Who know about hydraulics / power

  1. Justme

    Justme Member

    Messages:
    3,175
    Location:
    Pwllheli Wales
    I have a firewood processor that can be powered via an 11kw electric motor however it states the minimum pto to be 30kw.

    Both turn the same 3 hydraulic pumps.
    The elec motor directly at about 1500 rpm & the pto at 540 rpm but with a 3 to 1 gearbox to increase the rpm.

    I wish to power this either directly from an engine with a 2 to 1 reduction or with a 5 or 6 to one reduction into the pto input.

    How can the power needs be so different from pto to electric?

    What will the minimum engine hp I can use?
     
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  2. Justme

    Justme Member

    Messages:
    3,175
    Location:
    Pwllheli Wales
    Secondary question.

    If I fit the 11kw (230 or 400v available) motor what size genny would it need?

    I think 30 - 40hp.
     
  3. barking mat

    barking mat Barking at Pigeons

    Messages:
    4,612
    Location:
    Brittany, The Arz Valley.
    I used to run 2.0 litre diesels attached to hydraulic pumps, marine propulsion..

    I would have thought 50 hp, would suffice?

    But it's all about hydraulics... I would think the supply line pipes would be an indicator.

    Be careful with high pressure hydraulics.
     
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  4. 8ob

    8ob Forum Supporter

    Messages:
    6,704
    Location:
    moscow on thames
    I have made up a couple of diesel powerpacks using 4 pot perkins engines, both were to free up tractors. One was running a Stenner bandmill and the other a log processor. You can buy off the shelf SAE bellhousings which will bolt up to any truck engine, they can be used to direct pto drive from or bolt hydraulic pumps too. The one that went on the log processor ran a small leccy alternator off the front and the engine driven compressor was connected to a tank, that proved handy for maintenance and the leccy was good for worklights. A fixed speed/governed stationary engine is better if you can get one, if not fit a speedic.

    Bob
     
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  5. Justme

    Justme Member

    Messages:
    3,175
    Location:
    Pwllheli Wales

    Seeing as my digger has three huge pumps & only 40hp I think the recommended PTO hp is far too high.

    11kw is about 15hp so was hoping 22hp engine would be enough.

    Two pumps have 3/4" lines & one 1/2"
     
  6. mike os

    mike os just a little insane.....

    Messages:
    6,980
    Location:
    North Wales
    3 to 1 gearbox, 3 to 1 power conversion

    The additional power is to boost the rpm at the pump and gearbox speed conversion
     
  7. Justme

    Justme Member

    Messages:
    3,175
    Location:
    Pwllheli Wales

    So if I have this right you are saying that the 40hp in via the pto is reduced to 13.33hp at the pumps as the rpm has gone up?

    With that in mind the 22hp motor I have been offered with a 2 to 1 reduction is quite close.

    But I think better would be to direct mount 3 new pumps to the engine.

    Then they are rated for the higher rpm.
     
  8. All the gearbox is doing is increasing rpm, but reducing torque. The power loss should be less than 15%.
    It's likely the torque requirement, where electric motors excel, that requires a large pto hp.
     
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  9. mike os

    mike os just a little insane.....

    Messages:
    6,980
    Location:
    North Wales

    Pretty much... there are losses etc but really not worth worrying about
     
  10. 8ob

    8ob Forum Supporter

    Messages:
    6,704
    Location:
    moscow on thames
    To step up or down or make electricity to drive a motor to drive a pump is just a stack up of operating losses. The log bench will have a flow requirement, match this with a pump that flows that amount directly off the back of an adequately sized stationary engine, job done.

    Bob
     
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  11. Justme

    Justme Member

    Messages:
    3,175
    Location:
    Pwllheli Wales

    Thats my feeling two.

    The processor has 3 pumps stacked up.

    I need to get the part numbers of the existing pumps to find the spec & then see what pumps match that & what HP / rpm they need.
     
  12. Can all three parts of the pump be under full load at the same time? How many services will be working together?
     
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  13. 500e

    500e Always buy fire insurance a flood is hard to start

    Messages:
    4,969
    Location:
    SWest UK
    Torque is a factor you can have lot of HP with little torque so the load drags down the RPM & it is a vicious circle
     
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  14. frank horton

    frank horton V twins are great but 4"s rule.........

    Messages:
    2,227
    Location:
    Soon 2 B Crete
    would think only 2 processes at one time.....
    that loks like a modern tractor....dont they come with a 2 speed pto.....
    I know my 399 did.....540-1200 I think...been a while...
    if the high speed is around 1200 I'd bet this would do......can always up the eng speed a bit.....
    the pump will still work at a slightly slower speed and take a little longer to process the wood.....
    it aint a race.....other wise it's all gonna get a bit silly and expencive.....
     
  15. Justme

    Justme Member

    Messages:
    3,175
    Location:
    Pwllheli Wales

    I think you missed the point.

    i want to get rid of the tractor & power from a smaller engine.

    ps its 540 / 1000 rpm on tractors
    pps it sort of is a race when you are processing for other people.
     
  16. Justme

    Justme Member

    Messages:
    3,175
    Location:
    Pwllheli Wales

    Not sure yet which pump powers which bits.

    But this is a list of all the actions that I know about:-

    Splitter ram
    chainsaw motor
    conveyor out motor
    conveyor in motor
    splitting knife lift / lower ram
    sawdust extractor fan motor
    log clamp ram

    Conveyor out runs continuously
    plus
    You can split & cut (inc clamp ) at same time & they are the biggest users of flow & pressure.

    Or split & conveyor in motor
     
  17. m_c Member

    Messages:
    577
    Location:
    East Lothian
    Power specs will be as much to do with ensuring the tractor used is physically large enough, as it is the actual power needed.
    Otherwise you'll have people trying to run it on sub 20hp tractors, which will probably be as light as the machine.

    Also, you may find when supplied with an electric motor, different hydraulics are fitted.
    With the addition of electricity, they may use some electrical interlocks which limit how much hydraulic power can be used, whereas with PTO driven you may be able to use more hydraulic power.
     
  18. DaveB Member

    Messages:
    182
    North London
    The pto rating is probably engine peak power, but that will be at far higher revs than when the pto is active.
     
  19. Justme

    Justme Member

    Messages:
    3,175
    Location:
    Pwllheli Wales

    They spec power for pto & for transporting ie tractor max.

    The machine can stand on its own & weighs about 900kg.

    As far as I can tell the elec motor is a bolt on direct to the existing pumps.
    There are no electrical bits on this machine in either version.
     
  20. Justme

    Justme Member

    Messages:
    3,175
    Location:
    Pwllheli Wales

    PTO speed always used to be a direct effect of engine speed.
    Hence max power was always available.
    Now some use a hydraulic motor so you can set the rpm of the pto but at lower engine rpm for low outputs / fuel efficiency.
     
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