing internally. If it's always the same claw that springs open, that's the cylinder I'd rebuild first.

 

[flying belgian]

Well there is pressure to it. It only does it when he is running the valve.

I mean as aposed to it slipping past the cylinders

 

[BarnyardEngineering]

I mean as aposed to it slipping past the cylinders

When the steering cylinder on my rake hitch bypassed, it was sudden and violent. You'd glance forward for a second, and when you looked back again, the rake was in a completely different location.

 

[Nc995]

I don't know. He makes it sound like it goes so fast and violently that it seems like there must be pressure to it. So I'm going back to tractor valve.

It’s already quite jerky at anything above idle. I’m thinking it’s really going to need some restriction to cope with this setup.

Anyway, add in that one side may be clamped on a load and that it happens when not expecting it, and I think that might explain my perception of very violent movement.

 

[flying belgian]

It’s already quite jerky at anything above idle. I’m thinking it’s really going to need some restriction to cope with this setup.

Anyway, add in that one side may be clamped on a load and that it happens when not expecting it, and I think that might explain my perception of very violent movement.

Now I'm thinking it's plumbed wrong. Take it back to the dealer who installed it and tell him to fix it.

 

[Nc995]

Now I'm thinking it's plumbed wrong. Take it back to the dealer who installed it and tell him to fix it.

What makes you think that?

 

[used red MN]

A photo of the setup would not hurt. And to clarify, the third function valve that was added is all stock Kubota parts and now your tractor is set up just like if it would have came new with 3 remotes? Or is it some type of an aftermarket add on? The reason I asked is the stock third valve would be expected to work like the first two. Some type of add on valve may have its own set of idiosyncrasies.

 

[Jim.ME]

Jim - I have already stated that I have used this particular grapple.

You seem more focused on finding fault in posts than anything

I apologize I missed or misread the post you said that in. I am not trying to find fault with the posts, just trying to be sure I fully understand everything. Just like my asking about the third function arrangement, I am trying to understand how it is set up looking for valve switching conflicts.

If you have another machine around, you could put the grapple on, it would seem like an easy check to see if the grapple operated the same as it did in the past on other machines. If it does, then look towards the tractor.

Good luck, I will step away.

 

[Nc995]

A photo of the setup would not hurt. And to clarify, the third function valve that was added is all stock Kubota parts and now your tractor is set up just like if it would have came new with 3 remotes? Or is it some type of an aftermarket add on. The reason I asked is the stock third valve would be expected to work like the first two. Some type of add on valve may have its own set of idiosyncrasies.

It’s a land pride add-on; push buttons as opposed to manually operated valve.

 

[paul]

I’ve used the grapple before on a different skid steers without issue, but it’s been a while.

My reason in posting is this was thinking that perhaps there may be an issue with bleeding. That’s what it seems like to me. My thoughts are that the cylinders are small and with a short stroke, and there’s fairly long lines between the cylinders and tractor, and again long lines down the loader.

What I didn’t anticipate is that from this question everyone would conclude from the model number that it must be returned to the dealer. I don’t actually think there’s anything dysfunctional with the third function. It’s for sure worth considering, but there’s just no malfunction that I can think of that might explain one arm closing while the other directly connected wildly flips open…only sometimes.

Folk are generally 85% helpful around here. I’ve been around this place a few decades. Good folk with the occasional odd one.

Over the decades we find it is difficult to be accurate without knowing a ton of details.

Pics are always helpful.

You are asking a detailed question about a hydraulic and possibly electrical intermingled system. You yourself say you are pretty experienced with these and are stumped.

On the other hand we often get questions from people that have driven a tractor 2 hours and have zero experience.

Help us help you.

We need to understand the issue…. The details.

If your third function is an electric selinoid, it could be electrical. I don’t know.

If there is air in the lines, it could be air bleeding out. But not sure if you have used the setup before.

Could be a defect in the new third function, or it could have been plumbed wrong. That does happen even with experienced dealerships. That would be a warranty issue.

Common grapples here are a single grapple arm. From reading it may be you have a twin arm grapple with independent arms? That makes operation and bleeding air different, but - I don’t know what you have.

We are trying to help, but we do need the details. Help us.

 

[used red MN]

The grapple will function flawlessly while I am sitting,

When it worked flawlessly were you only idling the tractor. Higher engine speed will give more flow and thus a jerkier response. I would need a photo to see the setup in response to “one opens and one closes” Obviously there is no “feathering” with a push button, the more discussion here the more I believe a restrictor is maybe the answer as Samm suggests. This may cause it to be slower to respond than you’re expecting at times but just may be the nature of the beast.

 

[Nc995]

When it worked flawlessly were you only idling the tractor. Higher engine speed will give more flow and thus a jerkier response.

Either. I can run it at idle or at higher rpm, and it appears I can cycle the cylinders all day without a malfunction. 16-1700 is where I tend to run it. The grapple is snappy but not obnoxious at that rpm, and I still have enough oomph to run the loader.

 

[ss55]

Does the grapple get erratic when you actuate the grapple valve at the same time as you are actuating another hydraulic valve? It might be safest to only actuate one valve at a time until the problem is fixed.

Actuating two valves at the same time on an open center hydraulic system can allow oil to freely flow between the two valve circuits until the pressure is equal in both circuits. Say if you were lifting a heavy bale with the boom cylinder and developed 2000 PSI of back pressure in the boom cylinders. Now opening the grapple valve might allow a large volume of 2000 PSI oil in the boom circuit to back flow unrestricted into the grapple circuit until the pressure is both circuits is equalized - probably when the grapple hit its end of travel stops hard.

Is the tractor hydraulic system open center or closed center, and is the grapple valve the same open or closed center?

 

[Nc995]

Does the grapple get erratic when you actuate the grapple valve at the same time as you are actuating another hydraulic valve? It might be safest to only actuate one valve at a time until the problem is fixed.

I’ve tried to isolate my inputs to one at a time. It’s difficult as old habits die hard (and grappling brush just work better with loader motions at your disposal). Best I can tell, it matters not whether I’m giving a separate input when closing the grapple.

Is the tractor hydraulic system open center or closed center, and is the grapple valve the same open or closed center?

That I don’t know.