Log Splitter Hydraulic Reservoir

[Maticuno]

I'm in the process of converting a home built electric log splitter to gas. The pump and electric motor failed and my wood yard is too far away from an outlet to warrant replacing with electric parts again.

My question is about the sizing of the hydraulic reservoir. The tank on the electric unit is quite small, 2 gallons at most. The reservoirs on the splitters I see at Lowes and Home Depot are huge and I'm wondering why. Since it's a dual action cylinder, why would there need to be a giant reservoir?

 

[purplezr2]

I made mine 14 inch cube. Which works about 11.87 gallon capacity.

I have roughly 8 gallons of fluid in my tank. Works good and the oil seems to stay cool while splitting wood in the summer.

 

[Maticuno]

So cooling is the main benefit of a larger reservoir? I was hoping to reuse the one from the electric unit, but it is pretty small.

 

[gungatim]

yes cooling, and less cycle time of the fluid. the general rule of thumb is to size the tank at least 1/3 the capacity of your pumps rated GPM. keep it level or above the pump slightly and don't undersize the lines (<16gpm - 3/4" from tank to pump, go 1.5" for 17-25gpm). also don't forget a breather cap, suction strainer and return filter...

PM me if you want a digital copy of the design book I used when I built my last 2 splitters...

 

[purplezr2]

I have 1 1/4 inlet to my pump and 3/4 pressure outlet.

My lines to my cylinders are 1/2"

My cylinder is 5" and my pump is a 2 stage 16gpm

I would suggest calculating your cycle time before building your splitter.

 

[Spudland_Dave]

yes cooling, and less cycle time of the fluid. the general rule of thumb is to size the tank at least 1/3 the capacity of your pumps rated GPM. keep it level or above the pump slightly and don't undersize the lines (<16gpm - 3/4" from tank to pump, go 1.5" for 17-25gpm). also don't forget a breather cap, suction strainer and return filter...

PM me if you want a digital copy of the design book I used when I built my last 2 splitters...

Think you got your math backwards, and I'm going from memory of the Fluid Power portion of one of my power transmission classes in college 13 years ago.....TRADITIONAL, basic Hydraulic design states it should be 3X the pump GPM...so a 10gpm pump should have a 30 gallon tank.
That being said, you can design and allow for smaller tanks if you take other things into consideration...Duty Cycle, Ambient Temps, etc.. on a log splitter where you use it for 2 hours a day for what..couple days a year, I wouldn't be surprised if a tank 1/3 the GPM of the low side on a 2 stage splitter pump wouldn't be A-OK...

 

[DougWil]

8"x8" and 10"x10", etc thinner wall structural tubing remnants make a easy to fab up reservoir.

 

[Maticuno]

It's an 11gpm dual stage pump that will be driven by a 6.5hp engine. The ram is actually fairly short, I'd say a 24" stroke, maybe 5" or 6" diameter. I'd go out and measure it right now but El Nino finally decided to hit us and it's been pouring since 5AM.

 

[purplezr2]

Think you got your math backwards, and I'm going from memory of the Fluid Power portion of one of my power transmission classes in college 13 years ago.....TRADITIONAL, basic Hydraulic design states it should be 3X the pump GPM...so a 10gpm pump should have a 30 gallon tank.
That being said, you can design and allow for smaller tanks if you take other things into consideration...Duty Cycle, Ambient Temps, etc.. on a log splitter where you use it for 2 hours a day for what..couple days a year, I wouldn't be surprised if a tank 1/3 the GPM of the low side on a 2 stage splitter pump wouldn't be A-OK...

This is correct.

I made mine based on the high-side plus a little extra. Add in the fact that it is only used in the winter mostly and cooling is not really and issue.


Specs

8HP engine
16GPM LP and 3.5GPM HP
5"x30" ram

With a 11 gallon tank.

 

[brownbagg]

they sell them at tractor supply cheap

 

[Maticuno]

$90 for a 5 gallon tank seems a bit expensive to me, or maybe I'm just out of touch with what this stuff costs.

 

[EdT]

I made a small tank for a project feeling that $90 was a bit much too. By the time I got it cut out, bent up, welded, bungs installed, and fixed a couple of leaks, $90 sounded pretty reasonable. If you do decide to make one, get steel fittings for the bungs. The chicom iron fittings don't weld worth a damn.

 

[Maticuno]

Another, hopefully not too stupid, question. Does the breather cap have to be located above all other hydraulic components or does it matter? I've seen some splitters that have the cap/fill port below the pump and ram, and others I've seen a long extension on the reservoir to keep it above the ram and pump. With an open center valve can the system bleed down when shut off?

 

[DougWil]

Another, hopefully not too stupid, question. Does the breather cap have to be located above all other hydraulic components or does it matter? I've seen some splitters that have the cap/fill port below the pump and ram, and others I've seen a long extension on the reservoir to keep it above the ram and pump. With an open center valve can the system bleed down when shut off?

With an open center valve, the pump port is open to the tank, but both cylinder ports are closed and shouldn't drain back to the tank.
The oil does expand when warm.

The breather just has to be above the highest level in the tank.
But if you are towing that splitter around you want the breather higher so the oil doesn't slosh out.

$90 for a 5 gallon tank seems a bit expensive to me, or maybe I'm just out of touch with what this stuff costs.

If you use square or rectangular tube steel all you need is a baffle, end caps and a few bungs. Buy weld on bungs, or make them from mild steel.
Black iron fittings do not weld well.

 

[gungatim]

Think you got your math backwards, and I'm going from memory of the Fluid Power portion of one of my power transmission classes in college 13 years ago.....TRADITIONAL, basic Hydraulic design states it should be 3X the pump GPM...so a 10gpm pump should have a 30 gallon tank.
That being said, you can design and allow for smaller tanks if you take other things into consideration...Duty Cycle, Ambient Temps, etc.. on a log splitter where you use it for 2 hours a day for what..couple days a year, I wouldn't be surprised if a tank 1/3 the GPM of the low side on a 2 stage splitter pump wouldn't be A-OK...

I don't think so, that is directly from the Northern hydraulics log splitter design book. many common splitter pumps are around 13-16gpm, there's not a one I've ever seen with a 30 gallon tank or anything near that big....not doubting your education but I don't think that applies to splitters. I have a 5 gallon tank on the one I built, 4" cylinder, 24" stroke and it is overkill...

look at this one on Northerns site, 13 gpm, 8.5 gallon tank...
http://www.northerntool.com/shop/tools/product_200628783_200628783

 

[Spudland_Dave]

I don't think so, that is directly from the Northern hydraulics log splitter design book.

Answered your own question and mine

For a log splitter, 13gpm is only the Low pressure side of a 2 stage pump, completely different math with respect for sizing reservoirs... log splitter GPM are just like Air Compressor HP Ratings. Whats the high pressure side GPM rating?

Quote from the following link:
"A rule of thumb for sizing a hydraulic reservoir suggests that its volume should equal three times the rated output of the system's fixed-displacement pump or mean flow rate of its variable-displacement pump. This means a system using a 5-gpm pump should have a 15-gal reservoir."

Also..I didn't find too many specs on the Northern site about pump GPM's other then the Low Pressure flow (16gpm seems much more beefy then 1)...but did finda replacement pump which has 1.1 hi/11gpm rating...so using the above rule of thumb that would mean an 18 gallon reservoir would be normal spec...factoring in duty cycle, and other design factors, I bet 5-10 gallon reservoir is MORE then adqueate...most if not all splitters I've been around have spent 80% of the time on the low pressure side...

http://hydraulicspneumatics.com/200/TechZone/ReservoirsAcces/Article/False/6448/TechZone-ReservoirsAcces

 

[SteveH-CO]

I used a 10 gal. tank from Northern Hydraulic, and only put 5 gal. of AW-32 oil in the tank. This has worked well, and I have not had any sloshing-over issues, in spite of the breather cap and offroad towing of the splitter. I have an 8hp engine and a modified PTO log splitter (also made by Northern Hydraulic). After extensive splitting, the side of my oil tank is warm to the touch, but far from hot. More oil (to a point) is a good thing in a hydraulic system, as far as keeping things cool and keeping contaminants diluted. I don't know the capacity of the pump I bought from NH, but it's a pretty standard log splitter pump.

 

[ishiboo]

A cheap source of hydraulic tanks in small sizes is air reservoir tanks. Weld on the connections you need. 0 psi means they are not critical and simply have to be made not to leak. You could simply weld in black pipe bungs from your local hardware store.

5 gallon for ~$22: http://www.harborfreight.com/5-gallon-portable-air-tank-65594.html
11 gallon for ~$30: http://www.harborfreight.com/11-gallon-portable-air-tank-65595.html

 

[Maticuno]

A cheap source of hydraulic tanks in small sizes is air reservoir tanks. Weld on the connections you need. 0 psi means they are not critical and simply have to be made not to leak. You could simply weld in black pipe bungs from your local hardware store.

5 gallon for ~$22: http://www.harborfreight.com/5-gallon-portable-air-tank-65594.html
11 gallon for ~$30: http://www.harborfreight.com/11-gallon-portable-air-tank-65595.html

I had considered this option, but I've read that baffle plates in the tank are necessary.

 

[Maticuno]

Just found this tech article on reservoir design.

http://hydraulicspneumatics.com/200/TechZone/ReservoirsAcces/Article/False/6448/TechZone-ReservoirsAcces

 

[gungatim]

I had considered this option, but I've read that baffle plates in the tank are necessary.

The 5 gallon tank I used and recommended from the hydro mfgr. has no baffles in it, but then I don't tow it down the road either, just drag it around the yard...no ill affects whatsoever...don't know about driving down the road at 45 mph for an hour and no baffles if it would aerate the oil or not...I can only assume that is what the baffles are for? otherwise I see no reason for baffles. my auto transmission and power steering pump have no baffles either. (and they don't have 30 gallon reservoirs for that matter!)

 

[gungatim]

also to the OP, if you don't want to follow the book I sent, another good place to go for ideas is the "build it yourself" forum section on tractorbynet.com. those guys build stuff out of scrap and what not all the time, and you'll get a lot more advice from those that have built splitters (probably the most common project on there, you'll even see mine if you search) and a lot less of the Industrial tech info that is overkill for a project like a log splitter...JMHO...

 

[ishiboo]

I had considered this option, but I've read that baffle plates in the tank are necessary.

A log splitter doesn't move when its being used so I can't imagine a baffle would be necessary, especially on that size tank. With a breather it should be sufficient to get the cavitation out.

 

[Maticuno]

also to the OP, if you don't want to follow the book I sent, another good place to go for ideas is the "build it yourself" forum section on tractorbynet.com.

I read the entire book and got some good information from it. Thank you for that resource!

A log splitter doesn't move when its being used so I can't imagine a baffle would be necessary, especially on that size tank. With a breather it should be sufficient to get the cavitation out.

From one of the tech articles I was reading, the baffle is to separate the incoming return fluid from the suction line so that it has a longer chance to cool and increases internal surface area to help get rid of cavitation as well as allow contaminates to settle out before hitting the suction line. It might be completely unnecessary on a simple system like a low power, low use log splitter.

 

[Maticuno]

Kicked off the build by fabbing up engine mounts and getting the HF Predator engine mounted. I'll pick up the pump and valve from the post office tomorrow.

Looking through my spare parts loft, I found a 3 gallon air tank with a broken tank fitting that I think I'll turn into my reservoir.

 

[Maticuno]

When looking at other log splitter designs, I found one that had the valve mounted directly to the cylinder via the working ports. The reverse port was connected to the front of the ram by a 1/2" fitting of some type, probably 3 - 6" tall. See my horrible sketch for reference, the red piece.

Anyone have any idea what this type of fitting is? I know it can't be galvanized or black pipe for pressure reasons. Also, any potential reliability issues having the valve and cylinder connected by a hollow piece of steel that will have directional load when the valve handle is pushed/pulled?

 

[DougWil]

Probably just a seamless pipe ****** for hydraulics.
They are pretty stout.

Take your pick.
http://www.discounthydraulichose.com/category_s/928.htm

 

[Maticuno]

Probably just a seamless pipe ****** for hydraulics.
They are pretty stout.

Take your pick.
http://www.discounthydraulichose.com/category_s/928.htm

Now that is an excellent site! Thank you!

 

[Maticuno]

Got it all put together. I ended up buying a 3 gallon tank from Northern Tool. The whole thing works way faster than the old electric power system. Thanks for all of the input, folks!

 

[gungatim]

I think that is the same tank I used. thought it was 5 gal, but it is only 3. I sold that a few years ago for double what it cost to build and went and built another one. used a $99 HF engine on that one...

good job btw.