pto driven log splitter

MadDog · Jan 25, 2006

HIghbeam: I just re-read your post. Were you talking about the N.Tool PTO, driven pump? In that case, you're right, because that is a single stage pump. I am planning to use the Barnes 2 stage 28gpm pump, which can be run with 16 or 17hp (I forget which).

In that case, I probably just provided a long explanation that was unnecessary. /forums/images/graemlins/blush.gif

Highbeam · Jan 26, 2006

I may have misunderstood. I thought you were worried about insufficient tractor HP to run a PTO driven pump that produces big time hydraulic flow for a splitter that may not need that much hydraulic flow. My thought was that if you do not utilize all of the hydraulic flow from the PTO driven pump, you don't need as much tractor horsepower for everything to work happily.

Here's how I understand the hydraulic splitter to need flow.... During retract and extend cycles where the splitter isn't really splitting it will use all the flow you can provide, More flow means it moves faster. During this time the ram takes very little force to move so it should be really easy for the tractor to run the PTO pump at full flow and that ram will move right along.

When the splitter hits the wood things change to a low flow high pressure situation. During this time, if you were to apply full power to the ram you could stall the tractor. You'll have to feather the lever to prevent stalling.

I guess that's why you are looking at a 2 stage pump.

MadDog · Jan 26, 2006

Precisely. We're on the same page, now. /forums/images/graemlins/wink.gif

I would indeed have a problem with a single stage pump, even the Prince 21gpm pto pump.

Interestingly, N.Tool doesn't really say what the hp requirements of the pumps it sells are; you have to go to the Prince and/or Barnes websites for that. If I just assumed that my tractor could run whatever they sell, I'd run into exactly the problem you've described with a single stage pump.

Many thanks,

erich · Jan 26, 2006

I know it has been gone over before on this website but remember there are a bunch of variables involved such as bore size, rod size, gpm, desired cycle time, required pump input HP, etc. You have to optimize the variables to get the performance you are looking for. Force = pressure X area. The bigger the bore size the greater the force on extension for a given area but the slower the ram will travel. The bigger the rod size, the less the force on retraction but the faster the ram will travel. For a given input HP the single stage pump will peak out at a given pressure before a stall. Smaller HP equals smaller pressure but the force can be maintained with a bigger bore area at the expense of speed. Also you need to consider how much force the rod can take. larger rod and shorter length can take more than longer and slimmer. that has to be matched to the force available so you don't bend the rod. I have seen that happen.

Another thing to remember is that those 540 RPM pumps are brutes. They will last a long time partly because they are turning slower.

The splitter I have was built to split 4 ft long pieces of wood. the Massey 35 I have has never even grunted at the load. It is not a speed demon but in the time it takes a little splitter to cycle three 16" pieces I can easily split one 4 footer. The 4 ft length was chosen way back for several reasons one of which was marketing. In the old days different stove sizes needed different lengths of wood. From one four footer you could get two 2 foot pieces, three 16 inch pieces, or four 12 inch pieces. Cutting it a year before you delivered it, you did not always know what size your customer needed.

Someone posted a web site a while back with a military hydraulics manual that will give all the equations. That and a little time to think and you're on your way. It is definitely a project that will give you a taste of the power of hydraulics.

Eric

jimmysisson · Jan 26, 2006

I have a tow-behind homemade jobby like you're talking about building. It has a 4x36 cylinder, 8x8 beam, and a log lifter. Right now it's running off a 7 hp Briggs and a 13 GPM Barnes pump. It has plenty of power, but is slow. (That may be a partially plugged screen in the tank, will find out in a few weeks).
A decade ago I ran this splitter with a Prince pto pump off a Farmall A, maybe 12-15 hp, not sure. No bogging, though it would get on the governor pretty good when it found something gnarly. In all, about a good match of engine power to pump capacity to work energy. I used to run the farmall at probably 800 rpm, since it was over 40 yrs old then, though no tach to know the exact speed. Farmall 4-cylinder is a good-sounding engine at almost any speed.
Your invention sounds like it would work, since the 2-speed pumps are excellent for splitters. It sounds bulky and maybe a little tricky to remove for other uses? I'll be watching your progress.
Jim

Highbeam · Jan 26, 2006

Will the PTO pump mount right onto the tractor or will it be driven by a PTO shaft and fixed to the splitter?

RonMar · Jan 26, 2006

You can also lower the safety valve bypass pressure to match your available horse power. That way if you hit something really tough while splitting, the valve will bypass before the engine stalls.

Maddog. A good thing about your choice of a 2 stage pump is it basically gives you a automatic gear reduction when the going gets tough. A high volume single stage pump would require a large ammount of horsepower to reach it's maximum working pressure because it is trying to move a high volume of fluid. A two stage pump under no load is basically 2 pumps working in parallel to achieve the higher volume at it's rated RPM. When enough resistance/backpressure is encountered on the pump output, the internal valving in the pump shifts from parallel operation to series operation. Double the pressure, half the flow for the same HP input. Sounds like you are going about things the right way, keep us posted.

razorback98 · Jan 26, 2006

Wow. Lots of good information.

I am curious about the question of PTO rpm. What are the issues with running it at a higher RPM on a Japanese tractor.

You will give up some torque and power I know but what do you all think about it.

Thanks

RonMar · Jan 26, 2006

( I am curious about the question of PTO rpm. What are the issues with running it at a higher RPM on a Japanese tractor.)

I don't quite understand your question. Do you have a 2 speed PTO on your tractor? or is your PTO rated at 760 RPM?

PTO RPM is dependent upon engine RPM. If yours is a 540 then you get 540 RPM on the PTO shaft when the engine is running in the green arc on the tach. This is the RPM where your tractor develops maximum continous HP. It is also usually just below the RPM redline limit. If the tach is running any lower than this, you are getting less than the rated 540 RPM on the PTO. The only way to get a higher PTO RPM than rated is to exceed the RPM limits of the engine. If yours is a 760 or 1000 RPM PTO, then in order to get 540 RPM to run a particular impliment or pump, you need to run the engine at a lower engine RPM(and available HP)

I don't know that I would want the tractor setting there running at full rated RPM the whole while I am splitting wood. Here is where a 2 speed PTO is nice. Mine is selectable at either 540/1000 RPM. I can select 1000 RPM and then run the engine at around half the rated engine RPM to get 540 RPM on the PTO shaft. I am of course getting a lower HP to the PTO, but if it is enough to do the job...

Boondox · Jan 26, 2006

( I figure that parts should run about 50% of an equivilent power/quality Timberwolf splitter (probably somewhat higher proportion of what Northern is selling). )

Speaking of Timberwolf splitters, are they good enough to justify the cost? $3k for a 9hp splitter with a 4-way wedge is a lot of money. Or $2.3k for a 3PH splitter and wedge. Ahem, to go with a stand alone and have my tractor free for other things...or to go with a 3PH model and have one less engine to maintain. Choices, choices.

Pete