Who know about hydraulics / power

  1. 8ob

    8ob Forum Supporter

    Messages:
    6,692
    Location:
    moscow on thames
    Richie before you go much further you need to check a few things, first is pump rotation. Tractor PTO`s run clockwise when looking at the back of the tractor so you need to know what the existing reduction box is doing with pump rotation/rpm. If it suits and the existing pumps are happy to run at 1500rpm you may well be able to mount pumps directly to the back of an engine.Most pumps can be dismantled and cases flipped to get a reverse rotation.

    Bob
     
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  2. Bornfree Member

    Messages:
    106
    Location:
    England Norfolk
    The pressure washers we use at work are powered by either a 11kw electric motor or a 25hp diesel engine. Both using the same pump. The 11kw motor is 6 pole 1000rpm connected directly and the diesel engine is connected through a 3 to 1 reduction gearbox and running at 3000rpm.
     
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  3. Justme

    Justme Member

    Messages:
    3,175
    Location:
    Pwllheli Wales

    Yes I know about checking rotation.

    Existing pumps run at around 1500 rpm either via pto 3-1 or elec motor directly.

    To get the full hp from an engine I doubt I can run it at 1500rpm so will need a 2-1 reduction box.

    I did wonder if it would be easier to get pumps that can run at 3000-3600rpm directly.
     
  4. Justme

    Justme Member

    Messages:
    3,175
    Location:
    Pwllheli Wales

    6 pole ? is that 3 phase?

    This can have a single or 3 phase motor fitted.



    The more I think about it an engine & new pumps sounds best.
     
  5. Bornfree Member

    Messages:
    106
    Location:
    England Norfolk
    Yes 3ph I've never seen a single phase motor as big as 11kw
     
  6. Justme

    Justme Member

    Messages:
    3,175
    Location:
    Pwllheli Wales

    I was surprised when they listed a 230v 11kw as an option.
     
  7. Bornfree Member

    Messages:
    106
    Location:
    England Norfolk
    Are you sure it's not 230v 3ph
     
  8. Justme

    Justme Member

    Messages:
    3,175
    Location:
    Pwllheli Wales
    Nope lol

    But i thought that would be 200v ish
     
  9. Bornfree Member

    Messages:
    106
    Location:
    England Norfolk
    Normally listed as 220v on the motor plate.
     
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  10. Justme

    Justme Member

    Messages:
    3,175
    Location:
    Pwllheli Wales
    The 11kw can def be had in 230v single phase.

    The three pto powered pumps are 2 x 22.5cc & 1 x 8.2cc.
    Giving a total flow at 1500 rpm of about 80 gal per min.
    That specs out to about 30hp which seems about right for the recommended 40 hp pto.

    Oddly the elec motor comes with larger pumps 2 x 25cc & 1 x 11cc.
    Not sure how 11kw can power them at full output.

    This has now got me very baffled.

    The elec pumps have an even higher flow rate so in theory need even more hp not less.

    While on pto the pumps will be spinning at about 1500-1620 rpm.

    On the elec motor I would guess 1440rpm on the single phase.

    Which would explain the need for slightly bigger pumps, but not the much lower hp needed.

    I wish I could hire a PTO hp meter.
     
  11. Bornfree Member

    Messages:
    106
    Location:
    England Norfolk
    The starting current on a 11kw single phase must be massive. I guess the motor would be direct drive and the PTO model would be driving through a gearbox which will lead to some losses but not 25hp
     
  12. Justme

    Justme Member

    Messages:
    3,175
    Location:
    Pwllheli Wales

    Yes unless soft start.

    Yes pto pumps need 30hp & min input is 40hp.
    10hp is more losses than the gearbox would have.

    All I can think is that the min pto spec is as I have worked it out, just calculated from the pump spec.

    But the elec motor is what it actually needs.

    Or the elec motor has more torque but again I cant see that when the pto is from a tractor running at pto revs.

    I might try running it at lower pto revs to see how it performs.

    My tractor should have about 51hp at the pto (58hp from engine).

    Will be interesting to see if its the flow or the pressure that affects it most.
     
  13. m_c Member

    Messages:
    571
    Location:
    East Lothian
    Is there any point where all the hydraulics could be fully loaded?

    I suspect there is a bit of allowance that the electric motor could run at full HP all the time without any issues, not all hydraulics are fully utilised at any given time, and over sizing the recommended tractor just to ensure it's big enough.
     
  14. Justme

    Justme Member

    Messages:
    3,175
    Location:
    Pwllheli Wales
    The two big users can be used at same time.
     
  15. m_c Member

    Messages:
    571
    Location:
    East Lothian
    Having just run the calculations, I suspect they simply limit the performance when you spec a hydraulic motor.

    A single 22.5cc pump needs 9.5kw if it runs at 150bar.
    However given the cyclical nature of the loads, and allowing for brief overloading of the electric motor, you would probably be hard pushed to actually stall the motor. You would need to essentially stall the splitter, and try cutting a big log quickly at the same time. The power for the conveyor is probably minimal in the grand scheme of things.
    Although I do wonder if they drop max working pressures, or do some other seemingly subtle changes to limit hydraulic power needs between electric and PTO versions.
     
  16. Justme

    Justme Member

    Messages:
    3,175
    Location:
    Pwllheli Wales
    Max pressure pump 1 2800 psi pump 2 3000 psi pump 3 not quoted.

    On elec the three pumps are slightly bigger at 25-25-11cc's.
    You can cut and split at same time.
     
  17. Justme

    Justme Member

    Messages:
    3,175
    Location:
    Pwllheli Wales
    On pto pumps run at 1500rpm.
     
  18. m_c Member

    Messages:
    571
    Location:
    East Lothian
    There will most likely be relief valves elsewhere, as most standard hydraulic pumps don't have them built in.

    Having had a quick look at the sales brochure, the clue as to how they're achieving this with an 11KW motor is there.
    The motor is fitted with a thermistor, which means they need protection from prolonged overloading, as a motor rated at 11KW should manage to produce 11KW constantly without overheating, and they want a power supply capable of 400V and 32A via time lag fuses. 400V 3 phase and 32A actually gives you 21KW of power, so they're essentially relying on the operator not overloading the motor too much, which they probably won't unless you're trying to split knotty hard wood while cutting it with a blunt saw.

    Also, it's not got a 230V single phase option, it's just a 230V three phase option.
     
  19. Munkul

    Munkul Jack of some trades, Master of none

    Messages:
    3,144
    Location:
    Cumbria
    What sort of engine are you planning to use?
    Since you want a free standing machine, the simplest option would be to make a standalone engine skid that has a 540rpm PTO output. Then connect the two together with a standard PTO shaft.

    Reading between the lines a bit (and I think m_c has hit the nail on the head there) you're going to want something with at least 21kw (30hp). Then think about torque rise. A 30hp engine with a steep torque rise might hold up better under load than a 35hp engine with a flatter torque curve. OR, it just pulls the revs down to a speed where it can hang on, or at least until the operation has finished.

    Is it something like one of these you're wanting?

    https://www.daviesimplementsltd.co.uk/product/forestry/pto-power-pack/

    The bodger's way would be to do something like suggested here :D

    http://farmingforum.co.uk/forums/showthread.php?4536-PTO-Power-Pack
    He's not wrong...
     
    MCKDAVID likes this.
  20. Justme

    Justme Member

    Messages:
    3,175
    Location:
    Pwllheli Wales
    You seem to have found more than i have.
     
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