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Biofuel Rotting Hoses and Carb Rubbers?

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  • Biofuel Rotting Hoses and Carb Rubbers?

    Just had an oil breather pipe rot away plus fuel lines deteriorating; the oil breather hose apparently is vulnerable to the small contamination all four stroke engines get when choke starting, as the volatile Ethanol and other nasties washed down the cylinder walls boil off the main oil mass and exit via the breather.

    This is happening with Biofuels a lot apparently

    Did a bit of research after seeing even Halfords-bought fuel injection pipe start to go manky and found this:-

    http://www.advancedfluidsolutions.co...rol-2015-p.asp

    Chap on the helpline was top on his product knowledge and steered me away from lesser products. Even Silicone tubing suffers.

    Has this anything to do with carb rubbers on 912s splitting? always seems to be the bottom that goes, as you'd expect from pooled gas in the manifold

    Cheers

    Kev
    G-KEVA
    BMAA 5696

    "If anybody ever tells you anything about an aeroplane which is so bloody complicated you can't understand it, take it from me: it's all balls."

    R.J. Mitchell :- Designer of the Supermarine Spitfire

  • #2
    Biofuel Rotting Hoses and Carb Rubbers?

    Hi Kev,
    I share your concerns about Ethanol fuels - particularly when we go to E10 (ie 10%) ethanol. Vapour lock will be another problem I fear.

    A couple of thoughts
    - Is that fuel line you have found fire retardant?
    - it is available in 5.5mm and 7.3mm id - 6 or 6.5mm id is the norm we use.
    - not sure of the price as it just says 13 - but for what length? The Fuel line from P+M is not cheap at 10.50 / m but is fire retardant and lasts well and as it is 6.5mm id fits most connectors. The fuel line from Skydrive is cheaper, but as it is 6mm id it does not fit larger connectors so easily.
    - carb rubber manifolds - you may be right about fuel pooling there - but I think some of the problem is from the spring which is above the manifold, that pulls the carb itowards the engine, being too tight and putting the lower part of the rubber manifold into tension. I have found manifolds sheared at VERY low hours when these springs were too tight.

    Cheers
    AndyB

    PS - I think I saw you whizz overhead Caunton the other week, heading Northwards??

    Comment


    • #3
      Biofuel Rotting Hoses and Carb Rubbers?

      Hello Andy, all good points as usual

      Not fire proof but able to be shrouded with that orange insulating stuff

      I've used 5.5 mm and it grips a lot better than 6mm on 1/4" or 6mm hose barbs, but the Halfords 5.5mm isn't Ethanol proof enough.

      Price is per metre, thought it said that? My mistake if not.

      Carb manifold suggestion was just a thought that may not have occurred to anyone else?

      Yes, I did whizz overhead Caunton both times, but was concerned about dropping in as your runway plate wasn't printed off and on my map, would have liked to have shown you my engine

      Recently when delivering an aircraft to Sittles I thought 'Roddige' referred to it on the map, have been into Sittles before but it has moved location to within yards of Roddige.

      Followed what I thought were correct procedures and received a MASSIVE scolding lecture from a Mr Michael Shea, while his pupils looking in any other direction they could, from embarrassment; couldn't get a word of apology in edgeways.

      Flew out quickly whilst musing over the wisdom of hassling a tired pilot in case they omit checks when scarpering, which I did in haste....;-/

      So am a bit cautious since unless PPR'd and thoroughly researched...

      Question, was it too noisy? Am experimenting with different silencers

      cheers

      Kev
      G-KEVA
      BMAA 5696

      "If anybody ever tells you anything about an aeroplane which is so bloody complicated you can't understand it, take it from me: it's all balls."

      R.J. Mitchell :- Designer of the Supermarine Spitfire

      Comment


      • #4
        Biofuel Rotting Hoses and Carb Rubbers?

        Hi Kev,
        The noise was 'noticeable'. Not unpleasant, like some 2T engines, but a student did comment on it. Which is why we saw you. Abd it sounded different to most microlights - so I guessed it was you!

        Our details are at www.cauntonmicrolightclub.co.uk and like most (all??) airfields we have our procedures and no-fly areas.

        I did wonder if I might make it up to Beverley last Wednesday on my hang glider - and wondered about the procedures there - but in the end I landed short, just North of the Humber - about 50km from an aerotow launch at Caunton.

        Cheers
        AndyB

        Comment


        • #5
          Biofuel Rotting Hoses and Carb Rubbers?

          You should have given me a ring, would have been happy to assist; one heck of a HG flight eh?

          Beverley is very friendly and has a thriving paramotor and microlight population, all circuits are to the North, 30 or 12 with crossing strips for microlights; only thing to remember is avoid nearby Leven Village but that is well away from the field.

          Cheers

          Kev
          G-KEVA
          BMAA 5696

          "If anybody ever tells you anything about an aeroplane which is so bloody complicated you can't understand it, take it from me: it's all balls."

          R.J. Mitchell :- Designer of the Supermarine Spitfire

          Comment


          • #6
            Biofuel Rotting Hoses and Carb Rubbers?

            Most of the fuel fittings on a P&M trike are 8mm not 6mm.
            In my opinion - stretching a 6mm pipe over an 8mm fitting increases the likelihood of failure.
            If you go to 8mm you can buy a much better filter.

            That's my 2pth
            Laurie (2)

            Andy Buchan wrote: Hi Kev,
            I share your concerns about Ethanol fuels - particularly when we go to E10 (ie 10%) ethanol. Vapour lock will be another problem I fear.

            A couple of thoughts
            - Is that fuel line you have found fire retardant?
            - it is available in 5.5mm and 7.3mm id - 6 or 6.5mm id is the norm we use.
            - not sure of the price as it just says 13 - but for what length? The Fuel line from P+M is not cheap at 10.50 / m but is fire retardant and lasts well and as it is 6.5mm id fits most connectors. The fuel line from Skydrive is cheaper, but as it is 6mm id it does not fit larger connectors so easily.
            - carb rubber manifolds - you may be right about fuel pooling there - but I think some of the problem is from the spring which is above the manifold, that pulls the carb itowards the engine, being too tight and putting the lower part of the rubber manifold into tension. I have found manifolds sheared at VERY low hours when these springs were too tight.

            Cheers
            AndyB

            PS - I think I saw you whizz overhead Caunton the other week, heading Northwards??

            Comment


            • #7
              Biofuel Rotting Hoses and Carb Rubbers?

              Ace Cyclone pipes are 6mm Laurie, or 1/4" bore; My old Quik pipes were 1/4" and some fittings were 8mm requiring hot water to fit.

              Maybe your Quik is a more powerful version

              Kev
              G-KEVA
              BMAA 5696

              "If anybody ever tells you anything about an aeroplane which is so bloody complicated you can't understand it, take it from me: it's all balls."

              R.J. Mitchell :- Designer of the Supermarine Spitfire

              Comment


              • #8
                Biofuel Rotting Hoses and Carb Rubbers?

                Hi Laurie,
                The trouble is that some rubber fuel lines have fit over 6mm fittings at one end and and 8mm fittings at the other.
                It is the same with many aircraft types - CTs, Dynamics, Banbis......
                I have found that the P+M supplied (Gates) fuel line does this OK. I certainly would not want an 8mm fuel line on a 6mm fitting as it could lead to air ingress on the suction side of the pump or a leak on the pressure side.
                Cheers
                AndyB

                Comment


                • #9
                  Biofuel Rotting Hoses and Carb Rubbers?

                  I don't think biofuel is the problem with splitting carb rubbers. Since I had an issue with a blocked fuel pressure gauge pipe using ordinary mogas at 97 engine hours, which coincided with discovery of a split carb rubber, I changed to using BP Ultimate 97 which has been to date ethanol free. I changed both carb rubbers at this time. I do regular checks with my blue cotton bud kit to check for freedom from ethanol. I have recently had a carb rubber split at 324 hours (Rotax 912S) so the simple maths show that although completely free from ethanol for all of it's working life this rubber lasted just 227 hours. In this time the only deviation from the BP ethanol free mogas was the uplift of 35 litres of Avgas when I had no choice. Interestingly I have reduced the top carb support spring tension on the basis that my engine is fitted with Skydrive carb heaters which extend the carb distance from the flange, and increases spring pressure. So even with reduced spring tension my carb rubber has split, and around the bottom which is the normal reported failure mode.

                  Comment


                  • #10
                    Biofuel Rotting Hoses and Carb Rubbers?

                    During my engine research, discovered a Czech pilot has put his carbs on hoses on his kit plane, around 300mm long, to isolate vibration as the carb needle can suffer although Viton tipped.

                    The carbs on a 912 or S will be mounted on the engine as aero unit customers generally like a one piece package, but if we look at mass sensors on cars they generally mount on nearby structure and put flexy hose onto the engine.

                    Although the mod process might be a pain in the botty, if my carb rubbers persisted in failing this would be one mod to seriously consider, probably using fluoro silicone tubing as this is fuel resistant whereas ordinary silicone isn't.

                    Plenty of handy airframe just forward to hang the carbs off

                    Kev
                    G-KEVA
                    BMAA 5696

                    "If anybody ever tells you anything about an aeroplane which is so bloody complicated you can't understand it, take it from me: it's all balls."

                    R.J. Mitchell :- Designer of the Supermarine Spitfire

                    Comment


                    • #11
                      Biofuel Rotting Hoses and Carb Rubbers?

                      Following on from Kev's line of thought - I have not found split carb manifolds on aircraft which have airboxes or alloy drip trays that hold the carbs in position and stop them flapping around and flexing the manifolds.
                      The splits I have found have been on 912S engines (more shake on start up / shut down) which have unsupported carbs - as on most trikes, Skyrangers etc.

                      Had a 912 Quantum in with 1000hrs and the carb rubbers on that were JUST showing signs of cracking.

                      AndyB

                      Comment

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