Firewood processor help

[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..