@ pto pump on the same shaft like a double pump?

[Wyobuckaroo]

Millet..
What I have seen with a homemade log splitter is to start off working backwards. To explain, a given splitting cylinder with a given cycle time takes X amount of gallons per hour. Then you work backwards to the size pump you need for that gph, then to the PTO or engine horse power required to run that pump.

To me, the combination of other motors you want to run is another figure to blend into the equation to determine pump size, and power requirement. You see a trend here on how to work out the math.

I'm going to guess the conveyor will run constantly with a small power requirement. The saw, and log advance will run intermittently, not necessarily at the same time as the splitting ram under full load. With these details in mind that should let you size and run a pump not that much bigger than minimum for the biggest load, being the splitting ram.

My 5 cents of experience and opinion.

 

[Millet]

Oldnslo,

I have theses modeles of pumps in mind: PTO Pumps | Hydraulic Pumps | Hydraulics | www.surpluscenter.com
So if I understand correctly if you put 6 pumps , let's say 1 cubic inch of displacement each, and that the pressure on each pump is 1000 psi and they are on the same shaft, this shaft must resist a "torque" of 6000 psi.
Now if you have only one much, much bigger pump , let's say 100 cubic inch, with the same pressure of 1000psi the shaft must resist a 1000 psi "torque".

Put simpler is, that the GPM or the displacement volume, have nothing to do with the calculation of the right shaft for a pump?

Also my tractor have, like you guess 540/750/1000 rpm to the PTO. and I can also have direct PTO which is the same as the engine PTO.
The pto pump has you can see in the link, have a hole that go through the pump, my plan is to have a long shaft through 2 pumps.

Wyobuckaroo,

Great advice about the pattern of thinking.
You right, I intend to run the conveyer at a constant speed. I will try to achieve this with a control flow valve. like this for example:

4/3 GPM Prince Priority Flow Divider w/Relief | Divider Valves | Hydraulic Valves | Hydraulics | www.surpluscenter.com

with the excess flow to another actuator. If I understand correctly, this kind of valve divide the flow in two: E.F Excess Flow and CF Control Flow.
My CF will go to the conveyer . let's say 4 gpm. so the conveyer will have a constant speed. and the EF ,let's say 26 gpm to the saw.
My question, about this kind of valve is, do you know if the pressure change to the EF flow will increase or decrease the flow to the CF, or
if the CF flow can, under pressure, fluctuate. example the conveyer is free of wood, It receive 4 GPM and now it's full of wood and building
pressure and receive only 2-3 gpm?


Thanks to everybody about their opinion.

 

[oldnslo]

Millet,
So if I understand correctly if you put 6 pumps , let's say 1 cubic inch of displacement each, and that the pressure on each pump is 1000 psi and they are on the same shaft, this shaft must resist a "torque" of 6000 psi.
Now if you have only one much, much bigger pump , let's say 100 cubic inch, with the same pressure of 1000psi the shaft must resist a 1000 psi "torque".

Yes that is correct a correct statement.

Put simpler is, that the GPM or the displacement volume, have nothing to do with the calculation of the right shaft for a pump?

That is not entirely true. require pump drive torque is calculated based on displacement and pressure. torque in Nm = (cc/rev x pressure in Bar) divided by ( 20 pi x over all efficiency) I typically use 85% for efficiency.

so 100 cc x 200 bar = 20,000
20 pi x .85 = 53.41

20000 / 53.41 = 374.5 Nm torque require to drive this pump.

Not sure if you can stack multiple PTO together or not.

 

[Millet]

I found this pdf about PTO :

http://www.driveproducts.com/wp-content/uploads/2012/04/TR-G94-01.pdf

They say this page-19 about PTO shaft :

Correct PTO and pump shaft size are determined by selecting that which will withstand the torque load up to the designed Shaft Torque Limit (STL). The STL is calculated by multiplying the pump’s cubic displacement by the operating pressure. The resulting figure is the STL. If the pump is a tandem or triple section, the STL for the pump is the sum of those for each section. For maximum component life always choose the largest shaft available.