Kubota M108 3PH priority

[rolandjeff]

Hi,

We bought a Kubota M108 last year to use as our main seeding tractor. We grow row crop vegetables and were looking for a small light tractor that could handle our seeder. The tractor is great and works well. The only issue we have run into is that our seeder uses a hydraulic motor to run the fan for the seeder. When we get to the end of the row and try to raise the 3PH, it will not lift until we disengage the hydraulic motor. Any tractor we have used before provides the 3PH with priority over the remotes. Is there anyway to change this somehow. We have talked with our local dealer and they tell us that there is nothing we can do. This is frustrating because it knocks all the seed off our discs at the end of the row.

Thanks for any help.

 

[bigdeano]

It looks like your tractor has a large hydraulic flow, so you could use a priority flow divider to split the flow so both the 3ph and the remotes will work at the same time. If you use an adjustable one you can set the flow to your liking. Surplus Center has some.

 

[rolandjeff]

It looks like your tractor has a large hydraulic flow, so you could use a priority flow divider to split the flow so both the 3ph and the remotes will work at the same time. If you use an adjustable one you can set the flow to your liking. Surplus Center has some.

Thank you. I will look into this.

 

[Dave M7040]

Hi,

We bought a Kubota M108 last year to use as our main seeding tractor. We grow row crop vegetables and were looking for a small light tractor that could handle our seeder. The tractor is great and works well. The only issue we have run into is that our seeder uses a hydraulic motor to run the fan for the seeder. When we get to the end of the row and try to raise the 3PH, it will not lift until we disengage the hydraulic motor. Any tractor we have used before provides the 3PH with priority over the remotes. Is there anyway to change this somehow. We have talked with our local dealer and they tell us that there is nothing we can do. This is frustrating because it knocks all the seed off our discs at the end of the row.

Thanks for any help.

The flow divider is certainly an option. The challenge is getting to the lines to install the flow divider between the 3 pt hitch and existing rear remotes.

Your tractor has an open center hydraulic system so the first control valve closest to the pump output gets the flow ( which now is the rear remote feeding the motor) and other items downstream have to wait.

Unlike older tractors more, and more hydraulic valves are internal to the transmission so altering systems is challenging. I expect the rear remotes are fed internally in the same area of the transmission as is the 3 pt hitch.

My experience is the hydraulic flow on larger Kubotas goes to the steering, then FEL and next, using a power beyond feature of the FEL, to the rear of the tractor.

If there was a new flow divider on the power beyond outlet of the FEL, then part of the flow would constantly be going to the 3 pt and factory rear remotes and the other part of the flow divider could go to new quick couplers on the rear of the tractor which are just conveniently located but otherwise independent from the existing rear remotes. There would be a new control valve
feeding the new rear remotes so you can control the hydraulic motor.

If this explanation is not clear enough please ask some questions and I will expand my logic further.

Dave M7040

 

[ovrszd]

Dave nailed it.

 

[rolandjeff]

The flow divider is certainly an option. The challenge is getting to the lines to install the flow divider between the 3 pt hitch and existing rear remotes.

Your tractor has an open center hydraulic system so the first control valve closest to the pump output gets the flow ( which now is the rear remote feeding the motor) and other items downstream have to wait.

Unlike older tractors more, and more hydraulic valves are internal to the transmission so altering systems is challenging. I expect the rear remotes are fed internally in the same area of the transmission as is the 3 pt hitch.

My experience is the hydraulic flow on larger Kubotas goes to the steering, then FEL and next, using a power beyond feature of the FEL, to the rear of the tractor.

If there was a new flow divider on the power beyond outlet of the FEL, then part of the flow would constantly be going to the 3 pt and factory rear remotes and the other part of the flow divider could go to new quick couplers on the rear of the tractor which are just conveniently located but otherwise independent from the existing rear remotes. There would be a new control valve
feeding the new rear remotes so you can control the hydraulic motor.

If this explanation is not clear enough please ask some questions and I will expand my logic further.

Dave M7040

I just had a look and it looks like there is a line coming off the pump going to the rear remotes. We don't have a FEL. So we could put a divider right before it goes into the rear remotes. Have the one line set to go to the remotes and 3PH and the other one feeding the motor?
Now if we have 17GPM supply and i send 12GPM to the remotes and the rest to the motor, will we only ever have 12GPM available for the remotes, or if we are not running the motor would we get the oil its not using? My understanding is that the divider will split the flow, but what happens when one side isn't being used?

What about using a restrictor before the hydraulic motor?

Thanks for your help Dave.

 

[oldnslo]

Roland,
How much flow does the hydraulic motor on your planter require? Reason for asking is that using a priority flow control will reduce the flow to the motor which might cause the air planter to not generate enough blower pressure to to operate correctly.

 

[rolandjeff]

I am estimating about 6-7 GPM. I should know more accurately when we are able to hook it up and run it so i can count count the RPM we are using.

 

[bigdeano]

If you have the controlled flow port feeding the motor you can adjust the flow to the motor from zero to your max pump flow. What's left over would go out the excess flow port to the remotes and 3PH. If you're not using the motor, just set the flow control to zero and all the flow will go to the remotes and 3PH.

 

[rolandjeff]

If you have the controlled flow port feeding the motor you can adjust the flow to the motor from zero to your max pump flow. What's left over would go out the excess flow port to the remotes and 3PH. If you're not using the motor, just set the flow control to zero and all the flow will go to the remotes and 3PH.

So could i put something like this before the remote valves then? I am guessing i would need a pressure relief coming out the EF port then?

3/4 NPT Hydraulic Flow Control Valve w/Relief RDRS175-3 | Prince Mfg | Brands | www.surpluscenter.com

 

[bigdeano]

Do you know where the pressure relief valve is in your system? If you put the new valve before the PR valve the existing PR valve won't function on the controlled flow port (motor). So if you had the motor disconnected from it's quick disconnects and moved the flow control valve off zero, it would deadhead the pump. They make the flow control valves with a built in PR valve, but it dumps to the excess flow port, which may have pressure on it in your application. You may have to install a separate PR valve before the flow control valve and have a new hose to the tank.

 

[bigdeano]

So could i put something like this before the remote valves then? I am guessing i would need a pressure relief coming out the EF port then?

3/4 NPT Hydraulic Flow Control Valve w/Relief RDRS175-3 | Prince Mfg | Brands | www.surpluscenter.com

You posted while I was typing. That's the type of valve I was thinking of, however looking at the questions and answers on that link they say it's a percentage type valve, which is not what you want. You want one that maintains a constant flow on the controlled flow port. I have one on my tractor which does that, it's a Brand Hydraulics valve.

FC 0-30 GPM - Full Range Pressure Compensating Variable Flow Control | Brand Hydraulics Product Information

 

[Dave M7040]

I just had a look and it looks like there is a line coming off the pump going to the rear remotes. We don't have a FEL. So we could put a divider right before it goes into the rear remotes. Have the one line set to go to the remotes and 3PH and the other one feeding the motor?
Now if we have 17GPM supply and i send 12GPM to the remotes and the rest to the motor, will we only ever have 12GPM available for the remotes, or if we are not running the motor would we get the oil its not using? My understanding is that the divider will split the flow, but what happens when one side isn't being used?

What about using a restrictor before the hydraulic motor?

Thanks for your help Dave.

Because of the risk of not fully understanding the hydraulic system on your tractor, I think you should be going back to your dealer, and armed with more knowledge, insist they provide you with a solution.

For example, you undoubtedly have power steering. It is the most critical hydraulic system as the loss of steering can be fatal.
Some tractors have two hydraulic pumps. One for the steering and the other for what you have on your tractor, rear remotes and 3 pt.

On the tractors with only one pump, the hydraulic flow does to a priority valve, not unlike a flow divider but more sophisticated. The priority valve reserves the first say 6 gpm of hydraulic flow that the steering system gets before anything else.

The second or even the biggest risk is somehow you unknowingly dead head the pump, i.e. block the output from the pump. Now you can destroy the pump. There is a relief valve and if you have been smart enough to have it between the pump and where you have inadvertently dead head the pump, it will save the pump for a little while but will overheat the hydraulic system and in the end again serious damage.

With the divider, both sides need a path to the tank or reservoir. On the side not being used, like any open center device, the unused flow is going back to the tank.

Two additional suggestions for your dealer.

1. Have him install a FEL valve as if you had a FEL. Now things are plumbed properly, relief valves are where they should be. In fact you will have two relief valves. One in the FEL valve and another for the 3 pt and rear remotes. With the FEL valve installed, you have the equivalent of two rear remotes from the work ports on the FEL valve. Use one set of work ports to provide a rear hydraulic circuit for the hydraulic fan motor. The hydraulic circuit coming from the FEL valve is ahead of the 3 pt so will have priority over the 3 pt and rear remotes.

2. Hydraulic accumulator.

Here on this topic my knowledge is much more theoretical than practical.
Start by watching this brief video.
Parker Bladder Accumulators - Tutorial - YouTube

If you have a water well, you likely have a diaphragm tank which is charged with air and eliminates frequent cycling of the well pump. The well pump forces water into the tank compressing the air above the diaphragm. When you next need water, the compressed air pushes water out of the tank for you to use. Depending upon the size of the tank, a lot of water can be supplied before the well pump has to start again. When first installed, the tank will have a bicycle tube style valve for injecting air above the diaphragm called pre-charging.

Hydraulic systems also use accumulators. They use them so a hydraulic pump does not have to be sized to meet the brief high flow needs of a hydraulic circuit thus saving money and operating energy.

This hydraulic accumulator is a lot stronger than the water well type because the pre-charge pressure, which will be nitrogen gas, will be several thousand psi, in the same range as the pressure in your hydraulic system. The accumulator would be sized to deliver hydraulic flow to the motor during the time when you are raising the 3 pt hitch which sounds like seconds.

A check valve would be installed between the accumulator and the tractor to prevent flow from going backwards instead of towards the hydraulic motor which needs it.

Kubota already uses a small version of a accumulator with a feature for FEL's called something like easy ride. The hydraulic circuit for the loader arms has an accumulator Tee'd off the lift circuit and lets the arms move a little and thus reduce the jarring on the tractor. Now if you are driving somewhere bumpy, the accumulator, acts like shock on a car.

Your dealer might have to consult a specialty hydraulic manufacturer to come up the the needed size for your application. If I am correct in the amount of time you are raising the 3 pt hitch, the accumulator will not be excessively large.

As I type, I really think the accumulator will turn out to be the easiest safest solution for your issue.
Hope the above makes sense.

Please don't forget to come back when done and provide an update to help us all learn.

Dave M7040

 

[rolandjeff]

I think you are right Dave. With this added knowledge it is time to go back to the dealer to see what they think. I have not had great luck with them up until this point, but i understand it a lot better now to have a good discussion about our options. Thanks and I will report back on what we come up with.

 

[bigdeano]

Being that it's an open center system, there's no pressure to charge the accumulator. They're ordinarily used on closed center systems. Unless I'm missing something.

 

[rolandjeff]

Perhaps i should have checked out the manual on the tractor first. Kubota makes a flow control valve to place before whichever remote you want to control. It specifically talks about being able to use the 3PH at the same time as the remote that has the flow control on it.
I do not understand why our dealer never mentioned this as an option. I think we might need to look for a new dealer, or go green.

I will look into this option first and if it doesnt correct it then i might be back. Thank you all for your help.

 

[oldnslo]

Does this planter have the option of using the PTO to run the air blower? That might solve your problem.

 

[rolandjeff]

Does this planter have the option of using the PTO to run the air blower? That might solve your problem.

It did at one point but someone changed it to hydraulic. There would be too much angle on the shaft to run it ok, which i am guessing is why they changed it.

 

[Dave M7040]

With a check valve & next the accumulator, between the remote outlet and the hydraulic motor, the accumulator will charge to the operating pressure of the hydraulic motor. When the flow from the rear remote stops, the accumulator starts to discharge as the pressure drops. The check valve ensures that the flow is towards the hydraulic motor

You don't want to nor can you raise the accumulator pressure higher than the operating pressure.

Yes accumulators are more commonly found on closed center systems but then those systems are usually on more sophisticated pieces of equipment.

To me this is a simple solution for an uncommon problem.

Dave M7040

 

[Dave M7040]

Perhaps i should have checked out the manual on the tractor first. Kubota makes a flow control valve to place before whichever remote you want to control. It specifically talks about being able to use the 3PH at the same time as the remote that has the flow control on it.
I do not understand why our dealer never mentioned this as an option. I think we might need to look for a new dealer, or go green.

I will look into this option first and if it doesnt correct it then i might be back. Thank you all for your help.

Likely you are talking about a priority flow control, the same style of valve which ensures you have power steering at all times.

You had raised the concern about the loss of hydraulic output volume with fixes like flow dividers. A priority valve is going to do the same. You will never have the full pump volume available at a remote.

Dave M7040