John Deere Closed centered hydraulic pump

J. Schwiebert · Sep 7, 2014

FYI: I notied while I was gone there was some discussion about where deere closed center hydraulics originated. I uused to work with an engineer that had started with Deere and was in on the early development of that pump. He went to Dana and worked in their pump engineering department. When they were designing the pump they had not made up their minds if the pump was to be used to run a closed center or open center system. One other probably little know fact is that Chelsa PTO's had a mounting bracket in their catalog to use to mount the Deere pump to a Chelsea PTO on garabage trucks for New York City. It was run open center.

J. Schwiebert · Sep 7, 2014

Forgot to add this was in response to posts by TX Jim & JD seller

Tx Jim · Sep 7, 2014

(quoted from post at 13:39:12 09/07/14) One other probably little know fact is that Chelsa PTO's had a mounting bracket in their catalog to use to mount the Deere pump to a Chelsea PTO on garabage trucks for New York City. It was run open center.

J. Schwiebert
I would be curious to know if you're referring to JD piston pump being utilized in an open center configuration as that pump can't suck oil and with a faulty stroke control valve can break rockshaft castings. I suppose there could be some alterations to the pump head to go from closed to open center?
Thanks,Jim

pete 23 · Sep 7, 2014

By no means an expert on the John Deere closed center system, but have rebuilt a few and replaced a few others, I see no way that pump could be used open center. I have been wrong before though.

LarrySTN · Sep 7, 2014

Eliminate the stroke control valve and it could certainly be used open center. The resevoir would have to be above the pump but it would work.

Tx Jim · Sep 7, 2014

(quoted from post at 14:32:58 09/07/14) Eliminate the stroke control valve and it could certainly be used open center. The resevoir would have to be above the pump but it would work.

Larry
If stroke control valve was eliminated what will control pressure? I know for a fact I was quoted from a JD engineer about a nearly new JD 4430 under warranty that busted the rockshaft housing while lifting a rear JD 7 row flex bedder that the only limiting factor on now much pressure a JD CC piston pump could attain was the amount HP of the engine turning the pump IE unlimited pressure.

After giving this some thought I suppose a conventional hyd relief valve will work as long as the piston pump has a oil supply.

pete 23 · Sep 7, 2014

I'll buy that it would work, but I think a charge pump would be needed at the least, for reliability and if you are going to do that you might as well use a much cheaper gear pump. IH didn't fair well with their piston pumps, closed center when they didn't have a charge pump.

J. Schwiebert · Sep 7, 2014

Tx Jim The reservoir is indeed above the pump & PTO on a garbage truck. They also had snow plows mounted under the trucks as well in certain applications. A friend of mine that worked for Dana had a John Deere manual that Deere had provided him for teaching a class on pump operation and service in those applications as they were equipped on those trucks. I started with them (Dana) in 88, the brackets at that time were special order only. I also had to put together a one day session one time for a certain company that was selling snow plows with closed center hydraulics running gear pumps with unloader valves rather than a piston pump because of the cost factor and the mechanics serving the units were used to gear pumps, but not piston pumps.

LarrySTN · Sep 7, 2014

TX Jim, how many gear pump hydraulic systems have
you seen where the pressure relief is in the valve
bank an not part of the pump. Why would you need the
relief at the pump?

Tx Jim · Sep 7, 2014

LarrySTN
Evidently you did read my last sentence in my previous post.

LarrySTN · Sep 7, 2014

Yes, I didn't pay enough attention to the last
sentence. I apologize.

RodinNS · Sep 7, 2014

Actually, it could be used in an open center system without any alteration whatsoever. That pump by virtue of it's design is normally 'in stroke' and only goes out of stroke when the system pressure rises sufficiently that it acts against the stroke piston to destroke the pump. A spring puts the pump in stroke.
So.... if one wanted to run it on open or tandem center for some obscure reason all they would need to do is funnel the entirety of pump flow through said OC valve and return oil through a cooler to keep the whole mess cool because it's probably going to get hot.
I don't know off hand what charge pressure it would require but I suspect it's more than one atmosphere... so you'd still need a charge pump.
If one wants an open center system it's a lot easier to just run a commercial gear pump and be done of it.

Rod

Tx Jim · Sep 8, 2014

(quoted from post at 18:20:14 09/07/14) Yes, I didn't pay enough attention to the last
sentence. I apologize.

No apology needed as I also have reading comprehension problems from time to time.

Tx Jim · Sep 8, 2014

(quoted from post at 20:20:09 09/07/14) Actually, it could be used in an open center system without any alteration whatsoever. That pump by virtue of it's design is normally 'in stroke' and only goes out of stroke when the system pressure rises sufficiently that it acts against the stroke piston to destroke the pump. A spring puts the pump in stroke.Rod

Rod
That isn't exactly how I was taught the JD CC hyd pump operates. I was taught the pressure inside the crankcase exceeds the pressure on the springs on the pistons(4 or 8 depending on the size of the pump) therefore it pushes the pistons away from rotating shaft causing pumping to stop then when pressure in crankcase falls below system pressure then the pistons are pushed back against pump rotating shaft to pump oil again. Installing an open center valve on a CC without any alteration will not work very well at all. It will cause the pump to cavitate & run out of oil.

RodinNS · Sep 8, 2014

You may be correct on the exact method of control. It's a long time since I looked at Deere pump theory specifically... I tend to think more in terms of axial piston pumps rather than radial pumps... and swash plate control in a standard CC axial setup... the pump is normally in stroke whereas in a CCLS setup the pump is normally de-stroked.
Regardless, I still don't see why the radial pump can't operate in an open center system. That pump is still normally 'in stroke' unless it reaches high stand-by. All you're doing is limiting it's ability to reach high stand-by because there's nothing for it to build pressure against so it never de-strokes. I see no reason for it to cavitate as long as it's got sufficient charge flow. I don't see it working without a pressurised charge flow tho... unlike an axial piston pump which in most cases can operate without charge pressure from a static source.

Rod

Tx Jim · Sep 8, 2014

(quoted from post at 08:09:10 09/08/14) I see no reason for it to cavitate as long as it's got sufficient charge flow. I don't see it working without a pressurised charge flow tho... unlike an axial piston pump which in most cases can operate without charge pressure from a static source.

Rod

The key is "sufficient charge flow" which is one reason an open center valve will not work on a JD tractor CC hyd system which is my train of thought. I think JD piston pump would work with sufficient gravity feed charge flow.

RodinNS · Sep 8, 2014

That's only because the John Deere tractor doesn't supply FULL charge flow

If it had a sensible system with a 40-60% overage in charge flow like a proper system should... then there wouldn't be a problem. lol
I know you're correct that they do not recommend running an OC valve behind a Deere CC system because it will overheat. I just don't see it being a problem for the pump if a system was designed around it's flow requirements.

Rod

Tx Jim · Sep 8, 2014

(quoted from post at 12:32:12 09/08/14) That's only because the John Deere tractor doesn't supply FULL charge flow If it had a sensible system with a 40-60% overage in charge flow like a proper system should... then there wouldn't be a problem. lolRod

That may be true but the JD rowcrop tractors from '64 to '92 will still outsell your beloved Ford tractors of the same era. I think CCLS isn't the answer either. :lol:LOL

RodinNS · Sep 8, 2014

No doubt that is true... and likewise the Ford utilities of that era probably outsold the comparable Deere's in most markets. No matter, I'm only pickin' anyway.
CCLS in it's proper configuration using a load sensing axial piston pump is an excellent system. The load sensing system that Ford used... yeah... it kinda worked. I think it's biggest advantage is that it provided a quality remote with crisp control and good flow from pumps that are simple and relatively cheap to replace when they crap out. It's disadvantage is that it doesn't have pressure compensation... so it's all flow or no flow for the most part. Definitely far from ideal.

Rod

Tx Jim · Sep 8, 2014

I agree that JD utility tractors of the same era('64-'92) will not warm up the Ford utility tractors IMHO. I still remember going to JD sales meetings telling me how great the CC hyd's were with lower draft sensing vs OC hyd's and only one(1) place to check hyd oil vs the 3 places on some of the Ford's of the same HP. Most all major brands had some good points and some quirks.

John Deere Closed centered hydraulic pump

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