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Lay up in humid conditions

in General Tech Discussion 8 years ago

  • Re: Lay up in humid conditions

    by » 8 years ago

    ...
    I do not see the pressure back flowing the Oil in the engine because the pressure is also on the intake side of the oil pump, so the oil is in equilibrium with the crankcase pressure...


    I find it strange to be quoting myself....

    I would like to say, "I was Wrong!"
    But I find it more pleasant to use the technique the ladies like to use... "I changed my Mind!"

    The Input of the oil pump is not at Crankcase pressure.
    Unlike conventional engines with an Oil Pan, the Rotax and other engines with a dry sump system have their Oil Pump Inputs at oil tank pressure, which is at atmospheric pressure as the oil tank is vented.
    Therefore, there exists the possibility that Oil Might be pushed back through the oil pump to the oil tank leaving the Oil pump without a prime.

    Having said that, I think the process would be exceedingly slow or non-existent as the oil pump is a positive displacement gear pump and will effectively resist any attempt to move oil past it in either direction when it is not rotating.

    This is still something that will need to be investigated closely.

    99% of the reduction in combustion byproducts gasses in the crankcase are going to be purged in the first hour or so.
    It could be argued that purging the crankcase is a good thing but that as the crankcase is an isolated volume, it does not communicate with the atmosphere.
    An hour or so of purging with clean dry air would be sufficient to produce the corrosion resistance you are looking to accomplish.
    After the initial purge, you will just be blowing a bunch of air for no real gain.

    If you could determine the actual volume of the crankcase, passing the equivalent 5 time that volume through it will theoretically remove >99% of the original vapors. 12 volumes will get you to less than 1 part per million remaining.

    Example: If you were to pump 1 liter per minute into a volume of 10 liters, you would be >99% clear after 50 minutes, and >99.9999% clear after 120 minutes.

    Air purging for 1-3 hours initially may be all that is needed.
    An additional purge for an hour every month or so might boost your confidence but may not be required.

    Bill Hertzel
    Rotax 912is
    North Ridgeville, OH, USA
    Clicking the "Thank You" is Always Appreciated by Everyone.

    Thank you said by: Hann Redwin
      
    Report

  • Re: Lay up in humid conditions

    by » 8 years ago

    Good morning, and thank you Bill for the time spent here.

    I will keep you updated on the prototype.

    Hann
      
    Report
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