log splitter hydraulic psi question

[unixkid]

Hello,
After reading many pages regarding log splitter spec’s and builds I have a question which I can’t figure out from my research. I need to understand where hydraulic “psi” is created. By this I mean what makes something 3000 psi as opposed to say 1500 psi. I don’t think it’s the pump. It can’t be the cylinder or valve. Is it the resistance of the object ? (In this case the log being split or the log being lifted ?) If the log being split is so strong that 3000 psi can’t split it, does failure ensue? What does this failure look like ? Is it as simple as the log not split? or is there hot hydraulic oil spraying everywhere ? I feel the need to know this as I am putting together the hydraulic portion of my homemade log splitter. I am one of those people who want to know why instead of just taking something because it is. My concern is to have a component that is inadequate causing the potential for injury due to failure and being sprayed with hot hydraulic oil.

In the absence of knowing where psi is derived I have put together a list of hydraulic components which I think are all capable of 3000psi. Could you guys also put your eyes on this and give it a thumbs up or down ? I appreciate the help and feedback you can provide.

Thanks,
-unixkid

15.5 hp Briggs & Stratton from my old riding mower

All hoses & fittings to be ¾”

Hydraulic Pump:
Haldex Hydraulic Pump — 22 GPM, 2-Stage, Model#1080035 http://www.northerntool.com/shop/tools/product_200321057_200321057

Log Splitting Cylinder:
NorTrac Heavy-Duty Welded Cylinder — 3000 PSI, 5In. Bore, 24In. Stroke http://www.northerntool.com/shop/tools/product_200442472_200442472

Log Splitting Control Valve:
Prince Auto-Cycle Control Valve W/ Power Beyond Model RD5200 https://www.surpluscenter.com/item.asp?item=9-6587-PB&catname=hydraulic

Log Lift Cylinder:
NorTrac Heavy-Duty Welded Cylinder — 3000 PSI, 2In. Bore, 10In. Stroke http://www.northerntool.com/shop/tools/product_200442446_200442446

Log Lift Control Valve:
Logsplitter Valve - LS-3000-2 Pressure Release Detent - ¾" Work Ports http://stores.daltonhydraulic.com/-strse-223/LS-dsh-3000-Logsplitter-25GPM-Prince/Detail.bok

Hydraulic Oil Tank:
NorthStar Steel Hydraulic Oil Tank, 19.5 Gallon http://www.northerntool.com/shop/tools/product_22091_22091

Hydraulic Oil Filter:
Buyers Large Filter — 35 GPM Capacity http://www.northerntool.com/shop/tools/product_25131_25131

 

[sawkiller]

Your pressure will be developed in your pump! Although the amount of available pressure is usually regulated by the control valve. Most valves will bypass at a certain PSI meaning that the fluid bypasses the cylinder and goes back to the tank. I have not researched all the components you picked out but if I were you I would make sure all of them are rated with the pressure range you want to be in!

Also if the ram is stopped on a properly setup system the control valve will simply bypas fluid to the tank. Stopping midstroke is like stopping at the end of the stroke and the components know no different.

 

[sawkiller]

I just noticed its your first post so welocme to AS!

 

[Manatarms]

You also need enough horsepower from your engine to drive your pump to the get to 3000 PSI...if your engine is underpowered you will not make enough pressure.

 

[Blowncrewcab]

The Pressure is derived from the Load on the Cyl. I have a gauge on my splitter that I watch often, Most wood only takes 500psi or less. there are pieces that require more pressure, I have seen it ramp up to 2700psi then bust through the piece. I have also had pieces that the cyl comes to a dead stop and the relief valve kicks in at just over 2700psi. your pump puts out a set amount of fluid at XX rpm, with no load on the cyl the gauge would not move, as soon as you restrict the movement of the ram the pressure goes up, up to the point the relief valve kicks in..

Comprenda'

PS. Thats gonna be a heck of a splitter...

And welcome to AS..

 

[mlkdvm]

The pressure produced by a hydraulic system depends on the resistance against which the pump is working. If the resistance is low, like when a log splitter's cylinder(s) are not at their limits and are not moving, the pressure measured at any given point in the hydraulic system will be low. The pump may be capable of flowing oil up until the point where the resistance is 3000 psi, but if there is negligible resistance, pressure may be less than 100 psi. The pump has the capability of producing pressure but it won't work any harder than it has to.

If a cylinder under hydraulic pressure reaches the limit of its travel, the pressure produced by the pump will increase until the pump reaches its limit or until a valve reaches its limit and causes the oil to bypass and return to the tank. If valves didn't have pressure detents or some other form of bypass the pump would eventually burn up because it would produce no flow of oil after the pressure limit of the pump was reached.

I'm not sure if I've answered your question and I am certainly no expert on hydraulics, but I think what I wrote above is true. If it isn't correct I'm sure someone with more knowledge than me will respond.

 

[AKKAMAAN]

Very good question!! I'll do my best to answer you
Hydraulic is a sub-science to mechanic science. It follows the same rules as mechanics....The difference is, that in mechanic transfer of force we use a solid material, like steel or wood, in hydraulics we use a confined liquid to transfer the force.....
I say force of a reason, because force is the cause of motion. Google Newton's three laws of motion....
To move an object we have to change its state of motion. To make a change of motion on an object, accelerate or decelerate, we have to apply force. So if we want to move a splitter wedge through a log, we need to apply force. If our source of force, or power, is of limited size, we have to use leverage to increase the force. example of mechanical leverage is a gear reduction or a lever. Even inertia is used to increase size of force.
In hydraulics we use a pump and a motor (cylinder) to create leverage. With a small displacement pump and a large motor, we can create enormous leverage, almost unlimited force can be created.
The reason we need force to make an object move, is resistance.
There are three different types of resistance...FRICTION, GRAVITY, and INERTIA....
To split a log, we need our force to overcome friction. And maybe some small amount of inertia too.
If we push our wedge mechanically with or without a lever, we usually do not need to "mix in" PSI in our calculations, unless we need to calculate the strength in used material....
In hydraulics it makes more sense to use pressure instead of force in calculations, but pressure will represent the same thing, but per area unit. It is convenient calculate hydraulic leverage that way.

So to make the wedge to move we need to apply a force that are larger than the opposing force of resistance.

We usually use a rotating motor as source of force (torque). If a large force is needed there is going to be high tension in the drive line, the linkage that transfer the force. In hydraulics that tension is called pressure, PSI.

Hello,
After reading many pages regarding log splitter spec’s and builds I have a question which I can’t figure out from my research. I need to understand where hydraulic “psi” is created. By this I mean what makes something 3000 psi as opposed to say 1500 psi. I don’t think it’s the pump. It can’t be the cylinder or valve. Is it the resistance of the object ? (In this case the log being split or the log being lifted ?)

Now we can discuss what causes the pressure, and it is like discussing "the hen or the egg". In my opinion the friction is already there but in rest. So it must be the applied force that creates the tension or pressure. With in the limits of the hydraulic system, that will be the pump. But in a broader perspective it is actually the engine or motor. If we broaden the perspective even more we can tracke the source of force or power back to the fuel, whish is created by the sun over millions of years. Same thing with the electric motor, unless its powered by nuclear power.
Our source of power is also named "prime mower".

If the log being split is so strong that 3000 psi can’t split it, does failure ensue? What does this failure look like ? Is it as simple as the log not split? or is there hot hydraulic oil spraying everywhere ? I feel the need to know this as I am putting together the hydraulic portion of my homemade log splitter. I am one of those people who want to know why instead of just taking something because it is. My concern is to have a component that is inadequate causing the potential for injury due to failure and being sprayed with hot hydraulic oil.

Limiting the tension in the system is necessary to protect The mechanical parts from breaking/failing. Hydraulics makes it easy for us, we just use a valve that is by-passing the fluid when tension (pressure) is critical. It is called, a Pressure Relief Valve, PRV. It is basically a poppet or a ball, in a housing, that keeps the by-pass path closed by a spring. The spring tension ca be set by a set screw. More spring tension results in high pressure limit.
The PRV is usually integrated in to the Control Valve, CV.

In the absence of knowing where psi is derived I have put together a list of hydraulic components which I think are all capable of 3000psi. Could you guys also put your eyes on this and give it a thumbs up or down ? I appreciate the help and feedback you can provide.

15.5 hp Briggs & Stratton from my old riding mower

All hoses & fittings to be ¾”

Good start, should be fine for pressure lines....Suction need to be at least 1 3/4", I recommend 2".
Returnline need to be 1 1/4".

Hydraulic Pump:
Haldex Hydraulic Pump — 22 GPM, 2-Stage, Model#1080035 http://www.northerntool.com/shop/tools/product_200321057_200321057

Log Splitting Cylinder:
NorTrac Heavy-Duty Welded Cylinder — 3000 PSI, 5In. Bore, 24In. Stroke http://www.northerntool.com/shop/tools/product_200442472_200442472

Log Splitting Control Valve:
Prince Auto-Cycle Control Valve W/ Power Beyond Model RD5200 https://www.surpluscenter.com/item....ol.com/shop/tools/product_200442446_200442446

Log Lift Control Valve:
Logsplitter Valve - LS-3000-2 Pressure Release Detent - ¾" Work Ports http://stores.daltonhydraulic.com/-strse-223/LS-dsh-3000-Logsplitter-25GPM-Prince/Detail.bok

Hmmmm, that Prince RD5200 splittervalve, is a two spool valve, why not second spool for the log lift???

Make sure control valves are for an OPEN CENTER system.

Hydraulic Oil Tank:
NorthStar Steel Hydraulic Oil Tank, 19.5 Gallon http://www.northerntool.com/shop/tools/product_22091_22091

Hmmm, might be small for enough cooling capacity, rule of thumb for a open center system pump is at least 1 minute rest for fluid in tank, which makes 22 gallon....but I think you might be OK if you not cut corners on sizing/designing the lines...rather 1 size up than down, from recommendations...keep fluid velocity "as slow as possible" to avoid over heating.

Hydraulic Oil Filter:
Buyers Large Filter — 35 GPM Capacity http://www.northerntool.com/shop/tools/product_25131_25131

 

[JeffHK454]

Pumps makes flow and resistance creates pressure... all the other components manipulate the two.

AKKAMAAN will be here soon to describe it more eloquently..

Edit: Well said AKKAMAAN

 

[AKKAMAAN]

Pumps makes flow and resistance creates pressure... all the other components manipulate the two.

AKKAMAAN will be here soon to describe it more eloquently..

Edit: Well said AKKAMAAN

Thank you Jeff!
I think I pass comment for now and just stand by and read the other comments....

 

[unixkid]

Thanks to everyone for the helpful information, I have a better understanding now. I am sure glad I stumbled on to this site. I'll attempt to post pictures of the build if I can remember to take em in the first place.

Thanks again,

-unixkid

 

[pipehead]

Pumps makes flow and resistance creates pressure... all the other components manipulate the two.

AKKAMAAN will be here soon to describe it more eloquently..

Edit: Well said AKKAMAAN

+1. The pump does not create pressure, it creates flow. Pressure comes from resistance to the flow, by way of valving/orifices.
The pressure you see on your guage is not the actual outout of the cylinder, either. You take the guage pressure, and mulitply it by the total effective piston area. This is your actual working pressure.

 

[AKKAMAAN]

+1. The pump does not create pressure, it creates flow. Pressure comes from resistance to the flow, by way of valving/orifices.
The pressure you see on your guage is not the actual outout of the cylinder, either. You take the guage pressure, and mulitply it by the total effective piston area. This is your actual working pressure.

As I posted above, this is a deeper question....Like the "hen and the egg"....to make it move you need a larger force from the "prime mower" than the force of resistance....the net force must come from the prime mower....some times gravity is the prime mower.....

It does not matter so much, for the out come if you say the "egg" come first...LOL...
This is my last post about where pressure comes from....I am out!!!

 

[pipehead]

As I posted above, this is a deeper question....Like the "hen and the egg"....to make it move you need a larger force from the "prime mower" than the force of resistance....the net force must come from the prime mower....some times gravity is the prime mower.....

It does not matter so much, for the out come if you say the "egg" come first...LOL...
This is my last post about where pressure comes from....I am out!!!

I would never argue hydraulics with you.....

 

[Marc]

+1. The pump does not create pressure, it creates flow. Pressure comes from resistance to the flow, by way of valving/orifices.
The pressure you see on your guage is not the actual outout of the cylinder, either. You take the guage pressure, and mulitply it by the total effective piston area. This is your actual working pressure.

If a pump is causing fluid to flow, it is increasing pressure. One cannot have flow without a pressure differential. Fluids flow across pressure gradiants. Which is another way of saying they deform under applied stress.

 

[pipehead]

If a pump is causing fluid to flow, it is increasing pressure. One cannot have flow without a pressure differential. Fluids flow across pressure gradiants. Which is another way of saying they deform under applied stress.

You are correct. But suppose a pump with no hose/pipe/fittings attached, and the pump is turned on. If there is no "vessel" for the liquid to act upon, there is no "pressure" in the sense of the word. Think of Pascals laws - the liquid must be confined.

 

[Marc]

You are correct. But suppose a pump with no hose/pipe/fittings attached, and the pump is turned on. If there is no "vessel" for the liquid to act upon, there is no "pressure" in the sense of the word. Think of Pascals laws - the liquid must be confined.

I don't want to hijack the OP's thread, but you've got me curious. It feels like there is another part to this hypothetical I'm missing. What are the specifics of this supposed pump? Pumping what from what to what? What is your definition of an "unconfined" fluid... or liquid if you want to stick with liquids (that would be good for me since I slept through most of my compressible fluids class). I'd posit if you want to define "unconfined" that'd be a body of fluid in a vacuum (and I don't mean a Hoover, either).

 

[pipehead]

I don't want to hijack the OP's thread, but you've got me curious. It feels like there is another part to this hypothetical I'm missing. What are the specifics of this supposed pump? Pumping what from what to what? What is your definition of an "unconfined" fluid... or liquid if you want to stick with liquids (that would be good for me since I slept through most of my compressible fluids class). I'd posit if you want to define "unconfined" that'd be a body of fluid in a vacuum (and I don't mean a Hoover, either).

We are getting a bit deeper than is needed for a log splitter here. It's been a while for me in hydraulic theory as well. When I say "unconfined", I mean not in any sort of vessel or pipe. With no surface to act against, there can be no real "pressure".

 

[Marc]

We are getting a bit deeper than is needed for a log splitter here.

Well that's for sure, but that's why it's so interesting to me!

It's been a while for me in hydraulic theory as well. When I say "unconfined", I mean not in any sort of vessel or pipe. With no surface to act against, there can be no real "pressure".

Well there's no such thing as fake pressure, is there? Pressure is just force acting over an area, and within a gravitational field there will be gravitational force. As long as there is a non-infinitesimal quantity of fluid (has mass) within the gravitational field, there will be pressures involved(inviscid and super fluids excluded).

 

[pipehead]

Well that's for sure, but that's why it's so interesting to me!



Well there's no such thing as fake pressure, is there? Pressure is just force acting over an area, and within a gravitational field there will be gravitational force. As long as there is a non-infinitesimal quantity of fluid (has mass) within the gravitational field, there will be pressures involved(inviscid and super fluids excluded).

I think I see where you're coming from. So long as there is gravitational force, or atmospheric pressure, there is always a "pressure" of some sort being exerted. A bucket of water is exerting "pressure" on it's sides just from the natural forces acting upon it. Now we can get in to reading gauges at "PSIG", or "PSIA".
Inviscid - that made me dust off the cobwebs.

 

[Marc]

I think I see where you're coming from. So long as there is gravitational force, or atmospheric pressure, there is always a "pressure" of some sort being exerted. A bucket of water is exerting "pressure" on it's sides just from the natural forces acting upon it.
Inviscid - that made me dust off the cobwebs.

Sure. Look at our atmosphere for a good example. Fairly 'unconfined' except by the surface of the Earth and the Earth's gravitational field. But there's pressure through the atmosphere from gravity. And because we have solar heating the atmosphere and bodies of water (plus the Coriolis effect and the moving, relative to Earth, gravitational field of the moon), we have all kinds of pressure gradients causing wind and weather.