FEL grapple 'close' is weak...help please

[Patk]

FEL grapple \'close\' is weak...help please

My new Kubota L3130 (mini picture attached with hyd. diagram) has an AnBo 5' grapple that seems to have very weak closing strength but terrific opening strength.
Also the hydraulics sound under extreme load/strain while closing the grapple even in mid air. The hydraulics are diverted from the bucket curl circuit (electric) but the bucket curl seems fine both directions.

I borrowed a pressure guage from the dealer and checked the pressure and it seems fine at the one point I was able to test (2400 PSI ...close enough). I attached a diagram for the layout of the dual cylinders and hoses to help makes sense of this.

One of the things I wanted to do was reverse the control direction with the diverter engaged. I thought it would be a simple swap of the hose connections at the grapple (see attached diagram). I expected the open to now be weak and the close to be strong....a tolerable arrangement for the time being. BUT instead the grapple would not longer open at all. I did this in the closed position so I could never check to see if the close was now strong. I put it back the way it was. /forums/images/graemlins/frown.gif

I do not understrand why reversing the hoses did not reverse the weak/strong direction. Also, with the grapple in mid air, I can close the grapple (it's weak, but it will close) but the Hydraulic pump sounds like it's under severe load/strain. When I do this same thing with the bucket curl circuit ( not diverted), theere is no strain at all as I would expect.

Something sounds like there is a partial blockage in one of the lines/cylinders on the grapple.

Any thoughts would be appreciated.
Thanks /forums/images/graemlins/confused.gif

 

[om21braz]

Re: FEL grapple \'close\' is weak...help please

I'd expect you have the hoses right for it to open and close - even if not forcefully both ways. Check the grapple off the machine and make sure it is'nt binding up itself in the close direction (easier said than done) - especially being the bucket curl seems to be working properly. Rule out the simple stuff first.

 

[JerryG]

Re: FEL grapple \'close\' is weak...help please

I just wonder if a flow reducer was placed in the line somewhere?

 

[jmc]

Re: FEL grapple \'close\' is weak...help please

Patk,

One thing to consider is that cylinders are stronger as they extend then as they retract. (cross sectional area of rod is not pressurized in retract). If you had margin pressure in the strong direction (close), it may be inadequate pressure in the open direction because of the reduced piston area. So the problem may have actually reversed in your experiment but you couldn't confirm it with the jaws closed.

If that pressure gauge caps off the line so there is no flow required for a reading, there might be enough flow past the obstruction to build up full pressure on the guage. But in cylinder use, the restricted flow would have to fill up the cylinder as far as the pressure could extend it before you got a meaningful reading. That may take awhile.

I suspect your diverter. You ought to get good support from Anbo. It appears to be a smaller company with their president tending the sales booth at one convention and later answering my phone questions. When management is in the trenches, the trenches seem to be cleaner.

John

 

[LeRoi]

Re: FEL grapple \'close\' is weak...help please

Someone will correct me if I'm on the wrong track, but wasn't there a thread about weak closing on a 4in 1 bucket and some serious technical discussion on regenerative dump circuits and the way they affect auxiliary hydraulic functions.

 

[Jim_Fisher]

Re: FEL grapple \'close\' is weak...help please

</font><font color="blue" class="small">( wasn't there a thread about weak closing on a 4in 1 bucket and some serious technical discussion on regenerative dump circuits and the way they affect auxiliary hydraulic functions. )</font>

I don't recall the thread but I learned very quickly to lock out the regenerative dump on my John Deere 4300 when using the 4in1 bucket. Mine would sometimes move in the wrong direction if I didn't.

 

[Patk]

Re: FEL grapple \'close\' is weak...help please

Thank you for the great insights.......it sure sounds like the regenerative dump circuit is causing the 'weak open' of the grapple. Finally something is making some sense.

The dump circuit control is what has been plumbed up to perform the grapple close function. In reading about it, the rod and base ends of the cylinder are being presented with just about equal pressure and the larger area of the base end is intended to win out, but at the cost of very little net force on the base end. Works swell when dumping a loaded bucket, but is absolutely NOT what you want for a strong grapple close.

I'll have to see if there is a way to disable the regenerative circuit, or perhaps avoid using the dump circuit all together for the grapple hydraulics.

 

[Rip]

Re: FEL grapple \'close\' is weak...help please

I have an AnBo 5' Grapple Rake mounted on a Power Trac 1845 that works just fine with full power in both directions. It is operated by the standard Auxiliary hyd circuit on the PT, no special or custom diversion was needed.

So, I would guess the problem lies in the diversion (or regen/dump function) circuit somewhere.

Good Luck, I am really impressed with my unit.

Rip

 

[Patk]

Re: FEL grapple \'close\' is weak...help please

Well after learning more about the 4-way control for the loader and the regenerative dump circuit, I now know exactly why the grapple close was weak....I did not push the control stick far enough to the right to "turn-off"the renerative dump.

The set-up is far from optimal for gathering a load in the grapple though. I really wanted to have the bucket curl (roll-back) stick direction also be the stick dirtection that CLOSES the grapple, but the regenertive circuit does not allow for that. I had to settle for the curl/rollback to the left, and the grapple close (while depressing the diverter switch) to the right.

It makes for an awkward set of motions:
1. forward gathering slash in grapple while slowly curling grapple (stick left as you go forward)
2. stop return stick to center
3. depress button AND THEN move stick right to close grapple
4. WHILE still depressing diverter button return the stick to center
5. go back to step 1 and repeat till load is gathered and secured in grapple

If you make the mistake of releasing the grapple button while trying to close with stick right, you jump into bucket dump and drop the load most times.....very diffiuclt to do smoothly and reliably.


So....I asked the Dealer Service Manager about a non-renerative spool valve for the dump circuit and got this long confused commentary on how I should shorten the joy stick so the left-to-right motion is shorter....sigh.

I went home and switched the grapple diverter over to the boom circuit (non-regenerative) and now have nearly mastered the boom-up/grapple-close diverter botton. A mucj better arrangement than the regen-dump circuit.

 

[Jim_Fisher]

Re: FEL grapple \'close\' is weak...help please

Patk,

</font><font color="blue" class="small">( I now know exactly why the grapple close was weak....I did not push the control stick far enough to the right to "turn-off"the renerative dump. )</font>

Can you confirm that this will work if you push far enough to the right? On my Deere 4300 the regen doesn't activate until you move the joystick far right. Not sure that it would be very practical to have it work the way you describe since the fast dump would only happen when you feather the stick.

Sometimes folks transpose things when explaining how something works. If this is the case, then you should be able to fabricate a lockout device - a physical stop - to disable the regenerative function.


</font><font color="blue" class="small">( I really wanted to have the bucket curl (roll-back) stick direction also be the stick dirtection that CLOSES the grapple, but the regenertive circuit does not allow for that. I had to settle for the curl/rollback to the left, and the grapple close (while depressing the diverter switch) to the right. )</font>

I agree. When my tractor was delivered the 4in1 was set up so that the curl also opened the bucket. I immediately switched the lines. Close/curl - open/dump is the most intuitive way for this to work.


</font><font color="blue" class="small">( So....I asked the Dealer Service Manager about a non-renerative spool valve for the dump circuit and got this long confused commentary on how I should shorten the joy stick so the left-to-right motion is shorter....sigh. )</font>


The three hardest words to learn are "I don't know". They should always be followed by "but I'll find out". Unfortunately, some folks never learn them and tend to fabricate some sort of imagined solution off the top of their heads. Shortening the stick will make things harder to control - not easier.

At this point, two things are obvious.

1) It doesn't work the way that you want it to work.
2) The service manager knows less about the problem than you do.


Hopefully someone who has a good understanding of your tractor's regenerative dump circuit will be able to jump in and help. If not, then you will have to aquire that knowledge.

 

[Rip]

Re: FEL grapple \'close\' is weak...help please

Pat,

Sounds like you have found a workable arrangement regarding your diverter circuit.

It is one of my major frustrations in life to constantly come up against people who realy ought to know better (like your dealer) yet refuse to admit their ignorance and and ask a real authority. They then clearly display their lack of knowledge by spouting off with some really rediculous statements.

As I had mentioned, my Power Trac already had a front auxiliary circuit, but its control lever was under the dash in an awkward position for frequent use, so I did a fairly simple modification to place its control on top of the dash right next to the joy stick. Works well for me and my AnBo.

Living in the shadow of Mt Rainier must be beautiful, but it would make me nervous. Yet we live with the all too real threat of wildfire ourselves (had to evacuate 3 times in past 4 yrs). We do what we can... reduce fuels, 10K fire cistern, numerous portable and in-place fire suppression systems, etc.

Good Luck, Rip

 

[Patk]

Re: FEL grapple \'close\' is weak...help please

I'm positive the regenerative dump starts from center over to the right till you hit the detent, THEN it goes non-regenerative. I verified this by #1 putting a pressure guage inline on the rod side of the cylinder while extending the RAM (2400PSI), but goes to zip when you keep pushing right past the detent, and #2 the grapple grip gets strong after the detent.

Interesting, it sounds like the JD does the opposite...non-regen up to the detent, then regen beyond. If Kubota had that arrangement then locking/blocking out the stick motion beyond the detent would work fine.

I'm happy now with the grapple on the boom circuit and I love that AnBo grapple. Clearing brush, logs, and old stump debris for new walking trails through the woods.....It's too much fun to call it work. /forums/images/graemlins/laugh.gif

 

[Rip]

Re: FEL grapple \'close\' is weak...help please

The regen function on my NH TC-30 works like the JD, but I only use it sometimes. Now if they would reverse the Down and Float for the arms, I think I would like it better.

I know what you mean about the AnBo.... the guys I am working with are amazed at what it will do in conjunction with the low ground-impact and maneuverability of the PT 1845 on 20 to 35 deg hills. They keep saying "Awsome!" over and over.

Enjoy it while you can... I am sure you will get to some tasks that are less fun than playing "Jaws".

Rip

 

[Jim_Fisher]

Re: FEL grapple \'close\' is weak...help please

Patk,

</font><font color="blue" class="small">( I verified this by #1 putting a pressure guage inline on the rod side of the cylinder while extending the RAM (2400PSI), but goes to zip when you keep pushing right past the detent, and #2 the grapple grip gets strong after the detent. )</font>


I'm glad that you found a workaround.

I would expect the regenerative circuit to have a lower pressure since it's job is to supply a sufficient volume of oil to allow the weight of the load to dump the bucket. The only place from which that volume can be obtained is the return side of the system. If the pressure wasn't cut, it would pressurize both sides of the curl cylinders and cause the motion to stop.

With the grapple stronger at negligible pressure than it is at 2400 psi, there is obviously something at work here that we don't understand.

 

[Jim_Fisher]

Re: FEL grapple \'close\' is weak...help please

</font><font color="blue" class="small">( I verified this by #1 putting a pressure guage inline on the rod side of the cylinder while extending the RAM (2400PSI) )</font>

I just re-read this part. By the "rod side" do you mean "D" or "C" in your diagram? It almost sounds like you are checking the pressure on the return side of the circuit.

 

[Patk]

Re: FEL grapple \'close\' is weak...help please

In the diagram I initially checked pressure at C (the base end of the cylinder) to see what kind of pressure I had...it was 2400 PSI. I was confused by the weak closing force so I put the guage inline on the rod side ( D in the diagram) and was suprised to see ~2400PSI as well.

In my research into what the heck a regenerative circuit is, I found that the rod side discharge is pumped back into the base end circuit...but in doing so it see's nearly the same pressure as the base end. In this case you have nearly the same pressure on both sides of the cylinder, and it is only the large area of base side of the piston that allows the net force to extend the RAM. When I reversed the lines at the cylinders the RAM would only extend no matter which way the control stick was pushed, because the regen still applied pressure to both ends of the RAM, and in that case the base end wins and the RAM extends.

Yes, the boom circuit was the easiest route to make it all work as I 'expected' it to work.