PTO gear pump question

[Jims1025R]

I've been doing lots of reading here, while I consider my design for a loader mounted brush cutter. Someone wisely mentions that running a hydraulic cutter on the third function valve of the tractor hydraulics could result in power/speed variations with loader operation - good point! Thanks!

So... If I use a separate PTO gear pump, the 540 PTO runs the pump, and my cutter constantly, and the loader operates independently so I can thrash it about for cutting. My question is; if I set up PTO gear pump to cutter hydraulic motor, with only a reservoir, over pressure relief valve, and filter in the circuit, do I need a valve at all? Could I simply start and stop the cutter with the PTO run/stop? (dash switch in the case of my JD 1025R).

I make up a frame to hold the torque of the pump body to the three point hitch, with a reservoir and filter, and just run the two lines up to my cutter hydraulic motor? With no valve, I save cost, and flow restriction, neither of which benefit the design, if the PTO on/off is good enough for cutter run/don't run...

Thoughts?

 

[CalG]

Should work, but what is the cost difference between a control valve and an over pressure valve?

Might not be much savings.

 

[rScotty]

I've been doing lots of reading here, while I consider my design for a loader mounted brush cutter. Someone wisely mentions that running a hydraulic cutter on the third function valve of the tractor hydraulics could result in power/speed variations with loader operation - good point! Thanks!

So... If I use a separate PTO gear pump, the 540 PTO runs the pump, and my cutter constantly, and the loader operates independently so I can thrash it about for cutting. My question is; if I set up PTO gear pump to cutter hydraulic motor, with only a reservoir, over pressure relief valve, and filter in the circuit, do I need a valve at all? Could I simply start and stop the cutter with the PTO run/stop? (dash switch in the case of my JD 1025R).

I make up a frame to hold the torque of the pump body to the three point hitch, with a reservoir and filter, and just run the two lines up to my cutter hydraulic motor? With no valve, I save cost, and flow restriction, neither of which benefit the design, if the PTO on/off is good enough for cutter run/don't run...

Thoughts?

Only a problem if you run the loader and the cutter at the same time and both of them at full speed. Is that likely?

Tractors with simple PTO switches without a PTO clutch are cheap to make, but abrupt. That's hard on any system.

You will probably find a valve useful. It frees you from being next to the PTO switch. A valve controls cutter speed and power plus it reverses the cutter rotation to free it from a bind. Safer too. Most control valves include a relief valve. To avoid having to hold the valve open all the time, consider getting a valve with a detent.
luck,
rScotty

 

[LouNY]

It'll work, I think a motoring valve would be much more desirableness.
This would allow the drive motor to coast down, some hydraulic motors can not take being stopped suddenly
especially with a heavy load on them the back pressure will blow the motor seals.
A hydraulic motor valve will allow the motor to free spool till it stops.
Also you may need a cooling circuit in your system.

 

[rScotty]

It'll work, I think a motoring valve would be much more desirableness.
This would allow the drive motor to coast down, some hydraulic motors can not take being stopped suddenly
especially with a heavy load on them the back pressure will blow the motor seals.
A hydraulic motor valve will allow the motor to free spool till it stops.
Also you may need a cooling circuit in your system.

Good point. All of those control features can be done with a regular control valve and normally are by any experienced operator. So using a control valve is doable just as using a PTO switch is too. BTW, you will want a over-running clutch on the PTO. Always. Otherwise you may break something.

And ultimately a valve built specifially for motoring would no doubt be better.

Third functions on loaders are usually just added to tractors for occasional cylinder use, not for continuous use. Think grapples; not motors. The difference is cooling. But there again there is a difference between quickly setting up a project using common parts to prove if an idea is feasible or worth pursuing.... Versus refining it into an everyday product.

When designing anything, don't get hung up on the final steps before taking the first one. Just get in there and get something done. Change as needed. If it were me, I'd skip the PTO and run it off the 3rd function until I saw if it would even work and keep an eye on not letting it get too hot. Hydraulic return line radiators are cheap.

rScotty

 

[ptsg]

I've been doing lots of reading here, while I consider my design for a loader mounted brush cutter. Someone wisely mentions that running a hydraulic cutter on the third function valve of the tractor hydraulics could result in power/speed variations with loader operation - good point! Thanks!

So... If I use a separate PTO gear pump, the 540 PTO runs the pump, and my cutter constantly, and the loader operates independently so I can thrash it about for cutting. My question is; if I set up PTO gear pump to cutter hydraulic motor, with only a reservoir, over pressure relief valve, and filter in the circuit, do I need a valve at all? Could I simply start and stop the cutter with the PTO run/stop? (dash switch in the case of my JD 1025R).

I make up a frame to hold the torque of the pump body to the three point hitch, with a reservoir and filter, and just run the two lines up to my cutter hydraulic motor? With no valve, I save cost, and flow restriction, neither of which benefit the design, if the PTO on/off is good enough for cutter run/don't run...

Thoughts?

Yes, it will work perfectly fine without a spool valve, just the pump, relief valve and filter. Turn the PTO on to get the mower running and turning it back off to stop and motor will just slow down on its own. A nice and simple PTO power pack.

Cooling may or may not be needed. I would run it, monitor the temps and decide later on on that.

 

[oldnslo]

What size brush cutter you putting on the tractor. A 1025R is pretty small and would have very low flow rate on standard tractor hydraulics.

 

[Jims1025R]

Thanks for the thoughts... My plan is going to need refinement. I notice that there's a safety shroud around the PTO shaft, which is going to entirely prevent installing the PTO gear pump I'm thinking of. It folds up, but not enough to clear the pump. And, I like safety shrouds, so it'll stay. So... still thinking....

 

[thewalnutguy]

What size brush cutter you putting on the tractor. A 1025R is pretty small and would have very low flow rate on standard tractor hydraulics.

If you're thinking of running the cutter off of tractor hydraulics, make sure the tractor hydraulics can be used without damage. I recently bought a JD 5075e thinking I'd be using it at times for running my wood chipper which has hydraulic orbital motors to drive the feed rollers. Only after buying the tractor did I read through the owner's manual and discovered that it clearly states NOT to use the hydraulic port connections on the tractor to power orbital motors. So now I've got a new tractor that can't be used for one of the intended uses for which I bought it. Obviously I didn't do my homework before purchases the JD.

 

[oldnslo]

Walnutguy
Does the manual state a reason to not run a motor off your tractor? Just curious on reason provided if one was.

 

[thewalnutguy]

Not stated in the manual, but in the instructions for the installation and use of their power-beyond kit they state that even with the kit installed over-heating may still be encountered and that the temperature should be monitored and use discontinued if over-heating does occur.

 

[Jims1025R]

did I read through the owner's manual and discovered that it clearly states NOT to use the hydraulic port connections on the tractor to power orbital motors.

Firstly, good job reading the manual!

I have just re read the JD Power Beyond Kit Installation Instructions which accompanied the parts (all bought new with my 1025R new from the same JD dealer) and there is no mention whatever of any operating limitation for that hydraulic circuit.

However, the main manual for the tractor has the very subtle wording: "The third function valve (SCV) outlet may be operated in a momentary condition to operate attachments such as extending or retracting a hydraulic cylinder.". I could easily interpret this to mean not to run orbital motors (though those words are not used).

So my plan has no clear path forward - yet. I return to thinking about a PTO driven pump, with separate hydraulic system, but with more caution now.

A number of years ago I was responsible for the design and approval of a 10HP winch in both a research DC-3, and Cessna Caravan, airplanes. These winches would lower and raise a 300 - 400 pound towed research/survey "bird", about 300 feet. Another DC-3, which had been similarly modified years earlier, was reported to be unreliable (and winching this thing up by hand when the motor quit was a real chore!). I had a look at it, and it had a huge electric motor, which the airplane electrical systems could not power adequately. The airplanes both had lots of hydraulic power available, which, in fight, was not used for anything else. So I directed the design of engine hydraulic driven winches, which have been very trouble free all these years. If it works on a mission critical multi million dollar plane, it's gotta be able to work for a brush cutter on my tractor!

 

[oldnslo]

Walnutguy
Thanks for providing that information from the owners manual.

Jim
I commend you on looking at different options and doing the research for pros and cons for each option.

 

[KWentling]

If you're thinking of running the cutter off of tractor hydraulics, make sure the tractor hydraulics can be used without damage. I recently bought a JD 5075e thinking I'd be using it at times for running my wood chipper which has hydraulic orbital motors to drive the feed rollers. Only after buying the tractor did I read through the owner's manual and discovered that it clearly states NOT to use the hydraulic port connections on the tractor to power orbital motors. So now I've got a new tractor that can't be used for one of the intended uses for which I bought it. Obviously I didn't do my homework before purchases the JD.

I see my Kubota M7060 manual doesn't say anything regarding orbital motors, and it is comparable to the 5075. I even considered that tractor before deciding on the 7060. I have run a hydraulic post hole digger with it several times but that is pretty intermittent use. I'm sure they are concerned with the heat generated by a motor. I wouldn't be afraid of trying your chipper with it but I would keep a close eye on the temperature. I suppose the chipper could require such a minimal flow that the tractor would be forcing oil over the relief valve so that would be something to look out for.

 

[KWentling]

Thanks for the thoughts... My plan is going to need refinement. I notice that there's a safety shroud around the PTO shaft, which is going to entirely prevent installing the PTO gear pump I'm thinking of. It folds up, but not enough to clear the pump. And, I like safety shrouds, so it'll stay. So... still thinking....

My PTO shrouds reside on a shelf in the shop. They're just in the way when hooking up the pto shaft. You could possibly run the pump on a shaft extension to get it clear of the shroud. If you do that you might want to provide the pump with some support to take some of the weight off the shaft.

 

[CobyRupert]

I see my Kubota M7060 manual doesn't say anything regarding orbital motors, and it is comparable to the 5075. I even considered that tractor before deciding on the 7060. I have run a hydraulic post hole digger with it several times but that is pretty intermittent use. I'm sure they are concerned with the heat generated by a motor. I wouldn't be afraid of trying your chipper with it but I would keep a close eye on the temperature. I suppose the chipper could require such a minimal flow that the tractor would be forcing oil over the relief valve so that would be something to look out for.

Agree. I’d try it and keep an eye on temps, knowing what a true “high temp” is. That is, hydraulic/transmission temps can feel pretty warm when doing normal stuff.

Would the chipper rolls have there own a relief valve?

 

[Jims1025R]

My PTO shrouds reside on a shelf in the shop.

I had removed the bolt on PTO shroud on my JD650, for similar reasons. Then, in my capacity as a volunteer firefighter, we were paged out to a "severed hand" call. Well, it wasn't severed, it was just pulled off in pieces, right past the wrist. He had a winter mit on, touched PTO shaft end that he didn't notice was turning, wrapped up the mit, and the trail of blood lead us to where he was sitting at the house. I had the job of unwrapping the mit from the PTO shaft, but nothing usable in it. I went home, and the first thing I did was bolt back on the shroud over my PTO shaft. It's just me, but that was my message in life about PTO shafts, and guards. All my shrouds are in place, and my PTO driveshafts have working spinny things on them.

As a side note, the flip up shroud on the JD1025R, when properly lowered in place, also holds the pins in place for the three point arms.

 

[KWentling]

I had removed the bolt on PTO shroud on my JD650, for similar reasons. Then, in my capacity as a volunteer firefighter, we were paged out to a "severed hand" call. Well, it wasn't severed, it was just pulled off in pieces, right past the wrist. He had a winter mit on, touched PTO shaft end that he didn't notice was turning, wrapped up the mit, and the trail of blood lead us to where he was sitting at the house. I had the job of unwrapping the mit from the PTO shaft, but nothing usable in it. I went home, and the first thing I did was bolt back on the shroud over my PTO shaft. It's just me, but that was my message in life about PTO shafts, and guards. All my shrouds are in place, and my PTO driveshafts have working spinny things on them.

As a side note, the flip up shroud on the JD1025R, when properly lowered in place, also holds the pins in place for the three point arms.

Having grown up in a farming community I know a couple of people that have been wrapped up in pto shafts, so I know the risks.
Gloves and loose clothing are dangerous around spinning objects. Having spent the past 45 years in machine shops I've seen the results of that.

 

[rScotty]

You are inventing a problem that has already been solved and parts are readily available

A PTO shroud is there in case someone forgets and activates the PTO. It doesn't have a function if there is an implement attached to the PTO, so in that case remove the shroud. Perhaps the manual had a reason not to say that, but their omission doesn't make the opposite true. Just use normal caution. The shroud is there as a supposed convenience; it is not a absolute.

Consider this: most of your hydraulics are on constantly and are using the same pump that the 3rd function uses. The reason the 3rd function is restricted to low use is that the supplied hydraulic cooling system is only sized for normal ydraulic flow. It is not sized to include constant 3rd function flow. You can easily fix that.

There is not a reason in the world why you cannot put an accessory hydraulic cooler in the return line from the 3rd function. That's why they make them. Google search accessory hydraulic coolers. Most are a few hundred dollars. For the roughly $300 range you can get one rated for hydraulic fluid with a thermostat and a 12 volt fan. End of problem.

rScotty