Which O-Ring for piston ring?

Discussion in 'General Engine Discussion' started by Jack3M, Jan 14, 2020.

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  1. Jan 14, 2020 #1

    Jack3M

    Jack3M

    Jack3M

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    There are so many out there, I have no clue which to use for a piston ring. The one I got at the hardware store lasted about 10 minutes of run time.
    McMaster-Carr has a huge selection of types?
    https://www.mcmaster.com/o-rings
     
  2. Jan 14, 2020 #2

    Brian Rupnow

    Brian Rupnow

    Brian Rupnow

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    Use a Viton o-ring. they are heat resistant and last forever. You want 1/16" cross section, with outside diameter to match the cylinder bore. Groove in piston should be .094" wide x 0.058" deep. Only use one ring.---Brian
     
  3. Jan 18, 2020 #3

    BobsModels

    BobsModels

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    Jack

    I agree with Brian on the Vitron (hard not soft), I have over 800 hours on my Gade with the same ring. I have found another ring that I am using on a steam cylinder that gets much hotter than our gas engines. It is an Ultra-Chemical-Resistant Aflas O-Ring, get it from Mc Master. I will be trying it on my next gas engine. Also you really want minimum wall pressure so the depth of the groove in the piston needs to be based on the cylinder diameter. I attached a PDF that shows how to calculate for whatever cylinder diameter you have relative to your piston. Also remember that a 1/16 O Ring is not 1/16 in diameter but .070 so you need to account for that also. Your goal should be to get a nice rock and bounce like this.

    https://youtu.be/1QazAr4b3KY

    Let us know how it comes out for you

    Good Luck

    Bob
     

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  4. Jan 18, 2020 #4

    Jack3M

    Jack3M

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    That is what I ordered.
     
  5. Jan 29, 2020 #5

    Ken I

    Ken I

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    Backing up what Brian said - if you use two "O" rings - in any application, a pressure builds up between the two rings sufficient to cause extrusion / premature failure.
    You can use two (to prevent "rocking" for instance) but then the gap between the "O" rings must be vented (just a small "drain" hole) to either the HP or LP side to prevent this pressure build up.
    Two rings in a wide groove will fail - two grooves are obviously separated - but the void between them must be vented
    Seems a bit counter intuitive but it does work.
    Regards, Ken
     
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  6. Jan 29, 2020 #6

    Jasonb

    Jasonb

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    If the Viton are only lasting 10mins what is the surface of your cylineder like? At a minimum it wants to be honed but better if it is lapped.
     

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