coozer
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| posted on 3/7/14 at 08:19 PM |
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Any hydraulic peeps here?
Ok, I want to build a log splitter..
Not a mamby pamby thing but a decent powered hydraulic type.
Looking at a petrol driven maybe 10ton thing?
I've got a briggs motor off an old suffolk punch cylinder mower and am wondering it it will be up to the job?
What is the relationship between the size (GPM) of the pump and the HP of the motor?
As ever looking to do it as cheap as possible
Thanks,
Steve
1972 V8 Jago
1980 Z750
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Kdempsie
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| posted on 3/7/14 at 09:31 PM |
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Hydraulic horse power is pressure (psi) x flow rate (gpm)/1714.
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SteveWalker
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| posted on 3/7/14 at 10:00 PM |
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I'm not a hydraulic expert, but have vague memories of hydraulics as a small part of my education many years ago.
Any size motor will do the job, the question is what size motor, pump and ram to do it at a sensible speed!
Force is directly proportional to pressure and to ram area.
Linear speed is directly proportional to flow and inversely proportional to ram area.
Power is proportional to flow x pressure.
You can juggle with motor powers, rpm, pump flows and pump vs ram areas to get whatever you need.
I've done a quick Google and found http://www.engineershandbook.com/Tables/fluidpowerformulas.htm for proper formula that you can plug figures
into - or more simply, take a look at a commercially produced log splitter and check its specs and just use ratios to get your figures.
Just as an idea, if your motor had say half the power, at the same rpm, then a pump with half the flow rate at the same rpm and giving the same
pressure would give the same force on the same sized ram, but move it at half the speed.
If the motor had a quarter the power and you used a pump with half the flow and half the pressure, you would get the same force on a ram of double the
area, at a quarter the speed.
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mark chandler
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| posted on 3/7/14 at 11:01 PM |
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Not sure you will get a decent mounting on that, hydraulic pumps like a direct drive.
I guess you would need a small pump say 3cc per rev and get a decent sized ram and valve block, it all adds up very quickly so something like this may
be more cost effective
Petrol hydraulic power pack
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dinosaurjuice
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| posted on 4/7/14 at 07:56 AM |
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I dont think those suffolk engines are much more than 1.5kw (2hp).
some numbers though to give you an idea:
A 3cc gear pump spinning at 3000 rpm will give you 9 litres a minute, but with only 1.5kw available youll have to limit maximum operating pressure to
100 bar.
To get 10 tonne from a 100 bar you'll need a RAM with 110mm bore.
if you have a stroke of say 400 mm it will take 25 seconds to fully extend... thats quite slow.
there are many ways to get faster extension times, but all these add cost thats usually better spent on a bigger engine/pump.
To get anything reasonable you need to be looking at 5hp+
Will
[Edited on 4/7/14 by dinosaurjuice]
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Mr Whippy
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| posted on 4/7/14 at 12:16 PM |
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10 tons seems very excessive to cut a log with a blade, I’d be surprised if more than a couple of tons would be needed
Have a look on the web for commercial machines and base your spec on one of those, most manufactures supply enough info to copy their product!
That engine is a bit lame though
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garyo
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| posted on 4/7/14 at 12:52 PM |
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I have a big old home made one that I run off an MF135. It's slow and over powered, but it'll go through 18" diameter stumps
without fuss, but you still find that one stump in 20 will strain it slightly due to having a knot in the middle.
The thing I noticed the most is the amount of time wasted by the double acting ram needing to retract, during which not much is happening. If I had
some more spare time I'd make a design change such that the ram actually moves a square frame back and forth so that the log splits in two
directions.
In the mean time, I've sprung loaded the spool valve lever so that it retracts automatically and that allows me to switch logs or do other
housekeeping, but there's still quite a bit of standing around.
My ram has a rod diameter of around 3" and is around 3 feet long.
Gary
[Edited on 4/7/14 by garyo]
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