hydraulic force

Help Support SkidSteer Forum:

bludorbronc

Well-known member
Joined
Oct 17, 2008
Messages
58
hi, i am trying to build a log splitter that operates from the auxilliary control. i dont know what pressure is there but i dont think it matters right now. my cylinder that i am starting with has a 2.5 inch bore, 1.25 inch rod,retracted length 27 inches, extended length 42 inches. if i have a line pressure of 2000lbs (for instance)how does force multiply by diameter. by going to a 4 inch bore, can i get twice the force. so my question is ,with same psi does force change with diameter, ifso by what constant. i dont mind buying a cylinder just want to make sure it works. my bobcat is a 542b. thanks
 

flyerdan

Well-known member
Joined
Mar 7, 2009
Messages
983
Fortunately with the internet, chances are that someone has crated a calculator for almost any application, just a matter of finding it.
Is this what you're looking for? Force Calculator
 
OP
OP
B

bludorbronc

Well-known member
Joined
Oct 17, 2008
Messages
58
Fortunately with the internet, chances are that someone has crated a calculator for almost any application, just a matter of finding it.
Is this what you're looking for? Force Calculator
thanks. now another question, i have another cylinder like the one i am using, what if i stacked both of them so both applyed pressure to the log at the same time, since there are two cylinders acting together, do i multiply or add pressures to achieve a split log.
 

Tazza

Moderator
Staff member
Joined
Dec 7, 2004
Messages
16,829
thanks. now another question, i have another cylinder like the one i am using, what if i stacked both of them so both applyed pressure to the log at the same time, since there are two cylinders acting together, do i multiply or add pressures to achieve a split log.
If you are talking about using them in parallel you add the two together.
 
OP
OP
B

bludorbronc

Well-known member
Joined
Oct 17, 2008
Messages
58
If you are talking about using them in parallel you add the two together.
yes,parallel. my bore is 2.5 and rod is 1.25. so sticking those numbers in and using 1000 psi it figures 4900, if i run both its only 9800. if i buy a 4inch it figures 12500. i dont know what a log splitter usually has for pressure. now the hard part , do i save money and use both or buy the big one.
 

Tazza

Moderator
Staff member
Joined
Dec 7, 2004
Messages
16,829
yes,parallel. my bore is 2.5 and rod is 1.25. so sticking those numbers in and using 1000 psi it figures 4900, if i run both its only 9800. if i buy a 4inch it figures 12500. i dont know what a log splitter usually has for pressure. now the hard part , do i save money and use both or buy the big one.
For starters, your line pressure would be about 2,500 PSI so you can at least double the force you have calculated. The other thing is, it depends on how hard the wood is that you want to split and how big of a wedge you use for the splitting. The smaller it is, the less power it will take to push it through the log.
I see no problem with using two cylinders, but if you can get a cheap larger cylinder it does look more appealing for ease of building too.
Naturally, the larger the cylinder the slower it will move, so its all a trade off. More power = slower cycle time.
 

craigb93

Well-known member
Joined
Nov 9, 2010
Messages
163
Force= Line pressure times Cylinder Bore Area. I should think the *42 series Bobcats have a relief valve pressure of 2300 psi. Cylinder Area= Pi/4 x Dia x Dia. Pi/4= 0.7854 Your 2.5" cyl would deliver 2300*0.7854*2.5*2.5=11,300 lb A 4" cyl would deliver 28,900 lbf. A single cyl splitter would be superior to two cyls in parallel as the blade would cock and bind on the slide with any un-even cyl leakage that makes the force unbalanced. Craigb
 
OP
OP
B

bludorbronc

Well-known member
Joined
Oct 17, 2008
Messages
58
Force= Line pressure times Cylinder Bore Area. I should think the *42 series Bobcats have a relief valve pressure of 2300 psi. Cylinder Area= Pi/4 x Dia x Dia. Pi/4= 0.7854 Your 2.5" cyl would deliver 2300*0.7854*2.5*2.5=11,300 lb A 4" cyl would deliver 28,900 lbf. A single cyl splitter would be superior to two cyls in parallel as the blade would cock and bind on the slide with any un-even cyl leakage that makes the force unbalanced. Craigb
thanks people, looks like problem solved.
 
OP
OP
B

bludorbronc

Well-known member
Joined
Oct 17, 2008
Messages
58
thanks people, looks like problem solved.
well, i went with a 4inch ram from surplus center, according to the chart ,almost 2 1/2 times force than my other cylinder had, worked great. now i want to know more about how my machine works. when using the auxillary hydraulics to operate the log splitter, does it put out full pressure at idle or does the pump put out pressure depending on rpm. is it the same for lifting the arms and tilting the bucket. does more rpm just give me more road speed. i mounted the log splitter in the bucket so that the splitter points out of the bucket straight out, that way i could angle the bucket down, that way i could roll the big logs into the splitter and save my back. now when the bucket is pointed all the way down the bucket wont tilt back up. if i put down force on the arms, hold foot to try to tilt bucket back up and back the machine up, i can force it to tilt up. it just needs a little help because it takes off with just a little effort. whats going on. thanks
 

Tazza

Moderator
Staff member
Joined
Dec 7, 2004
Messages
16,829
well, i went with a 4inch ram from surplus center, according to the chart ,almost 2 1/2 times force than my other cylinder had, worked great. now i want to know more about how my machine works. when using the auxillary hydraulics to operate the log splitter, does it put out full pressure at idle or does the pump put out pressure depending on rpm. is it the same for lifting the arms and tilting the bucket. does more rpm just give me more road speed. i mounted the log splitter in the bucket so that the splitter points out of the bucket straight out, that way i could angle the bucket down, that way i could roll the big logs into the splitter and save my back. now when the bucket is pointed all the way down the bucket wont tilt back up. if i put down force on the arms, hold foot to try to tilt bucket back up and back the machine up, i can force it to tilt up. it just needs a little help because it takes off with just a little effort. whats going on. thanks
If the pump is in good shape, it will be putting out full pressure even at idle. When you throttle up it just moves more oil and makes things faster.
As for the bucket, does it on;y do this when you are operating the splitter? as the problem could just be because the oil is being diverted to the splitter and not your tilt cylinder. Did it always do this? as when i rebuilt a tilt cylinder many years ago i had a friend machine a new piston as i didn't have a lathe. When fully tilted it would not come back up because the piston covered the inlet port so no oil could enter till the cylinder was pushed down by the bucket resting on the ground. Machining a small bevel on the piston to allow oil to come in was all that was needed. Could it be something simple like that?
 
OP
OP
B

bludorbronc

Well-known member
Joined
Oct 17, 2008
Messages
58
If the pump is in good shape, it will be putting out full pressure even at idle. When you throttle up it just moves more oil and makes things faster.
As for the bucket, does it on;y do this when you are operating the splitter? as the problem could just be because the oil is being diverted to the splitter and not your tilt cylinder. Did it always do this? as when i rebuilt a tilt cylinder many years ago i had a friend machine a new piston as i didn't have a lathe. When fully tilted it would not come back up because the piston covered the inlet port so no oil could enter till the cylinder was pushed down by the bucket resting on the ground. Machining a small bevel on the piston to allow oil to come in was all that was needed. Could it be something simple like that?
i took off the splitter and made sure the auxillary stick was centered and now it works. so i will not think about it until it quits again, then i will give a few choice words and think about it again. thanks
 
Top