How to increase "flow" on a splitter???
- Thread starter AKKAMAAN
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AKKAMAAN
ArboristSite Guru
Thanks Wooodchip1!!
Well, it is really very simple, but it is so easy to strat discussing on the wrong track, with pressure and flow. And that will further on screw up the trouble shooting......
If a fixed displacement pump is turning, fliud HAVE to go some where.....
If pump is worned out, a large part of fluid will backwards, back to inlet.....
If RV is leaking or by passing, pump flow is still "the same"....
A common thing that make one lose flow, is when control valve spool is between nuetral and FULL stroke...flow goes partially to cylinder and partially to tank thru the partly open center...this is really a bad way of operating a splitter.....we both lose splitting force and cycle speed...
Maximum force (pressure) will only be available when RV opens and that wont happen until we operate a full CV spool stroke!
carpenter383
ArboristSite Lurker
SWI Don
ArboristSite Guru
Can you explain this? I've always thought that liquids don't compress
For the scope of the discussions on arboristsite, we can assume that fluids are incompressible. If the fluid is acting compressible, you probably will have some air entrained in your oil.
If we were discussing the details of designing and building a water-jet cutter we may have to consider compressibility of fluids more do to the much higher pressures involved.
If you get a lot of air bubbles traveling in your hydraulic fluid you fluid can act like it is compressible due to the air bubbles ability to compress.
Don
SWI Don
ArboristSite Guru
Avalancher:
On the cat the restriction did cause a loss in flow and pressure downstream but that was due to the relief valve in the pump bypassing at the same old pressure as it did before the restriction was placed in the system. If the relief valve had somehow been adjusted to compensate for the restriction, you would have had the same pressure and flow downstream of the restriction. However, the pressure upstream of the restriction would now be higher. This would have taken more horsepower to run the oil pump, and may have had other issues (pump drive breaking when cold) as a result of stressing the pump system more than designed.
Don
AKKAMAAN
ArboristSite Guru
Can you explain this? I've always thought that liquids don't compress
I am sorry I brought this up here.
I agree with Don in the previous post...It is definately not necessary to concider oils compressability here at forum....but it still is a fact that oil compress.during pressure....and most of the compressability is from gas/air content in fluid....up to one % in a normal system....this is not any more strange than the vaporing that occur when fluid is under vacuum....
Oil compressability comes to play in large precision controlled system....like a press or a lifting system for a 1000ton bridge element at the new bay bridge construction site..
Here is an article about it.....
avalancher
Arboristsite Raconteur
Your right part way.When we had a loss of flow to the top end, the first thing we did was screw down the relief valve all the way,assumed that was where the trouble was,faulty relief/pump.Made do difference.We then screwed in a portable pressure pump for testing trying to determine where the blockage was.The pump again replicated the same thing as the onboard pump.Because the engine was an older model we had no onboard diagnostics to pinpoint top end,lower end etc.I knew all the work we had done up to that point was good,proper clearance in mains,camshaft,etc and were faced with a complete tear down again to explore oil passages when I noticed the newer oil lines supplying juice to the turbo and accesory oil seperator/purifier.A quick check with the book revealed totally different lines normally found on that engine.Prior to swapping them out we had 70psi from the portable pump and only 14ozpm returning to the pump.After the lines and their narrow restricting fittings where replaced we had a little over 40psi and the flow shot up to 35ozpm back to the test pump.
There is no doubt that the incorrect lines caused a restriction,hindering fluid volume, and in the end cost the company a little over 8 bills worth of repair.
Been doing this for many years now, and while a little science can be applied in many ways, real world experience will often contradict a theorist opinion.
Here is another example, and we are talking woodsplitters here.Got a splitter with a 6hp engine, 11gpm pump.Swapped out the pump and engine to a 11hp and 16gpm pump I had laying around.Cycle time didnt increase but a second shaved, a look at the troybilts fittings at the cylinder indicated some real heat due to the small restricting fittings.swapped back over to the old power plant and started construction on a homemade splitter.Needless to say,it will be cheaper and better to start from scratch rather than dump the money into modifying the fittings on the cylinder and just go with a bigger cylinder.Then sell off the old troybilt splitter to cover the construction cost.
Any restriction in a system,regardless of pump slippage or any other reason you want to throw at it causes a loss of flow.In the real world,at least in ours,there is no such thing as a 100 percent efficient pump.Only saw one in my days while I was in the Navy, and according to the GE tech installing the thing on part of reactor cooling system,it cost 20 grand for that little baby.
AKKAMAAN
ArboristSite Guru
I dont argue that your bad hose caused restriction so pressure increased. But if you lose flow from that, part of flow must have been bypassed, in one way or another. Either thru internal leakage, dropped pump rpm,external leakage, or other bypass in the system. And this my point regarding fixed displacement
pumps.
Oldtimer
Addicted to ArboristSite
My poor head hurts....
I have a question:
Since my reservoir is well below my pump, and I seem to always have a bit of air in the fluid....should I re-configure the set up so that the reservior outlet is slightly above the pump intake?
I have a factory made Mighty Merc, it's tank is down under the engine and beam...a good 18" from the fluid uptake point to the pump intake point..
I have a question:
Since my reservoir is well below my pump, and I seem to always have a bit of air in the fluid....should I re-configure the set up so that the reservior outlet is slightly above the pump intake?
I have a factory made Mighty Merc, it's tank is down under the engine and beam...a good 18" from the fluid uptake point to the pump intake point..
avalancher
Arboristsite Raconteur
I guess i am a little confused,I thought that your whole point was that you cant increase flow or volume by removing any restrictions such as small or undersized couplings and hoses?
Lets say, just for the sake of argument,the standard old log splitter is built with a fixed displacement pump,the hoses and fittings are undersized to save cost,which in turn causes the pump to have less than maximum efficiency due to fluid passing around the gears doing the pumping.Wouldnt it increase the flow if you replaced the restrictions?
I know the difference would be slight,maybe not even noticeable except in long term wear on components,but it would seem prudent to examine known trouble spots such as elbows and universal fittings and replace them if they are undersized.
I think on high end splitters it may not be a problem, but on the lower consumer grade hydralic equipement I think you will find a great deal more manufactures trying to get by with the minimum amount of hardware to go along with the setup.I know on my troybilt,its almost worth crying over, the poor small couplings to the cylinder.It it wasnt for that fact alone, I would have been all for kicking that thing up a notch by increasing the horsepower and pump size.The rest of the machine has held up good.
But if I swap out hoses,cylinder,engine,and pump I might as well build the splitter that I want from scratch.
AKKAMAAN
ArboristSite Guru
This whole discussion is basically about the fact that a displaced volume of fluid out of a fixed displacement pump, have to come out somewhere if there is no leakage. I do hear voices about water buckets, in home water supply systems etc. These do not apply here.
This like comparing to a driveline, rpm in have to come out, unless there are slippage....
This like comparing to a driveline, rpm in have to come out, unless there are slippage....
AKKAMAAN
ArboristSite Guru
30ft of head equalsize 15psi charge pressure. so putting the pump 1ft lower will give you 0,5psi extra charge pressure....
Oldtimer
Addicted to ArboristSite
30ft of head equalsize 15psi charge pressure. so putting the pump 1ft lower will give you 0,5psi extra charge pressure....
Yes, but should I do it? The splitter works fine right now...but will it work better or last longer if I re-do it?
AKKAMAAN
ArboristSite Guru
Sorry Oldtimer! my first reply was off my cellphone.....
for 0.5psi gain.....nae...I would not bother....keep up with cleaning strainer and breathing filter if you have either of those....Make sure you use right viscosity on fluid and that you have an appropriate system temp....100-140F...
You also can make sure you have straight and simple plumbing on suction side....no leaks, kinks or sharp elbow fittings and the "real" suction hose....
AKKAMAAN
ArboristSite Guru
Not unless you are recovering already bypassed oil....or I say it like this....You have restricting hoses and fitting, and you have low flow!!! THAT means that flow is bypassing due to the raised pressure. IF you then upsize your fittings and hoses so pressure decreases....THEN you will recover that bypassed flow!!! BUT there have to be some bypassed flow to recover!!!!!
MY post concidered that there was NO bypassed flow to recover!!!
Now we are talking...."fluid passing around the gears" is by passing in my way to look at it....NOW WE AGREE!!!
Yes!! Agree!! But if you have noticeable low flow...there must be a noticeable bypass somewhere.....which is NOT normal internal leakage in a pump...you should then have a badly worned pump, broken piston seal or a leaking RV etc...the pump need a special flow meter to troubleshoot...but the rest can be examined just by bending/squezzinig a few hoses....
The small hoses do not affect the flow that much, more the pressure that will reacch cylinder during it is moving. When cylinder stalls, full pressure will reach the piston and you get full splitting force.
You want the power you put into the pump be 100% availbale at the piston. 100% is impossible, but you want as much as possible....all power loss is wasted into heat...This is the main purpose with upsizing the hoses and fittings!!!
SWI Don
ArboristSite Guru
I will add one thing. Most of our log splitters have two stage pumps. Akkaman's example in its purest form is assuming a one stage fixed displacement pump with no method of relief except for the relief valve in the control valve. It's a good example because he is trying to convey a basic rule of hydraulics Vout = Vin.
Now since our logsplitters have a two stage pump, there is a "relief" of sorts that happens at ~6-900 psi when the large section kicks out and the pump goes into low volume high pressure mode (small section only). When this happens we see a large drop in speed and have the ability to build up high pressure without stalling our engine.
If your hydraulic lines / fittings are undersized to the point that you build the 6-900 psi of backpressure on the pump without building any appreciable force in the moving cylinder, you will be operating in the second stage all the time. The Barnes 9, 11, and 13 gpm pumps have the same high pressure stage at 0.194 in³ displacement. The 16 gpm is larger at 0.258 in³. I don't know what the other brands of two stage pumps have for section sizes so their may be more variety.
The second stage is slow and you want to avoid it if you can. With a smaller cylinder it is harder to avoid as the pressure required to build enough tonnage to crack a log open goes up as cylinder size goes down. With a 5" cylinder and a 900 psi setting on the kick down, I only have it kick down on about 5-10% of the rounds, usually the ugly ones. I have a < 100 psi no load cycling back pressure for the system as measured just before the control valves.
Avalancher - I am guessing when you went to the 16 gpm pump, your system was restrictive enough to kick you into the low stage a lot more than the 11 gpm pump did. I did a quick calc and for a restriction that would give you a 200 psi back pressure at 11 gpm would net you a 424 psi backpressure at 16 gpm. If the kickdown pressure was set at 600 psi, it would go to low stage without much force on the round ~ 2200 lbs (4" cyl). At 11 gpm it would generate ~5000 lbs before kicking down. (My splitter generates ~15700 lbs before kicking down) If it stayed in the "fast" speed more with the 11 gpm pump I can see how you got a very small gain in cycle time with a larger pump.
If both pumps were single stage gear pumps, your cycle time would have decreased proportionately with the increase in gpm. You may have made a lot more heat with the larger pump, if it had a borderline sytem size with the smaller pump.
I think the original reason for this thread is that Akkaman was seeing threads on guy's porting their hydraulic systems like you would port a cylinder head for more air flow. His point is you will not see an appreciable increase in speed from a port job as long as you weren't up against a relief pressure to start with. There may have been some concern if members start drilling out fittings oversize to "get more speed" and end up with potential safety issues because the fitting is now too thin the pressure and vibration it might be exposed too. I don't want to get penetrated by 3000 psi oil, it's bad news. If "porting" gains you speed then your system is way undersized and barely functioning properly to start with. As long as the pump can generate the required back pressure of the sytem the speed will be unchanged.
The problem is that a fluid in a fixed displacement system doesn't act like a compressible gas in an air system. Vin = Vout on a fluid based system and Vin does not necessarily equal Vout on an air system. Mass in = Mass out on both systems but since gasses are compressible Volume is related to pressure, temperature, and density all of which change when going through restrictions or being compressed.
Don
Now since our logsplitters have a two stage pump, there is a "relief" of sorts that happens at ~6-900 psi when the large section kicks out and the pump goes into low volume high pressure mode (small section only). When this happens we see a large drop in speed and have the ability to build up high pressure without stalling our engine.
If your hydraulic lines / fittings are undersized to the point that you build the 6-900 psi of backpressure on the pump without building any appreciable force in the moving cylinder, you will be operating in the second stage all the time. The Barnes 9, 11, and 13 gpm pumps have the same high pressure stage at 0.194 in³ displacement. The 16 gpm is larger at 0.258 in³. I don't know what the other brands of two stage pumps have for section sizes so their may be more variety.
The second stage is slow and you want to avoid it if you can. With a smaller cylinder it is harder to avoid as the pressure required to build enough tonnage to crack a log open goes up as cylinder size goes down. With a 5" cylinder and a 900 psi setting on the kick down, I only have it kick down on about 5-10% of the rounds, usually the ugly ones. I have a < 100 psi no load cycling back pressure for the system as measured just before the control valves.
Avalancher - I am guessing when you went to the 16 gpm pump, your system was restrictive enough to kick you into the low stage a lot more than the 11 gpm pump did. I did a quick calc and for a restriction that would give you a 200 psi back pressure at 11 gpm would net you a 424 psi backpressure at 16 gpm. If the kickdown pressure was set at 600 psi, it would go to low stage without much force on the round ~ 2200 lbs (4" cyl). At 11 gpm it would generate ~5000 lbs before kicking down. (My splitter generates ~15700 lbs before kicking down) If it stayed in the "fast" speed more with the 11 gpm pump I can see how you got a very small gain in cycle time with a larger pump.
If both pumps were single stage gear pumps, your cycle time would have decreased proportionately with the increase in gpm. You may have made a lot more heat with the larger pump, if it had a borderline sytem size with the smaller pump.
I think the original reason for this thread is that Akkaman was seeing threads on guy's porting their hydraulic systems like you would port a cylinder head for more air flow. His point is you will not see an appreciable increase in speed from a port job as long as you weren't up against a relief pressure to start with. There may have been some concern if members start drilling out fittings oversize to "get more speed" and end up with potential safety issues because the fitting is now too thin the pressure and vibration it might be exposed too. I don't want to get penetrated by 3000 psi oil, it's bad news. If "porting" gains you speed then your system is way undersized and barely functioning properly to start with. As long as the pump can generate the required back pressure of the sytem the speed will be unchanged.
The problem is that a fluid in a fixed displacement system doesn't act like a compressible gas in an air system. Vin = Vout on a fluid based system and Vin does not necessarily equal Vout on an air system. Mass in = Mass out on both systems but since gasses are compressible Volume is related to pressure, temperature, and density all of which change when going through restrictions or being compressed.
Don
Last edited:
AKKAMAAN
ArboristSite Guru
I pointed this out in my first post....
"If we are lucky, the increased size on fittings, ports and hoses, might lower the pressure that much so pump will stay in low pressure/high flow stage. "
Great support post Don! Thanks! I might have an "swedish accent problem" in english, that limits me to explain.....LOL...You are "spot on" with the purpose of my initial post......
/Later
avalancher
Arboristsite Raconteur
hunter0182
ArboristSite Member
Troybuilt 27 ton log splittter
Ok I have a troybuilt 27 ton log splitter with a 8 hp briggs on ,great splitter after adding tables,just a little slow,i have the same splitter with a honda motor on it it is about 8 seconds faster, i only paid about 950.00 each for them as i have a friend who gets a discount through lows,i cant hardly build one for that,how can i increase the cycle time.
Ok I have a troybuilt 27 ton log splitter with a 8 hp briggs on ,great splitter after adding tables,just a little slow,i have the same splitter with a honda motor on it it is about 8 seconds faster, i only paid about 950.00 each for them as i have a friend who gets a discount through lows,i cant hardly build one for that,how can i increase the cycle time.
==========================================================
I think you ment to say your decrease cycle time to split :^).
As this subject only digresses;
The cylinder fittings hose size is what totally
regulates both the flow and speed of the process.
If you are at the high idle speed of the motor
its all you can really do.
I do not want to get in an argument about
regenerative valves or increasing the
relief valves pressure setting
About your splitter
a. change the air filter and oil and the spark plug
b. change the oil filter or clean the
suction screen of the log splitter if
it has one.
c. have the cylinder checked for bypassing of oil by
a hydraulic repair shop on its test bench.
The only legitimate way to accomplish this is to buy
four disposable hydraulic accumulators which contain
dry nitrogen gas to accomplish several wonderful
benefits for you.
a. store hydraulic energy(system pressure) to be used.
This provides instant energy until it is slowed by
the resistance of the splitter wedge against the load
being the wood chunk.
b. provide additional fluid power and energy to the cylinder
with no additional energy drain to the splitters hydraulic pump.
c. absorb shock loads from the splitter wedges initial contact
with the wood to be split.
By installing two small ones on both hydraulic lines to the cylinder
it gives you more usuable energy/fluid power to split wood.
Please find and download my "racetrack oil flow diagram"
on the web site here and it will help you to heat up
your oil faster(if you do not own a salmander) to heat
the log splitter up to temperature-yes you should do it
even in the summer months.
leon
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