Variable displacement piston pump for splitter

[preppypyro]

Hey guys and gals,

I'm looking to build a wood splitter and have been reading a bunch of stuff on here and other sites regarding pumps.

I know what the general consensus is, buy a two stage.

Before I do that I wanted to see if anyone here has any experience with the variable displacement piston pumps.

I have a couple of them kicking around with a max flow of 13.8 GPM at full throttle (according to the manufacturer)

Anyone know much about them? Would they work well on a splitter application?

I've tried reading a little about the differences between a 2 stage pump and the ones I have, but coming up with more questions than answers!

Respectfully save the comments like "just buy a 2 stage"

I'm not opposed to that idea yet, but want to learn if I can make what I have work first.

Thank you for any insight!

 

[Del_]

13.8 is a small pump for a five inch cylinder.

Just buy a two stage.

I run a 28 gpm that kicks down to a 7 gpm when back pressure gets over 600 psi. This is on an 18 Briggs IC running about 2,400 rpm with a 5 inch cylinder. This combo works great and I've got a mechanical auto return set up with forward detent and really improves usability. It's nice to put a chunk on and being able to pick up the next piece and have the cylinder fully retracted and the beam empty.

 

[nedsim]

Another caveat: Piston pumps are much fussier about oil cleanliness than gear pumps. And they're a lot noisier, though that's probably not a huge deal on an IC engine powered splitter. But, if you're fastidious about keeping the oil clean, and can match the pump's displacement range and max pressure to a suitable cylinder, it could make for a slick setup.

How is the displacement controlled on your pumps?

 

[preppypyro]

Thanks for the replies so far.

I will look at the size of cylinders I have that I would use, likely not 5 inch but I haven't even looked at them for awhile. I'd love a 28 GPM pump but they are around 600 bucks up here in my area, and I'm not interested in that cost!

Noise and cleanliness are not a concern to me, I would be filtering and whatnot anyways, and the noise is what it is.

Right now the pump is on a mower, with an 18 horse engine. I also have an 20? Horse diesel engine but I'm thinking I want to stay with gas for a splitter setup, especially for cold weather use.

As for displacement control, I have no idea yet. I'm still learning about these pumps.

 

[muddstopper]

vairible piston pumps use a swash plate to allow oil to bypass internally to control working flow. I cant see any advantage to wanting to run you cyl, whatever size you choose to use, with varying travel speed. Will it work, its oil flow and pressure, so yes it will work, but its alreay going to be slow if you choose a 5inch bore cyl. If you cant afford a 2 stage pump. then consider using two single stage gear pumps. Set them up as a high/low system with a unloader valve so you have high fluid volume at low pressure, and low fluid flow at high pressure. It will be cheaper than a $600 2 stage pump and you can get away with a smaller more fuel efficient engine.

 

[sean donato]

vairible piston pumps use a swash plate to allow oil to bypass internally to control working flow. I cant see any advantage to wanting to run you cyl, whatever size you choose to use, with varying travel speed. Will it work, its oil flow and pressure, so yes it will work, but its alreay going to be slow if you choose a 5inch bore cyl. If you cant afford a 2 stage pump. then consider using two single stage gear pumps. Set them up as a high/low system with a unloader valve so you have high fluid volume at low pressure, and low fluid flow at high pressure. It will be cheaper than a $600 2 stage pump and you can get away with a smaller more fuel efficient engine.

That's not really how a varriable piston pumps works, there's no bypass internally. The swash plate varies the stroke limiting or increasing flow. When the plate is centered flow can be basically zero with the roating assembly still spinning, awhile maintaining a desired pressure. One of the reason close center systems use them.
There are a few other variables depending on pump model, there can be pressure or flow compensation or both. (Also known as "load sensing")

This is a fairly decent article covering some of the basics.
https://blogs.umass.edu/shwalker/20...There are several,pumps, and bent axis pumps.
Truthfully, you'll be adding a large kevel of complexity you don't need in such a simple system. You would likley be better off selling the pumps you currently have and getting a fixed displacement 2 stage pump.
I will say, you will get by fine with 16gpm pump with a 5" cylinder. It's the set up I currently use, works fast enough when I'm splitting by myself. It is a tad slow when I have help. Which is rare.

 

[preppypyro]

Thanks for all of the input. I still have to go check at what size cylinders I have kicking around as I am trying to do a build with spare junk I have kicking around. Truth be told I only split a couple of cords of wood per year which my little electric splitter does well at, but I like building stuff and figure I have just about enough stuff kicking around to build one minus the pump (which is why I was inquiring) and the auto cycle valve.
So my goal is to build one as fast as I can get it, with what I have. I would love to build a super nice fast one, but I cant justify the costs for how little I actually split. But at the same time i dont mind going as overboard as I can haha.

So far for my build I have an 18 horse vanguard, and a 20 horse diesel engine to choose from. I have a pretty large chunk of I beam, and a variety of cylinders kicking around that I have salvaged from old tractor front end loaders, and other various farm equipment. Im positive something there will work. I wouldnt mind building a hydraulic 4 way wedge (but likely just do a fixed 4 way) and Im really undecided if I want to make a lift for it. For a tank I will likely build one.

I have done a ton of reading about different splitter builds and had figured I would just check in here in case someone knew how a guy could set up the pumps I do have, to work so that there would be the whole 13.8 gpm like a regular pump.
What I have found for pumps so far here up in Canada, one is a 9hp stage 2 (says low pressure 15 gpm) and one is a 16 gpm. Likely both chinese, but thats about my budget I have allocated to parts I dont have. Let me know what you guys think of the pumps below.

https://www.princessauto.com/en/9-hp-2-stage-aluminum-body-hydraulic-pump/product/PA0008725947
https://www.vevor.ca/gear-pump-c_10...splitter-parts-hydraulic-motor-p_010859226370

 

[sean donato]

So, just for your information you'll need a closed center valve with the varriable displacement pump to get the benefits out of it. Ie, typically more expensive, and not very many splitter specific options.
The China pumps work just fine. Mines been going for nearly 10 years now. I do 10+ cord a year for myself, nearly as much for my dad and both brothers cone and grab it for their needs. Now I've gone through 3 auto return valves in that time period. The first one didn't make it more then a few months. The second one was just replaced a few weeks ago. All cheap junk. If I didn't have plans to build a bigger splitter in the near future with a full auto cycle valve, I would have gotten a prince valve for my current splitter. Just couldn't justify spending half the money of the auto cycle valve when I know I'll be going a different route soon.

 

[Del_]

I've been using a double detent 3/4 inch ports valve for 20 years on my homemade splitter (built in 1992). A dozen years or so ago I came up with a way to make the double detent (detents in push and return) function as an auto return. Just simple parts I had around the place.

What a time saver it is to get back to the splitter after splitting a piece and having the beam and ram sitting there open. And catching the pieces off of the end of the beam as the auto return finishes the split and returns. I run the 18 Briggs IC at about 2,200 RPM using a 2 speed pump pushing a 5 inch cylinder. I could have easily gone with a smaller engine and a smaller two stage pump and ran the engine at a higher RPM, but I didn't know that at the time of the build.

 

[kshansen]

Del all I can say is don't let anyone else use that splitter. If some idiot does I can bet there would be fewer fingers or other limbs attached in short order.

Then again some would say I'm at risk by having my wife run the controls while I feed my splitter. But I figure if she was smart enough to marry me she's smart enough to run the splitter control!

 

[Del_]

Del all I can say is don't let anyone else use that splitter. If some idiot does I can bet there would be fewer fingers or other limbs attached in short order.

Then again some would say I'm at risk by having my wife run the controls while I feed my splitter. But I figure if she was smart enough to marry me she's smart enough to run the splitter control!

Two way detents and auto return are standard on a lot of the larger splitters.

 

[Oletrapper]

That's not really how a varriable piston pumps works, there's no bypass internally. The swash plate varies the stroke limiting or increasing flow. When the plate is centered flow can be basically zero with the roating assembly still spinning, awhile maintaining a desired pressure. One of the reason close center systems use them.
There are a few other variables depending on pump model, there can be pressure or flow compensation or both. (Also known as "load sensing")

This is a fairly decent article covering some of the basics.
https://blogs.umass.edu/shwalker/20...There are several,pumps, and bent axis pumps.
Truthfully, you'll be adding a large kevel of complexity you don't need in such a simple system. You would likley be better off selling the pumps you currently have and getting a fixed displacement 2 stage pump.
I will say, you will get by fine with 16gpm pump with a 5" cylinder. It's the set up I currently use, works fast enough when I'm splitting by myself. It is a tad slow when I have help. Which is rare.

A tad slow? They must be drinking beer between strokes? lmao jmho OT

 

[sean donato]

A tad slow? They must be drinking beer between strokes? lmao jmho OT

No one that would come to help would drink or be allowed to drink when we're splitting. Never the less it's not that slow.

 

[Oletrapper]

No one that would come to help would drink or be allowed to drink when we're splitting. Never the less it's not that slow.

I was just kidding Sean. Have a good day. OT

 

[muddstopper]

A tad slow? They must be drinking beer between strokes? lmao jmho OT

A 13gpm flow with a 5in bore cyl would be slow. I have the 28gpm twostage pump and 5in bore cyl on my splitter and feel like it could be speeded up a bit, but only if I have lots of help. I usually run it by myself at half throttle. My opinion and not everyone would feel the same.

Since I am again responding to this thread, I want to clarify a statement about internal bypass. Technically I am correct. Every hyd pump, motor, valve, cyl, will have a certain amount of internal bypass. The amount of oil bypass is usually minimal, but is the reason these things have efficientcy ratings of 85%, 90%, 95%, etc. All the oil isnt being directed where its supposed to be going. With that said, Sean is also correct in that isnt how variable displacement pumps work. I didnt intend to write a tutorial paper to explain how a variable pump works, and I aint going to now. I will provide a link I found that explains it a little better than I could anyhow.

https://www.oilgear.com/variable-di...upon a stationary, variable angle, swashblock.

 

[kevin j]

Couple other issues to think about. You'll need a close center valve, because most piston pumps don't work well with an open center valve. if they're at max flow at a very low pressure they tend to hammer out the pistons they need a couple hundred psi back pressure. Then if you use a close center Depending on the speed and flow you can have throttling issues that create a lot of heat when it's part load and part speed. All in all even though you said not to say it, I vote like most of them make a two-stage or buy a two-stage fixed displacement gear pump or even couple vane pumps

 

[Big_Eddy]

Visit your local hydraulics shop instead of PA. 28gpm 2 stage pumps are about $400, not the $600+ at PA. But do have all your hoses made at PA. Way lower costthan any of the 3 hydraulic shops local to me.

Also be aware that the Prince Auto return valves are only rated for 25GM, but if you run at 3200rpm instead of 3600, you’re in that range.

Here is my most recent splitter build, with 15hp engine, 28 gpm pump, 4 inch cylinder and auto split being put through its paces . Plenty fast enough to tire out one or two operators

.

 

[drivfour]

I have an old no name splitter that is really slow-has dual pressure. Is speeding it up as simple as getting a higher flow pump? The no load extend and retract is very slow. I will try to see if I can determine engine horsepower but think its between 3-5 hp. ram diameter maybe 1-1.5 inches.

 

[sean donato]

I have an old no name splitter that is really slow-has dual pressure. Is speeding it up as simple as getting a higher flow pump? The no load extend and retract is very slow. I will try to see if I can determine engine horsepower but think its between 3-5 hp. ram diameter maybe 1-1.5 inches.

Given your valves are rated for the extra flow, and the enhinenhas the power, jumping up a few gpm usually isn't an issue.

 

[sean donato]

Visit your local hydraulics shop instead of PA. 28gpm 2 stage pumps are about $400, not the $600+ at PA. But do have all your hoses made at PA. Way lower costthan any of the 3 hydraulic shops local to me.

Also be aware that the Prince Auto return valves are only rated for 25GM, but if you run at 3200rpm instead of 3600, you’re in that range.

Here is my most recent splitter build, with 15hp engine, 28 gpm pump, 4 inch cylinder and auto split being put through its paces . Plenty fast enough to tire out one or two operators

.

They make a 3/4" and -12 work port models that are good for a bit more flow. If not on paper, in use they are just fine.