I would like to know more ???

[ns_in_tex]

On my kubota L4610, we have a rotary implement on the fel, which is powered by a hydraulic motor, fed off the rear remotes.

When the fel is not moving, the implement seems to run at a constant speed, depending on the engine rpm ( gpm of flow), but if we raise the fel, the implement slows down or if we lower the fel, the implement speeds up.

I presume the hydraulic flow rate is changing to the rear remotes while this is happening.

Can someone explain to me what causes this to happen and I also wonder if the extra flow (while lowering the fel) maintains the full pressure (up to 2500 psi) of the normal hydraulic system, or is it dependent of the amount of weight on the fel, pushing oil back into the system?

 

[J_J]

Your FEL valve is first in the series flow path and has priority. and can us all of the flow or just some of the flow.

Actually, if the FEL is using all the flow as in full lever, there is no flow downstream.

If the FEL is only using half lever on the FEL,, then about half pump flow is available for downstream work.

If you want to run the motor at a constant speed, then you need a flow divider, or priority valve to the motor.

They come in various configuration, like 5/5, or 2/5, in GPM's etc.

You can also use a priority valve that will always provide the first part of the flow to say a hyd motor, and what pump flow is left, will pass on to the FEL.

</title> endstream endobj 12 0 obj 17 endobj 13 0 obj << /Type /XObject /Subtype /Image /Name /background0 /Width 3060 /Height 3960 /BitsPerComponent 8 /Length 14 0 R /ColorSpace /DeviceRGB /Filter /DCTDecode >> stream

So if you have 16 GPM's, and the priority port is getting getting 10 GPM, then the rest of the system is getting 6 for FEL and remotes and 3pt.

How many GPM does the hyd motor require.

What is your tractor flow?

Here is a 16 GPM priority flow divider.

You dial in what the priority hyd flow should be to the motor.

The excess flow will feed the rest of the hyd system.

So if you have a 16 GPM or less hyd supply, and the motor requires say 10 GPM to run at the speed you choose, then 6 GPM will feed the rest of the hyd system.

If you set the lever at 0 GPM, the FEL , remotes and 3pt will get all the flow.

Hydraulics:
Type: open center
Pump flow: 9.6 gpm [36.3 lpm]
Total flow: 14.4 gpm [54.5 lpm]
Steering flow: 4.8 gpm [18.2 lpm]

 

[ns_in_tex]

We like the fact that it slows down as we raise the fel.
I think, I like the fact that it speeds up as we lower the mower, but do not understand exactly what is happening when it is doing so.

We are running a limb saw to trim tree limbs which are hanging down & dragging on the tractor cab, so if we go up over the top limb to be cut, then lower, the blade speeds up on the way down, so it gets greater flow on the down stroke cut.
This means we can run our engine rpm slower to get the job done.

Oh, I think the full rpm flow is about 9 gpm.

 

[J_J]

The FEL valve has priority and is simply using the fluid before the motor get any.

The hyd pressure is developed by the hyd component and determined by the load.

If you had a hyd gage installed, you may not even see anything close to the max pump pressure potential.

However, the gage will show any pressure developed by any hyd component in the hyd system. This can give you a clue as to the load on the hyd.

 

[ns_in_tex]

Thanks, J.J. for the info

We do now, understand The FEL valve has priority and is simply using the fluid before the motor gets any.

We do have a fitting to mount a gauge to set the relief valve to the motor, and I understand the pressures may vary according to the load applied.

One thing we still would like to know is, if there is any way to at least estimate, the added gpm of flow to the motor, when the loader is being lowered, and I realize the faster we lower it, probably the more the flow increases. Since we may be running the blade pretty fast, we wonder if there is a danger of over speed on the blade and are trying to estimate blade speed.

Also, will this added flow from lowering the fel be maintained and the pressure just rise (hyd motor HP go up), as the blade is loaded with sawing, just the same as the flow from the pump when the fel is inactive?

 

[J_J]

When a FEL cyl is using flow, the hyd motor speed will decrease in rpm, and when the FEL is back in neutral, the flow will return to the motor.

Actually, if you use full flow to the FEL cyl, the hyd motor will slow down because it has no fluid. .

 

[ns_in_tex]

I understand that part. I think you may have missed part of my original post.

"if we lower the fel, the implement speeds up."

I presume the fluid from the fel cylinders is somehow returned into working pressure "above and beyond the pump capacity". At least it sure seems that way to me. We can figure the blade speed by pump capacity, but if we have return fluid capacity being changed into "working fluid gpm" then our blade is increasing speed also. It is enough to be noticeable by sound and watching the work being done.

I believe on the down stroke of the fel, is producing flow, not using it.

When a FEL cyl is using flow, the hyd motor speed will decrease in rpm, and when the FEL is back in neutral, the flow will return to the motor.



Actually, if you use full flow to the FEL cyl, the hyd motor will slow down because it has no fluid. .

 

[J_J]

I am assuming you know how a cyl extends and retracts and where the fluid goes.

When you move the lever to extend the rod the pump pushes fluid into the base end of the cyl. At the same time the rod end fluid is push out to the return port and sent to tank. It is gone.

When you retract the rod, the pump pushes fluid into the rod end and the base end fluid is pushed out to the return port and to the tank.

Return fluid is going to tank period. It is never working fluid.

The hyd motor can only run if there is flow. At a certain GPM flow, the hyd motor will run at a certain rpm, and if you increase the flow, the motor will run faster.

So if you are using fluid to operate the FEL, you take fluid away from the hyd motor, and the only way to recover the rpm is to let the FEL valve go to neutral. Now, the pump is providing full flow to the hyd motor.

How much GPM does your saw require? What pressure rating?



I hope this is all clear now.

 

[boggen]

Thanks, J.J. for the info

We do now, understand The FEL valve has priority and is simply using the fluid before the motor gets any.

We do have a fitting to mount a gauge to set the relief valve to the motor, and I understand the pressures may vary according to the load applied.

One thing we still would like to know is, if there is any way to at least estimate, the added gpm of flow to the motor, when the loader is being lowered, and I realize the faster we lower it, probably the more the flow increases. Since we may be running the blade pretty fast, we wonder if there is a danger of over speed on the blade and are trying to estimate blade speed.

Also, will this added flow from lowering the fel be maintained and the pressure just rise (hyd motor HP go up), as the blade is loaded with sawing, just the same as the flow from the pump when the fel is inactive?

your getting into a lot of math and very specific variables. and it will dynamically change constantly. even a animated computer model will most likely be off to some extent on an estimate. for blade tip speed / chain rotation speed.

there should be some sort of "max pressure relief valve" built into hyd motor and/or saw, to deal with it getting hung up on something. (pinching saw in a tree branch for example)
the manufacture should have taken into account max GPM and pressure from a hyd pump on a tractor. when they denote min/max specs for the saw / hyd motor.
i suppose if there was a big deal, a "over run clutch" or shear bolt, or slip clutch or like might be built in between hyd motor and actual saw blade/chain.

 

[J_J]

ns_in_tex

I sure would like to see the saw in operation, and the hyd gage is plain view.

Good sound without a lot of wind noise would be helpful also.

With all due respects, the reason for this is that some of the things you say are not logical.