Firewood processor questions

[CDN Farm Boy]

Like many on here, I'm in the planning stages of a processor build. Hopefully I'll be able to build it this summer. A couple questions for you hydraulic masters....

What is so special with the F11 motor that is apparently THE choice for the saw motor? If you can afford it that is. I'm sure there are others that are more than sufficient and cost WAY less.


Pump type/style? I know most guys building their own are using a two stage pump like the 28/7 because it is a simple way to get the job done. I know the big processors are running multi-stage pumps to be able to do many functions at the same time for maximum productivity. Being able to run the splitter and saw at the same time would be nice but I'm not doing hundreds of cords a year so an extra few seconds on each cycle isn't the end of the world. What about using one of the PTO powered pumps? Seems to me that using one of the 40gpm pumps (60ish hp @ 1000 rpm) could be powered by an old truck engine and provide more than enough flow/pressure to do everything. A GM 4.3/TH350 combo is all but free and those pumps are only $500 or so.


Splitter cyl? 5" for sure. Is it worth considering a 6"?

 

[Wild Bill the 2nd]

From what I understand the F11 is a piston style motor rather than a gear motor. The seals on the piston make the F11 more efficient than a gear model and it can run to higher RPMs. That said I believe the F11 is about $1500. I figured that we will go with a 5000 RPM gear model and run a larger sprocket to get the chain speed up.

Our design uses two lawn tractor engines because they are sitting in my barn unused. A decent 4 or 6 cylinder from a junk vehicle would probably be a better choice.

As to the splitter cylinder, you nearly double your cycle time by going to a 6 cylinder

Cylinder Dia	Tons @ 3000 PSI	Time to Extend @ 7 GPM	Time to Retract @ 28 GPM
6	42.4	25.18	6.3
5	29.5	17.5	4.4
4	18.9	11.2	2.8

A lot of the commercial processors actually use 4" cylinders to keep the cycle time down. It isn't really till you get to the bigger models that you find 5" cylinders. I don't think the 6" is a good tradeoff on the whole tonnage vs time scale.

 

[CDN Farm Boy]

$1500 for an F11? That's cheap. My research was coming up with $2500-3000. F*&^ing hydraulics are expensive up here. I'm eager to see how your motor works out. The price of it is certainly more attractive.

The 4 or 6 cyl motor is an easy option to get big (for this application) power. If I had the spare lawnmower engines, I'd likely go that route also. Seeing how I can get a whole vehicle for scrap price, keep the powertrain and still scrap the rest, seems like a good option to me -- if it's worth it. A 40 gpm pump like this : 9.9 CU IN PRINCE HC-P-K11C PTO PUMP CI 1000 RPM seems wonderful but it's only 2250 psi compared to 3000 in a dual stage pump. That drops the force of the 5" cyl from 30 ton to 22 ton but it would be moving lightning fast at 4 seconds to extend if only using 30 of the available 40 gpm. For comparison, the 6" cyl running on the 2250 psi 40 gpm pump would give 32 ton and take 6 seconds to extend (using 30 gpm). This seems like too easy of an option considering how much people focus on cycle times yet i haven't seen one done like this on here yet. Sure there are lots of POS on youtube that are assembled from whatever junk is lying around but they look like crap and even though they get the job done (sort of), everything built here has some care taken as to how it looks.

 

[oldnslo]

Some of the benefits of using a double pump or multiple pumps are:
The saw motor on a separate pump keeps the speed more constant.
No flow dividers required to split flow to saw, splitter, etc.
Allows cutting and splitting at the same time. I.e. simpler circuit with less variables.
Less power consumption / heat generation since you can size the pump flow to match the work load. With one large pump the heaviest load dictates operating pressure and flow controls are required for slower speeds which create heat.

Yes the Parker F11 or Rexroth A2F motors are bent axis piston motors capable of high speed and are typically more efficient which translates to more consistant saw speed. Both $$$$ but for hard high use worth it. For average home owner probably not.

 

[muddstopper]

As with everything, the motor you use will require some trade offs. The f11 motors cut using speed and require lots of oil flow and high pressure to get maximum power. I think what you will find with the f11 motor is its not only the motor thats expensive, but also the pump, (high flow/high pressure) and the necessary high pressure hoses that are going to also cost a ton of money. With out high pressure, f11 motors are high speed/ low torque hydraulic motors and will bog down in large dia wood before the cut is complete. Thats just my opinion..

Gear motors are at the other end of motors. Low speed/high torque and is what the majority of the factory processors, (at least the one I have actually seen or ran), use for saw motors. They are cheap when compared to the f11's, but from what I have gathered, most of the manufacturers overflow the oil to get the speed they need for the saw.

Middle ground is a axil piston motor. More speed and torque than a gear motor, less speed than a f11 motor, not to bad expensive and just a better choice in my opinion. This is the choice I made for my processor build.

While I am at it, forget trying to figure chain saw speed in rpms. Saw chains are not measured in rpms, but in inches per minute. Rpms are just part of the equation to compute chain speed. Heres a handy link to help you compute your chain speed. Chainsaw Comparisons and Facts from Procut Portable Chainsaw Mills

a axial piston motor can run 4400rpms, using a 13tooth sprocket on a .404 pitch chain will get your cut speed durn near the same as a 3120 husquvarnia chainsaw. Size your displacement of your hydraulic motor to match your available oil flow to obtain the 4400rpms and you will out cut the 3120 chainsaw because you will have more hp and torque. You dont need a hydraulic motor that turns 8000rpms to cut wood. Chain saws turn high rpms because they have little dia chain sprockets and need the rpms to get there chain speed up. A 13pin sprocket will create the same chain speed at 4400rpms as a chainsaw turning 8000rpms with a 7pin sprocket.

I have a proclain 1.3cuin motor for my saw motor. 13pin sprocket and .404 chain. I plan on 25gpm of oil and will start my pressure out at 700psi (not a misprint),and this will provide 1.5 times more hp than the 3120 husky gas chainsaw and about 3 times more torque.

My setup calls for a 15/30/60 gpm stacked pump. My current splitter has a 28gpm 2stage pump and because of the low pressure needed I am planing on a test of my saw motor using that 2 stage pump. Kind of just want to prove to myself that a 2 stage pump will work with a saw motor. Plus all its going to take to test it out is to hook my splitter to the saw motor and let er rip and see what happens.

 

[CDN Farm Boy]

I have a proclain 1.3cuin motor for my saw motor. 13pin sprocket and .404 chain. I plan on 25gpm of oil and will start my pressure out at 700psi (not a misprint),and this will provide 1.5 times more hp than the 3120 husky gas chainsaw and about 3 times more torque.

My setup calls for a 15/30/60 gpm stacked pump. My current splitter has a 28gpm 2stage pump and because of the low pressure needed I am planing on a test of my saw motor using that 2 stage pump. Kind of just want to prove to myself that a 2 stage pump will work with a saw motor. Plus all its going to take to test it out is to hook my splitter to the saw motor and let er rip and see what happens.

Interested to see how that motor works out for you. Are you using a pressure regulator for the 700 psi? With similar chain speed but more hp and torque that should mean much harder to bog down I presume?

What are you powering the pump with? 120 GPM will take a fair bit of power won't it?

What are you running off the different pump sections?

Looking like a good chance I might have a Jetta with a 2.0 come available (my son's car that will likely get replaced before next winter and isn't worth anything more than scrap price) Specs say 122 ft-lb @ 2200 rpm and 115 hp @ 5200. Should be more than enough to do what I need and I'd rather give him $500 for his car than some stranger $500 for an unknown junker.

Hyd circuits I'm planning:

5" splitter cyl
Log trough motor
Saw motor (would rather hyd but if it gets too expensive I'll use a separate chainsaw)
Adjustable wedge

Other circuits depending on available funds and design:
conveyor motor
live deck motor
log clamp cyl
log lift cyl
???

The basic plumbing I can figure out. I get lost when trying to size the components