Slightly OT -- hydraulics for a log splitter

I've been looking at the possibility of building a log splitter, vaguely
following some old plans from Mother Earth magazine. The metalwork presents
no problems (perhaps famous last words!) but I have never messed with
hydraulics. I've been looking at the parts that Northern Tool sells, and am
not entirely sure what I am looking at.
For the hydraulic pumps, there seem to be two styles, one that is rated in
GPM and one that is rated in cu. in. Why the different ratings? Are these
two different types of pumps, intended for different uses?
For pumps that are rated in GPM: If the max PSI is the same for two
different pumps, would they both be able to create the same amount of
splitting force -- but the one with higher GPM would move faster than
other -- or am I totally off track here?
NT also sells a variety of hydraulic rams, ranging considerably in price.
They all seem to have three specs: max PSI (generally either 2500 or 3000),
stroke, and bore. Okay--how do I compare these specs to the commercial log
splitters advertised as "20 ton splitter" or "25 ton splitter"? Is the
overall force exerted related to the PSI--but the rams and pumps all seem to
have similar maximum PSI?? Or is it a function of PSI and bore size?
I guess what I need is a quick course in basic hydraulics. Is there a good
website to read up on this stuff? Many thanks to anyone who takes pity on my
ignorance!
Andy
Reply to
Andrew H. Wakefield
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go down to the local co-op or tractor supply co. or such in your area and spend a few minutes with one of their new models , looking at how they are built and the size of their equipment will give you a really good idea
a few guidelines
a four inch bore cylinder has 12.57 square inches approximately so for every 100 psi you get 1200 pounds of force
at 2000 psi this is a twelve ton cylinder , at four thousand it is a 24 ton cylinder ,
horsepower required to run your pump can be figured on the base of
1 horsepower = one gpm @1500 psi
most of the log splitters i see are
5-8 horsepower two stage pump 12 gpm@800-1000 psi,2-4 gpm @3000psi manually operated valve a four inch bore cylinder
i built mine netirely with stuff i scrounged , though SurplusCenter is a good place to buy, way cheaper than NT
RAMBLE OFF
Reply to
williamhenry
You need to match your pump in regards to yur engines horsepower. Look at the Barnes 2 stage pumps, thats what you want to use, unless you have a big engine, want to get into more work on hydrualics etc. The 2 stage pumps are fine, with their smaller one being suitable for a 5 or so hp gas engine, and the next size for at least a 8 to 10 hp engine, and the largest you need at least a 16 hp for them to work fine.
GPM is how much the time it takes to cycle due to flow in an unloaded operation. More load, GPM is going to drop, and pressure will increase..So look for a pump (2 stage) thats capable of at least 3000 psi which is more than sufficient. Lower GPM flowrate is just a bit longer in cycling the cylinder in and out, unloaded.
Tonnage developped is proportional to the surface area of the piston in the cylinder. You may have a 4inch cylinder, and you times the square inches of that pistons face by the PSI to come up with tonnage produced.......Its a given. However you also have a rod attached to that cylinder which in all reality is going to reduce the pistons surface area on the rod side, so you need to deduct the area the rod takes up on the pistons face. The opposite side of the piston is usually going to have more surface area as it has no rod attached to it, so it generates greater force one way than the other.
Most log splitters you see at builder supply and garden places are from 20 to 25 ton on average and most have anything from 4" to 5 inch cylinders. A bigger cylinder in diameter will generate more tonnage or force with the same pressure applied to a 4 inch cylinder, but to make cycle times faster to make up for the larger cylinder you may need to step up to a larger GPM pump.
To make it simple go with their 11.x GPM 3000 2 stage pump,. 5 to 6.5 horsepower gas engine, and a 4 to 4 1/2 x whatever length cylinder you need for the ram. But the open center single spool with detent retract position control valve and the length hoses you need, and a filter assembly, and also a strainer breather assembly. Thats it. the rest is steel welded up to make the design you want. Hydraulics is simple, especially on a log splitter. Open center control valve will continually allow fluid to free flow back to resivoir, when its not closed by the lever to divert fluid to the cylinder. If y ou use a closed center valve you have much faster cycle times or break out times, as there is a pressure relief valve that holds the fluid pressure up to or close to the operating prressure at all times.........not needed with a log splitter, and by not using a closed center valve it will reduce heat buildup, and wear and tear on your hyd components.
REMEMBER: "This is worth repeating for benefit of al newbies! Jo Ann asked Dr. Solo to remind people that while she has retired from selling GF (and sold the business to Ken Fischer
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she has NOT retired from helping people with sick GF and koi FOR FREE. 251-649-4790 phoning is best for diagnosis. but, can try email put "help sick fish" in subject. Get your fish at Dandy Orandas Dandy Orandas Dandy Orandas........you guys got that DANDY ORANDAS
Reply to
Roy
The hydraulics are just plumbing; HP hydraulic lines and fittings are available everywhere in industrialized sections; NT notwithstanding. A 4" DA cylinder and 11 GPH pump is plenty for up to 24" dia. bucks. My home built splitter uses a 12" stroke cylinder, which is plenty, since I buck all my logs to 18" lengths for my fireplaces. You pretty much can't build a splitter for much less than you can buy one, unless you snag the major components free or very cheap. JR Dweller in the cellar
Andrew H. Wakefield wrote:
Reply to
JR North
It's traditional to use "two-stage" pumps in splitters. The first stage produces high flow at low pressure to move the ram quickly to and from the work. The second stage produces very high pressures at low flow to build the large forces necessary to actually split the wood.
Northern sells Prince pumps (not the best, but they last many years if your wet circuit is maintained clean and moisture-free... and they're CHEAP). They offer an 11gpm two-stage "log splitter" pump that mates well with an 8hp gas engine. Mine's an old cast iron updraft-carb Briggs.
With a 4" diameter, 24" stroke cylinder, you can generate roughly 14 tons of splitting force at 2200psi (well within the capabilities of the pump and engine).
That doesn't sound like much, compared to their 20 and 25 ton splitters, until you realize that they're advertising what the press COULD do if the system ran at the maximum pressure rating for the components -- which they never do.
With 14 tons and a clean wedge, I can split an 18" diameter well-cured white oak butt 20" long. (needs a wedge at least longer than the radius of the piece.. mine's 11")
LLoyd
Reply to
Lloyd E. Sponenburgh
I have never seen Prince pumps offered by NT in 2 stage configurations. All I have ever seen is Barnes brand 2 stage pumps. They are a good pump. I have some over 20 years old and work fine..... Prince is a large manuf of cylinders though, and I have had mixed results with them, but their more than sufficient on a log splitter.
I routinely run my system at 2200 to 2500 psi not the full rated 3000 and it works just fine, and makes for lots less wear and tear on components.
REMEMBER: "This is worth repeating for benefit of al newbies! Jo Ann asked Dr. Solo to remind people that while she has retired from selling GF (and sold the business to Ken Fischer
formatting link
she has NOT retired from helping people with sick GF and koi FOR FREE. 251-649-4790 phoning is best for diagnosis. but, can try email put "help sick fish" in subject. Get your fish at Dandy Orandas Dandy Orandas Dandy Orandas........you guys got that DANDY ORANDAS
Reply to
Roy
The next splitter I build will have a 2 stage pump to speed the cycle time. Also the ram will be a 5 inch bore with a 4 inch rod to speed the retract time.
Current splitter has a 4 X 24 and a Vickers pressure compensating pump. That is a rotary swash plate style and the swash plate rotates flat at a preset pressure setting (no flow). It was built with available parts some 20 years ago and still serves me well. Beam rotates vertical and horizontal, Briggs model 19 7.25 HP engine.
Last fall I had 2 young men and my g/f helping. It was the easiest harvest by far. Here is how it went;
Weekend 1 spent 2 days in the woods cutting trees, 20 -25 ft length sections. Loaded trailer with case backhoe with 4 in 1 bucket.
At home, picked up the log with the tractor and held it about 3.5 ft. g/f backed the Kawasaki mule under the end of the log, and I cut a piece off 18 inches long. 4 or 5 pieces in the Mule, drive over to the splitter and dump the pieces off to the splitter and stackers. Repeat until wood is all in the barn. We did 6 cords in a day! No sore back!
I like the design of the Timberwolf Manufacturing TW-6 machine.
Bob
Reply to
Bob
Greetings Andy, To figure how fast the system will work you need the GPM and the volume of the cylinder. The volume of the cylinder is 3.1416 times the radius squared of the cylinder times the travel. Because of friction losses etc. your top speed will be lower than the calculated max, but it will give you an idea. So if the cylinder volume is 1 gallon, and you have a 10 GPM pump, the shortest time for the full cylinder travel is 6 seconds. ERS
Reply to
Eric R Snow
snip
A 4" rod in a 5" bore cylinder.........for what reason would this be beneficial? With so much reduction on the retract side it would be awfully low power and slow............A 2" rod is more than sufficient for any splitter if the moveable slide with ram or wedge is sufficiently sturdy.
REMEMBER: "This is worth repeating for benefit of al newbies! Jo Ann asked Dr. Solo to remind people that while she has retired from selling GF (and sold the business to Ken Fischer
formatting link
she has NOT retired from helping people with sick GF and koi FOR FREE. 251-649-4790 phoning is best for diagnosis. but, can try email put "help sick fish" in subject. Get your fish at Dandy Orandas Dandy Orandas Dandy Orandas........you guys got that DANDY ORANDAS
Reply to
Roy
Care to share what you're seeing that Roy isn't?
Reply to
Dave Hinz
The rod subtracts from the cylinder area for retraction, so the bigger the rod, the faster it moves for a given volume per second (you can think of the rod as filling up a lot of the cylinder so it takes less hydraulic fluid). The example would retract as fast as a 3" cylinder extends. You could also use a regenerative circuit to get it to extend faster at low power before it starts to split.
Best regards, Spehro Pefhany
Reply to
Spehro Pefhany
Yea I know a bigger rod would mean less volumne needing to be filled but its certainly way overkill on a simpole machine like a log splitter.......I did type in slow but intended to refer just to the low power end, which really does not mean anything on a retract cyucle of a splitter, but heck a 4" rod.............hmmmmmmmmmm
REMEMBER: "This is worth repeating for benefit of al newbies! Jo Ann asked Dr. Solo to remind people that while she has retired from selling GF (and sold the business to Ken Fischer
formatting link
she has NOT retired from helping people with sick GF and koi FOR FREE. 251-649-4790 phoning is best for diagnosis. but, can try email put "help sick fish" in subject. Get your fish at Dandy Orandas Dandy Orandas Dandy Orandas........you guys got that DANDY ORANDAS
Reply to
Roy
snip
Well not that I can think of off hand, but I would have to think the price of a cylinder with such a rod in it would be pretty darn pricey compaared to say the next higher flow pump.....I really doubt I would even consider using a 4" rod in a 5" cylinder if I had it for free. Heck why not grab an old Chevy 427 or even a 283 and use it with a big pump............better yet one of the old J-79 engines that Davis Monathan AFB boneyard is full of and use it with their high flow high pressure hydrualic pumps that are normally installe don them for in the old F4.....now that would be some fast cycle times, but pretty expensive to operate...........
REMEMBER: "This is worth repeating for benefit of al newbies! Jo Ann asked Dr. Solo to remind people that while she has retired from selling GF (and sold the business to Ken Fischer
formatting link
she has NOT retired from helping people with sick GF and koi FOR FREE. 251-649-4790 phoning is best for diagnosis. but, can try email put "help sick fish" in subject. Get your fish at Dandy Orandas Dandy Orandas Dandy Orandas........you guys got that DANDY ORANDAS
Reply to
Roy
I rented a splitter last year that spoiled me. I'll never even consider hydraulics for splitting wood again.
The splitter was "Gripo" brand name. It used a rack driven by a pinion on a shaft with a fairly substantial flywheel on it.
The cool part was that it had a cycle time of around a second a shot. Place block, lift toggle handle, SHUNK!, place block. The ram was retracted by springs and was ready to go before I was in all cases.
No problem blowing through the knots or crotch wood. Blew through a couple blocks sideways to shorten them, it grunted at that.
All on a 160cc Honda motor.
Wish I had taken some pictures of the linkage that connected the rack to the pinion. I've been keeping an eye out for a suitable rack and pinion set since then. I figure a flywheel is easy, as there is usually a scrapped out baler at most farm auctions I've been to.
Hmmmm.... A google search finds Super Split made in the US that uses the same mechanism. Cool stuff!
Cheers Trevor Jones
Reply to
Trevor Jones
Roy, power does mean _something_ on the retract stroke of a splitter.
Didja ever get a slivver stuck under your guides? Sure, it doesn't take as much power as the splitting cycle.
LLoyd
Reply to
Lloyd E. Sponenburgh
LOL, a little knowledge can be erroneous.. Tom
Reply to
Tom
A 4" piston would mean a fast retract as the volume per inch of stroke required would be 7 odd cubic inches. With a 2" rod it would be that much slower, as 16.5 cubic inches per inch of stroke would be required.
5" bore = 19.635 square inches 4" rod = 12.566 " " 2" rod = 3.1416 " "
The maths are quite simple..
Tom
Reply to
Tom
Bit of a typo in the previous! :-(
A 4" rod would mean a fast retract as the volume per inch of stroke required would be 7 odd cubic inches. With a 2" rod it would be that much slower, as 16.5 cubic inches per inch of stroke would be required.
5" bore = 19.635 square inches 4" rod = 12.566 " " 2" rod = 3.1416 " "
The maths are quite simple..
Tom
Reply to
Tom
Can you think of a cheaper way of getting a faster retract cycle?
Tom
Reply to
Tom
Many thanks for all the helpful replies. You have confirmed some of what I was thinking, plus given me insight into issues I didn't know enough even to ask about!
I know I'll have a couple more questions to follow up; after I digest all this info, I'll put up a new post with follow up questions.
Thanks again!
Andy
Reply to
Andrew H. Wakefield

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