Splitter pumps and cycle times.
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Let me know what pump you get. I'd like to do the same. Mine has about a 60 second cycle time right now, across 36 inches of travel.
Fittings- some of the 1/2" fittings only have about 3/8" internal dia. Need to look for Hi-flow fittings. Speed is a matter of how Fast you can fill/ empty the cylinder. Most units only have 1/2" ports on the cylinder so guys get bigger pumps to push more fluid through the restrictive lines/ports creating heat from friction which is the enemy of hydro. Years ago when I redid my splitter I went to all 3/4" lines and control valve ports at 3/4" also and 1/2" hi flow fittings on the cylinder. same 11 gpm pump and cylinder it did get a bit quicker but my main goal at the time was reducing the excessive heat being generated ( My cylinder would get so hot after an hour or so that you would get burned if bare flesh contacted it) which I achieved. As I still have not worn out the cylinder ( harbor freight 20 years old- go figure) I have not gone any further on the speed issue. 3/4" port cylinders are available or having current cylinder ports enlarged ( not cost effective). Same with the pump- Did replace original valve with a 3/4" port unit as I wore out the chicom one. Bigger pump is cheaper than a new cylinder with 3/4" ports but the gain is less. One also has to pay attention the return line to tank- got to have the capability on that side of the circuit as well.
Hmm, I'm pushing a 13gpm pump now but maybe my restriction is my 1/2 detent valve (the handle). All my lines are 3/4" but that sucker is small. Good post. Here's a 3/4 port model, but it's only 25 gpm where the 1/2" model is 20gpm so....
Currently have 1/2" lines. Probably cheap fittings(restrictive). Not sure of the size of current pump. Got some research to do. Was looking at getting a new splitter(quicker cycle times, better ergos, etc.) but I might just modify the one I got and make it what I want.
I have a 5" cylinder, may get warm but by no means hot. Sounds like hi flow fittings and a new valve getting added to parts list.
sometimes the oil tank is so small that the oil never gets any delay time to cool a bit as well. On my old hf unit if you filled it too full after about a 1/2 hr of run time it would puke oil out the fill port due to heat expansion of the oil. ( lovely mess) so I made a separate fill and expansion tank located above the orginial tank problem solved.
With an open loop, fixed displacement pump, flow is speed. Larger pump = faster speed
Larger cylinder = more force, but slower speed.
Line sizes and fittings do NOT change the speed (unless they are extremely restrictive and put the pump partially across the relief valve).
Restrictions only increase the pressure drop required to push the pump flow through the restriction. That pressure drop is wasted energy converted to heat, so larger lines and fittings and valve will reduce the operating temperature but will NOT change cycle time. I know some will claim it did, but there is something else in play, as the physics rules otherwise.
I would not waste the money changing parts. For the amount of hours a wood splitter gets, just live with the extra fuel Costs.
What I would do though, depending on the wood you split, is reduce the cylinder size to increase speed. I built one with 13 gpm pump, 3 inch cylinder. (Ran it about 5 hrs yesterday splitting up to 16 inch oak.) It has 3 seconds out 20 inches, a bit less on retract. Anything bigger I can’t lift and wrestle anymore anyway.
But really, just live with what you have, save money to a faster one, and sell this one someday. Upgrading and modifying gets expensive fast. Increasing cylinder, beam, hoses, valve, engine, pump, until what is left of the original one....
Larger cylinder = more force, but slower speed.
Line sizes and fittings do NOT change the speed (unless they are extremely restrictive and put the pump partially across the relief valve).
Restrictions only increase the pressure drop required to push the pump flow through the restriction. That pressure drop is wasted energy converted to heat, so larger lines and fittings and valve will reduce the operating temperature but will NOT change cycle time. I know some will claim it did, but there is something else in play, as the physics rules otherwise.
I would not waste the money changing parts. For the amount of hours a wood splitter gets, just live with the extra fuel Costs.
What I would do though, depending on the wood you split, is reduce the cylinder size to increase speed. I built one with 13 gpm pump, 3 inch cylinder. (Ran it about 5 hrs yesterday splitting up to 16 inch oak.) It has 3 seconds out 20 inches, a bit less on retract. Anything bigger I can’t lift and wrestle anymore anyway.
But really, just live with what you have, save money to a faster one, and sell this one someday. Upgrading and modifying gets expensive fast. Increasing cylinder, beam, hoses, valve, engine, pump, until what is left of the original one....
The flow volume of the pump is not altered by hose and fittings unless you restrict it to the point that you run out of horsepower or you bypass the relief valve. It will increase heat and "at rest" pressure but not flow speed. That's just fluid dynamics.
Of course this does ignore the possibility of a 2 stage pump reaching the pressure required to kick it into low gear.
Of course this does ignore the possibility of a 2 stage pump reaching the pressure required to kick it into low gear.
One of the reasons I like this forum, many knowledgeable folks. I always like to do my homework before starting a project. May just live with my current splitter til the right one comes along.
Is there any kind of oil cooler that could be installed to help the heat problem? My splitter is pretty fast, but the cylinder gets pretty hot as mentioned.
It’s okay to get the thing warm. Not like flesh burning hot though. The equipment and oil can handle pretty high temperatures and I like that it gets warm enough to cook off some water.
Really sort of depends on where you are on the power curve of your engine/motor.
If you have extra/unused torque in the motor to pull a larger GPM pump, then you might gain some extra speed. But if the motor is already maxed out, a bigger pump will just bog it down, scrubbing any speed benefit.
If it is a 'professionally' manufactured splitter, I'd expect the components to all be pretty close. A manufacturer would crunch the numbers and choose well matched parts... unlikely they would give you a much larger engine than needed, or hobble a big engine with a tiny/undersized pump.
The other key thing to watch out for is not so much the outlet sizing, but the inlet. If you have small inlet hoses/fittings, and put on a large pump, it can cause fluid cavitation at the pump. This is basically bad for the whole system. A quick way to lower performance and destroy parts at the same time.
It would be good to consult the flow specs and HP requirements for the pump you intend to get and make sure the rest of the system is up to spec, too.
Deets
Member
Heat is hard on pumps and seals. As mentioned above, more oil capacity is an easy way to mitigate heat. A dump valve on the return side will reduce heat generated and increase return time. These are usually only used on larger setups pushing upwards of 20 gpm. I have never seen them on smaller units, but they may still work ok.
Isaac Carlson
Minister of Fire
More gpm means faster cycle time, BUT you need to be careful not to "over pump" the system. Ports, hoses, filters, valves, and the tank need to handle the flow12-16 gpm is the max for most systems, and 16 will likely generate a good deal of heat on some splitters. I am running an 11 gpm pump at a real 3500 rpm. It gets warm but not hot. I am sure a 16 gpm pump would add some heat and would also max out my hydraulic lines/fittings.
One very important thing to remember is flow on the return stroke. Assume the return stroke will flow about 50% more gpm than the pump is rated for. This is because of the displacement of the rod. 11 gpm turns into 15 gpm, and 16 gpm turns into 22 gpm.
This is what a lot of people don't think of when deciding what size pump to use.
Another thing to look at is the high/low gpm rating of the pump. A lot of 11 gpm pumps have 2.5-3.5 gpm on the high pressure side. It varies. My old pump was ~9.5 gpm with ~2.5 gpm on the high pressure side. My new pump is 11 gpm and 1.7 gpm on the high pressure side. I used this pump because it is faster when not under a high load, which improves cycle times and productivity, and the lower gpm on the high pressure side allows me to max out my pressure at 3,600 psi With my 3hp electric motor. I have not had to use all of that pressure, but it's there if I need it. I was going to buy a speeco 11 gpm pump, but the high pressure side was 3.5 gpm, which limited me to 1800 psi at 3.6 hp. That was not ok, so I went with the 1.7 because I already had it. I could use 2-2.5 gpm but I am not going to buy one just to get a bit more speed in the tough stuff.
One very important thing to remember is flow on the return stroke. Assume the return stroke will flow about 50% more gpm than the pump is rated for. This is because of the displacement of the rod. 11 gpm turns into 15 gpm, and 16 gpm turns into 22 gpm.
This is what a lot of people don't think of when deciding what size pump to use.
Another thing to look at is the high/low gpm rating of the pump. A lot of 11 gpm pumps have 2.5-3.5 gpm on the high pressure side. It varies. My old pump was ~9.5 gpm with ~2.5 gpm on the high pressure side. My new pump is 11 gpm and 1.7 gpm on the high pressure side. I used this pump because it is faster when not under a high load, which improves cycle times and productivity, and the lower gpm on the high pressure side allows me to max out my pressure at 3,600 psi With my 3hp electric motor. I have not had to use all of that pressure, but it's there if I need it. I was going to buy a speeco 11 gpm pump, but the high pressure side was 3.5 gpm, which limited me to 1800 psi at 3.6 hp. That was not ok, so I went with the 1.7 because I already had it. I could use 2-2.5 gpm but I am not going to buy one just to get a bit more speed in the tough stuff.
