Pump and reservoir size

[big red 18]

I have an 220d yanmar and I'm setting up a pto pump for a log splitter. I was thinking 4 to 5 gallon reservoir. 2250 psi 18gph pump. Any thoughts. Thanks

 

[muddstopper]

Lets look at some numbers first. To pump 18gpm@2250psi you are going to need about 26hp. Your tractor is rated at 22hp, so your already under powered for what your trying to do. Now unless you already own the pto pump, you can expect to pay $500+ for a PTO pump, assuming you can even find one that will produce 18gpm in that price range. If you decide to use something other than a standard pto pump, your pto only runs 540rpms. Pump flow is determined by the pump displacement and the rpms it turns. At 540 rpms, its going to take a very big pump to give you the 18gpm you are looking for. Then you also have the issue of coupling the pump to your pto shaft. Once you have found the pump, then you are going to need a oil tank. Recommended tank size is usually one gallon capacity for every gallon of flow, so a 18gal tank. And dont forget the return and possibly suction oil filters. What I am trying to suggest is that by the time you assemble all the parts to build your splitter, its going to be expensive. Now if you have the parts just laying around, by all means use them, but if you are going to have to buy everything new, it might make more sense to just buy a stand alone wood splitter with its own power supply.

Hooking a hyd cyl to your tractors hyd system is also another option. The loader valve can have quick connect fittings added so you can unhook the bucket lines and snap on the splitter lines, easily and cheaply. If your loader valve has Power beyond, thats even better. Your splitter speed will be limited to the oil flow available from the tractor, but it will work.

 

[LD1]

Usually the rule of thumb without a cooler is 3:1 for tank size. So 18 gpm pump would need 50-60 gallon tank.

2- stage pumps, or systems with a oil cooler can go as low as 1:1. Given a log splitter isn't continuous use, you can cheat that some. But I'd want at least 30 gallon tank on a 18 gpm single stage splitter

 

[big red 18]

Thanks I appreciate the input. Quick connection would seem to fix my problems.

 

[LD1]

If by quick connect you mean running it off the tractors hydraulics, I think you will be disappointed. Don't know for sure the tractors specs, but a 22 hp tractor usually has somewhere around a 3-4 gpm pump.

Have you ever ran a stand alone splitter? One that has a two stage pump that kicks down to low speed when splitting? Well, that very slow speed is going to be how fast one will operate off your tractor hydraulics. So instead of the normal 10-15 seconds out and back (cycle time) like a store bought splitter, you are looking at 45 seconds, maybe a minute, just to make one split.

You could always go with a Regen valve. Or a more manageable 12-13 gpm pto pump.

 

[big red 18]

Thanks for the input. I have the splitter but I'm not sure what I'm gonna do

 

[IceStationZebra]

For what its worth - you can go below the 1:1 rule of thumb if you have a sufficiently sized external cooler and don't have air entrainment issues. I did the integration work on an industrial forklift line that turned the oil over every 15-25 seconds depending on the engine and chassis combo! For something like a splitter that has to deal with displaced cylinder volume I would probably shoot for about 1.5:1, but I'd do the calculations to make sure the oil stays at least 1 diameter above the pump feed fitting with cold oil, and doesn't come out when hot.

I mentioned this on another thread here, but big reservoirs do not add much cooling. If you do the calculations you will find that painted steel tanks don't actually reject much heat, and plastic is even worse. What you are really doing is buying time. Just simple physics that the more mass in the system the longer it will take to heat up, and just maybe it is so big that you will take a break before that happens. And remember that every pressure drop is just converting hydraulic energy to heat - try to keep the restrictions to a minimum. (properly sized valve and hose, use hoses with radiused 90° ends instead of sharp 90° fittings, etc.)

I think the old 4:1 or 3:1 rule goes back to the early days of medium pressure industrial hydraulics where the heat load was small enough to get away without a cooler, but those systems are a rare bird today. Most systems today have coolers while space, contamination and fire concerns work to minimize reservoir size. ISZ

 

[LD1]

Most small hydraulic home-grown type machines do not have coolers. Thus the issue. Maybe some of the $3000+ splitters like iron and oak, or timber wolf have a cooler. But I have never seen a splitter with a cooler.

 

[big red 18]

Ok then could I go 11gpm pump with 10 to 15 gallon tank ? If so would the splitter have a reasonable splitting rate

 

[LD1]

Depends on what you define as reasonable. And what is the bore and stroke of the cylinder?