Firewood processor help

[jonix]

If you were reaching 5000psi with the other cylinder, and now you just reach 1000 psi with the same log, I would say that something was causing all that excessive pressure in the cylinder. I don't believe that the old cylinder could not split that wood. I have a 80 mm bore cylinder in my Log splitter that had already split logs even larger than the one you had, with something like 1500/2000 psi.

but do you have an 8 splitting wegde at it?

 

[ptsg]

but do you have an 8 splitting wegde at it?

No, but I've looking to your wedge, and the vertical one, goes in first than the others, so I though that could help a bit.

 

[jonix]

well, i have been working with a single wedge splitter for years..and with 10 TON of force i was able to split almost anything..i only have about 2 M3 of pieces that i couldn´t split in all this years..and most of those were "rancas" (sorry, think google will not tell me the translation for "rancas" of a 20 ton old eucalyptus tree..it helps a bit, but think only a bit..

i was able to split 800, or even 900 mm diametters with single wedge..no big problems..

there is big diference with 8 wedge..and if you going on 12, or 16 splitting wedges on eucalyptus, then you will need real big splitting power..and a very good wedge design..

 

[muddstopper]

Heres a online calculator to help you with the math.Surplus Center your numbers appear close. Another way you can increase your chain seed is by going to a 13tooth sprocket. Since you are currently using a 12tooth sprocket, you should only need to change the sprocket and not the bar. If you go to a even larger sprocket size, you will also have to change out your saw bar to a wider one.

 

[J_J]

If you change rpm, you also change torque.

 

[muddstopper]

If you change rpm, you also change torque.

good point, doubling the size of the motor with same oil flow and pressure will slow the motor down to half speed, but increase torque. Adding pullies to increase speed will reduce torque and then you have the extra reduction in efficiency caused by using pullies and belts. I suspect his saw will not be any better,, maybe worse, than it was before the motor swap.

Something else isnt adding up here also. His numbers for oil flow and pressures keeps changing. I'm finding it hard to keep up with what he actually is working with.

 

[jonix]

I was trying us to think beyond my pressures and flows and my machine in last post..

If you read my first post, my numbers always were the same..i only mess around a litlle bit along this thread because i confused brithish gallons with american gallons, so the flows rates i have been mencioning may have had some variations..

I swap the F11-005 for the F11-010 because that was the only choice that the company give to me..i canｴt spend any more money for now..and my plans in near future is to swap the 8 GPM (or so, is not easy to convert metric to american at each frase or word) pump i have for saw circuit, for a 20 GPM one..

my old f11-005 has a limit of 14 GPM flow..i was not going any were with that, will need high pressure to get torque..the new F11-010 can work with 25 GMP, and i think is better for me work with lower pressure, and more oil flow to get the result..THIS IS WHY I SWAP MY SAW MOTORS at no charge..

As soon i can get a 20 GPM pump for saw, i will turn chain speed to around 6500 feet/minute (with no pulleys), 21 HP and 165 lbs in of torque, with 24 HP of power suplly and 1850 PSI of pump pressure..i think i am not thinking so wrong as you say..

..if i get a gear motor with 2 cu in as you said, i will have to pack and store the F11-005, and i will not have a F11-010 "for free" (this parker motor is very very expensive!)..and since my pump for saw circuit is a 8 GPM pump, i will have to buy another pump too, because i donｴt think i will go anywere with this configuration too..tell me, am i wrong? I'm trying to save some euros..

Donｴt forget that I already pay the all hydraulic circuit for months, and was not me who draw it..if it was today I would never do it this way..

so..i am still interested in your opinion about my theory: for the same amount of power suplly, we will have allways the same results at torque and chain speed, if we use diferent displacement hydraulic saw motors?

 

[jonix]

If you change rpm, you also change torque.

Torque= [ Displacement (cm3/rev) X differencial pressure (BAR) X mechanical efficiency (~85-90%) ] divided by 63 constant for N.m

Think that is wrong..if you change rpm, you are not changing torque, you are changing HP (Power)

 

[jonix]

good point, doubling the size of the motor with same oil flow and pressure (pressure will not slow down the motor)will slow the motor down to half speed, but increase torque. Adding pullies to increase speed will reduce torque and then you have the extra reduction in efficiency caused by using pullies and belts. I suspect his saw will not be any better,, maybe worse, than it was before the motor swap.

YES, THAT IS CORRECT

But..was not that "my theory" talking about? and you are saying me to change to a 2 cu inch one? "good point"?!?!?

do you know what will happen if i "double" 6 or 7 times my motor size?!?!?

 

[muddstopper]

YES, THAT IS CORRECT

But..was not that "my theory" talking about? and you are saying me to change to a 2 cu inch one? "good point"?!?!?

do you know what will happen if i "double" 6 or 7 times my motor size?!?!?

I didnot say lower pressure will slow down motor. what I said is that using the same oil flow and doubling the size of the motor will slow down motor speed. Using pullies to get the chain speed back up will negate any torque or power (at saw chain). My other post stated that you can swap out your sprocket from 12 tooth to 13 tooth and increase chain, but not enough of a difference to be worth the change. Just something to consider for future upgrades.

I suggested a 2 cuin gear motor because you can run it with a lot of flow and low pressure to get your chain speed and power in the range it needs to be. Everything is a swap off. More flow requires more engine hp, lower pressure, lower hp, High pressure, high hp. Your F 11 motors are small cuin, high rpm, low flow, high pressure motors. cutting down the hyd pressure without increaseing flow has already decreaded the cutting power to your saw. You will get the power back by using a larger motor, but then you lose cutting speed. Your running around in circles amking changes without improving the situation.

"Think that is wrong..if you change rpm, you are not changing torque, you are changing HP (Power)

You are not taking into consideration that torque at the motor is not torque to the saw sprocket. In between the sprocket and the motor, you have added a 2:1 pulley ratio to increase speed. Yes you will still have torque at the motor, but torque at the sprocket will be cut in half.
If you have 25gpm available to run the f11 motor, then you should still have the same to run a gear motor. Just use a smaller cuin gear motor, (less than 2 cuin) to power your saw.
1.3cuin gear motor using 25gpm will give you a rpm of 4442. Now before you say the gear motor isnt meant to run that fast, its not, but it will as long as pressures are kept low., and it a common practice for processor manufacturers to over flow their oil to increase chain speed. Using a PSI of 1200 will give you about 20ftlbs of torque and 17hp at the saw sprocket. Using a 13tooth sprocket will give you a chain speed of 3888 ftmin using a .404 chain. Not quite what a 3120 husky chainsaw runs, but twice the hp. File the rakers down on the chain and let the hp pull the chain thru the wood. You can go up to a 14 tooth sprocket ( you would also have to change out your saw bar),and that would increase chain speed to 4180ftmin. Going up 6-7 times motor size wont benefit you unless you have a way to get more oil flow to the motor, If all you have is 25gpm, going to a bigger motor is only going to make matters worse. Another motor choice would be a High Speed Axials Pistons Motors. thesw are sort of a compromise between a gear motor and the bent axis F 11 motors. They are made to run around 4600 rpms and create power at much lower pressures than the f 11, yet will handle more PSI than a gear motor.

Edit to add,
What size, gpms, are your twin pumps for the splitter. Is it possible that you can combine their flows with your saw circuit to increase oil flow. Probably not as you would have to much going own with the different pressure settings.

 

[J_J]

Can you tell us what you told the engineer what you wanted?

I am thinking he let you down by not taking your electric motor HP, cu in and pressure required, relief valve settings, to get the job done with available HP. etc.

 

[J_J]

Torque= [ Displacement (cm3/rev) X differencial pressure (BAR) X mechanical efficiency (~85-90%) ] divided by 63 constant for N.m

Think that is wrong..if you change rpm, you are not changing torque, you are changing HP (Power)

If you change the rpm of the final drive, you absolutely change torque.

Say you had a hyd motor rpm of 1000 rpm and a torque of 500 in lbs.

If you gear that motor down to 500 rpm, the torque increases, and if you double the 1000 rpm to 2000 rpm, you lose torque.

The HP developed by your motor is determined by the torque in ft lbs and rpm.

Your electric motor at 25 HP, could only support a hyd pump, pumping 13 GPM, at 3000 psi, or 7.7 GPM at 5000 psi.

The engineer should have started with your electric motor HP, GPM and pressure required to figure a pump size, or multiple pump displacements if you insisted on 3 or 4 pumps.

Someone took your money and provided poor service.

Seems like you put a lot of work in your machine, that don't work as expected.

I would be highly pissed.

You might be able to show the guy where he is wrong and get some retribution.

Recommend you go back over your notes for what you wanted and then, see if you did give the engineer the correct data?

You have got to do your own homework, or double check your building process.

Don't know if you want to use another electric motor or a gas engine to power a 28 GPM 2 stage pump just for the log splitter.

Why do you need 5000 psi? Your motor/pump setup can not support the pressure and GPM's you need.

I am looking at the pressure on your pumps and see a max of 300 bar, which = 4351 psi. So even if the saw can handle 6000 psi, you would run out of HP to turn the pump. Max continuous on that saw is maybe 7 GPM's.

There is so much wrong here. How could your friend the engineer screw things so bad.

I think I would go back and set those reliefs to just below the pumps max pressure, and it is not 5000 psi, according to your workup sheet.

 

[muddstopper]

Let me add something that will cost a little money but might save your build. A 28gpm 2 stage pump only takes 16hp. It flows 28gpm at around 900psi. It is possible that you can run your saw off the same pump you power your splitter with. Of course its going to make doing everything in automatic and at the same time sort of impossible, but the 28gpm pump is only around $200 depending on brand and who you buy it from. You can still run your smaller conveyor pump and use it to power your conveyors and saw cylinder. And it might be possible to piggy back your 28gpm pump to the back of your small gear pump. The biggest draw back to using a 2stage pump to power your saw is in the event that your saw motor cant develope enough power to turn the saw chain. If this happens, the 2 stage pump would kick down into low flow/high pressure mode and the saw might or might not stop cutting. Most of the bigger 2stage pumps are pressure adjustable in the high flow mode, but I dont know just how high you can adjust the pressure before the high pressure mode kicks in.

 

[J_J]

400-900 PSI IS THE ADJUSTABLE RANGE ON THE 28 gpm PUMP.

Those hyd pumps are probably designed to run at around 3600 rpm, and his electric motor only turns at 1470, so he is only pumping about half the advertised GPM.

So whatever the rated GPM was, he is pumping about half.

 

[muddstopper]

Did he say somewhere that his electric motor only turns 1470rpms. I remember he said it was 3 phase and some of those motors do turn 3200rpms.

 

[J_J]

In post #1 his diagram shows the rpm at 1470, and 25 HP.

http://www.tractorbynet.com/forums/...firewood-processor-help-hydraulic-circuit-jpg

 

[muddstopper]

I missed that diagram completely. I kept wondering where stuff like the 6in cylinder measurements came from, as I never read it in any of his other post. I now can guess why the 6in cyl didnt split the 15"dia wood, but the even bigger cyl did. His motor couldnt build the pressure without stalling before the wood was split. With the bigger cyl, it simply didnt need to build as much pressure. I wonder at what rpms his pumps need to turn to give his stated flow rates. A lot of gear pumps have a rated flow at around 2000rpms. Whoops, looked again at the chart and his flows rates are at 2800 to 4000 rpms for his pumps. So at 1470 rpms he is about half or less the flow capacity of his pumps. Me thinks he is going to have to completely redesign his hydraulic system or get a bigger motor to make it work.

 

[J_J]

He might get away with one task at a time.

It looks like he put a lot of money in the project for someone to provide bad service and wrong parts.

I believe the flow on a hyd pump is linear, and therefore, the rpm dictates the flow in GPM's.

On a 1.0 cu in displacement pump, one revolution of the pump will pump out 1.0 cu if fluid, and 10 turns of the pump shaft will pump 10 times the displacement. 3600 turns of the pump will pump 3600 times the displacement.

So, a motor running at 3600 rpm matched to a pimp designed for 3600 rpm, will pump max volume.

Same motor running at half speed will pump half of max pump volume.

 

[jonix]

man..you are messing all it up..

The pump flows we have being talking are rated for 1500 rpm..my electric motor have 1470 rpm..

and JJ, are you telling me that the mathematical formula for TORQUE is WRONG..is that it..?

..later i´m going to post the hydraulics again..to much things going on at the same time..

Mudstopper, YES you are right!! the thing is I have to put this machine working ..I have no firewood drying..as soon as i have the time, i will put some oil flow in the F11-010..maybe I will try to put my twin pumps doing it..i don´t know if that is possible, but i am going to ckeck it out..

And guys, yesterday we were testing all moving parts manually, i was hable to mesure times and discovered my "twin Pumps" for splitter work exactly like your 28 GPM 2 stage pumps..mine works like this: 30 GPM at low pressure (I can set the relief up to pumps limit pressure, but it will work at 1000 PSI or so) and 12,5 GPM at high pressure (my limit is 4000 PSI for pump ratings, but only have 25HP, have to work with max 3000 PSI) (I Know 2 stage pump usually work with a 4:1 flow ratio, well, mine have 2,5:1 ratio)
I almost have 40 Tonnes of splitting force, i think this part is no bad..the extend and rectract times are not to bad too..

 

[jonix]

He might get away with one task at a time.

It looks like he put a lot of money in the project for someone to provide bad service and wrong parts.

I believe the flow on a hyd pump is linear, and therefore, the rpm dictates the flow in GPM's.

On a 1.0 cu in displacement pump, one revolution of the pump will pump out 1.0 cu if fluid, and 10 turns of the pump shaft will pump 10 times the displacement. 3600 turns of the pump will pump 3600 times the displacement.

So, a motor running at 3600 rpm matched to a pimp designed for 3600 rpm, will pump max volume.

Same motor running at half speed will pump half of max pump volume.

The formula for pump flow calculation is: displacement X rpm X volumetric efficiency (around 95%)..

So thats right..