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Discussion Starter #1
I have a buddy who is moving. He's closing on the house he lives in and the new people take over this week:banghead3 well anyone who's ever moved knows that you gotta "clean house" and just "get rid of" alot.

Well in the last few weeks I have been over there helping him do just that; and I have ended up with alot of "Stuff" in the back of my pickup.
Among that "stuff" is everything I need to build my own log splitter; except for an engine. 3 different cylinders (I will probably pick the longest one) the I beam, the fluid tank, the filter mount, hoses, valve, axle and more.
I wasn't figuring on building one of these since I no longer have my own fireplace; but since I have all the "makings", "why not"?

How do I figure out how big an engine I need for that pump? I've seen spliters from 5-16 HP; some store bought some home made.
I have recently been splitting ALOT of firewood; (something else he needs to find a buyer for in the next few days) and we had a borrowed store bought "MTD" vertical model w/a 6.5HP Briggs vertical engine; and a home made horiz. model w/ an old L head 8HP Briggs. the 6.5 seemed plenty for that machine yet the 8HP seemed under powered. (based on how much the respective engines "bogged" under the load of splitting an average sized log)

is there a chart of "gallons per minute of pump capacity, vs HP required" or does it go by cylinder size, or what?
 

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Among that "stuff" is everything I need to build my own log splitter; except for an engine. 3 different cylinders (I will probably pick the longest one) the I beam, the fluid tank, the filter mount, hoses, valve, axle and more.
I wasn't figuring on building one of these since I no longer have my own fireplace; but since I have all the "makings", "why not"?

How do I figure out how big an engine I need for that pump? I've seen spliters from 5-16 HP; some store bought some home made.
I have recently been splitting ALOT of firewood; (something else he needs to find a buyer for in the next few days) and we had a borrowed store bought "MTD" vertical model w/a 6.5HP Briggs vertical engine; and a home made horiz. model w/ an old L head 8HP Briggs. the 6.5 seemed plenty for that machine yet the 8HP seemed under powered. (based on how much the respective engines "bogged" under the load of splitting an average sized log)

is there a chart of "gallons per minute of pump capacity, vs HP required" or does it go by cylinder size, or what?
1 hp. = 1 gpm. @ 1500 psi.
1 hp. = 0.5 gpm. @ 3000 psi.
1 hp. = 2 gpm. @ 750 psi.

Pushing force = area of the cylinder x-section X psi.
Pulling force = area of the cylinder x-section minus area of the rod x-section X psi.

1 gal. = 231 cubic inches.

Cylinder volume = x-sectional area X length of stroke.

Time for full stroke out = 60/ gpm. (converted to cu. in.)/ cylinder volume (cu. in.) = # of seconds.

A smaller diameter cylinder will require higher pressure to split a given block. If the flow on both splitters was the same, that could explain the larger engine "bogging".

Playing with hydraulics is a numbers game if you want to have a unit that will work at the best efficiency for time, force and horsepower. Lots of math and formulae. There are handbooks available with all the necessary info. I have several.......... somewhere :banghead3, but I haven't been in the right stores to look for them for years. Perhaps Northern Tool?

Here's a couple of study guides.

http://www.edgeroamer.com/sweethaven/mechanics/hydraulics01/

http://www.hydraulicsupermarket.com/technical.html

A 3.5" - 4" diameter cylinder with a 20" - 24" stroke makes an excellent log splitter. Smaller diameters need a lot higher pressure, but a smaller volume to do the same job in the same time.

Oil under pressure can be dangerous if you spring a leak in a line or fitting. The higher the pressure, the greater the danger.
 

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Discussion Starter #3
I have the 3.5"-4" cylinders "covered" in lengths from ~20-32" IDK if the pump I have will work; I may have to look for something different; the one I have is way too huge; it is marked "Cessna" (yeah the plane people) and is splined, and is a huge (compared to any I have seen on a log splitter) and given the direction arrow it looks to be set up to be splined from what would be the "flywheel side" of a typical small engine; so i'd have to run it off a chain drive with the shaft pointing the same way as the PTO side of my engine instead of directly coupled like a typical splitter pump (running it that way would make the pump run backwards) so I'm looking at Farm and Fleet; they have an 11GPM and a 16 GPM pump.
 

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I'd look into a different pump,the 2 stage pumps that they sell in Northern Tool and the big box farm stores don't need near as much hp as the single stage pumps,most of the new splitters are only using about 5-6hp engines to power splitters that are rated at 22-27tons.If you use their pumps,they also sell a bracket to bolt the pump right onto the engine,that makes mounting the pump that much simpler also.
 

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I run my splitter off of my FEL system, 8 gpm. @ 1500 psi. That's a little light in both departments for a 3.5" cylinder, but it uses an existing system and saves on engines. I rarely use full throttle and have the hp. for a pump over twice the size, but it would be too quick on the loader which doesn't need all that much pressure anyway.

The double pump that bstrucker is talking about makes a great stand alone system for a splitter, but it's pretty much useless for a lot of other types of projects, especially if they involves a hydraulic motor. Just remember that the cylinder speed drops dramatically when the unloader valve pops on the larger pump section and you only have the flow from the smaller pump to work with.
 

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Discussion Starter #6
yeah bstrucker; I've seen those coupler brackets to mount a pump to an engine;
I found an(other) engine candidate yesterday for this project;
I now have (2) hor. shaft B&S 5HP's here to choose between as well as, now a (elec start!) Kohler 8 HP "Magnum" added that I just got yestreday. I saw that 8HP sitting there and "had to have it" thinking it would be about right for this splitter.

I am planning on building this as a "convertible" vertical-horizontal splitter and as such am thinking of a 2nd, smaller, cylinder to raise/lower the I beam, between the vert and horizontal positions. If I went with the "2 stage" pump I'm thinking that it would be able to handle that function on the "lower power" setting thouygh I know it would mean a 2nd lever and a few more hoses though they would not need to be as large as the ones feeding the "splitting" valve and hoses. .

the local farm store has 2 different logsplitter pumps on the shelf, a 11GPM and an 16GPM version that are both a lil higher priced than I want to spend; I think both are 2 stage type; should I just "buy the big one"? I'm still scouting garage sales, auctions flea markets etc looking for a "deal" before I bite the bullet; this isnt really a "high priority" project it's not something that I need right away so I can wait til I find what I need; ideally I would like to trade that "Cessna" pump for a more suitable one, even up.
 

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A rule of thumb, for logsplitter pumps, the HP of the engine should be half the GPM of the pump. So your 8HP Kohler should be mated to a 16GPM pump or smaller.
 

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Discussion Starter #8
A rule of thumb, for logsplitter pumps, the HP of the engine should be half the GPM of the pump. So your 8HP Kohler should be mated to a 16GPM pump or smaller.
seems a lot easier than all the other "formulas" others have come up with....
 

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It is specific only to the double pumps used on log splitters, but it is a good rule of thumb for those pumps. :fing32: Just don't try to use it elsewhere.
 
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