Question about log splitter on M6800

[BSawyer]

Hello all!

I posted this in the attachments forum on 9/1, but haven't gotten any responses so I thought I'd try it here also. Hope that's OK.


I picked up a used log splitter last year and thanks to advice found here, got the right connectors to hook up to my M6800, flushed the old fluid and split a bit of wood last year.

The way I would use it was to take the hyd. lever control on the tractor and push or pull it one way or the other until it locked into place.

Then I would move back to the splitter and use the control lever on it to expand or retract the cylinder to split the wood.

The only bad thing was that when I expanded the cylinder too far or retracted it all the way, the splitter cylinder would quit moving and the pump seemed to make a different noise. The only way I could get it to reset was to move the hyd lever on the M6800 thru it's positions and then lock it back down. Then at that point I could resume splitting, again using the splitter's hyd control lever.

Any body have any ideas what is wrong? I don't know if the problem lies in the log splitter hydraulics or maybe there is a over-pressure relief valve on the M6800 that needs adjustment. I'm not strong in hydraulics workings...

The M6800 has less than 40 hours on it, and is my first.

Let me know if you need any more details.

http://img.photobucket.com/albums/v469/bowfan/TractorStuff/splitter.jpg

 

[rbargeron]

Without seeing and hearing it up close, this is a bit of a guess - but it sounds like the relief valve on the splitter's control valve is set too high. When the cylinder extends or retracts to its mechanical limit, the pressure spikes. The M6800 has an internal relief valve to protect itself - but from your description it will only reset itself by cycling the control valve for the remotes (momentarily reduces pressure in the system).

The splitter control valve should have a built-in relief - but it may not. On a valve designed for splitters, there is usually a shim-adjustable relief for the extend stroke, and an auto-centering feature for the retract stroke (so you can set it to retract and go get another chunk while it's traveling. If your splitter control doesn't have a relief, the answer might be to replace it. Splitter valves are readily available - example here Prince Log Splitter Detent Valve

Another possibility is that the control valve for the remotes has a relief valve that' set too low - and that's the one that doesn't reset itself. Like I said, I'm guessing from this distance. As always, prompt cheerful refund if info is bogus. Take care, DickB

 

[BSawyer]

Thank you RB, I appreciate the insight!

I've got lots to learn still. But you've got me thinking. I googled around today and found my control valve is made by Cross Mfg (as well as my cylinder). It's a model BA I think. I wasn't too sure of where to look for the relief valve. Pic of mine: Left side
Right side

Found the CM website and downloaded some PDFs with part lists, troubleshooting, etc. One of them said the points of failure possible 1) external leak, 2) internal leak, and 3) spool bind -> caused by contamination, excessive heat, improper mounting, and misalignment of valve linkage.

I thought about checking for any contamination or adjustment in the relief valve but wasn't sure where or what it was. Found a part chart that identifies what I circled as "A" on my pic above as the relief valve.

But then the diagram goes on to say there are 3 types of relief valves: 1) no relief option, 2) non-adjustable relief option (HP - LP), 3) adjustable relief. The PDF pic of adjustable relief doesn't look like mine. It seems to have a couple nuts capped with an acorn nut. You can get an idea what I mean on this page although the example pic shows a 3 spool unit: Valves Look at the model BA.

I guess I need to determine exactly what I have before I can decide if there is a problem I can fix.

And I don't know about some of the following: "open center in neutral" I guess this means that the hyd fluid just passes thru as if open when the lever is left in the center position?

"Conversion plug allows for Closed center systems or for use in power beyond application"? Mine does not appear to have a factory plug in the portion of the above right side pic that I marked "B" It may be something someone put together when they lost the original part, I don't know. It may be a power beyond unit adapter that someone has plugged.

In this diagram is appears to be short, smooth, and one piece : BA Model
I don't know how old my model is, or how much it differs from the current info from Cross Mfg.

If possible, I'd like to fix / use what I have unless anyone thinks I would be much better off with a different design. I don't know that this one has the "auto-centering retract stroke" feature, for instance.

I do appreciate the good advice!

 

[rbargeron]

Good pics - I agree the A detail is the relief valve - looks like the shim type, which is called non-adjustable because you can't turn something to change the pressure - but you can put in different shim thicknesses. Cross parts should be available. The valve could be shimmed for 3000 psi - which would be higher than the 2200 or so the M6800's relief is likely set for. With a 4" splitter cylinder, 2000 is plenty.

I noticed the BA single spool page does not mention an auto-return-to-neutral function. And the feature they list that isn't needed on a splitter is the load check valve - but I don't think it's a real problem unless you get the wedge stuck in a tough piece and can't move it back. The closed center plug may be original, or somebody may have used the splitter with a closed-center system (Deere?).

You are on the right track to understanding this and resolving it. My bet is you'll find a way to use the valves you have - maybe with some minor mods. It would be good if MadReferee checks in - he may have more ideas.

 

[BSawyer]

Thanks again,

That does sound likely, if the valve on the splitter is never hitting the relief pressure point then it forces the M6800 to do the relief work.

I noticed the Kubota M6800 Spec page shows the max operating pressure is 2770 psi, but this probably is not the same as the the relief pressure number you mentioned.

I'm guessing the logical usage would be to add shims to increase the pressure, and remove shims to reduce pressure. I guess I'll pull it apart and count the shims and check for contamination.

I believe the previous owner had a Ford 4000 tractor or clone, although that doesn't guarantee that was the tractor he used it with. Maybe he added shims to make sure he was getting max pressure...? I don't know, may just have some junk in it.

At some point I should probably get a gauge and see what pressures I'm hitting. Last year it cut thru oak and hickory like butter.

 

[rbargeron]

Sounds like a plan - I should add some cautionary words about connecting gauges, fitings, etc. - be sure everything is safe for the pressure, and limit the spectators. Mostly just be safe. But have fun.

 

[MadReferee]

The relief on the splitter MUST be set lower than the tractor's system relief. I agree that square A is probably the relief and that shims will most likely need to be removed to lower the setting.

You really should have a valve that auto returns the spool to neutral when the relief pops. Northern Tool sells them with adjustable relief for $79.99 (part #2020-1701). It would be a wise investment.

The load check is pretty much a standard on any valve that may be used in an application where lifting is required. It's function is to overcome the forces of gravity when the spool is activated by preventing the exhaust work port from opening for that fraction of a second or so until enough pressure is built up in the pressure work port to hold the cylinder load. Basically it keeps a loader/lifter from jerking when the spool is activated. For a splitter application it is not necessary but it's there anyway.

 

[BSawyer]

So with the MaxOperatingPressure of the M6800 being 2770 PSI, I should use 3000 PSI, hoses - gauges... etc? Would that be safe?

It may sound like a simple or stupid question... but I know it can be dangerous if burst occurs. And I don't really have a lot of experience in hydraulics. I don't know if there are rules that apply such as (max pressure x ).

At the Cross Mfg website, I had to fill out a form in order to download the PDFs. Today, I got a quick response:

>Dear B, From your picture, I am wondering if you have made
>the valve closed center by putting a plug in a power byd sleeve
>in the byd port - this would block the power core and cause the
>tractor valve to kick out so can you please advise. thanks,
>Linda

Hmmm, wheels are turning again. It looks like the power beyond option also acts as a closed center option? Here's some more pics :

Open Center

Closed Center

Power Beyond Adapter

She gave a part number and said it should be "a standard 1 5/16-12 plug".

She seems to know her stuff, could it be that simple to fix the high pressure problem? Just remove the closed center option?

I think so, just wanted to get a second opinion.

 

[BSawyer]

Mad,

Thanks for the advice about the Prince LS3000, that's probably the best way to go. But it's fun to try to figure things out, and learn a little.

 

[MadReferee]

So with the MaxOperatingPressure of the M6800 being 2770 PSI, I should use 3000 PSI, hoses - gauges... etc? Would that be safe?

It may sound like a simple or stupid question... but I know it can be dangerous if burst occurs. And I don't really have a lot of experience in hydraulics. I don't know if there are rules that apply such as (max pressure x ).

I would use noting less than a 2-wire 4000 psi hose (aka R2 3/8"). Stay away from 1-wire hoses. They are not as strong and won't last.

At the Cross Mfg website, I had to fill out a form in order to download the PDFs. Today, I got a quick response:

>Dear B, From your picture, I am wondering if you have made
>the valve closed center by putting a plug in a power byd sleeve
>in the byd port - this would block the power core and cause the
>tractor valve to kick out so can you please advise. thanks,
>Linda

Hmmm, wheels are turning again. It looks like the power beyond option also acts as a closed center option?

The power beyond sleeve, the closed center plug and a simple port cover plug are three different animals. If you have your splitter connected to a power beyond connection or to a remote on the tractor then that is a cover plug since your tractor system is an open center system. An open center system has fluid continuously flowing thru the valve. A closed center system does not and has fluid flowing on demand from a variable displacement pump.

A power beyond option does not act as a closed center option. Removing the cover plug from the BYD port (B in your diagram) and installing a power beyond sleeve will isolate the outlet port from the power beyond port and turn the outlet port into the return to tank port.

If there is a power beyond sleeve in there and you have plugged up the hole in any fashion then you have effectively turned the valve into a closed center valve. This is not good since with fluid always wanting to flow thru the remote and into the valve it will now have nowhere to go WHEN THE SPLITTER LEVER IS IN NEUTRAL. When the lever is activated fluid will be able to exhaust thru the return to tank outlet.

Your original problem is not closed center related but pressure relief related.