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New owner of a Magni M-16 with a 912 here. I would like to install a fuel flow gauge with an EI “red cube” transducer. These have 1/4” NPT female fittings.

The gyro has Gates 7mm 3225 series fuel lines (apparently a European option). That’s closest to 9/32” dia, I believe.

I’ve seen AN840-5D fitting at auto race supply sites, typically. Will those work? They have a 5/16” barbed end. I saw in other posts here that barbed is really not ideal for fuel lines.

It seems unlikely I’m the first to install one of these on a 912 so any suggested solutions are greatly appreciated.

/Ed
  • Re: Fuel Flow Install Question

    by » 6 years ago


    There are many Red Cube installs and you can supply your own fittings. Most seem to use 5/16" with barbed fittings. The issue with many owners is they want to over crimp the hose on the fitting and making it too tight may cause the barbed part to gut into the hose liner. So you can use it just don't get heavy handed when you crimp it. It doesn't take much pressure to keep it from leaking or coming off.

    Ideally an AN smoothed shaft fitting is best.

    Roger Lee
    LSRM-A & Rotax Instructor & Rotax IRC
    Tucson, AZ Ryan Airfield (KRYN)
    520-349-7056 Cell


  • Re: Fuel Flow Install Question

    by » 6 years ago


    Thanks, Roger.

    I’ve looked around and all I can seem to find for the 5/16” (AN840-5D) is the barbed. I picked up a couple of AN840-6D smooth ones at OSH hoping they’d work but they’re way too big. If you know of a source for 5/16” smooth ones, I’d appreciate it! I suspect, though, it’s as you say and people use the barbed ones.

    /Ed

  • Re: Fuel Flow Install Question

    by » 6 years ago


    If you are not against a little custom machining...

    If you know anyone with a lathe, The 5/16(7.9MM) barbed fitting could be turned to take the points off the barbs.
    Take it down to about 7.5mm to keep it snug.
    Or, take them down to 7mm except for the last one at 7.5 approximating a smooth adaptor.
    With the sharp points of the barbs removed, you won't have to worry about overtightening.

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


  • Re: Fuel Flow Install Question

    by » 6 years ago


    I've used belt sanders to remove barbs. I personally have no issue with barbed fittings. Just don't over clamp them.

    Roger Lee
    LSRM-A & Rotax Instructor & Rotax IRC
    Tucson, AZ Ryan Airfield (KRYN)
    520-349-7056 Cell


  • Re: Fuel Flow Install Question

    by » 6 years ago


    Thanks for the inputs. I’ll give the AN840-5D’s a try and possibly sand the barbs down a bit, if only to have them fit the 7mm hose better.

    /Ed

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