Loader Third function does not work with curl, only lift lower on mx5200, is this typical?

[MechanicalGuy]

Dealer installed third function for grapple but it doesn't work with curl simultaneously, only by itself or with lift. Is this a characteristic of the valve, the installation, the tractor, or something that I'm not listing?

Just trying to understand "why".

 

[dstig1]

Is it a diverter? That is what i have on my tractor. It is an electric solenoid that taps into the curl/dump circuit. I push the little button on the joystick and curl/dump motion of the joystick now becomes grapple open/close. Release button, back to curl/dump

 

[Fallon]

Only the closest valve in an open center (of which all CUTs are) hydraulic system will get flow. When you activate the valve, every other valve downstream gets starved until its released. Move the loader & the 3pt at the same time & the 3pt wont move until you let off the loader control.

Lift & curl are really the only exceptions to that because they are contained in a single valve assembly & plumbed in wierd. Its theoretically possible to have a 3rd function in the same valve block, but super uncommon.

The question of it being a diverter or true 3rd function is kind of moot. Either it's a diverter, which diverts curl to the 3rd function or the 3rd function valve is downstream of your loader block. In either case neither will work the same time as your curl function.

My L4060 3rd function is like that. Lowering the loader stops flow to the 3rd function (TnT & 3pt too). Its really noticable when it stalls my SSQA hydraulic post hole digger. Similar pain to wanting to curl & clamp at the same time I expect.

If you want multiple functions to work at once, you need to go to a different caliber of machine. 100+ HP tractor, skid steer or excavator really. They all have multiple pumps & hydraulic circuits and/or open center hydraulics.

 

[JWR]

Fallon is correct, as usual. "Only the closest valve [that one tries to use][to the source pump] in an open center (of which all CUTs are) hydraulic system will get flow." I have described this often as "one track mind hydraulics."

Essentially all the tractors we talk of here have open center hydraulics which means only one device gets flow under pressure at a time. The rest are precluded. By clever use of gravity assisting motions of some loader actions, etc.[for example tip downward motion of a loaded bucket while raising or lowering the loader frame] the ILLUSION that you are powering more than one thing at a time is often enabled.

This one-track-mind limitation is especially visible using 3rd function things. Hydraulic motor driven devices like FEL mounted cutters are a huge graphic example. You would be amazed how many older, very experienced, dealers and mechanics fail to understand this reality. I've even seen heated arguments on TBN claiming the opposite of this reality.

There are gadgets (like flow dividers) which enable multiple devices "sort of simultaneous" by tapping into open center hyd systems and creating a side circuit which is in truth no longer open center internally -- smaller amounts of pressurized flow going to each of the side devices. This plumbing can be quite expensive, is poorly understood or explained, and rare is the dealer who knows what they are doing in this area. I have seen both Kubota and New Holland upper end machines with these gadgets. If you are into creating specific non-standard capabilities these things can get very complicated.

 

[MechanicalGuy]

Thanks for all the detailed explanations. I suspected that it had something to do with the caliber of machine that I had purchased. It's still an awesome tractor.

 

[David_Kb7uns]

Could be if the valve is regenertive or not.

Have a GL3130 LA723 loader with the Husco valve made for Kubota and the WR Long 3rd function valve. I can trigger the valve and then curl and the cylinders will both move at the same time with half the force, release either one then you have full force of the hydraulics.

Have gotten pretty good at scooping and clamping on the run when moving brush, on boulders have to stop and get a good clamp otherwise they will slip out.

David

 

[JWR]

Could be if the valve is regenertive or not.

Have a GL3130 LA723 loader with the Husco valve made for Kubota and the WR Long 3rd function valve. I can trigger the valve and then curl and the cylinders will both move at the same time with half the force, release either one then you have full force of the hydraulics.

Have gotten pretty good at scooping and clamping on the run when moving brush, on boulders have to stop and get a good clamp otherwise they will slip out.

David

Yep. You are using a diverter valve or flow divider. Probably works well.

 

[rbargeron]

I believe the issue is that in the "dump" position the curl valve pressurizes BOTH ENDS of the cylinders. It's an often-overlooked design feature of loader valves on Kubota (and other) models. The purpose is to prevent bucket loads dumping too fast. The cylinders move ok because the extend area is larger than the retract area. In the "dump" position the return hose is pressurized too, so can't act as a free drain.

The curl circuit can still be used for other hydraulic cylinders - but connected so the "big end" can prevail.

 

[MechanicalGuy]

I believe the issue is that in the "dump" position the curl valve pressurizes BOTH ENDS of the cylinders. It's an often-overlooked design feature of loader valves on Kubota (and other) models. The purpose is to prevent bucket loads dumping too fast. The cylinders move ok because the extend area is larger than the retract area. In the "dump" position the return hose is pressurized too, so can't act as a free drain.

The curl circuit can still be used for other hydraulic cylinders - but connected so the "big end" can prevail.

Oh wow, that sounds like something I've never heard before. Thanks for the info

 

[MechanicalGuy]

I found this post that seems to support that thought also:

More "clues" to the curling culprit.
We decided to get away from the two single-action hydraulic actuators on the snow plow (to push left, or push right), and tried to use one, dual-action acutuator.
So when we hook up a dual-action hydraulic actuator to the "bucket curl" lines, guess what? We get it to extend when the joystick is left (CURL UP) and it extends even further when the joystick is right (CURL DOWN), but it never retracts in that position. So we reversed the hydraulic lines, just for Sh1ts and giggles, and it works just fine extending and retracting.
The best we can figure out is that the curling is controlled on the CURL DOWN, to prevent the weight of the bucket and the weight of the load from just dropping the bucket in freefall (if the return hydraulic line were allowed to free-flow the fluid back to the resevoir). It seems that 2750psi of pressure is put on the main piston to push the bucket down, which overcomes the 2750psi on the perimeter side of the actuator (which pushes the bucket to curl up). It's weird, but that's the best we can figure.
Anyone have any ideas/experience along these lines?