Splitter design help

[allforham]

Hello all

New Zealand based, do occasional small time forestry with a komatsu pc138 excavator with grapple. Looking to be doing firewood for the next few years, mostly big old pines.

Currently have a small splitter, slow and labour intensive. Have had an idea for a larger splitter, based somewhat on this one:

https://globallandequipment.com/product/f80/

But minus the attached grapple and the extra hydraulic adjustments. Wanting to be able to load a large round into it with the komatsu and split the whole thing in one go, ideally mounting it up high on long legs so split wood can fall straight into my trailer.

Have had the idea of using long hoses and borrowing the blade hydraulics to run the splitter ram, leaving the machine free to grab anything within reach.

I am confident in the fabrication side of things but where I am clueless is in the sizing of the ram. I understand the larger the bore the slower and more powerful it will be but how is this converted into tonnes? Guess I will aim for 80t like that other splitter. The komatsu supposedly has 240L/min flow but unsure whether the blade circuit sees all of this.

Any advice on sizes/types of rams to be looking for would be greatly appreciated! My usual method of trial and error might end up costly!

Thanks in advance
Adam

[Wlmedley]

I worked quite a bit on Komatsu excavators before I retired a few years ago.The pc138 main relief should be around 325kgcm2 or around 4500psi.So if cylinder size was 10 square inches you would have 45000 pounds of force.Komatsu also uses a variable displacement piston pump which means you will have max flow when resistance is minimum and pump flow will decrease as pressure increases.This is to keep engine from pulling down excessively.Not sure if blade circuit gets full flow.Series of machine model may make a difference.

[thecfarm]

WOW!!
Now THAT'S a splitter!!!!

[Ianab]

WOW!!
Now THAT'S a splitter!!!!

Common firewood logs in NZ are big old pines, cypress or eucalyptus. Being able to pick up large rounds with an excavator and drop them onto that sort of rig makes a lot of sense.

[allforham]

Thanks wlmedley, so if im after approx 180k lbs I should be looking for around 40 sq inches so a ram diameter around 7 inches if my maths is correct? Big bugger! Is it just a case of picking one around the right size with the stroke I need or is it more complex than that? Will go with the trial and error method with regards to using the blade hydraulics

Ianab- yes these trees are 80 odd years old and the rounds are a pain to move around by hand, especially while having the komatsu sitting there doing nothing!

[fluidpowerpro]

Ya, its that simple. 

With a 7" bore, your going to need a lot of flow to get a reasonable speed. 

If you want to extend 24" in 5 seconds, your going to need close to 50 GPM.

[allforham]

Thanks fluidpowerpro.

Machine has 63gpm available so that speed sounds about spot on. Hopefully the blade circuit isn't way down on flow or pressure, lifts one end of the machine off the ground off the ground in a hurry though so must have a bit of grunt. Will update with some pics once I've made a start

[jmur1]

Hi allforham:

there are lots of online calculators for this and the cycle time that you can find handy.  Also note these are calcs without losses so in the real world it will be slower yet.
for the force generated you just take the piston area of the ram in inches² (the area of the plunger) and times it by the pressure in PSI.  This gives you lbs-force

For the cycle time you calculate the inner volume of the cylinder in inches³. Then find the flow of the system in GPM and convert to inches³.  Then you divide the volume by the flow to get the time for 1 way.  To get the open and close you need to add the close time which has less volume due to the ram volume.  (Just subtract this area from the volume) and then put the two times together to get the total time.

https://logsplitterplans.com/calculators/hydraulic-cylinder-force-calculator.htm

jmur1

[Hilltop366]

I guess another option would be to make a attachment for your excavator to break down the large pieces to more manageable size for your existing splitter. 

[beenthere]

I just make an additional cut or two with the chainsaw to break down those big blocks into manageable sizes. Different ways to skin a cat, so to speak. 

[Wlmedley]

If or when you get a cylinder make sure it is made to handle at least 5000 psi.Most Komatsu excavators have a power max function which uses a two stage main relief valve to temporarily set pressure up to 5000 psi.I’d want it to be able to handle a little more just to play it safe.You could check cycle time of blade cylinder and measure diameter and get a rough estimate of flow going to it.Check it extending cylinder.No way of really knowing how thick barrel is but would give you a pretty good idea of flow.May want to unhook rod end from blade when doing cycle time check.

[allforham]

Thanks guys, have my eye on a bucket ram from a cat 330d. Only 160mm bore which I believe gives 64t but not painfully expensive and hopefully up to the pressure. Heaps of stroke too. Anything off larger machines goes up in price heaps! Found a few real big ones from other applications but most are rated for much lower pressures.

Will try the blade test once I'm back with the machine

[allforham]

Me again, quick question re beams in case anyone else has some experience with real big splitters. Hoping for simplicity and easy access with the grapple to just use one big beam but most available here are much taller than they are wide for structural uses.

 Thinking of using a 610x230mm I beam (24x9") with  20mm(4/5") flange and 12mm(1/2") web. With the flange being thick enough to hopefully not need additional plating. My mind is saying I need a couple side by side but looking at other splitters in the 30-40t range they run much smaller single beams so with 60t might be ok? Anyone have any thoughts? For a similar price I could run a couple of lighter 300-400mm beams side by side but these have much lighter flanges and would likely need a plate on top 

[John Mc]

I know almost nothing about excavators, but I would be really surprised if the whole 63 GPM was available to the blade. I can't think of any reason why they'd design the full flow to go to that component. (I can think of reasons why they'd want to restrict the flow to the blade.)

You may want to test that flow rate out before you get too far in to that part of the design.

If I'm all wet on my guesses, I'm sure someone with more knowledge of these systems will comment.

[jmur1]

Me again, quick question re beams in case anyone else has some experience with real big splitters. Hoping for simplicity and easy access with the grapple to just use one big beam but most available here are much taller than they are wide for structural uses.

 Thinking of using a 610x230mm I beam (24x9") with  20mm(4/5") flange and 12mm(1/2") web. With the flange being thick enough to hopefully not need additional plating. My mind is saying I need a couple side by side but looking at other splitters in the 30-40t range they run much smaller single beams so with 60t might be ok? Anyone have any thoughts? For a similar price I could run a couple of lighter 300-400mm beams side by side but these have much lighter flanges and would likely need a plate on top

Hi allforham:
It is difficult to predict the strength of the beam until you have all the system parts designed/sized.   You mentioned that the machine would similar to a Ø31 1/2" GLE splitter.  That splitter appears to have two large HSS sections dead center on the log chunk connecting the rear of the cylinder to the wedges.  If you tried to use a single beam under that wedge that they have setup you would undoubtable bend it up.  If you post (or send me) sketches of your planned geometry I can tell you how the design would measure up.  
jmur1