Firewood Processor Hydraulic Questions

[Wild Bill the 2nd]

In the process of building a firewood processor (main post here) I am about to pull the trigger on about $3000 of equipment and wanted to post this diagram to see if anyone sees anything that doesn't look right.



The main questions I have are on the saw side of things. I am following the recommendations that Danzco lays out for their saws but I like to double check things.

I have a 22HP Kohler out of a lawn tractor that I'm planing to run a 1.22ci 17 GPM pump.
17 GPM at 900 PSI requires about 22 HP
Is there anything I need to do to keep the pressure down around 900 PSi? As long as I don't push things too hard too fast pressure shouldn't build past that point correct?

My assumptions are as follows:
Husquevarna 3120 Specs .404 chain, 7 tooth sprocket, 8.4 HP, 9000 RPM, 4,242 Ft/Min chain speed
8.4 HP @ 9000 RPM = 4.9 ft/lb or 59 in/lb

.58 ci saw motor at 650 PSI = 60 in/lb

That would leave 250 PSI of headroom.

I have an adjustable priority flow divider valve in place after the pump to direct the majority of the fluid to the saw but then direct some fluid to the remaining system (except for the splitter, that has its own engine and pump). The only thing that I would do on the circuit while sawing is to advance the saw through the log. I am worried about driving the saw to fast into the log and stalling out the motor. I put an adjustable relief valve (only found 500 PSI though) to keep pressure down and then put a 1-way flow control valve inline after that. Overkill?

I think the last thing is the hydraulic tank size. The saw motor will run 17 GPM and the splitter will run 28 GPM in the HI flow mode. Does that mean I really need 50 gal of fluid? I'm thinking I would put an oil cooler on the thing. Could that keep me down a little bit or no?

Thanks for the help!

 

[J_J]

Just curious why you are limiting the saw pump to 900 psi.

You are losing a lot of torque that the motor can develop.

 

[Wild Bill the 2nd]

Just curious why you are limiting the saw motor to 900 psi.

You are losing a lot of torque

When I run the numbers that is all the 22 HP gas engine that I have available to me will put out with a 17 GPM pump. Not sure if I am misunderstanding something or not?

Would I be better served with a lower displacement pump so I could run higher pressures? I was thinking I wanted higher flow to get decent RPM out of the saw. Even if that meant I couldn't achieve max pressure on the pump.

I believe 17GPM at 2000 psi requires about 50 HP

 

[glastron23]

curious about the 900 psi also, we run a F11 motor with a 10 gpm pump, it normal runs about 1400 to 1600 psi (any higher and we need to sharpen the chain) the speed is lower but the torque is there. the feed speed is the critical thing (and hardest thing to control) when using lower motor flows, still plenty fast enough to have to wait for the knife to be cleaned out. Have fun with the build...Jim

 

[J_J]

No, 17 GPM at 2000 psi will need 23 HP.

 

[Wild Bill the 2nd]

No, 17 GPM at 2000 psi will need 23 HP.

That is the same power requirement I get when I run the numbers but I have seen in multiple locations that you are supposed to double the HP required if you are powering the pump with a gas engine.

I have no issues running higher pressures if the engine will handle it.

the feed speed is the critical thing (and hardest thing to control) when using lower motor flows, still plenty fast enough to have to wait for the knife to be cleaned out.

Do you think that my relief valve and flow control are waranted for saw control? Is the relief valve with a 500 PSI minimum sufficient? Is there a valve readily available that goes lower?

At this point we couldn't cough up the dough for the F11 pump. I understand that is the end all be all pump for saws.
I would think that I need some more flow with a gear pump as they are not as efficient.

 

[glastron23]

just going to ask one question, do you have a GOOD hydraulic shop near you?? if so go and ask them to build you a tandem pump, one for the saw motor (17 or 18 gpm)and the other (2 or 3 gpm) for the cylinders and feed motors you are going to run. This will save you a lot of problems/headaches trying to bleed off enough to supply them.
Lucked into the F11's, when talking to the shop for a gear pump he had 2 F11's with drive gears and chain catchers, rebuilt the one i'm using

 

[Wild Bill the 2nd]

I have a hydraulic shop in the area. Don't know if they could build be a pump or not...
I can certainly ask.

 

[glastron23]

they built us a triple Salami sectional pump and was happy with the cost (10 -10-5) at the time we were using a single 15 hp engine, the next year we installed a 25 hp, solved a lot of problems. As far as the cooler you can dump it and just expand the tank, we never get to 120f even when pushing it hard.

 

[J_J]

This is a front pump and you can piggyback another pump on the back of this pump to meet your flow demands.

2.008 cu in PRINCE HYD FRONT PUMP SPD232A9H1R