Fire Wood Processor Hydraulics

[SCOOP56]

Building a firewood processor and have gathered most parts.
My attention is now to gather "hydraulics". I have 2 hydraulic motors to drive the chain saw and the log advance.
My splitter ram is 5" bore and 2" rod diameter, 24" stroke, 3500psi max.
My cylinders for log lift, holding bar, and saw pressure are 2 1/2 bore, 1 1/8 rod diameter 12" stroke, 2500 psi.
What size "pump" should I use? 2 stage?
Thanks Glen

 

[J_J]

What size engine do you have.

HP determines the pump you can use.

 

[SCOOP56]

4 cyl gas engine. 80hp.

 

[J_J]

Then you definitely can run the largest 2 stage pump Surplus has, a 28 GPM pump.

28 GPM DYNAMIC 2-STAGE PUMP

 

[oldnslo]

scoop56,
I would suggest you look at a sequence of operation to determine what functions will be running at what times.
Then estimate speeds and forces required for function.

Doing this will help determine if a single hi-lo pump will work or if you would have better performance using multiple pumps.

Example: one pump somewhat dedicated to the saw & log advance for a more controlled speed. Splitter, log lift & clamp, possibly one pump depending on how they cycle in respect to each other. My guess is you would probably get the best performance using a double pump with one section for saw & log advance, the other for lift and clamp. Use a totally separate pump for splitter.

 

[J_J]

Something like this maybe.

 

[muddstopper]

I would not recommend trying to run the hydraulic saw motor and all the other hydraulics with a 2stage wood splitter pump. A lot depends on what cuin size motor you plan for your saw. Your best bet is to run a double pump setup. One pump dedicated to the saw, and one, or possibly two, more pumps to run the splitter cylinder and the log lift, conveyor, or other accesseries. A good saw motor, will need 20+gpm to get the proper chain speed out of the saw your 2stage wood splitter pump will only make that kind of flow in the low pressure side of the pump. Pressure for saw motor will probably need to be in the 1800-2000psi min. range, again on the high flow side of you pump, you wont be able to build the pressure you need. A good case can be made for adding a third low volume pump to your system to power all the small cylinders. Yes you can rob oil and use flow controls and pressure reliefs to control the speed and power for the lift cylinders and bar cylinders, and the log advance (conveyor??) motors, but all those extra parts might cost more than say a 5gpm gear pump. Also, you will notice a performance drops in the speed of the saw, or splitter cylinder, if you decide to use a little of their available oil flow while sawing or splitting. In the future, you might decide to add a off feed conveyor to move the split wood, another oil robber. You have the hp to run the saw and splitter with plenty left over for add ons, even if you dont decide to add anything now, I would plan on it incase yo change yuor mind later on.

 

[glastron23]

muddstopper said it about the 2 stage pump is a real problem. If i had to do it over i would bite the bullet and buy a pressure/flow compensated pump, it would solve a lot of problems. we used a triple gear pump, 1 for the saw, 1 for the splitter and 1 for the rest of the hydraulic cylinders and advance motor.

 

[oldnslo]

glastron,
nice looking rig you have there.

 

[SCOOP56]

To everyone, thanks for the advice, certainly cures my queries.
Scoop56

 

[muddstopper]

Tell us more about the setup you plan to build. What size are your hydraulic motors. How big a saw bar do you plan to use. What size saw chain. What speed you desire to run your saw chain. I have seen many saw designs where the improper hyd motor was selected and unsatisfactory performance was realized. This usually results in the builder either accepting the weak cutting performance or swapping out the saw motor for a different one, and even a few projects completely abandoned because the machine couldnt do what was needed.

Sequence of the hydraulics also plays a big part of the processing equation. Noting like waiting for the splitter to complete its cycle before you can make another cut, or waiting for the saw to cut a round before you can split it. There are times in the cycle where you are not using the full power of the splitting cyl or the saw motor. The saw only runs when it is cutting and the splitter only needs full power while it is splitting. The return of the cyl doesnt take as much power as it does to split. Usually while the splitter is actually extending, you will be advanceing the log for the next cut. By the time the cut is made the splitter is fully retracted and waiting for the next round to split. To small a saw motor or not enough oil flow will mean you splitter is sitting idle while it waits for the next round to drop. If timing is right, the next round should drop into the splitting trough just as the cyl is fully retracted. Most of the small factory processors use 25hp engines to pull all of the pumps. Some of the manufactors have started using little bigger engines to speed up the cycles times. With your 80hp engine, you should be easily able to pull a multiple pump setup and provide more then enough power for a very fast processor. Part selection is going to be key for performance. Hp cant make up the difference if you choose the wrong part combinations.

Often a saw motor is choosen because of rpms it will turn. While a gas saw might turn 9000 rpms, they have very little torque and need the rpms to make the cut. A proper hyd motor will produce more torque, but unless you go with a very expensive F11-F12 motor, they simply wont be able to reach the high rpms of a gas saw. It should be noted that gas saws have very small sprockets to pull the saw chain. With a hydraulic motor, you will be able to choose a larger dia sprocket to pull the chain. Most people look as rpms's when trying to guesstimate the speed their saw chain needs to run. this is a mistake. Chain speed should be measured in feet per min, and it is the easiest way to compare the saw to a known working saw that cuts at the speed you require. Rpm of motor, sprocket tooth count and chain pitch can be used to determine fpm cutting speed.

You asked for help chooseing a hydraulic pump to run your hydraulics, but you failed to give us the specifics of the parts you wish to use. Without the specifics of the saw motor, the size of the saw chain, or the sprocket to pull the chain, its simply not possible to choose the correct pump to run it.

 

[glastron23]

Muddstopper has the right thoughts on this, the one that really needs to be answered is the amount of wood do you want to process per hour, are you simply going to dump in a big pile or are you going to stack when it comes off the knife. we stack and with 2 or 3 people you do about 1 1/2 cord per hour. During a normal cut/split cycle i'm waiting for the wood to be cleared and if we are cutting 12/14 foot lengths then i can really keep them busy.
The saw motor is the big thing, we were lucky and have an F11 with the 404 chain setup. I'm running about 10 gpm on the saw and it should have 15 to 20 but it is fast enough to do the job.
The thing is the saw feed cylinder, trying to keep it smooth, it takes very little pressure to drop the saw into the wood, the 2 1/2 cylinder is really big for this job. We have a sequencing valve so the the wood clamp has to be down on the log before the saw will drop and the saw has to be up before the clamp is released so as not to be able to advance the log with the saw down. We also installed a shutoff when the saw stops when it is all the way up.
The next thing is the oiling system, are you going to bleed oil from the hydraulics or are you going to have a a chain oiler on its own.

 

[muddstopper]

I believe saw bar downfeed is supposed to be around 50#-75# pressure. It would be hard to get a 2 1/2in bore cyl restricted to 50# down pressure. A 2.5 bore cyl at 10psi is 49lbs of push force. 15psi would be 74lbs of force. Those low pressures are about what you would expect from the return to tank oil flow as it goes thru the hydraulic filters. It might be possible to get the fluid you need to run the saw bar off the return side of the hydraulic saw, but i dont know how you would regulate it, nor how fast the cyl would extend once activated. Restricted fitting would probably be a must have item.

Personally, I think a seperate saw oiler is the best bet. Hydraulic oil isnt the best lubricant for a saw chain.

A sequencing valve made specificly for a firewood processor cost around $500. The valve controls, the saw motor, log clamp and the down feed of the saw bar. There are other ways to accomplish the same thing. A series of electric control valves and limit switches can be used to make sure everything cycles in the proper order. Dont know which method would be cheapest or work best.

 

[glastron23]

saw feed pressure is really low.. for the sequencing we built our own using 2 Sun cartridges SCCA | Sun Hydraulics and a reducer valve on the saw piston down stroke side PBBB | Sun Hydraulics works well. limit switches are not a good idea because of the dirt,saw dust and oil thats floating around the saw.
we also built the chain oiler, will try to get pics.. Jim