Ingersol Rand Model B rpm/HP?

  1. Hood

    Hood Forum Supporter

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    I have an Ingersol Rand Model B compressor that I am using for the plasma. I have had it for years and it has had a couple of motors on it in the time I have had it.
    I have been looking around to see if I could find out what the motors HP and RPM should be and what the speed of the pump should be, but so far not really come up with much.
    At the moment it has a 920 rpm 1Hp motor but that is too slow. It is not keeping up with the plasma at the moment, from what I have seen it should be about 4 or 4.5 CFM and the plasma draws 100LPM, so about 3.5CFM if my calcs are correct.

    Anyone know what motor RPM should be on this or even better what RPM the pump should be?


    ScreenHunter_369 Nov. 16 18.54.jpg
     
  2. Mee Banned

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    Older Ingersoll Rand were normally 1400/1500 RPM motors and reduced at the pulleys for the drive belts.
     
  3. Hood

    Hood Forum Supporter

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    Ok thanks, pulleys are original as far as I can make out, both cast and same style and same paint as the rest of the compressor. I will likely just get a bigger pulley for the motor to increase the RPM as that will be the cheapest option although thinking about it I may well have a 0.75Kw motor that is new sitting in the store cabin. Not sure what RPM it is but will check tomorrow.
     
  4. Mee Banned

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    If you increase the pulley size you may overload the motor, it was common to buy industrial compressors cheaply and bodgers fitted single phase motors to them which were neither powerful enough, or they changed the pulleys to under gear them to make them run in a fashion.

    I would opt for a 1400/1500 RPM motor which would be a 4 pole motor and develop twice the torque of a 2 pole motor and go for around 2 HP and have some power in reserve to protect the motor, you can experiment with the pulleys if you like then, but even the extra speed over your current motor would increase your CFM output.
     
  5. Hood

    Hood Forum Supporter

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    Well just looked and the motor I have is 1.1Kw and 2800 rpm so a bit on the fast side but I could reduce the pulley size to get the equivalent rpm at the pump that a 1500rpm motor would have.
     
  6. rtbcomp

    rtbcomp Moderator Staff Member

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    You would have to halve (ish) the motor pulley size, this runs the risk of the pulley being too small to grip the belt. Go for the slower motor. As a rule of thumb, a 2hp motor will give 9cfm, a 3 hp 14 cfm, assuming the pump itself can deliver those volumes.

    Driving the pump too fast can actually produce less air output, as the piston will be on its way down before all the air has had time to be expelled from the cylinder.

    Basically, CFM depends on motor speed, maximum pressure depends on motor torque and Power = Torque x Speed, so you can see how they all interrelate.
     
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  7. Hood

    Hood Forum Supporter

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    The thing I am most concerned about is the RPM of the pump, don't want to exceed what it was designed for. So if 1500rpm motor was what the original was then that is what I will aim for.
    From what I have found with looking around the CFM was 4 to 4.5 which should be fine for my needs of 3.5CFM.
    The 2800rpm 1.1Kw should be fine witha reduced pulley. I think the original is 120/125mm Dia so I could go down to 65-70mm or so and that would be about the correct rpm at the pump and it should be plenty big enough for the belt as I have at least 250mm more travel left on the slides to accommodate a longer belt.

    The other option I have is to swap this compressor with the one I have in the workshop, it is 14cfm and I do not really need it there as it is only used for the Chirons tool changer and some bow guns.
     
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  8. Mee Banned

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    If you have the pump numbers and details you can get the full details online if you search for them, this will give the pump running speeds which will usually be an upper and lower speed, they dictate the CFM output. This will give you the information to calculate the pulley sizes for any motor, IR made a smaller range of pumps and drove them at different speeds, hence the pump speed range, and often fitted a choice of motors depending on markets and available voltages.
     
  9. Hood

    Hood Forum Supporter

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    As far as I can see the numbers in the pic in original post are the only ones on the pump.
    I have searched using them and drawn a blank. The Model B gets some hits but no real info.
     
  10. Mee Banned

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    Ingersoll Rand used to have a section dedicated to old or obsolete models which gave all the information.
     
  11. Mee Banned

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  12. Hood

    Hood Forum Supporter

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    Already tried there but got no where, maybe I am just doing it wrong.
     
  13. Pat W. New Member

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    I have a Model B and use it regularly. Mine is an old gasoline service station pump from the 1950's. It is a low volume compressor, about 2 cfm. I run mine at 900 rpm and it takes roughly 20 minutes to fill an 60 gallon (oversized) tank to 125psi. That is plenty of air for me. I contacted IR about 20 years ago. They had no data in files, but one guy found some notes. I think he said it is designed to go to about 150psi. He said it would last a long time if I keep it to 900 to 1100 rpm, and that it was never designed to run fast or for high volume. It has a really nice deep sound, not loud like modern compressors (ear protection not necessary). If you need high volume, you likely need a bigger pump. If I can find my notes on the pump curve, I will post them.
     
  14. Pat W. New Member

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    Location:
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    Found It!!! (...a small miracle) Here is what the Tech Specialist at Ingersoll-Rand provided me for that Model B pump. I think my recollection of "(up) to 1100 rpm" was in error.

    Ingersoll-Rand Model B Compressor Pump Characteristics

    0.75 HP 80 psi 2 CFM 575 RPM

    1.00 HP 150 psi 2 CFM 760 RPM

    1.50 HP 150 psi 2 CFM 990 RPM

    575 to 990 RPM is good operating range
     
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  15. Hood

    Hood Forum Supporter

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    Thanks for the info.
    Mine is running faster than that and is ok at the moment, if it blows then will just have to get another but as you say they are a lovely sound compared to new ones.
     
  16. Mee Banned

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    Good old plodders.
     
  17. Seadog

    Seadog Forum Supporter

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    As you'll see from my current post, I've just bought one of these in completely original condition. Does anyone have a copy of the manual for it?
     
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