Home made log spliter

[sean donato]

22 gpm is way too much for an 18 hp motor. As a rule of thumb, it takes about 1 & 1/4 hp to make 1 gpm of flow at 2000 psi. Mathematically you need 26 hp to flow 22 gpm at 2000 psi. Right now you have LOTS of flow, but not enough horse power to make 2000 psi. The pump must be sized in relation to the motor. Too big a pump = lots of flow, but not enough pressure. Too small a pump = lots of pressure capability, but not enough flow. Decide what psi you want for your system, then plug in the numbers and do the math.

For a wood splitter, the best of both worlds is a two-stage pump. A large gpm pump for fast travel speed under light load, with a smaller pump stacked onto it to generate the high pressure needed for that last stage hard push.
https://www.calcunation.com/calculator/hydraulic-pump-horsepower.php

View attachment 1214152

It's a 2 stage pump, around 700 psi it kicks down to like 1gpm.

 

[Doug]

Hey,

I had a old log splitter give to me, the engine was shot so I bought a 13Hp brigs and stratton, and it is running a 22gpm pump. and small and medium logs work just fine for spitting, but when it comes to bigger logs it won't split, it doesn't have enough power. The hydraulic cylinder is only 16 old crappy one but it is going to be replaced eventually to a bigger. An then i adjusted the pressure on the pump and now it just bogs the engine down to the point it shuts it off. What am I doing wrong. I can upload a video and pictures of my log splitter. Is the engine to small for the pump or what. Thanks

Chris

YES, the engine is too small for the pump. 22 gpm is way too much for an 13 hp motor. As a rule of thumb, it takes about 1 & 1/4 hp to make 1 gpm of flow at 2000 psi. Mathematically you need 26 hp to flow 22 gpm at 2000 psi. Right now you have LOTS of flow, but not enough horse power to make 2000 psi. The pump must be sized in relation to the motor. Too big a pump = lots of flow, but not enough pressure. Too small a pump = lots of pressure capability, but not enough flow. Decide what psi you want for your system, then plug in the numbers and do the math.

For a wood splitter, the best of both worlds is a two-stage pump. A large gpm pump for fast travel speed under light load, with a smaller pump stacked onto it to generate the high pressure needed for that last stage hard push.
https://www.calcunation.com/calculator/hydraulic-pump-horsepower.php

 

[buzz sawyer]

22 gpm is way too much for an 18 hp motor. As a rule of thumb, it takes about 1 & 1/4 hp to make 1 gpm of flow at 2000 psi. Mathematically you need 26 hp to flow 22 gpm at 2000 psi. Right now you have LOTS of flow, but not enough horse power to make 2000 psi. The pump must be sized in relation to the motor. Too big a pump = lots of flow, but not enough pressure. Too small a pump = lots of pressure capability, but not enough flow. Decide what psi you want for your system, then plug in the numbers and do the math.

For a wood splitter, the best of both worlds is a two-stage pump. A large gpm pump for fast travel speed under light load, with a smaller pump stacked onto it to generate the high pressure needed for that last stage hard push.
https://www.calcunation.com/calculator/hydraulic-pump-horsepower.php

View attachment 1214152

That's exactly what I ran into on my first splitter attempt. Motor was about 8hp and the pump was off a backhoe - spare parts someone gave me. I'm running two stacked 2.5" cylinders, but the motor wouldn't even run with the pump attached. I'm now running a 7hp motor with a smaller single stage pump. Had a gauge on it at one point and I think it showed about 2000 - 2500 psi. Not the fastest but I haven't found anything it won't split yet. btw, I built it about 40 years ago and it still runs fine. Motor was replaced about ten years ago.

 

[Patrick62]

with a little assumption, here. I forget that the real world has single stage pumps, and engines sized for them.
With a log splitter (and other industrial applications) a 2 stage pump is assumed to be...

One of the best features is less violence when a troublesome knot separates.
Change that to a single stage pump, there would be flying firewood, and damaged operators!

 

[Doug]

It's a 2 stage pump, around 700 psi it kicks down to like 1gpm.

That does solve a lot of problems

 

[pdqdl]

The low volume/high pressure side is exactly 1/5th the high volume displacement, so when the 2nd stage kicks in, he's pumping only 4.4 GPM at up to 3000 psi.

He's got lots of leftover power to run that pump.

Has anyone ever tried running a two-stage pump backwards? I imagine it would pump, but perhaps not kick-down as needed.
If it isn't dropping the volume and kicking up the pressure correctly, you should make sure the inflow & outflow on the pump are done correctly!

 

[Patrick62]

long journey of try this, try that. fix this, fix that.
I know what the attraction of free or cheap stuff is. Been there, done that. I ran a vertical 8 hp for awhile on this. smaller pump, it worked, but was problematical with the start on the motor being a pos. Then ran a china diesel for awhile with a larger pump. Ran cheap, but kept being under powered, and noisy. Eventually got to where it would not start. That generated the thought of I am NOT going to be under powered again on this. A 15 would do it, but why not a 18 ? Sure it uses a little more fuel, but the darn thing runs so smooth now! and that 22 pump isn't a problem for it. I can stall it out on some pieces. At that point the beam flexes about 1/4 inch. 22 tons.


The self propelled feature of this machine is a lot of fun once a year I drive it in the local 4th parade...

 

[cledoux]

If you're planning on beefing that splitter up I'd just start from scratch. Beam is too small for a 5" cylinder, attachment points are the same, valve is pushing the limits @22gpm. (I'm saying this from experience, and destroying several versions of my current splitter)
It's expensive to get into larger higher flow hydraulics. Been slowly collecting parts for a mini processor over the past year or so, had most the steel for years now, actually using mic channel instead of I beam, but that's another story for the reason (s).
Any who, this still brings us back to the issue at hand. Without a basic pressure gauge it's impossible to tell what's going on. A simple T and 3k psi gauge before the inlet of the valve will give us a pretty good story Of what's going on

The best I can tell from the picture of your valve is it's an internal, non adjustable relief model.

ok thanks, yes steel these days is way to expensive. Hopefully it comes down in our next election.

 

[sean donato]

The low volume/high pressure side is exactly 1/5th the high volume displacement, so when the 2nd stage kicks in, he's pumping only 4.4 GPM at up to 3000 psi.

He's got lots of leftover power to run that pump.

Has anyone ever tried running a two-stage pump backwards? I imagine it would pump, but perhaps not kick-down as needed.
If it isn't dropping the volume and kicking up the pressure correctly, you should make sure the inflow & outflow on the pump are done correctly!

1/5 ratio isn't a hard or fast rule for log splitter pumps. Not certain where you came up with that. I checked specs on several pumps and came out all over the place. No clear ratio. Rugged made shows the same 6.7gpm high pressure side on both the 22 and 28 gpm pump.
can't comment on the running one backwards. Never tried it.

 

[pdqdl]

1/5 ratio isn't a hard or fast rule for log splitter pumps. Not certain where you came up with that. I checked specs on several pumps and came out all over the place. No clear ratio. Rugged made shows the same 6.7gpm high pressure side on both the 22 and 28 gpm pump.
can't comment on the running one backwards. Never tried it.

The OP told us what pump he had. I looked up the high-flow and the low-flow displacement, then did the math.
It is assuredly 5:1 volume reduction, presuming equal internal leakage & bypass.

I don't think I've ever disassembled a two-stage pump. Many gear and piston pumps can run backward and they just reverse the flow, although the inlet and outflow lines are usually not built for that. It occurred to me that if a two-stage pump was running backward, it might pump fine, and generate flow and pressure, but never step down to low pressure.

It's just a thought... I've never been there, nor seen that.

 

[norbert77]

New engine, does it run at rated speed? Got a way to check? Also it might run lean and just not give enough power?