Log Splitter Hydraulic Plumbing Question

[fluidpowerpro]

I read through the original post but not all of the replies so forgive me if the questions have been answered.
Regarding line size. 
The sizes you are using are good for the flow rates you are running. Yes, bigger is typically better but at some point the returns are diminished. A general rule of thumb for a 3600 PSI max system is 15 ft/second on a pressure line, 5 ft/second on a return line and less on a suction line. 
These are just guidelines and in practice dictated by products that are commercially available.

The port size of the directional valve is what it is and yes, that is your greatest restriction however it not influencing your speed to any large factor. The distance the fluid travels in that fitting is short so not a big deal. This restriction does add pressure drop which ultimately results in heat, however in a manual log splitter, I dont expect heat will become an issue.

There are lots of ways to calculate cylinder speed however the one I memorized and always used is:
Area x Length x .26 / GPM = time (seconds).
If you have a 5" bore cylinder:
19.63 x 1" x .26 / 16GPM = .318"/Sec.
This is theoretical, so any loss in efficiency will reduce this speed.
To calculate the retract speed you would need to deduct the area of the rod from the area of the bore before using the same formula. 

Assuming you dont want to reduce force, and your engine is running at its rated RPM, if you want to increase speed, you will need a bigger pump.

Regarding sealing NPT threads in a hydraulic system, I have had the best luck with an anaerobic sealant such as Locktite 545. Make sure the surfaces are clean and let it sit overnight before pressurizing.



 

[doc henderson]

that formula checks out.  I will see in a week if there is any room left to add that to my brain.  doubt it.  I was told the benefit of a dump valve to unload the back end of a cylinder straight back to the tank is 28 gpm and a 5-inch cylinder or greater.  any thoughts?

[Rob in NC]

I will be 64 in October, and you are a man next to my own heart.  I love improvements, but also do not want junk that can snag going through a wooded area or look cobbled.  I added fleet wiring to my splitter so it can charge my 12-volt power to a conveyor.  It can all run off my truck and I could even jump start my truck from the splitter or conveyor.  I even bought copper tubing to wrap around the car muffler on the rig, to reduce now and allow for a way to heat water in the field for hot chocolate or tea/coffee as desired.  Lots of good ideas.  Never got that installed.  considered the auto cycle now that my son is older.  Have the dump valve but not yet installed.  see the shade tree mechanic thread.  busy with life as well.  I have enjoyed this exercise.  Doc.

Shade tree mechanic! Whatcha workin on. - Page 2 (forestryforum.com)

ongoing splitter and conveyor upgrade. - Page 2 (forestryforum.com)

your conveyor is a great idea again i dont really do enough work to justify one but it sure would be nice.. I did look at the range road brand and they are priced very reasonable but im sure the quality follows the cost like anything. 

[fluidpowerpro]

that formula checks out.  I will see in a week if there is any room left to add that to my brain.  doubt it.  I was told the benefit of a dump valve to unload the back end of a cylinder straight back to the tank is 28 gpm and a 5-inch cylinder or greater.  any thoughts

The flow rate out of the cap end of the cylinder will be greater than the pump flow due to the reduced area of the rod side and the cylinder will retract faster than extending.
To deal with this added flow, connecting the cap side directly to tank when retracting will reduce the restriction of the directional valve however I would think by the time you add the dump valve you might as well just get a bigger directional valve.
Also, most times the return line filter on a log splitter is on the tank line of the directional valve. If you dump the oil directly to tank, you would be by-passing the filter. You could T it in before the filter, but the you still have the back pressure from the filter which is kind of counter productive to why you added the dump valve.

[doc henderson]

Thsnkd FPP.

Rob, Yes, but it is fun!

[Rob in NC]

I read through the original post but not all of the replies so forgive me if the questions have been answered.
Regarding line size.
The sizes you are using are good for the flow rates you are running. Yes, bigger is typically better but at some point the returns are diminished. A general rule of thumb for a 3600 PSI max system is 15 ft/second on a pressure line, 5 ft/second on a return line and less on a suction line.
These are just guidelines and in practice dictated by products that are commercially available.

The port size of the directional valve is what it is and yes, that is your greatest restriction however it not influencing your speed to any large factor. The distance the fluid travels in that fitting is short so not a big deal. This restriction does add pressure drop which ultimately results in heat, however in a manual log splitter, I dont expect heat will become an issue.

There are lots of ways to calculate cylinder speed however the one I memorized and always used is:
Area x Length x .26 / GPM = time (seconds).
If you have a 5" bore cylinder:
19.63 x 1" x .26 / 16GPM = .318"/Sec.
This is theoretical, so any loss in efficiency will reduce this speed.
To calculate the retract speed you would need to deduct the area of the rod from the area of the bore before using the same formula.

Assuming you dont want to reduce force, and your engine is running at its rated RPM, if you want to increase speed, you will need a bigger pump.

Regarding sealing NPT threads in a hydraulic system, I have had the best luck with an anaerobic sealant such as Locktite 545. Make sure the surfaces are clean and let it sit overnight before pressurizing.



 

I ordered some of that loctite 545 to try on the fittings hopefully that will do the trick.. now to undo them all, clean them and reinstall.. again.   learning how to do things right on your own is exhausting.. i need an old timer around this place bad.. 

[Gary_C]

When you consider the overall cycle time of a log splitter, you have to look at the extend time separately from the return time. On the extend time it depends on the volume of fluid you need to move on the piston side of the cylinder. On the return time it depends on the same volume as on the piston side LESS THE VOLUME OF THE ROD. So the not so simple way to make the overall cycle time shorter is to get a hydraulic cylinder with a very large diameter rod.

If you have not changed the cylinder, the only way to reduce cycle time is to increase the GPM of the pump. Increasing line size or pressure (relief valve setting) will have little effect. 

[Rob in NC]

When you consider the overall cycle time of a log splitter, you have to look at the extend time separately from the return time. On the extend time it depends on the volume of fluid you need to move on the piston side of the cylinder. On the return time it depends on the same volume as on the piston side LESS THE VOLUME OF THE ROD. So the not so simple way to make the overall cycle time shorter is to get a hydraulic cylinder with a very large diameter rod.

If you have not changed the cylinder, the only way to reduce cycle time is to increase the GPM of the pump. Increasing line size or pressure (relief valve setting) will have little effect.

So if i were to pick one - dump valve add on or 2 stage 22gpm pump im assuming the dump valve would make little noticeable difference compared to the pump because i would be gaining 2-stage as well as 22GPM vs my current 16GPM single stage. 

what's your experience with split-ez line of cheaper pumps? i currently have a haldex and they seem to be really good pumps which im assuming is why they are double the cost of the other line they carry. Mines 30 years old and works fine. 

another question - with a 13hp engine im assuming im not going to be able to run a 28GPM pump even if i ran it on the easy side and never pushed it?

[doc henderson]

I just rebuilt my log splitter valve, and the dump valve on mine is to reduce heat to save the valve more that increase cycle time.  In the second state the speed will drop, but splitting force goes up.  I am told by James that he has had no problems with his cheaper line of pumps.  I have the haldex/concentric 28 gpm 2 stage, but they were 300 bucks 12 years ago.  I think your biggest bang for the buck, is the 22 gpm pump.  I would add a pressure gage if you do not have one.  most of the speed will be retracting and going forward to contact the log.   I think the 28 would pull you motor down, and you would have to reduce the pressure for bypass, so you do not kill the engine.  then you lose ability to get through an elm log or whatever is your tuff to split stuff.  there is always a weakest link, and as I split, I can see the wedge torque a bit, so I back off and let the pusher, log and wedge reset without the torque.  I do not want to bend or break my wedge off.  that was the other reason I did not do the auto cycle.  now they are more expensive.