Various questions about a future project

  1. Memmeddu

    Memmeddu Member

    Messages:
    1,691
    Location:
    Italia Sardegna
    Hi everyone
    I've various probably stupid questions about an idea I have thought for a future projects.
    I have a compressor pump that I recovered from an old air compressor
    It's a .2L displacement pump and was spinning roughly at 1000 RPM so 200L/minute
    2hp motor
    I was thinking about making a small portable engine driven air compressor
    Because various reasons , first of all I will buy a plasma cutter once is allowed to buy from China again ,my country avoid that for 6months because the virus.
    Second I can't use both plasma and air compressor together
    Third I would like to get an air hammer (170L/minutes) and needle attachment for cleaning masonry equipment.
    I've already figured out how to put things together and how to deal with discharge and throttle
    Is worth making an engine driven air compressor?
    What's happen if I overspin the pump ?
    I mean not to much 1700rpm rather than 1000
    I will use a CO2 cylinder as reservoir (an old fire extinguisher)
    Few holes an some 7018
    We bought an high pressure testing pump so after welding I will hydro test the tank
    It will be a future project so I have time to study more about

    Now a question about the air hammer ,on eBay I found an Einhell set for 90 euro ,I will not buy this one because saving 60 euros I can get an Ingersol Rand
    The specs say 1.2joules , how much power should need a small air hammer for light work on slag peeling , removing concrete from mixers , and normal hobbyist tasks ?

    Thanks an sorry
     
  2. p0689109 Member

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    1,701
    Location:
    stoke on trent,england
    The rpm overspeed would be 70% so too much I would have thought.
     
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  3. Memmeddu

    Memmeddu Member

    Messages:
    1,691
    Location:
    Italia Sardegna
    Same thing I thought
    So I probably need another pump with higher displacement to give me more output flow
    The cheapest engine driven air compressor I can get costs around 600 euros
    A friend has two big engine driven , but I don't know how much he wants for one of them
    Both have engine issues
    One is gasoline
    One is diesel
     
  4. hotponyshoes Member

    Messages:
    1,695
    Location:
    Somerset. Uk
    .2 x 1000 is 200lpm but that is free air delivery.
    You will loose at least 10% (probably nearer 25%) as it will not be 100% efficient.

    If you get 170lpm that will still only be at atmospheric pressure. If you want to run something at pressure you need to know the pressure requirement to do the maths.
    So if the air hammer wants 170lpm at 35psi the pump will not be big enough so you probably want a bigger reservoir than a co2 bottle.
     
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  5. Memmeddu

    Memmeddu Member

    Messages:
    1,691
    Location:
    Italia Sardegna
    The hammer needs 170L/minute 6.3 bar (I'm not confident with PSI)
     
  6. ukracer Forum Supporter

    X it by 15.
     
  7. hotponyshoes Member

    Messages:
    1,695
    Location:
    Somerset. Uk
    A starting point is 170x6.3 = 1071.
    So about the equivalent of 1000lpm free flow would be required.
    As the pressures build so do the losses so I would be guessing you could double that number.

    A big 30l co2 tank that you could run up to 12bar is going to have 360l of compressed air in it so would run the hammer for maybe 4 minutes not allowing for the fact the pressure is going to be dropping in the tank as you go along so you could half that at least.

    I think you need a bigger pump or a bigger tank.
    Or multiples of one or both.
     
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  8. hotponyshoes Member

    Messages:
    1,695
    Location:
    Somerset. Uk
    A 48kg lpg bottle must hold about 100 litres...
     
  9. Memmeddu

    Memmeddu Member

    Messages:
    1,691
    Location:
    Italia Sardegna
    That's why engine driven would be a great option ,I thought that once charged it will run continuously to keep the pressure but I'm not an expert about air tools because I haven't own none yet .
    I had a compressor but I thrash it because the tank was compromised
     
  10. Memmeddu

    Memmeddu Member

    Messages:
    1,691
    Location:
    Italia Sardegna
    So 170x15 or 6.3x15 ?
    2550
    94.5
     
  11. hotponyshoes Member

    Messages:
    1,695
    Location:
    Somerset. Uk
    If you can get the capacity then engine driver would be ok.
    The advantage with an electric one is ot will fill however many tanks you want, turn itself off and not turn on again until you start using air.
    I'm sure you could set an engine up to do that but more complicated and expensive than electric.
    For mobile use engine may be the only option?
     
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  12. hotponyshoes Member

    Messages:
    1,695
    Location:
    Somerset. Uk
    To convert bar to psi X15.
    So 2bar = 30psi
     
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  13. ukracer Forum Supporter

    1 bar = 15 psi. So it's the 6.3.
     
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  14. dannyp Member

    one thing i found about making small engine drive compressors they are all the better for a centrifugal clutch, best one i bodged up had the enigne off a wackerplate on it with the centrifugal clutch still on it. it makes starting them so much easyer as your not dragging the pump round with engine.

    also when they are on a clutch you can controll the revs get a punmatic ram with enough stroke to open / close the throttel, don't skimp on the bore ether, use a spring to bias it so it revs the enigne when at rest, connect the tank to the side of it that pulls the throttel open, and T the other side into the pipe that runs from the compressor input side of the NRV to the unloader on teh pressure switch ( if it was electric )

    when you fire it up it'll now run flat out till the tanks full the when the pressure switch blows off the pnumatic ram shuts the throttel revs drop centrifugal clutch drops out and it just idels rather than continuosly blowing the pressure relife valve off.


    as for overspeeding compressors some take it some dont, the pumps tend to be crap in terms of volumetric efficency spin them to fast and they just don't pump any more air. tho a 2 hp belt drive and a 3 hp belt drive often the pump is the same it just goes faster on the 3 hp
     
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