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

 

[Wild Bill the 2nd]

Would you suggest I go that high in displacement?
I see I can get a 1.14ci or 1.35ci front and couple that with a .5ci back for everything else.

 

[Wild Bill the 2nd]

So for now my plans would be to run a 1.35ci front and a .5ci back. That would give me 17.4 and 6.5 GPM at 3000 RPM.

I would assume that with a multi-section pump I would be getting the right flow for the application with a single engine. The high flow would simply go to the saw. The lower flow would run the rest of the hydraulic cylinders.

Correct me if I’m wrong but I wouldn’t need to worry about running 23.9 GPM (17.4+6.5) with a 22 HP engine since I would never be running both pumps to max pressure at the same time. I like that.

So your pretty much saying the “double the HP requirement for gas engines” statement is pretty much bupkis?

 

[J_J]

If you ever did need the 23.9 GPM, at 3000 psi you would need 49 HP.

17 GPM at 3000 psi needs 35 HP.

6.5 at 3000 psi needs 13 HP

 

[oldnslo]

So your pretty much saying the “double the HP requirement for gas engines” statement is pretty much bupkis?

Depends on the true HP / torque capability of the gas engine. A lot of motor manufacturers over rated the HP capabilities of there gas engines.

 

[J_J]

Using a 13 GPM two stage pump in low pressure high GPM at 650 psi requires about 6 HP.

---------3.4 GPM------3000 psi---------------7 HP

They use a 6.5 Hp engine on this log splitter.

 

[glastron23]

you will very rarely be using more than 2 functions at one time, when sawing you will be using the down force cylinder and not the feed motor, when splitting you will be advancing the log for the saw but will not be sawing because you need to wait for the ram to retract,you will only be seeing max psi when you stall the saw or splitting ram, the saw down cylinder will never see max psi.
we installed a sequence valve on the log clamp/ saw down cylinder spool valve, this requires the log clamp to come down and hold the log (set at 400 psi) before the saw will lower, then when finished sawing you raise the saw and then the log clamp will release, this will help prevent you advancing the log with the saw in the way.

 

[Wild Bill the 2nd]

We are actually planning on being able to cut and split at the same time. We have two seperate engines and pumps for splitter and saw. The splitter will have a plate on top of it that the cut log can rest on until the cylinder fully retracts. At which point the log will in theory drop into place in the splitter.

I like the idea of not mangling the saw or the clamp by advancing the log too early.
This will be something I need to look into. Is it a cartridge model that is required in order to release the clamp?

Do you happen to know the Mfr / Model?

 

[glastron23]

we used the Sun hydraulics SCCA units http://www.sunhydraulics.com/sites/default/files/media_library/tech_resources/TT_US_Sequence-New.pdf

 

[Wild Bill the 2nd]

I've looked at some of their stuff, it looks nice. Did you contact the company directly, find a local distributer, or are there online distributes that carry their products?

 

[Scooby074]

Depends on the true HP / torque capability of the gas engine. A lot of motor manufacturers over rated the HP capabilities of there gas engines.

^This.

HP ratings are usually correct for electric motors. Gas motors, particularly small engines can be all over the board for torque and HP regardless of what the labels say on the box. So much so that I believe there has been a lawsuit over it.

The 2x Hp for gas engines rule of thumb comes from that. I know that even though I technically should have enough HP in my Subaru small engine to run my pump over 2200Psi, in practice the engine comes up short. Its always to better to have too much power as opposed to be trying to find more.